Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

.github/CONTRIBUTING.md

@@ -111,6 +111,8 @@ context which existing file needs to be extended, and only very few cases requir
 When fixing a bug, edit `unit-regression3.cpp` and add a section referencing the fixed issue.
 `unit-regression2.cpp` holds the older tests; the two files exist because a single one grew large enough for the
 MinGW linker to fail relocating it, so please keep adding to the smaller file rather than growing the larger one.
+Tests that call `sax_parse` go into `unit-sax_parse.cpp` rather than into a large test file: every call instantiates
+the parser and the binary reader that recover from errors, which grows a test file considerably.
 
 #### Exceptions
 

BUILD.bazel

@@ -36,7 +36,6 @@ cc_library(
         "include/nlohmann/detail/input/parser.hpp",
         "include/nlohmann/detail/input/position_t.hpp",
         "include/nlohmann/detail/input/pow5_table.hpp",
-        "include/nlohmann/detail/input/simd_scan.hpp",
         "include/nlohmann/detail/input/string_scan.hpp",
         "include/nlohmann/detail/iterators/internal_iterator.hpp",
         "include/nlohmann/detail/iterators/iter_impl.hpp",

README.md

@@ -495,7 +495,7 @@ bool key(string_t& val);
 bool parse_error(std::size_t position, const std::string& last_token, const detail::exception& ex);
 ```
 
-The return value of each function determines whether parsing should proceed.
+The return value of each function determines whether parsing should proceed. For `parse_error`, returning `true` [recovers from the error](https://json.nlohmann.me/features/parsing/error_recovery/): the parser repairs the input and continues.
 
 To implement your own SAX handler, proceed as follows:
 
@@ -503,7 +503,7 @@ To implement your own SAX handler, proceed as follows:
 2. Create an object of your SAX interface class, e.g. `my_sax`.
 3. Call `bool json::sax_parse(input, &my_sax)`; where the first parameter can be any input like a string or an input stream and the second parameter is a pointer to your SAX interface.
 
-Note the `sax_parse` function only returns a `bool` indicating the result of the last executed SAX event. It does not return a  `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error -- it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file [`json_sax.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/json_sax.hpp).
+Note the `sax_parse` function only returns a `bool` indicating whether the input was parsed without errors and no SAX event returned `false`. It does not return a  `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error -- it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file [`json_sax.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/json_sax.hpp).
 
 ### STL-like access
 

docs/mkdocs/docs/api/basic_json/accept.md

@@ -132,10 +132,6 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
 - [operator>>](../operator_gtgt.md) - deserialize from stream
 - [`JSON_STRICT_NUL_HANDLING`](../macros/json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input
   instead of treating it as end of input
-- [`JSON_DISABLE_STREAM_BULK_SCAN`](../macros/json_disable_stream_bulk_scan.md) - read a `std::istream` one character
-  at a time
-- [`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md) - read a `FILE*` with the locking stdio
-  functions
 
 ## Version history
 
@@ -147,10 +143,6 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
 - Extended overload (2) to accept heterogeneous iterator+sentinel pairs (C++20 ranges support) in version 3.13.0.
 - `JSON_STRICT_NUL_HANDLING` added in version 3.13.0 to optionally reject a NUL byte in the input instead of treating
   it as end of input; planned to become the default in version 4.0.0.
-- Parsing from an `std::istream` scans the characters in its stream buffer in bulk in version 3.13.0
-  ([`JSON_DISABLE_STREAM_BULK_SCAN`](../macros/json_disable_stream_bulk_scan.md)).
-- Parsing from a `FILE*` locks the file once instead of once per character in version 3.13.0
-  ([`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md)).
 
 !!! warning "Deprecation"
 

docs/mkdocs/docs/api/basic_json/parse.md

@@ -112,16 +112,6 @@ By default, a `'\0'` (NUL) byte anywhere in the input is treated as end of input
 outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-bytes-in-the-input) for details and the
 [`JSON_STRICT_NUL_HANDLING`](../macros/json_strict_nul_handling.md) macro to opt into rejecting it instead.
 
-!!! tip "Performance"
-
-    Contiguous inputs (strings, string views, vectors, arrays, pointer ranges) are the fastest to parse. A
-    `#!cpp std::istream` comes close: the parser scans the characters its stream buffer holds in bulk, without reading
-    ahead, so the stream is left exactly where it would be after reading one character at a time. A `#!cpp FILE*` is
-    read one character at a time, but the file is locked only once, so other threads that use the same `FILE` object
-    wait until parsing is done. See [input sources and performance](../../features/parsing/index.md#input-sources-and-performance),
-    [`JSON_DISABLE_STREAM_BULK_SCAN`](../macros/json_disable_stream_bulk_scan.md), and
-    [`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md).
-
 ## Examples
 
 ??? example "Example: (1) parse from a character array"
@@ -257,10 +247,6 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
 - [operator>>](../operator_gtgt.md) - deserialize from stream
 - [`JSON_STRICT_NUL_HANDLING`](../macros/json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input
   instead of treating it as end of input
-- [`JSON_DISABLE_STREAM_BULK_SCAN`](../macros/json_disable_stream_bulk_scan.md) - read a `std::istream` one character
-  at a time
-- [`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md) - read a `FILE*` with the locking stdio
-  functions
 
 ## Version history
 
@@ -275,11 +261,6 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
   it as end of input; planned to become the default in version 4.0.0.
 - Extended empty-input detection to also cover an `std::istream` without a stream buffer, and fixed a crash
   (`std::terminate`) when parsing from an `std::istream` with `eofbit` in its exception mask, in version 3.13.0.
-- Parsing from an `std::istream` scans the characters in its stream buffer in bulk in version 3.13.0
-  ([`JSON_DISABLE_STREAM_BULK_SCAN`](../macros/json_disable_stream_bulk_scan.md) restores reading one character at a
-  time).
-- Parsing from a `FILE*` locks the file once instead of once per character in version 3.13.0
-  ([`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md) restores `std::fgetc`).
 
 !!! warning "Deprecation"
 

docs/mkdocs/docs/api/basic_json/sax_parse.md

@@ -96,7 +96,9 @@ The SAX event lister must follow the interface of [`json_sax`](../json_sax/index
 
 ## Return value
 
-return value of the last processed SAX event
+`#!cpp true` if the input was parsed without errors and no SAX event returned `#!cpp false`; `#!cpp false` otherwise.
+In particular, the result is `#!cpp false` for input with errors, even if the SAX parser recovered from all of them
+(see [error recovery](../../features/parsing/error_recovery.md)).
 
 ## Exception safety
 
@@ -116,10 +118,6 @@ consumer `sax` has a super-linear complexity.
 
 A UTF-8 byte order mark is silently ignored.
 
-When reading from a `#!c FILE*`, the file is locked while it is parsed. The lock is recursive, so the SAX handler may
-use the same file with stdio functions, but it must not wait for another thread that uses the same `FILE` object; see
-[`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md).
-
 ## Examples
 
 ??? example
@@ -141,10 +139,6 @@ use the same file with stdio functions, but it must not wait for another thread
 
 - [parse](parse.md) - deserialize from a compatible input
 - [accept](accept.md) - check if the input is valid JSON
-- [`JSON_DISABLE_STREAM_BULK_SCAN`](../macros/json_disable_stream_bulk_scan.md) - read a `std::istream` one character
-  at a time
-- [`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md) - read a `FILE*` with the locking stdio
-  functions
 
 ## Version history
 
@@ -153,13 +147,10 @@ use the same file with stdio functions, but it must not wait for another thread
 - Added `ignore_trailing_commas` in version 3.13.0.
 - Added `tag_handler` in version 3.13.0.
 - Extended container support (1) to include types with lvalue-only ADL `begin`/`end` (matching `std::begin`/`std::end` semantics) in version 3.13.0.
+- Recovering from parse errors (see [`parse_error`](../json_sax/parse_error.md)) added in version 3.13.0.
 - Extended overload (2) to accept heterogeneous iterator+sentinel pairs (C++20 ranges support) in version 3.13.0.
 - `JSON_PRECISE_STREAM_POSITION` added in version 3.13.0 to optionally leave a `#!cpp std::istream` positioned right
   after the parsed value when `strict` is `#!cpp false`.
-- Parsing from an `std::istream` scans the characters in its stream buffer in bulk in version 3.13.0
-  ([`JSON_DISABLE_STREAM_BULK_SCAN`](../macros/json_disable_stream_bulk_scan.md)).
-- Parsing from a `FILE*` locks the file once instead of once per character in version 3.13.0
-  ([`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md)).
 
 !!! warning "Deprecation"
 

docs/mkdocs/docs/api/json_sax/index.md

@@ -7,7 +7,8 @@ struct json_sax;
 
 This class describes the SAX interface used by [sax_parse](../basic_json/sax_parse.md). Each function is called in
 different situations while the input is parsed. The boolean return value informs the parser whether to continue
-processing the input.
+processing the input; for [`parse_error`](parse_error.md), it decides whether to
+[recover from the error](../../features/parsing/error_recovery.md).
 
 For instance, parsing the JSON text `{"a": [1, true]}` triggers the following callbacks, in order:
 

docs/mkdocs/docs/api/json_sax/parse_error.md

@@ -21,11 +21,18 @@ A parse error occurred.
 
 ## Return value
 
-Whether parsing should proceed (**must return `#!cpp false`**).
+Whether to recover from the error:
+
+- `#!cpp false` stops parsing.
+- `#!cpp true` recovers from the error: the error is repaired and parsing continues. If that is not possible, which
+  happens in the binary formats when the end of the item with the error is unknown, the value read so far is completed
+  and parsing stops. See [error recovery](../../features/parsing/error_recovery.md) for how errors are repaired.
+
+Either way, [`sax_parse`](../basic_json/sax_parse.md) returns `#!cpp false`.
 
 ## Examples
 
-??? example
+??? example "Example: (1) the SAX interface"
 
     The example below shows how the SAX interface is used.
 
@@ -39,12 +46,29 @@ Whether parsing should proceed (**must return `#!cpp false`**).
     --8<-- "examples/sax_parse.output"
     ```
 
+??? example "Example: (2) recovering from errors"
+
+    The example below shows how a SAX parser recovers from errors.
+
+    ```cpp
+    --8<-- "examples/sax_parse__error_recovery.cpp"
+    ```
+    
+    Output:
+    
+    ```
+    --8<-- "examples/sax_parse__error_recovery.output"
+    ```
+
 ## See also
 
 - [sax_parse](../basic_json/sax_parse.md) - SAX parser
 - [Parsing and Exceptions](../../features/parsing/parse_exceptions.md) - the article on handling parse errors without
   exceptions
+- [Error Recovery](../../features/parsing/error_recovery.md) - the article on recovering from parse errors
 
 ## Version history
 
 - Added in version 3.2.0.
+- Returning `#!cpp true` recovers from the error since version 3.13.0; before, parsing stopped, but the result of
+  [`sax_parse`](../basic_json/sax_parse.md) could be wrong.

docs/mkdocs/docs/api/macros/index.md

@@ -16,10 +16,6 @@ header. See also the [macro overview page](../../features/macros.md).
 
 ## Parsing
 
-- [**JSON_DISABLE_STREAM_BULK_SCAN**](json_disable_stream_bulk_scan.md) - read a `std::istream` one character at a time
-  instead of scanning its stream buffer in bulk
-- [**JSON_DISABLE_UNLOCKED_FILE_IO**](json_disable_unlocked_file_io.md) - read a `FILE*` with `std::fgetc` instead of
-  locking it once and using the unlocked stdio functions
 - [**JSON_PRECISE_STREAM_POSITION**](json_precise_stream_position.md) - opt in to leaving an input stream positioned
   right after a parsed number
 - [**JSON_STRICT_BINARY_UTF8**](json_strict_binary_utf8.md) - opt in to checking strings for valid UTF-8 in the CBOR,
@@ -38,7 +34,6 @@ header. See also the [macro overview page](../../features/macros.md).
 - [**JSON_HAS_THREE_WAY_COMPARISON**](json_has_three_way_comparison.md) - control 3-way comparison support
 - [**JSON_NO_AUTOMATIC_UDLS**](json_no_automatic_udls.md) - do not include the user-defined string literals (UDLs) automatically
 - [**JSON_NO_IO**](json_no_io.md) - switch off functions relying on certain C++ I/O headers
-- [**JSON_NO_SIMD**](json_no_simd.md) - use only portable code instead of vector instructions (SSE2, SSSE3, NEON)
 - [**JSON_NO_THREAD_LOCAL**](json_no_thread_local.md) - switch off the use of `thread_local` storage
 - [**JSON_SKIP_UNSUPPORTED_COMPILER_CHECK**](json_skip_unsupported_compiler_check.md) - do not warn about unsupported compilers
 - [**JSON_USE_GLOBAL_UDLS**](json_use_global_udls.md) - place user-defined string literals (UDLs) into the global namespace

docs/mkdocs/docs/api/macros/json_disable_stream_bulk_scan.md

@@ -1,145 +0,0 @@
-# JSON_DISABLE_STREAM_BULK_SCAN
-
-```cpp
-#define JSON_DISABLE_STREAM_BULK_SCAN /* value */
-```
-
-When defined to `1`, parsing from a `#!cpp std::istream` reads the input one character at a time through the stream
-buffer, as in version 3.12.0 and earlier, instead of scanning the characters that the stream buffer already holds in
-bulk.
-
-The macro is an escape hatch for stream buffers that do not follow the usual contract of `std::basic_streambuf` (see
-the requirements on the stream buffer in the notes below). It does not change any result: values, exceptions, and the
-position of the stream after parsing are the same either way. Only the speed differs.
-
-## Default definition
-
-The default value is `0`: streams are scanned in bulk.
-
-```cpp
-#define JSON_DISABLE_STREAM_BULK_SCAN 0
-```
-
-## Notes
-
-!!! note "How streams are scanned"
-
-    A `std::streambuf` keeps the part of the input it has read but not yet handed out in its *get area*, the range
-    from `gptr()` to `egptr()`. A `std::filebuf`, for instance, reads the file in blocks of a few kilobytes into its get
-    area, and a `std::stringbuf` exposes its whole string as one get area.
-
-    When parsing from a `std::istream`, the parser scans this get area directly, with the same fast paths that it uses
-    for a `std::string`: runs of ordinary string characters, numbers, and indentation are recognized several bytes at a
-    time instead of being requested from the stream buffer one character at a time. When the parser reaches the end of
-    the get area, it asks the stream buffer for the next character as before, which makes the stream buffer refill its
-    get area.
-
-    The parser only reads characters that it would also have read one at a time, and it advances the stream buffer
-    exactly over the characters it consumes. Nothing is read ahead, buffered elsewhere, or put back. Therefore, the
-    stream is left exactly where it was left before:
-
-    - [`operator>>`](../operator_gtgt.md) and [`sax_parse`](../basic_json/sax_parse.md) with `strict = false` can still
-      read several values from one stream, and the stream can still be used with other `std::istream` functions after a
-      value has been read.
-    - With [`JSON_PRECISE_STREAM_POSITION`](json_precise_stream_position.md), the stream is still positioned right after
-      a parsed number.
-    - Exception messages, including the line, the column, and the last read token, are unchanged.
-
-!!! note "Performance"
-
-    Parsing from a `std::ifstream` or `std::istringstream` is typically 1.5 to 2 times as fast as before, and reading
-    many small values from one stream with `operator>>` 1.4 to 4 times as fast. Parsing from a stream is then within
-    about 10 to 20 % of first reading the whole file into a `std::string` and parsing that.
-
-    A stream buffer without a get area (one that only overrides `underflow()` and `uflow()` and hands out every
-    character from there) offers nothing to scan in bulk, so it is read one character at a time as before.
-
-!!! note "Requirements on the stream buffer"
-
-    The bulk scan relies on the following behavior, which every stream buffer of the standard library and every stream
-    buffer that keeps its input in its get area has:
-
-    - When `sgetc()` returns a character while `gptr() < egptr()`, that character is `*gptr()`; when `sbumpc()` returns
-      one, it was at `gptr()` before the call.
-    - Characters in the get area are not changed while they are in the get area.
-    - `underflow()` or `uflow()` either sets up a get area that holds the returned character at `gptr()` (or at
-      `gptr() - 1` after `uflow()`), or leaves the get area empty.
-
-    A stream buffer that returns characters from `uflow()` while leaving unrelated characters in its get area, or that
-    changes the characters in its get area in place, does not meet these requirements. Define the macro to `1` for
-    such stream buffers.
-
-!!! warning "Define consistently"
-
-    The macro selects between two definitions of the library's internal stream input adapter. It must therefore be
-    defined identically for **every** translation unit that includes the library; mixing translation units that define
-    it with ones that do not is an ODR violation. Prefer setting it as a compile definition on the target rather than
-    with `#!cpp #define` in individual source files.
-
-!!! note "Other inputs"
-
-    Strings, string views, vectors, arrays, and pointer or iterator ranges over contiguous memory are scanned in bulk
-    anyway. Reading from a `#!cpp FILE*` is not affected by this macro; see
-    [`JSON_DISABLE_UNLOCKED_FILE_IO`](json_disable_unlocked_file_io.md) for that input.
-
-## Examples
-
-??? example "Example: reading values from a stream (default)"
-
-    The stream is scanned in bulk, and the values are read one after the other:
-
-    ```cpp
-    #include <iostream>
-    #include <sstream>
-    #include <nlohmann/json.hpp>
-
-    using json = nlohmann::json;
-
-    int main()
-    {
-        std::istringstream input(R"({"id": 1} {"id": 2} 42 rest)");
-        json j1, j2, j3;
-        input >> j1 >> j2 >> j3;  // {"id":1}, {"id":2}, 42
-
-        std::string word;
-        input >> word;            // "rest"
-    }
-    ```
-
-??? example "Example: reading one character at a time (macro defined to 1)"
-
-    With the macro, the same program reads the stream one character at a time, with the same results:
-
-    ```cpp
-    #define JSON_DISABLE_STREAM_BULK_SCAN 1
-    #include <iostream>
-    #include <sstream>
-    #include <nlohmann/json.hpp>
-
-    using json = nlohmann::json;
-
-    int main()
-    {
-        std::istringstream input(R"({"id": 1} {"id": 2} 42 rest)");
-        json j1, j2, j3;
-        input >> j1 >> j2 >> j3;  // {"id":1}, {"id":2}, 42
-
-        std::string word;
-        input >> word;            // "rest"
-    }
-    ```
-
-## See also
-
-- [**parse**](../basic_json/parse.md) - deserialize from a compatible input
-- [**operator>>**](../operator_gtgt.md) - deserialize from stream
-- [**sax_parse**](../basic_json/sax_parse.md) - generate SAX events
-- [**JSON_PRECISE_STREAM_POSITION**](json_precise_stream_position.md) - leave an input stream positioned right after a
-  parsed number
-- [**JSON_DISABLE_UNLOCKED_FILE_IO**](json_disable_unlocked_file_io.md) - read a `FILE*` with the locking stdio
-  functions
-- [Parsing: input sources and performance](../../features/parsing/index.md#input-sources-and-performance)
-
-## Version history
-
-- Added in version 3.13.0.

docs/mkdocs/docs/api/macros/json_disable_unlocked_file_io.md

@@ -1,113 +0,0 @@
-# JSON_DISABLE_UNLOCKED_FILE_IO
-
-```cpp
-#define JSON_DISABLE_UNLOCKED_FILE_IO /* value */
-```
-
-When defined to `1`, parsing from a `#!cpp FILE*` reads every character with `std::fgetc`, as in version 3.12.0 and
-earlier, instead of locking the file once and reading it with the unlocked stdio functions.
-
-It does not change any result: values, exceptions, and the position of the file after parsing are the same either way.
-Only the speed and the locking of the file differ (see the notes on locking below).
-
-## Default definition
-
-The default value is `0`: the file is locked once and read with the unlocked stdio functions where they are available.
-
-```cpp
-#define JSON_DISABLE_UNLOCKED_FILE_IO 0
-```
-
-## Notes
-
-!!! note "Background"
-
-    The C standard library makes every `std::fgetc` call thread-safe by locking and unlocking the `FILE` object. When
-    parsing from a `FILE*`, the parser reads one character at a time, so this happens for every character of the input.
-
-    Instead, the parser locks the file once when parsing starts and unlocks it when parsing ends - also when an
-    exception is thrown - and reads the characters in between without locking:
-
-    | C library                                                  | functions                                          |
-    |------------------------------------------------------------|----------------------------------------------------|
-    | glibc (Linux), Apple (macOS, iOS), Android, FreeBSD, NetBSD, OpenBSD, DragonFly BSD | `flockfile`, `getc_unlocked`, `funlockfile` (POSIX) |
-    | Microsoft (MSVC, clang-cl)                                 | `_lock_file`, `_fgetc_nolock`, `_unlock_file`       |
-    | others (e.g., musl, MinGW, newlib)                         | `std::fgetc`, as before                             |
-
-    This makes parsing from a `FILE*` 3 to 4 times as fast with the Apple C library and 1.1 to 1.3 times as fast with
-    glibc, whose locking is cheaper. The binary formats ([`from_cbor`](../basic_json/from_cbor.md),
-    [`from_msgpack`](../basic_json/from_msgpack.md), ...) read from a `FILE*` the same way.
-
-!!! note "Locking"
-
-    While a value is parsed from a `FILE*`, the parsing thread holds the file's lock. The lock is recursive, so the
-    parsing thread itself - for instance, a [SAX](../json_sax/index.md) handler or a
-    [parser callback](../basic_json/parser_callback_t.md) - can keep using the file with stdio functions such as
-    `std::ftell`. Other threads that use the same `FILE` object wait until the parser is done. Before, they could
-    interleave their reads with the parser's, which made the parsed input unpredictable anyway.
-
-    A program in which a SAX handler or parser callback waits for **another** thread that uses the **same** `FILE`
-    object would deadlock. Define the macro to `1` for such programs.
-
-!!! warning "Define consistently"
-
-    The macro selects between two definitions of the library's internal `FILE*` input adapter. It must therefore be
-    defined identically for **every** translation unit that includes the library; mixing translation units that define
-    it with ones that do not is an ODR violation (and can leave a file locked). Prefer setting it as a compile
-    definition on the target rather than with `#!cpp #define` in individual source files.
-
-!!! note "Other inputs"
-
-    Reading from a `#!cpp std::istream` is not affected by this macro; see
-    [`JSON_DISABLE_STREAM_BULK_SCAN`](json_disable_stream_bulk_scan.md) for that input.
-
-## Examples
-
-??? example "Example: parsing from a `FILE*` (default)"
-
-    The file is locked once while it is parsed:
-
-    ```cpp
-    #include <cstdio>
-    #include <nlohmann/json.hpp>
-
-    using json = nlohmann::json;
-
-    int main()
-    {
-        std::FILE* f = std::fopen("example.json", "rb");
-        json j = json::parse(f);  // f is locked until parse() returns
-        std::fclose(f);
-    }
-    ```
-
-??? example "Example: locking for every character (macro defined to 1)"
-
-    With the macro, every character is read with `std::fgetc`, with the same result:
-
-    ```cpp
-    #define JSON_DISABLE_UNLOCKED_FILE_IO 1
-    #include <cstdio>
-    #include <nlohmann/json.hpp>
-
-    using json = nlohmann::json;
-
-    int main()
-    {
-        std::FILE* f = std::fopen("example.json", "rb");
-        json j = json::parse(f);  // std::fgetc for every character
-        std::fclose(f);
-    }
-    ```
-
-## See also
-
-- [**parse**](../basic_json/parse.md) - deserialize from a compatible input
-- [**sax_parse**](../basic_json/sax_parse.md) - generate SAX events
-- [**JSON_DISABLE_STREAM_BULK_SCAN**](json_disable_stream_bulk_scan.md) - read a `std::istream` one character at a
-  time
-- [Parsing: input sources and performance](../../features/parsing/index.md#input-sources-and-performance)
-
-## Version history
-
-- Added in version 3.13.0.

docs/mkdocs/docs/api/macros/json_no_simd.md

@@ -1,83 +0,0 @@
-# JSON_NO_SIMD
-
-```cpp
-#define JSON_NO_SIMD
-```
-
-When defined, the library uses only portable C++ code where it would otherwise use vector instructions: when scanning
-strings during parsing, and when writing floating-point numbers during serialization.
-
-The macro is an escape hatch, for example for toolchains that cannot compile the vector code, for sanitizers or
-analyzers that do not understand it, or to compare the speed of both variants. It does not change any result: values,
-exceptions, and error positions are the same either way. Only the speed differs.
-
-## Default definition
-
-By default, `#!cpp JSON_NO_SIMD` is not defined, and vector instructions are used where the target has them.
-
-```cpp
-#undef JSON_NO_SIMD
-```
-
-## Notes
-
-!!! note "Which instructions are used"
-
-    - **x86-64:** SSE2, which every x86-64 CPU has, finds the end of runs of plain string characters 16 bytes at a time
-      and writes the digits of floating-point numbers. The UTF-8 check of non-ASCII text needs SSSE3, which is not part
-      of x86-64: it is compiled for SSSE3 with a function attribute and used when the CPU has SSSE3 (every x86-64 CPU
-      since about 2011), else the portable check. Code compiled for SSSE3 anyway (e.g., with `-mssse3` or `-march=native`)
-      skips this check of the CPU. 32-bit x86 uses SSE2 for strings when the compiler targets it.
-    - **AArch64:** NEON, which every 64-bit Arm CPU has, checks UTF-8 text and long runs of plain string characters 16
-      bytes at a time, and writes the digits of floating-point numbers. With MSVC, only the floating-point digits use
-      NEON.
-    - **Other targets:** portable code only.
-
-    Strings are only scanned this way for contiguous input and for the characters a `#!cpp std::istream` holds in its
-    stream buffer (see [`JSON_DISABLE_STREAM_BULK_SCAN`](json_disable_stream_bulk_scan.md)); other inputs are read one
-    character at a time.
-
-!!! note "Interaction with `JSON_USE_SIMDUTF`"
-
-    With [`JSON_USE_SIMDUTF`](json_use_simdutf.md), runs of string characters are first validated by simdutf; the code
-    described here is used for what simdutf does not accept, so that errors are reported at the same position.
-    `JSON_NO_SIMD` does not affect simdutf.
-
-!!! warning "Define consistently"
-
-    The macro selects between two definitions of the library's internal scanning and formatting functions. It must
-    therefore be defined identically for **every** translation unit that includes the library; mixing translation units
-    that define it with ones that do not is an ODR violation. Prefer setting it as a compile definition on the target
-    rather than with `#!cpp #define` in individual source files.
-
-## Examples
-
-??? example "Example: switching off vector instructions"
-
-    The program parses and serializes the same values with and without the macro:
-
-    ```cpp
-    #define JSON_NO_SIMD
-    #include <iostream>
-    #include <nlohmann/json.hpp>
-
-    using json = nlohmann::json;
-
-    int main()
-    {
-        const json j = json::parse(R"({"name": "日本語 text", "pi": 3.141592653589793})");
-        std::cout << j.dump() << '\n';  // {"name":"日本語 text","pi":3.141592653589793}
-    }
-    ```
-
-## See also
-
-- [**parse**](../basic_json/parse.md) - deserialize from a compatible input
-- [**dump**](../basic_json/dump.md) - serialization
-- [**JSON_USE_SIMDUTF**](json_use_simdutf.md) - use the simdutf library to accelerate UTF-8 validation
-- [**JSON_DISABLE_STREAM_BULK_SCAN**](json_disable_stream_bulk_scan.md) - read a `std::istream` one character at a time
-- [Parsing: input sources and performance](../../features/parsing/index.md#input-sources-and-performance)
-
-## Version history
-
-- Added in version 3.13.0.

docs/mkdocs/docs/api/macros/json_precise_stream_position.md

@@ -72,12 +72,6 @@ The default value is `0` (disabled — existing behavior is preserved).
     distinct symbol names. Translation units compiled with and without it can therefore be linked into the same program
     without One Definition Rule (ODR) violations, but they cannot exchange instances of library types.
 
-!!! note "Bulk scanning"
-
-    The parser scans the characters in the stream buffer in bulk (see
-    [`JSON_DISABLE_STREAM_BULK_SCAN`](json_disable_stream_bulk_scan.md)), but it never reads ahead. The stream is left
-    at the same position with and without bulk scanning, in both modes of this macro.
-
 !!! tip "Workaround without the macro"
 
     Separate the values in the stream with whitespace. The character consumed after a number is then the separator,

docs/mkdocs/docs/api/macros/json_use_simdutf.md

@@ -6,16 +6,14 @@
 
 When defined, the parser validates the UTF-8 content of JSON strings that come from a **contiguous byte input**
 (`std::string`, `std::vector<char>`/`<std::uint8_t>`, string literals, `const char*` ranges, …) using the
-[simdutf](https://github.com/simdutf/simdutf) library instead of the built-in validator (which uses SSSE3 or NEON where
-available, see [`JSON_NO_SIMD`](json_no_simd.md)). On text with many non-ASCII characters (e.g. CJK or emoji) this can
-validate faster, depending on the CPU.
+[simdutf](https://github.com/simdutf/simdutf) library instead of the built-in scalar validator. On text with many
+non-ASCII characters (e.g. CJK or emoji) this can validate several times faster.
 
 This is an **opt-in external dependency**. The library itself remains header-only and its behavior is unchanged: the
 same input is accepted or rejected either way, and every parse error is reported at the same position with the same
 message (simdutf is only used to fast-path *valid* runs; anything it flags falls back to the scalar path so the exact
-diagnostic is preserved). A `std::istream` uses simdutf for the characters its stream buffer holds (see
-[`JSON_DISABLE_STREAM_BULK_SCAN`](json_disable_stream_bulk_scan.md)); other streaming inputs (`FILE*`, wide strings,
-user-defined adapters) always use the scalar path.
+diagnostic is preserved). Streaming inputs (files, `std::istream`, wide strings, user-defined adapters) always use the
+scalar path.
 
 When `JSON_USE_SIMDUTF` is defined you must make the `simdutf.h` header available on the include path and link the
 simdutf library. When it is not defined, no simdutf header is included and there is no dependency.

docs/mkdocs/docs/api/operator_gtgt.md

@@ -121,7 +121,6 @@ being read.
 - [`JSON_STRICT_NUL_HANDLING`](macros/json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input
   instead of treating it as end of input
 - [`JSON_PRECISE_STREAM_POSITION`](macros/json_precise_stream_position.md) - opt in to leaving the stream positioned right after a number
-- [`JSON_DISABLE_STREAM_BULK_SCAN`](macros/json_disable_stream_bulk_scan.md) - read the stream one character at a time
 
 ## Version history
 
@@ -134,6 +133,3 @@ being read.
   crash (`std::terminate`) when `i` has `eofbit` in its exception mask, in version 3.13.0.
 - Changed to the strong exception safety guarantee in version 3.13.0: `j` is no longer left with a partially parsed
   value if parsing throws.
-- Scans the characters in the stream buffer of `i` in bulk in version 3.13.0; the position of `i` after the call is
-  unchanged ([`JSON_DISABLE_STREAM_BULK_SCAN`](macros/json_disable_stream_bulk_scan.md) restores reading one character
-  at a time).

docs/mkdocs/docs/examples/sax_parse__error_recovery.cpp

@@ -0,0 +1,43 @@
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+// a SAX parser that creates a JSON value like json::parse does, but that
+// recovers from parse errors instead of stopping at the first one
+class recovering_parser : public nlohmann::detail::json_sax_dom_parser<json>
+{
+  public:
+    explicit recovering_parser(json& result)
+        : nlohmann::detail::json_sax_dom_parser<json>(result, false)
+    {}
+
+    bool parse_error(std::size_t position,
+                     const std::string& /*last_token*/,
+                     const json::exception& ex)
+    {
+        std::cout << "byte " << position << ": " << ex.what() << '\n';
+
+        // repair the input and continue
+        return true;
+    }
+};
+
+int main()
+{
+    // JSON text with several mistakes that ends too early
+    const std::string text = R"({
+    "name": "Hello World",
+    "tags": ["a" "b",],
+    "valid": tru,
+    "size": 1.,
+    "nested": {"x": 1)";
+
+    json result;
+    recovering_parser sax(result);
+    const bool valid = json::sax_parse(text, &sax);
+
+    std::cout << "\nvalid JSON: " << std::boolalpha << valid << '\n'
+              << std::setw(4) << result << std::endl;
+}

docs/mkdocs/docs/examples/sax_parse__error_recovery.output

@@ -0,0 +1,19 @@
+byte 49: [json.exception.parse_error.101] parse error at line 3, column 20: syntax error while parsing array - unexpected string literal; expected ']'
+byte 51: [json.exception.parse_error.101] parse error at line 3, column 22: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal
+byte 70: [json.exception.parse_error.101] parse error at line 4, column 17: syntax error while parsing value - invalid literal; last read: '"valid": tru,'
+byte 86: [json.exception.parse_error.101] parse error at line 5, column 15: syntax error while parsing value - invalid number; expected digit after '.'; last read: '1.,'
+byte 109: [json.exception.parse_error.101] parse error at line 6, column 22: syntax error while parsing object - unexpected end of input; expected '}'
+
+valid JSON: false
+{
+    "name": "Hello World",
+    "nested": {
+        "x": 1
+    },
+    "size": 1,
+    "tags": [
+        "a",
+        "b"
+    ],
+    "valid": null
+}

docs/mkdocs/docs/features/macros.md

@@ -133,14 +133,6 @@ When defined, default parse and serialize functions for enums are excluded and h
 
 See [full documentation of `JSON_DISABLE_ENUM_SERIALIZATION`](../api/macros/json_disable_enum_serialization.md).
 
-## `JSON_DISABLE_STREAM_BULK_SCAN`
-
-When defined to `1`, parsing from a `#!cpp std::istream` reads one character at a time instead of scanning the
-characters that the stream buffer holds in bulk. Results are the same either way; the macro is an escape hatch for
-stream buffers that do not follow the usual `std::streambuf` contract. The default value is `0`.
-
-See [full documentation of `JSON_DISABLE_STREAM_BULK_SCAN`](../api/macros/json_disable_stream_bulk_scan.md).
-
 ## `JSON_DISABLE_TUPLE_REFERENCE_CONVERSION`
 
 When defined to `1`, a JSON value can no longer be created from a one-element `std::tuple` holding a reference to a JSON
@@ -149,14 +141,6 @@ is planned to become the default in version 4.0.0.
 
 See [full documentation of `JSON_DISABLE_TUPLE_REFERENCE_CONVERSION`](../api/macros/json_disable_tuple_reference_conversion.md).
 
-## `JSON_DISABLE_UNLOCKED_FILE_IO`
-
-When defined to `1`, parsing from a `#!cpp FILE*` reads every character with `std::fgetc`, which locks the file each
-time, instead of locking the file once and reading it with the unlocked stdio functions. Results are the same either
-way. The default value is `0`.
-
-See [full documentation of `JSON_DISABLE_UNLOCKED_FILE_IO`](../api/macros/json_disable_unlocked_file_io.md).
-
 ## `JSON_NO_AUTOMATIC_UDLS`
 
 When defined, `<nlohmann/json.hpp>` does not include `<nlohmann/json_literals.hpp>` with the user-defined string literals
@@ -174,13 +158,6 @@ security reasons (e.g., Intel Software Guard Extensions (SGX)).
 
 See [full documentation of `JSON_NO_IO`](../api/macros/json_no_io.md).
 
-## `JSON_NO_SIMD`
-
-When defined, the library uses only portable code instead of vector instructions (SSE2, SSSE3, NEON) for scanning
-strings and writing floating-point numbers. Results are the same either way. It is not defined by default.
-
-See [full documentation of `JSON_NO_SIMD`](../api/macros/json_no_simd.md).
-
 ## `JSON_NO_THREAD_LOCAL`
 
 When defined, the library does not use `#!cpp thread_local` storage. Copying a value and comparing two values then

docs/mkdocs/docs/features/parsing/error_recovery.md

@@ -0,0 +1,122 @@
+# Error Recovery
+
+By default, parsing stops at the first error. With the [SAX interface](sax_interface.md), you can instead ask the
+parser to *recover*: to repair the error and continue, so that you get as much as possible out of malformed input, for
+instance a file that was cut off, JSON edited by hand, or the output of a language model.
+
+## Recovering from errors
+
+The SAX parser's [`parse_error`](../../api/json_sax/parse_error.md) function is called for every error. Its return value
+decides what happens next:
+
+- `#!cpp false` stops parsing. This is what the SAX parsers of the library do, so [`parse`](../../api/basic_json/parse.md)
+  and [`accept`](../../api/basic_json/accept.md) never recover.
+- `#!cpp true` repairs the error and continues parsing.
+
+When recovering, the SAX parser still receives well-formed events: every `start_object` or `start_array` is followed by
+the matching `end_object` or `end_array`, and every `key` is followed by exactly one value. A SAX parser that creates a
+JSON value, such as the one in the example below, therefore gets a complete value. Parsing always ends, and
+[`sax_parse`](../../api/basic_json/sax_parse.md) returns `#!cpp false` for input that is not valid JSON, even if every
+error was repaired. Each token is reported at most once, and the SAX parser can stop at any error by returning
+`#!cpp false`.
+
+!!! example
+
+    The example below derives a SAX parser from the library's parser for `json` values (`json_sax_dom_parser`),
+    and recovers from all errors.
+
+    ```cpp
+    --8<-- "examples/sax_parse__error_recovery.cpp"
+    ```
+    
+    Output:
+    
+    ```
+    --8<-- "examples/sax_parse__error_recovery.output"
+    ```
+
+## How errors are repaired
+
+Each error is repaired with the smallest local edit: a missing separator is inserted, a stray token is removed, what can
+be read of a broken string or number is kept, and a value that cannot be read at all becomes `#!json null`.
+
+| Mistake                   | Repair                                                                         | Example                                  | Result                     |
+|---------------------------|--------------------------------------------------------------------------------|------------------------------------------|----------------------------|
+| missing `,` or `:`        | inserted                                                                       | `#!json [1 2]`, `#!json {"a" 1}`         | `[1,2]`, `{"a":1}`         |
+| missing value             | `#!json null` for an object key or between commas in an array                  | `#!json {"a":}`, `#!json [1,,2]`         | `{"a":null}`, `[1,null,2]` |
+| trailing comma            | removed                                                                        | `#!json [1,2,]`                          | `[1,2]`                    |
+| broken string             | invalid escapes and bytes are replaced (see below); a line break ends the string | `#!json ["a\qb"]`                        | `["aqb"]`                  |
+| broken number             | the longest valid beginning is kept                                            | `#!json [1., 2e+]`                       | `[1,2]`                    |
+| unreadable value          | `#!json null`                                                                  | `#!json [1, NaN, tru]`                   | `[1,null,null]`            |
+| number too large          | passed as infinity, together with its text                                     | `#!json [1e999]`                         | infinity (see below)       |
+| stray `:`                 | removed                                                                        | `#!json ["a":1]`                         | `["a",1]`                  |
+| member without a key      | skipped up to the next `,` or `}`                                              | `#!json {1:2, "b":3}`                    | `{"b":3}`                  |
+| wrong closing bracket     | closes the innermost array or object                                           | `#!json {"a":[1,2}, "b":3}`              | `{"a":[1,2],"b":3}`        |
+| input ends too early      | all open arrays and objects are closed                                         | `#!json {"a":[1,2`                       | `{"a":[1,2]}`              |
+| text before the value     | skipped                                                                        | `#!json )]}'{"a":1}`                     | `{"a":1}`                  |
+
+In a string, an unknown escape like `\q` stands for the escaped character (`q`), as in JavaScript. An invalid `\u`
+escape, a lone surrogate, and ill-formed UTF-8 are each replaced by U+FFFD (REPLACEMENT CHARACTER), and control
+characters are kept. A string without its closing quote ends at the next line break or at the end of the input.
+
+The input after the top-level value is not repaired: as without recovery, it is reported as an error, and parsing stops.
+
+## Binary formats
+
+The binary formats ([BJData](../binary_formats/bjdata.md), [BON8](../binary_formats/bon8.md),
+[BSON](../binary_formats/bson.md), [CBOR](../binary_formats/cbor.md), [MessagePack](../binary_formats/messagepack.md),
+and [UBJSON](../binary_formats/ubjson.md)) have no delimiters to find the next value by. So what can be repaired depends
+on whether the end of the item with the error is known, a distinction that
+[RFC 8949, Section 5.3](https://www.rfc-editor.org/rfc/rfc8949.html#section-5.3) makes for CBOR, too.
+
+If the item is complete, but cannot be passed on as it is, it is replaced, and parsing continues after it:
+
+| Mistake                                                             | Formats                 | Repair                                                                  |
+|---------------------------------------------------------------------|-------------------------|-------------------------------------------------------------------------|
+| tag, if `tag_handler` is `cbor_tag_handler_t::error` (the default)  | CBOR                    | ignored                                                                 |
+| simple value other than `false`, `true`, and `null`, like undefined | CBOR                    | `#!json null`                                                           |
+| number too large for a custom `number_float_t`, like `float`        | all                     | infinity                                                                |
+| character (`C`) that is not ASCII                                   | BJData, UBJSON          | U+FFFD                                                                  |
+| invalid high-precision number (`H`)                                 | BJData, UBJSON          | the longest valid beginning is kept, as for JSON text, or `#!json null` |
+| high-precision number too large                                     | BJData, UBJSON          | passed as infinity, together with its text                              |
+| object key that is not a string                                     | BON8, CBOR, MessagePack | the member is skipped                                                   |
+| element of a type the library does not read, like ObjectId or date  | BSON                    | `#!json null`                                                           |
+| string without its terminator                                       | BSON                    | kept                                                                    |
+| document whose size does not match its content                      | BSON                    | kept                                                                    |
+
+CBOR tags and simple values are repaired as [RFC 8949, Section 6.1](https://www.rfc-editor.org/rfc/rfc8949.html#section-6.1)
+suggests for converting CBOR to JSON. By default, [`sax_parse`](../../api/basic_json/sax_parse.md) reports every tag as
+an error; when recovering, tags are then ignored like with
+[`cbor_tag_handler_t::ignore`](../../api/basic_json/cbor_tag_handler_t.md). Strings that are not valid UTF-8 are no
+error: like [`from_cbor`](../../api/basic_json/from_cbor.md) and the other functions by default, `sax_parse` passes
+them on as they are.
+
+After any other error, the end of the item is unknown: the input ended, a byte is not a valid type marker, or a size
+cannot be right. Parsing then stops, and the value read so far is completed: a key that waits for its value gets
+`#!json null`, and all open arrays and objects are closed. This keeps everything before the error of an input that was
+cut off. The exception is BSON, which stores the size of every document: an element whose end is unknown gets
+`#!json null`, the rest of its document is skipped, and parsing continues after the document.
+
+## Limitations
+
+- A repair is a guess. For example, `#!json {"a" "b": 1}` could be meant as `#!json {"a": "b"}` or as
+  `#!json {"a": null, "b": 1}`; it is repaired to the former. Treat recovered values as a best effort, and check the
+  reported errors.
+- A closing bracket always closes the innermost array or object. If a bracket is missing rather than wrong, the
+  repair differs from the intention: `#!json {"a": {"b": [1, 2}, "c": 3}` is repaired to
+  `#!json {"a": {"b": [1, 2], "c": 3}}`, although `#!json {"a": {"b": [1, 2]}, "c": 3}` may have been meant.
+- Keys without quotes, and strings in single quotes, are not supported; such members are skipped.
+- In the binary formats, a member that is skipped because its key is not a string is lost, and so are the elements of a
+  BSON document after one whose end is unknown.
+- A number that is too large for `number_float_t` is passed as positive or negative infinity. The SAX parser's
+  `number_float` also gets the number's text, but a JSON value cannot store it, and
+  [`dump`](../../api/basic_json/dump.md) serializes infinity as `#!json null`.
+- When parsing is not strict (see [`sax_parse`](../../api/basic_json/sax_parse.md)), a repair may read parts of the
+  input after the value, for instance of the next value in a stream of concatenated values.
+
+## See also
+
+- [SAX interface](sax_interface.md) - implement a custom SAX handler
+- [`parse_error`](../../api/json_sax/parse_error.md) - the SAX event for parse errors
+- [`sax_parse`](../../api/basic_json/sax_parse.md) - generate SAX events
+- [parsing and exceptions](parse_exceptions.md) - control error handling

docs/mkdocs/docs/features/parsing/index.md

@@ -55,34 +55,6 @@ whitespace, because `operator>>` consumes the character that terminates a number
 [`JSON_PRECISE_STREAM_POSITION`](../../api/macros/json_precise_stream_position.md) is defined to `1` — see the
 [`operator>>` notes](../../api/operator_gtgt.md#notes) for details and examples.
 
-## Input sources and performance
-
-All inputs produce the same values and the same exceptions, but they are read in different ways, which makes some of
-them faster than others:
-
-| input                                                                                      | how it is read                                                                     |
-|--------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------|
-| strings, string views, string literals, contiguous containers, pointer or iterator ranges over contiguous memory | the whole input is scanned in bulk: runs of string characters, numbers, and indentation are recognized several bytes at a time |
-| `#!cpp std::istream` (`#!cpp std::ifstream`, `#!cpp std::istringstream`, ...)            | the characters the stream buffer holds are scanned in bulk like a string; the stream buffer is asked for more when they are used up |
-| `#!cpp FILE*`                                                                              | one character at a time, with the file locked once for the whole parse              |
-| other iterator ranges (e.g., `#!cpp std::list<char>`, `#!cpp std::istreambuf_iterator<char>`), wide strings | one character at a time                                                             |
-
-Parsing a file from a `#!cpp std::ifstream` is therefore only about 10 to 20 % slower than reading the whole file into a
-`#!cpp std::string` first and parsing that, and it needs no memory for a copy of the file. The stream is never read
-ahead: after parsing, it is positioned exactly as if every character had been read one at a time, so
-[`operator>>`](../../api/operator_gtgt.md) can still read several values from one stream (see also
-[JSON Lines](json_lines.md)).
-
-Two macros switch these optimizations off without changing any result:
-[`JSON_DISABLE_STREAM_BULK_SCAN`](../../api/macros/json_disable_stream_bulk_scan.md) for stream buffers that do not
-follow the usual `std::streambuf` contract, and
-[`JSON_DISABLE_UNLOCKED_FILE_IO`](../../api/macros/json_disable_unlocked_file_io.md) for programs in which another
-thread must use the same `#!cpp FILE` object while it is parsed.
-
-Where the target has them, strings are scanned with vector instructions: SSE2 on x86-64 (and SSSE3 for UTF-8 text, when
-the CPU has it) and NEON on AArch64. [`JSON_NO_SIMD`](../../api/macros/json_no_simd.md) selects portable code instead,
-again without changing any result.
-
 ## SAX vs. DOM parsing
 
 The library offers two parsing models:
@@ -103,7 +75,7 @@ You can influence a DOM parse without switching to the SAX interface by passing
 When the input is not valid JSON, the `parse` function throws an exception by default. If exceptions are undesired or
 unavailable, the parser can instead return a discarded value, or [`accept`](../../api/basic_json/accept.md) can be used
 to only check whether an input is valid JSON. See [parsing and exceptions](parse_exceptions.md) for the available
-options.
+options. To get as much as possible out of malformed input, a SAX parser can [recover from errors](error_recovery.md).
 
 ## See also
 
@@ -114,4 +86,5 @@ options.
 - [parser callbacks](parser_callbacks.md) - influence the parsing by a callback function
 - [SAX interface](sax_interface.md) - implement a custom SAX handler
 - [parsing and exceptions](parse_exceptions.md) - control error handling
+- [error recovery](error_recovery.md) - get as much as possible out of malformed input
 - [parsing untrusted input](untrusted_input.md) - what to consider when parsing input from untrusted sources

docs/mkdocs/docs/features/parsing/parse_exceptions.md

@@ -64,7 +64,8 @@ bool parse_error(std::size_t position,
                  const json::exception& ex);
 ```
 
-The return value indicates whether the parsing should continue, so the function should usually return `#!cpp false`.
+The return value decides whether to stop parsing (`#!cpp false`) or to repair the error and continue
+(`#!cpp true`); see [error recovery](error_recovery.md) for the latter.
 
 ??? example "Example: report parse errors without exceptions"
 

docs/mkdocs/docs/features/parsing/sax_interface.md

@@ -60,7 +60,8 @@ bool key(string_t& val);
 bool parse_error(std::size_t position, const std::string& last_token, const json::exception& ex);
 ```
 
-The return value of each function determines whether parsing should proceed.
+The return value of each function determines whether parsing should proceed. For `parse_error`, returning
+`#!cpp true` [recovers from the error](error_recovery.md).
 
 To implement your own SAX handler, proceed as follows:
 
@@ -68,7 +69,7 @@ To implement your own SAX handler, proceed as follows:
 2. Create an object of your SAX interface class, e.g. `my_sax`.
 3. Call `#!cpp bool json::sax_parse(input, &my_sax);` where the first parameter can be any input like a string or an input stream and the second parameter is a pointer to your SAX interface.
 
-Note the `sax_parse` function only returns a `#!cpp bool` indicating the result of the last executed SAX event. It does not return `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error - it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file `json_sax.hpp`.
+Note the `sax_parse` function only returns a `#!cpp bool` indicating whether the input was parsed without errors and no SAX event returned `#!cpp false`. It does not return `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error - it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file `json_sax.hpp`.
 
 ## See also
 

docs/mkdocs/docs/home/architecture.md

@@ -59,7 +59,7 @@ below are relative to `include/nlohmann`.
 |-----------|----------|
 | Value type enumeration | [`detail/value_t.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/value_t.hpp) |
 | Input adapters | [`detail/input/input_adapters.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/input_adapters.hpp) |
-| Lexer | [`detail/input/lexer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/lexer.hpp), [`detail/input/number_parse.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/number_parse.hpp), [`detail/input/string_scan.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/string_scan.hpp), [`detail/input/simd_scan.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/simd_scan.hpp) |
+| Lexer | [`detail/input/lexer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/lexer.hpp), [`detail/input/number_parse.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/number_parse.hpp), [`detail/input/string_scan.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/string_scan.hpp) |
 | Parser | [`detail/input/parser.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/parser.hpp) |
 | SAX interface and DOM builders | [`detail/input/json_sax.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/json_sax.hpp) |
 | Binary format readers | [`detail/input/binary_reader.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/binary_reader.hpp) |

docs/mkdocs/mkdocs.yml

@@ -88,6 +88,7 @@ nav:
       - features/performance.md
       - Parsing:
           - features/parsing/index.md
+          - features/parsing/error_recovery.md
           - features/parsing/json_lines.md
           - features/parsing/parse_exceptions.md
           - features/parsing/parser_callbacks.md
@@ -297,9 +298,7 @@ nav:
           - 'JSON_DELETE_DEPRECATED_FUNCTIONS': api/macros/json_delete_deprecated_functions.md
           - 'JSON_DIAGNOSTIC_POSITIONS': api/macros/json_diagnostic_positions.md
           - 'JSON_DISABLE_ENUM_SERIALIZATION': api/macros/json_disable_enum_serialization.md
-          - 'JSON_DISABLE_STREAM_BULK_SCAN': api/macros/json_disable_stream_bulk_scan.md
           - 'JSON_DISABLE_TUPLE_REFERENCE_CONVERSION': api/macros/json_disable_tuple_reference_conversion.md
-          - 'JSON_DISABLE_UNLOCKED_FILE_IO': api/macros/json_disable_unlocked_file_io.md
           - 'JSON_HAS_CPP_11, JSON_HAS_CPP_14, JSON_HAS_CPP_17, JSON_HAS_CPP_20, JSON_HAS_CPP_23, JSON_HAS_CPP_26': api/macros/json_has_cpp_11.md
           - 'JSON_HAS_EXPERIMENTAL_FILESYSTEM, JSON_HAS_FILESYSTEM': api/macros/json_has_filesystem.md
           - 'JSON_HAS_RANGE_VIEW_CONVERSION': api/macros/json_has_range_view_conversion.md
@@ -310,7 +309,6 @@ nav:
           - 'JSON_NO_AUTOMATIC_UDLS': api/macros/json_no_automatic_udls.md
           - 'JSON_NOEXCEPTION': api/macros/json_noexception.md
           - 'JSON_NO_IO': api/macros/json_no_io.md
-          - 'JSON_NO_SIMD': api/macros/json_no_simd.md
           - 'JSON_NO_THREAD_LOCAL': api/macros/json_no_thread_local.md
           - 'JSON_PRECISE_STREAM_POSITION': api/macros/json_precise_stream_position.md
           - 'JSON_SKIP_LIBRARY_VERSION_CHECK': api/macros/json_skip_library_version_check.md

include/nlohmann/detail/conversions/to_chars.hpp

@@ -23,12 +23,12 @@
 #endif
 
 // SSE2 (every x86-64 CPU) and NEON (every 64-bit Arm CPU) convert the 16
-// digits of a double at once (unless JSON_NO_SIMD selects the portable code)
-#if !defined(JSON_NO_SIMD) && (defined(__x86_64__) || (defined(_M_X64) && !defined(_M_ARM64EC)))
+// digits of a double at once
+#if defined(__x86_64__) || (defined(_M_X64) && !defined(_M_ARM64EC))
     #include <emmintrin.h>
     #define JSON_DTOA_SSE2 1
     #define JSON_DTOA_NEON 0
-#elif !defined(JSON_NO_SIMD) && (defined(__aarch64__) || defined(_M_ARM64)) && !defined(_M_ARM64EC) && !defined(__ARM_BIG_ENDIAN)
+#elif (defined(__aarch64__) || defined(_M_ARM64)) && !defined(_M_ARM64EC) && !defined(__ARM_BIG_ENDIAN)
     #include <arm_neon.h>
     #define JSON_DTOA_SSE2 0
     #define JSON_DTOA_NEON 1

include/nlohmann/detail/input/input_adapters.hpp

@@ -14,12 +14,10 @@
 #include <cstdint> // uint32_t
 #include <cstring> // strlen
 #include <iterator> // begin, end, iterator_traits, random_access_iterator_tag, distance, next, reverse_iterator
-#include <limits> // numeric_limits
 #include <streambuf> // streambuf
 #include <string> // string, char_traits
 #include <type_traits> // enable_if, is_base_of, is_pointer, is_integral, remove_pointer
 #include <utility> // pair, declval
-#include <vector> // vector
 
 #ifndef JSON_NO_IO
     #include <cstdio>   // FILE *
@@ -32,24 +30,6 @@
 #include <nlohmann/detail/meta/type_traits.hpp>
 #include <nlohmann/detail/string_utils.hpp>
 
-#ifndef JSON_NO_IO
-    // Which unlocked stdio functions file_input_adapter uses (see
-    // JSON_DISABLE_UNLOCKED_FILE_IO): 1 = POSIX flockfile/getc_unlocked,
-    // 2 = Microsoft CRT _lock_file/_fgetc_nolock, 0 = none (std::fgetc, which
-    // locks the file for every character). Only C libraries known to declare
-    // the functions are listed; the macros are tested after <cstdio>, which
-    // defines __GLIBC__.
-    #if JSON_DISABLE_UNLOCKED_FILE_IO
-        #define JSON_UNLOCKED_FILE_IO 0
-    #elif defined(_MSC_VER)
-        #define JSON_UNLOCKED_FILE_IO 2
-    #elif defined(__GLIBC__) || defined(__APPLE__) || defined(__ANDROID__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || defined(__DragonFly__)
-        #define JSON_UNLOCKED_FILE_IO 1
-    #else
-        #define JSON_UNLOCKED_FILE_IO 0
-    #endif
-#endif  // JSON_NO_IO
-
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
 {
@@ -76,38 +56,18 @@ class file_input_adapter
         : m_file(f)
     {
         JSON_ASSERT(m_file != nullptr);
-        lock();
     }
 
     // make class move-only
     file_input_adapter(const file_input_adapter&) = delete;
-    file_input_adapter(file_input_adapter&& rhs) noexcept
-        : m_file(rhs.m_file)
-    {
-        // the lock is owned by the thread, not the adapter: hand it over
-        rhs.m_file = nullptr;
-    }
+    file_input_adapter(file_input_adapter&&) noexcept = default;
     file_input_adapter& operator=(const file_input_adapter&) = delete;
     file_input_adapter& operator=(file_input_adapter&&) = delete;
-    ~file_input_adapter()
-    {
-        if (m_file != nullptr)
-        {
-            unlock();
-        }
-    }
+    ~file_input_adapter() = default;
 
     std::char_traits<char>::int_type get_character() noexcept
     {
-        // the file is locked for the lifetime of the adapter, so the
-        // per-character lock of std::fgetc can be skipped
-#if JSON_UNLOCKED_FILE_IO == 1
-        return getc_unlocked(m_file);
-#elif JSON_UNLOCKED_FILE_IO == 2
-        return _fgetc_nolock(m_file);
-#else
         return std::fgetc(m_file);
-#endif
     }
 
     // returns the number of characters successfully read
@@ -118,27 +78,6 @@ class file_input_adapter
     }
 
   private:
-    // Lock the file once for the whole parse instead of once per character.
-    // The lock is recursive, so fread() and the user's own stdio calls on the
-    // same thread keep working.
-    void lock() noexcept
-    {
-#if JSON_UNLOCKED_FILE_IO == 1
-        flockfile(m_file);
-#elif JSON_UNLOCKED_FILE_IO == 2
-        _lock_file(m_file);
-#endif
-    }
-
-    void unlock() noexcept
-    {
-#if JSON_UNLOCKED_FILE_IO == 1
-        funlockfile(m_file);
-#elif JSON_UNLOCKED_FILE_IO == 2
-        _unlock_file(m_file);
-#endif
-    }
-
     /// the file pointer to read from
     std::FILE* m_file;
 };
@@ -188,26 +127,15 @@ class input_stream_adapter
     input_stream_adapter& operator=(input_stream_adapter&) = delete;
     input_stream_adapter& operator=(input_stream_adapter&&) = delete;
 
-    input_stream_adapter(input_stream_adapter&& rhs) noexcept
-        : is(rhs.is), sb(rhs.sb)
 #if JSON_PRECISE_STREAM_POSITION
-        , lookahead(rhs.lookahead)
-#endif
-#if !JSON_DISABLE_STREAM_BULK_SCAN
-        , token_carry(std::move(rhs.token_carry))
-        , token_segment(rhs.token_segment)
-        , current_in_get_area(rhs.current_in_get_area)
-        , tracking_token(rhs.tracking_token)
-#endif
+    input_stream_adapter(input_stream_adapter&& rhs) noexcept
+        : is(rhs.is), sb(rhs.sb), lookahead(rhs.lookahead)
     {
         rhs.is = nullptr;
         rhs.sb = nullptr;
-#if JSON_PRECISE_STREAM_POSITION
         rhs.lookahead = false;
-#endif
     }
 
-#if JSON_PRECISE_STREAM_POSITION
     // Whether the character last returned by get_character() can be given back
     // to the input with release_lookahead().
     static constexpr bool supports_lookahead = true;
@@ -227,41 +155,17 @@ class input_stream_adapter
             sb->sbumpc();
         }
 
-#if !JSON_DISABLE_STREAM_BULK_SCAN
-        // sgetc() refills the get area if it is exhausted
-        const bool refill = streambuf_access::get_ptr(sb) == streambuf_access::get_end(sb);
-        if (JSON_HEDLEY_UNLIKELY(refill))
-        {
-            save_token_segment();
-        }
-#endif
-
         auto res = sb->sgetc();
         // set eof manually, as we don't use the istream interface.
         if (JSON_HEDLEY_UNLIKELY(res == std::char_traits<char>::eof()))
         {
             // there is nothing to step over next time
             lookahead = false;
-#if !JSON_DISABLE_STREAM_BULK_SCAN
-            current_in_get_area = false;
-#endif
             is->clear(is->rdstate() | std::ios::eofbit);
         }
         else
         {
             lookahead = true;
-#if !JSON_DISABLE_STREAM_BULK_SCAN
-            if (JSON_HEDLEY_UNLIKELY(refill))
-            {
-                // the peeked character is at gptr(), unless the streambuf has
-                // no get area
-                after_refill(res, streambuf_access::get_ptr(sb) != streambuf_access::get_end(sb));
-            }
-            else
-            {
-                current_in_get_area = true;
-            }
-#endif
         }
         return res;
     }
@@ -275,6 +179,13 @@ class input_stream_adapter
         lookahead = false;
     }
 #else
+    input_stream_adapter(input_stream_adapter&& rhs) noexcept
+        : is(rhs.is), sb(rhs.sb)
+    {
+        rhs.is = nullptr;
+        rhs.sb = nullptr;
+    }
+
     // std::istream/std::streambuf use std::char_traits<char>::to_int_type, to
     // ensure that std::char_traits<char>::eof() and the character 0xFF do not
     // end up as the same value, e.g., 0xFFFFFFFF.
@@ -283,37 +194,12 @@ class input_stream_adapter
     // stays consumed after parsing; see JSON_PRECISE_STREAM_POSITION.
     std::char_traits<char>::int_type get_character()
     {
-#if !JSON_DISABLE_STREAM_BULK_SCAN
-        // sbumpc() refills the get area if it is exhausted
-        const bool refill = streambuf_access::get_ptr(sb) == streambuf_access::get_end(sb);
-        if (JSON_HEDLEY_UNLIKELY(refill))
-        {
-            save_token_segment();
-        }
-#endif
-
         auto res = sb->sbumpc();
         // set eof manually, as we don't use the istream interface.
         if (JSON_HEDLEY_UNLIKELY(res == std::char_traits<char>::eof()))
         {
-#if !JSON_DISABLE_STREAM_BULK_SCAN
-            current_in_get_area = false;
-#endif
             is->clear(is->rdstate() | std::ios::eofbit);
         }
-#if !JSON_DISABLE_STREAM_BULK_SCAN
-        else if (JSON_HEDLEY_UNLIKELY(refill))
-        {
-            // the consumed character is at gptr() - 1, unless the streambuf
-            // has no get area and returned it from uflow()
-            const char* const next = streambuf_access::get_ptr(sb);
-            after_refill(res, next != nullptr && next != streambuf_access::get_begin(sb));
-        }
-        else
-        {
-            current_in_get_area = true;
-        }
-#endif
         return res;
     }
 #endif
@@ -332,165 +218,7 @@ class input_stream_adapter
         return res;
     }
 
-#if !JSON_DISABLE_STREAM_BULK_SCAN
-    // The lexer may scan the characters in the get area of the streambuf
-    // directly (SWAR fast paths). The get area is only a window into the
-    // input: it ends wherever the streambuf's buffer ends, and is refilled by
-    // the next get_character(). The lexer therefore keeps counting the
-    // position itself and treats the end of the window as "unknown", not as
-    // the end of the input.
-    static constexpr bool supports_bulk_scan = true;
-    static constexpr bool bulk_window = true;
-
-    // Pointer to the next unread character; only valid when
-    // bulk_remaining() > 0. The character before it is the one last returned
-    // by get_character().
-    const char* bulk_data() const
-    {
-        return current_end();
-    }
-
-    // Number of unread characters in the get area.
-    std::size_t bulk_remaining() const
-    {
-        if (!current_in_get_area)
-        {
-            return 0;
-        }
-        return static_cast<std::size_t>(streambuf_access::get_end(sb) - current_end());
-    }
-
-    // Consume @a n characters previously inspected via bulk_data(); the last
-    // of them becomes the character last returned by get_character().
-    void bulk_skip(std::size_t n)
-    {
-        JSON_ASSERT(n <= bulk_remaining());
-        // gbump() takes an int, but a get area (e.g., of a std::stringbuf) can
-        // be larger
-        constexpr auto max_bump = static_cast<std::size_t>((std::numeric_limits<int>::max)());
-        for (; n > max_bump; n -= max_bump)
-        {
-            streambuf_access::bump(sb, static_cast<int>(max_bump));
-        }
-        streambuf_access::bump(sb, static_cast<int>(n));
-    }
-
-    // The adapter keeps the current token for the lexer's error messages: the
-    // part in the get area is only remembered as a pointer, and copied out
-    // when the get area is about to be refilled.
-    static constexpr bool supports_token_tracking = true;
-
-    // Start a token with the characters read from now on. Until this is
-    // called, nothing is tracked (the binary readers never call it).
-    void begin_token() noexcept
-    {
-        tracking_token = true;
-        token_carry.clear();
-        token_segment = current_end();
-    }
-
-    // Start a new token with the character @a c last returned by
-    // get_character().
-    void mark_token_start(std::char_traits<char>::int_type c)
-    {
-        tracking_token = true;
-        token_carry.clear();
-        if (current_in_get_area)
-        {
-            token_segment = current_end() - 1;
-        }
-        else
-        {
-            token_segment = nullptr;
-            token_carry.push_back(std::char_traits<char>::to_char_type(c));
-        }
-    }
-
-    // Copy the characters read since mark_token_start() to @a out, without the
-    // last one if @a drop_last.
-    void copy_token(std::vector<char>& out, bool drop_last) const
-    {
-        out = token_carry;
-        if (token_segment != nullptr)
-        {
-            out.insert(out.end(), token_segment, current_end());
-        }
-        if (drop_last && !out.empty())
-        {
-            out.pop_back();
-        }
-    }
-#endif
-
   private:
-#if !JSON_DISABLE_STREAM_BULK_SCAN
-    // Reads the protected get-area pointers of any std::streambuf. Naming the
-    // members through a derived class makes forming the member pointers
-    // accessible; calling them on another streambuf object is then ordinary
-    // member access through a pointer to member.
-    struct streambuf_access : std::streambuf
-    {
-        static const char* get_ptr(std::streambuf* s)
-        {
-            return (s->*(&streambuf_access::gptr))();
-        }
-        static const char* get_end(std::streambuf* s)
-        {
-            return (s->*(&streambuf_access::egptr))();
-        }
-        static const char* get_begin(std::streambuf* s)
-        {
-            return (s->*(&streambuf_access::eback))();
-        }
-        static void bump(std::streambuf* s, int n)
-        {
-            (s->*(&streambuf_access::gbump))(n);
-        }
-    };
-
-    // one past the character last returned by get_character(), if that is in
-    // the get area
-    const char* current_end() const
-    {
-#if JSON_PRECISE_STREAM_POSITION
-        // the character is peeked at gptr() and not stepped over yet, unless
-        // it was given back with release_lookahead()
-        return streambuf_access::get_ptr(sb) + (lookahead ? 1 : 0);
-#else
-        return streambuf_access::get_ptr(sb);
-#endif
-    }
-
-    // the get area is about to be replaced: copy the token's part in it
-    void save_token_segment()
-    {
-        if (token_segment != nullptr)
-        {
-            token_carry.insert(token_carry.end(), token_segment, streambuf_access::get_end(sb));
-            token_segment = nullptr;
-        }
-    }
-
-    // character @a c was just read into a new get area (@a in_get_area) or
-    // returned without one
-    void after_refill(std::char_traits<char>::int_type c, bool in_get_area)
-    {
-        current_in_get_area = in_get_area;
-        if (!tracking_token)
-        {
-            return;
-        }
-        if (in_get_area)
-        {
-            token_segment = current_end() - 1;
-        }
-        else
-        {
-            token_carry.push_back(std::char_traits<char>::to_char_type(c));
-        }
-    }
-#endif
-
 #if JSON_PRECISE_STREAM_POSITION
     // Step over the character last returned by get_character(). The character
     // has already been peeked successfully, so for every streambuf with a get
@@ -512,16 +240,6 @@ class input_stream_adapter
     /// whether get_character() peeked a character that is not consumed yet
     bool lookahead = false;
 #endif
-#if !JSON_DISABLE_STREAM_BULK_SCAN
-    /// the part of the current token that was in earlier get areas
-    std::vector<char> token_carry{}; // NOLINT(readability-redundant-member-init)
-    /// start of the current token's part in the get area, or nullptr
-    const char* token_segment = nullptr;
-    /// whether the character last returned by get_character() is in the get area
-    bool current_in_get_area = false;
-    /// whether a token is tracked at all; the binary readers never start one
-    bool tracking_token = false;
-#endif
 };
 #endif  // JSON_NO_IO
 

include/nlohmann/detail/input/json_sax.hpp

@@ -132,7 +132,9 @@ struct json_sax
     @param[in] position    the position in the input where the error occurs
     @param[in] last_token  the last read token
     @param[in] ex          an exception object describing the error
-    @return whether parsing should proceed (must return false)
+    @return whether to recover from the error: false stops parsing; true
+            repairs the error and continues, or, if that is not possible,
+            stops after completing the value read so far
     */
     virtual bool parse_error(std::size_t position,
                              const std::string& last_token,
@@ -326,9 +328,12 @@ a pointer to the respective array or object for each recursion depth.
 After successful parsing, the value that is passed by reference to the
 constructor contains the parsed value.
 
-@tparam BasicJsonType  the JSON type
+@tparam BasicJsonType     the JSON type
+@tparam InputAdapterType  the input adapter of the lexer that can be passed to
+                          the constructor to record diagnostic positions; it
+                          does not matter if no lexer is passed
 */
-template<typename BasicJsonType, typename InputAdapterType>
+template<typename BasicJsonType, typename InputAdapterType = string_input_adapter_type>
 class json_sax_dom_parser
 {
   public:
@@ -552,7 +557,7 @@ class json_sax_dom_parser
     lexer_t* m_lexer_ref = nullptr;
 };
 
-template<typename BasicJsonType, typename InputAdapterType>
+template<typename BasicJsonType, typename InputAdapterType = string_input_adapter_type>
 class json_sax_dom_callback_parser
 {
   public:

include/nlohmann/detail/input/number_parse.hpp

@@ -275,53 +275,13 @@ JSON_HEDLEY_ALWAYS_INLINE std::uint32_t parse_eight_digits(std::uint64_t v) noex
     return static_cast<std::uint32_t>(((v & 0x0000FFFF0000FFFFu) * 42949672960001u) >> 32u);
 }
 
-/// whether the eight bytes in @a v (see read_eight_bytes()) are all ASCII
-/// digits (after fast_float)
-JSON_HEDLEY_ALWAYS_INLINE bool is_eight_digits(std::uint64_t v) noexcept
+/// whether [first, last) contains a digit other than '0'
+inline bool has_nonzero_digit(const char* first, const char* last) noexcept
 {
-    return ((v & 0xF0F0F0F0F0F0F0F0u) | (((v + 0x0606060606060606u) & 0xF0F0F0F0F0F0F0F0u) >> 4u)) == 0x3333333333333333u;
-}
-
-/*!
-@brief skip the ASCII digits starting at data[i] and accumulate their value
-
-Eight digits are taken at a time while at least eight bytes remain. @a w wraps
-around after 19 digits; the caller only uses it for shorter digit runs.
-
-@return the index of the first byte at or after @a i that is not a digit
-*/
-JSON_HEDLEY_ALWAYS_INLINE std::size_t accumulate_digits(const char* data, std::size_t i, std::size_t avail, std::uint64_t& w) noexcept
-{
-    while (avail - i >= 8)
+    return std::any_of(first, last, [](char c) noexcept
     {
-        const std::uint64_t v = read_eight_bytes(data + i);
-        if (!is_eight_digits(v))
-        {
-            break;
-        }
-        w = (w * 100000000u) + parse_eight_digits(v);
-        i += 8;
-    }
-    while (i < avail && data[i] >= '0' && data[i] <= '9')
-    {
-        w = (w * 10u) + static_cast<std::uint64_t>(data[i] - '0');
-        ++i;
-    }
-    return i;
-}
-
-/// whether [first, last) contains a digit other than '0'; a plain loop, as
-/// GCC calls std::any_of out of line even for the usual empty range
-JSON_HEDLEY_ALWAYS_INLINE bool has_nonzero_digit(const char* first, const char* last) noexcept
-{
-    for (; first != last; ++first)
-    {
-        if (*first != '0')
-        {
-            return true;
-        }
-    }
-    return false;
+        return c != '0';
+    });
 }
 
 /// the value of the validated exponent digits [+-]?[0-9]+ in [first, last),
@@ -367,7 +327,7 @@ truncated is set.
                                    std::string::npos if there is none
 @param[in] mantissa_end            index of the 'e'/'E', or the token length
 */
-JSON_HEDLEY_ALWAYS_INLINE float_significand parse_float_significand(const char* first, const char* last,
+inline float_significand parse_float_significand(const char* first, const char* last,
         std::size_t decimal_point_position, std::size_t mantissa_end) noexcept
 {
     float_significand s;

include/nlohmann/detail/input/parser.hpp

@@ -51,20 +51,6 @@ template<typename BasicJsonType>
 using parser_callback_t =
     std::function<bool(int /*depth*/, parse_event_t /*event*/, BasicJsonType& /*parsed*/)>;
 
-/// whether a SAX handler ignores the text of float tokens (the library's own
-/// handlers do), so that the parser need not materialize it
-template<typename SAX>
-struct sax_ignores_number_text : std::false_type {};
-
-template<typename BasicJsonType, typename InputAdapterType>
-struct sax_ignores_number_text<json_sax_dom_parser<BasicJsonType, InputAdapterType>> : std::true_type {};
-
-template<typename BasicJsonType, typename InputAdapterType>
-struct sax_ignores_number_text<json_sax_dom_callback_parser<BasicJsonType, InputAdapterType>> : std::true_type {};
-
-template<typename BasicJsonType>
-struct sax_ignores_number_text<json_sax_acceptor<BasicJsonType>> : std::true_type {};
-
 /*!
 @brief syntax analysis
 
@@ -153,24 +139,59 @@ class parser
     bool accept(const bool strict = true)
     {
         json_sax_acceptor<BasicJsonType> sax_acceptor;
-        return sax_parse(&sax_acceptor, strict);
+        return sax_parse_impl<false>(&sax_acceptor, strict);
     }
 
+    /*!
+    @brief public SAX interface
+
+    If the SAX parser's parse_error() returns true, the parser recovers from
+    the error: it repairs the input and continues (see #3989).
+
+    @param[in] sax     the SAX parser
+    @param[in] strict  whether to expect the last token to be EOF
+    @return whether the input was parsed without errors and no SAX event
+            returned false
+    */
     template<typename SAX>
     JSON_HEDLEY_NON_NULL(2)
     bool sax_parse(SAX* sax, const bool strict = true)
+    {
+        return sax_parse_impl<true>(sax, strict);
+    }
+
+  private:
+    /// what sax_parse_internal() does after an object key was expected
+    enum class next_step : std::uint8_t
+    {
+        /// stop parsing
+        stop,
+        /// parse a value that begins with last_token
+        parse_value,
+        /// evaluate the state of the innermost container, which reads
+        /// last_token again
+        evaluate_state
+    };
+
+    template<bool AllowRecovery, typename SAX>
+    JSON_HEDLEY_NON_NULL(2)
+    bool sax_parse_impl(SAX* sax, const bool strict)
     {
         (void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
-        const bool result = sax_parse_internal(sax);
+        const bool result = sax_parse_internal<AllowRecovery>(sax);
 
         if (result)
         {
             if (strict)
             {
-                // strict mode: next byte must be EOF
-                if (get_token() != token_type::end_of_input)
+                // strict mode: next byte must be EOF; after recovering from an
+                // error, the end of the input may already have been read
+                if (last_token != token_type::end_of_input && get_token() != token_type::end_of_input)
                 {
-                    return syntax_error(*sax, exception_message(token_type::end_of_input, "value"));
+                    // the value is complete, so there is nothing to recover
+                    static_cast<void>(report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr),
+                                                   std::integral_constant<bool, AllowRecovery> {}));
+                    return false;
                 }
             }
             else
@@ -181,25 +202,7 @@ class parser
             }
         }
 
-        return result;
-    }
-
-  private:
-    /// the text of the current float token for @a sax (see sax_ignores_number_text)
-    template<typename SAX>
-    const string_t& number_float_text(SAX* /*sax*/)
-    {
-        return number_float_text(std::integral_constant<bool, sax_ignores_number_text<SAX>::value> {});
-    }
-
-    const string_t& number_float_text(std::true_type /*ignored*/) const noexcept
-    {
-        return m_lexer.get_ignored_number_text();
-    }
-
-    string_t& number_float_text(std::false_type /*ignored*/)
-    {
-        return m_lexer.get_string();
+        return result && !error_reported;
     }
 
     /*!
@@ -219,7 +222,7 @@ class parser
     template<typename DomSax>
     bool parse_dom(DomSax& sdp, const bool strict)
     {
-        sax_parse_internal(&sdp);
+        sax_parse_internal<false>(&sdp);
 
         if (strict)
         {
@@ -239,14 +242,23 @@ class parser
         return !sdp.is_errored();
     }
 
-    template<typename SAX>
+    /*!
+    @brief parse a JSON value and pass it to a SAX parser
+
+    @tparam AllowRecovery  whether to recover from an error if the SAX parser's
+                           parse_error() returns true; false for the SAX parsers
+                           of parse() and accept(), which never do, so that no
+                           code for recovering is generated for them
+    */
+    template<bool AllowRecovery, typename SAX>
     JSON_HEDLEY_NON_NULL(2)
     bool sax_parse_internal(SAX* sax)
     {
+        const std::integral_constant<bool, AllowRecovery> allow_recovery{};
+
         // stack to remember the hierarchy of structured values we are parsing
-        // true = array; false = object (bytes, not std::vector<bool>, whose
-        // push_back() is a call with GCC)
-        std::vector<std::uint8_t> states;
+        // true = array; false = object
+        std::vector<bool> states;
         // value to avoid a goto (see comment where set to true)
         bool skip_to_state_evaluation = false;
 
@@ -274,12 +286,20 @@ class parser
                             break;
                         }
 
-                        // parse key
+                        // remember we are now inside an object
+                        states.push_back(false);
+
+                        // parse key (the steps of parse_key(), which are
+                        // repeated here and below for speed)
                         if (JSON_HEDLEY_UNLIKELY(last_token != token_type::value_string))
                         {
-                            return syntax_error(*sax, exception_message(token_type::value_string, "object key"));
+                            if (!continue_after(key_error(sax, allow_recovery, false), skip_to_state_evaluation))
+                            {
+                                return false;
+                            }
+                            continue;
                         }
-                        if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string_token())))
+                        if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string())))
                         {
                             return false;
                         }
@@ -287,12 +307,13 @@ class parser
                         // parse separator (:)
                         if (JSON_HEDLEY_UNLIKELY(!get_token_expecting(token_type::name_separator)))
                         {
-                            return syntax_error(*sax, exception_message(token_type::name_separator, "object separator"));
+                            if (!continue_after(key_error(sax, allow_recovery, true), skip_to_state_evaluation))
+                            {
+                                return false;
+                            }
+                            continue;
                         }
 
-                        // remember we are now inside an object
-                        states.push_back(0);
-
                         // parse values
                         get_token();
                         continue;
@@ -316,7 +337,7 @@ class parser
                         }
 
                         // remember we are now inside an array
-                        states.push_back(1);
+                        states.push_back(true);
 
                         // parse values (no need to call get_token)
                         continue;
@@ -328,12 +349,14 @@ class parser
 
                         if (JSON_HEDLEY_UNLIKELY(!std::isfinite(res)))
                         {
-                            return sax->parse_error(m_lexer.get_position(),
-                                                    m_lexer.get_token_string(),
-                                                    out_of_range::create(exception_id::number_overflow, concat("number overflow parsing '", m_lexer.get_token_string(), '\''), nullptr));
+                            if (!overflow_error(sax, res, allow_recovery))
+                            {
+                                return false;
+                            }
+                            break;
                         }
 
-                        if (JSON_HEDLEY_UNLIKELY(!sax->number_float(res, number_float_text(sax))))
+                        if (JSON_HEDLEY_UNLIKELY(!sax->number_float(res, m_lexer.get_string())))
                         {
                             return false;
                         }
@@ -379,7 +402,7 @@ class parser
 
                     case token_type::value_string:
                     {
-                        if (JSON_HEDLEY_UNLIKELY(!sax->string(m_lexer.get_string_token())))
+                        if (JSON_HEDLEY_UNLIKELY(!sax->string(m_lexer.get_string())))
                         {
                             return false;
                         }
@@ -398,16 +421,63 @@ class parser
                     case token_type::parse_error:
                     {
                         // using "uninitialized" to avoid an "expected" message
-                        return syntax_error(*sax, exception_message(token_type::uninitialized, "value"));
+                        if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::uninitialized, "value"), nullptr), allow_recovery))
+                        {
+                            return false;
+                        }
+
+                        // recover: keep what can be read of the token
+                        recover_token(allow_recovery);
+                        if (last_token != token_type::uninitialized)
+                        {
+                            // a string or a number
+                            continue;
+                        }
+                        if (states.empty())
+                        {
+                            // look for the value after the garbage
+                            if (!skip_to_value(allow_recovery))
+                            {
+                                return false;
+                            }
+                            continue;
+                        }
+                        // nothing could be read
+                        if (JSON_HEDLEY_UNLIKELY(!sax->null()))
+                        {
+                            return false;
+                        }
+                        break;
                     }
                     case token_type::end_of_input:
                     {
                         if (JSON_HEDLEY_UNLIKELY(m_lexer.get_chars_read_total() == 1))
                         {
-                            return syntax_error(*sax, "attempting to parse an empty input; check that your input string or stream contains the expected JSON");
+                            // there is nothing to recover
+                            static_cast<void>(report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(),
+                                                           "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr), allow_recovery));
+                            return false;
                         }
 
-                        return syntax_error(*sax, exception_message(token_type::literal_or_value, "value"));
+                        if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::literal_or_value, "value"), nullptr), allow_recovery))
+                        {
+                            return false;
+                        }
+
+                        // recover: the input ends where a value is missing
+                        if (states.empty())
+                        {
+                            // there is no value
+                            return false;
+                        }
+                        if (!recover_missing_value(sax, states, allow_recovery))
+                        {
+                            return false;
+                        }
+                        // the state evaluation reads the token again
+                        unget_token(allow_recovery);
+                        skip_to_state_evaluation = true;
+                        continue;
                     }
                     case token_type::uninitialized:
                     case token_type::end_array:
@@ -417,7 +487,35 @@ class parser
                     case token_type::literal_or_value:
                     default: // the last token was unexpected
                     {
-                        return syntax_error(*sax, exception_message(token_type::literal_or_value, "value"));
+                        if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::literal_or_value, "value"), nullptr), allow_recovery))
+                        {
+                            return false;
+                        }
+
+                        // recover
+                        if (states.empty())
+                        {
+                            // look for the value after the garbage
+                            if (!skip_to_value(allow_recovery))
+                            {
+                                return false;
+                            }
+                            continue;
+                        }
+                        if (last_token == token_type::name_separator)
+                        {
+                            // a stray ':'; the value may follow
+                            get_token();
+                            continue;
+                        }
+                        if (!recover_missing_value(sax, states, allow_recovery))
+                        {
+                            return false;
+                        }
+                        // the state evaluation reads the token again
+                        unget_token(allow_recovery);
+                        skip_to_state_evaluation = true;
+                        continue;
                     }
                 }
             }
@@ -433,7 +531,7 @@ class parser
                 return true;
             }
 
-            if (states.back() != 0)  // array
+            if (states.back())  // array
             {
                 // comma -> next value
                 // or end of array (ignore_trailing_commas = true)
@@ -468,7 +566,30 @@ class parser
                     continue;
                 }
 
-                return syntax_error(*sax, exception_message(token_type::end_array, "array"));
+                if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::end_array, "array"), nullptr), allow_recovery))
+                {
+                    return false;
+                }
+
+                // recover
+                if (last_token == token_type::end_of_input)
+                {
+                    // the input ends inside the array
+                    return close_containers(sax, states, allow_recovery);
+                }
+                if (last_token == token_type::end_object)
+                {
+                    // a wrong closing bracket closes the innermost container
+                    if (JSON_HEDLEY_UNLIKELY(!sax->end_array()))
+                    {
+                        return false;
+                    }
+                    states.pop_back();
+                    skip_to_state_evaluation = true;
+                }
+                // otherwise, a missing ',' (or a stray ':', which value
+                // parsing drops): the next value begins here
+                continue;
             }
 
             // states.back() is false -> object
@@ -485,10 +606,13 @@ class parser
                     // parse key
                     if (JSON_HEDLEY_UNLIKELY(last_token != token_type::value_string))
                     {
-                        return syntax_error(*sax, exception_message(token_type::value_string, "object key"));
+                        if (!continue_after(key_error(sax, allow_recovery, false), skip_to_state_evaluation))
+                        {
+                            return false;
+                        }
+                        continue;
                     }
-
-                    if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string_token())))
+                    if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string())))
                     {
                         return false;
                     }
@@ -496,7 +620,11 @@ class parser
                     // parse separator (:)
                     if (JSON_HEDLEY_UNLIKELY(!get_token_expecting(token_type::name_separator)))
                     {
-                        return syntax_error(*sax, exception_message(token_type::name_separator, "object separator"));
+                        if (!continue_after(key_error(sax, allow_recovery, true), skip_to_state_evaluation))
+                        {
+                            return false;
+                        }
+                        continue;
                     }
 
                     // parse values
@@ -524,10 +652,546 @@ class parser
                 continue;
             }
 
-            return syntax_error(*sax, exception_message(token_type::end_object, "object"));
+            if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::end_object, "object"), nullptr), allow_recovery))
+            {
+                return false;
+            }
+
+            // recover
+            if (last_token == token_type::end_of_input)
+            {
+                // the input ends inside the object
+                return close_containers(sax, states, allow_recovery);
+            }
+            if (last_token == token_type::end_array)
+            {
+                // a wrong closing bracket closes the innermost container
+                if (JSON_HEDLEY_UNLIKELY(!sax->end_object()))
+                {
+                    return false;
+                }
+                states.pop_back();
+                skip_to_state_evaluation = true;
+                continue;
+            }
+            if (!continue_after(recover_member(sax, allow_recovery), skip_to_state_evaluation))
+            {
+                return false;
+            }
         }
     }
 
+    /*!
+    @brief continue sax_parse_internal() after a recovery
+    @return whether to continue parsing
+    */
+    bool continue_after(const next_step step, bool& skip_to_state_evaluation)
+    {
+        if (step == next_step::evaluate_state)
+        {
+            // the state evaluation reads the token again
+            m_lexer.unget_token();
+            skip_to_state_evaluation = true;
+        }
+        return step != next_step::stop;
+    }
+
+    /// the parser for parse() and accept() never recovers: stop parsing
+    JSON_INTERNAL_ALWAYS_INLINE
+    static std::false_type continue_after(std::false_type /*step*/, bool& /*skip_to_state_evaluation*/) noexcept
+    {
+        return {};
+    }
+
+    /*!
+    @brief parse an object key and the name separator (:) after it
+
+    last_token is the token where the key is expected. sax_parse_internal()
+    repeats these steps rather than calling this function, which is used
+    when recovering from an error.
+
+    @return next_step::parse_value if the value follows, with last_token its
+            first token; next_step::evaluate_state if the object's state is
+            to be evaluated after recovering from an error; next_step::stop
+            to stop parsing
+    */
+    template<typename SAX>
+    next_step parse_key(SAX* sax)
+    {
+        const std::true_type allow_recovery{};
+
+        if (JSON_HEDLEY_UNLIKELY(last_token != token_type::value_string))
+        {
+            return key_error(sax, allow_recovery, false);
+        }
+
+        if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string())))
+        {
+            return next_step::stop;
+        }
+
+        // parse separator (:)
+        if (JSON_HEDLEY_UNLIKELY(get_token() != token_type::name_separator))
+        {
+            return key_error(sax, allow_recovery, true);
+        }
+
+        // the value begins with the next token
+        get_token();
+        return next_step::parse_value;
+    }
+
+    /*!
+    @brief report a number that is too large for number_float_t, and recover
+           from the error by passing the value on; the SAX parser gets the
+           number's text as well
+
+    This is a separate function, as reading other numbers is measurably
+    slower if the error is handled where they are read.
+
+    @param[in] sax    the SAX parser
+    @param[in] value  the value that is not finite
+    @return whether to continue parsing
+    */
+    template<typename SAX>
+    bool overflow_error(SAX* sax, const number_float_t value, std::true_type allow_recovery)
+    {
+        if (!report_error(sax, out_of_range::create(exception_id::number_overflow, concat("number overflow parsing '", m_lexer.get_token_string(), '\''), nullptr), allow_recovery))
+        {
+            return false;
+        }
+        return sax->number_float(value, m_lexer.get_string());
+    }
+
+    /// @copydoc overflow_error
+    template<typename SAX>
+    JSON_INTERNAL_ALWAYS_INLINE
+    std::false_type overflow_error(SAX* sax, const number_float_t /*value*/, std::false_type allow_recovery)
+    {
+        return report_error(sax, out_of_range::create(exception_id::number_overflow, concat("number overflow parsing '", m_lexer.get_token_string(), '\''), nullptr), allow_recovery);
+    }
+
+    /*!
+    @brief report a missing key, or a missing name separator (:) after the
+           key; the parser for parse() and accept() never recovers
+
+    @param[in] key_read  whether the key was read, so that the name separator
+                         is missing
+    @return std::false_type, see report_error()
+    */
+    template<typename SAX>
+    JSON_INTERNAL_ALWAYS_INLINE
+    std::false_type key_error(SAX* sax, std::false_type allow_recovery, const bool key_read)
+    {
+        return report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), key_read
+                            ? exception_message(token_type::name_separator, "object separator")
+                            : exception_message(token_type::value_string, "object key"), nullptr), allow_recovery);
+    }
+
+    /*!
+    @brief report a missing key, or a missing name separator (:) after the
+           key, and recover from it
+
+    @param[in] key_read  whether the key was read, so that the name separator
+                         is missing
+    */
+    template<typename SAX>
+    next_step key_error(SAX* sax, std::true_type allow_recovery, const bool key_read)
+    {
+        if (!key_read)
+        {
+            if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::value_string, "object key"), nullptr), allow_recovery))
+            {
+                return next_step::stop;
+            }
+            return recover_key(sax);
+        }
+
+        if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::name_separator, "object separator"), nullptr), allow_recovery))
+        {
+            return next_step::stop;
+        }
+        return recover_name_separator(sax);
+    }
+
+    /////////////////////
+    // error recovery
+    /////////////////////
+
+    /*
+    The functions below repair an error after the SAX parser's parse_error()
+    returned true (see #3989). Each mistake is repaired by the smallest local
+    edit: a missing ',' or ':' is inserted, a stray token is removed, what can
+    be read of an invalid string or number is kept (see
+    lexer::recover_token()), a missing value becomes null, a wrong closing
+    bracket closes the innermost container, and the end of the input closes
+    all of them. The events stay balanced, and every key() is followed by
+    exactly one value.
+
+    A repair hands a token to the state evaluation, by returning it to the
+    lexer (lexer::unget_token()) so that the state evaluation reads it again,
+    only if it is ',', ']', '}', or the end of the input. The state evaluation
+    hands a token to value or key parsing only if it is none of them, so a
+    token is never handed back and forth. Every other step reads a token or
+    closes a container, so parsing always ends.
+    */
+
+    /*!
+    @brief report an error to the SAX parser; the parser for parse() and
+           accept() never recovers
+
+    @return std::false_type rather than false: its value is known where the
+            function is called even if the call is not inlined, so the code
+            for recovering is not generated
+    */
+    template<typename SAX, typename Exception>
+    JSON_INTERNAL_ALWAYS_INLINE
+    std::false_type report_error(SAX* sax, const Exception& ex, std::false_type /*allow_recovery*/)
+    {
+        static_cast<void>(sax); // MSVC 2015 does not count calling a static parse_error() as using it
+        error_reported = true;
+        static_cast<void>(sax->parse_error(m_lexer.get_position(), m_lexer.get_token_string(), ex));
+        return {};
+    }
+
+    /*!
+    @brief report an error to the SAX parser
+    @return whether to recover from the error
+    */
+    template<typename SAX, typename Exception>
+    bool report_error(SAX* sax, const Exception& ex, std::true_type /*allow_recovery*/)
+    {
+        static_cast<void>(sax); // MSVC 2015 does not count calling a static parse_error() as using it
+        const std::size_t position = m_lexer.get_position().chars_read_total;
+        if (error_reported && position == last_error_position && last_token == last_error_token)
+        {
+            // a repair handed on the token of the error it repaired; the
+            // token was reported already, and the SAX parser asked to recover
+            return true;
+        }
+
+        error_reported = true;
+        last_error_position = position;
+        last_error_token = last_token;
+
+        if (!sax->parse_error(m_lexer.get_position(), m_lexer.get_token_string(), ex))
+        {
+            return false;
+        }
+
+        // the token string of the next error begins here
+        m_lexer.restart_token_string();
+        return true;
+    }
+
+    /*!
+    @brief keep what can be read of the token that the lexer rejected
+
+    The error was reported for the rejected token, so it is not reported again
+    for the token it is repaired to (see lexer::recover_token()).
+    */
+    token_type recover_token()
+    {
+        last_token = m_lexer.recover_token();
+        last_error_position = m_lexer.get_position().chars_read_total;
+        last_error_token = last_token;
+        return last_token;
+    }
+
+    // The functions below are called from sax_parse_internal() after an error
+    // was reported. The parser for parse() and accept() stopped there, so for
+    // it they are stubs: the code for recovering is then not even referenced,
+    // and unoptimized builds do not emit it either.
+
+    /// @copydoc recover_token()
+    JSON_INTERNAL_ALWAYS_INLINE
+    token_type recover_token(std::true_type /*allow_recovery*/)
+    {
+        return recover_token();
+    }
+
+    /// @copydoc recover_token()
+    JSON_INTERNAL_ALWAYS_INLINE
+    static std::false_type recover_token(std::false_type /*allow_recovery*/) noexcept
+    {
+        return {};
+    }
+
+    /// return the token that was read last to the lexer (see lexer::unget_token())
+    JSON_INTERNAL_ALWAYS_INLINE
+    void unget_token(std::true_type /*allow_recovery*/)
+    {
+        m_lexer.unget_token();
+    }
+
+    /// @copydoc unget_token(std::true_type)
+    JSON_INTERNAL_ALWAYS_INLINE
+    static void unget_token(std::false_type /*allow_recovery*/) noexcept {}
+
+    /// @copydoc skip_to_value
+    JSON_INTERNAL_ALWAYS_INLINE
+    static std::false_type skip_to_value(std::false_type /*allow_recovery*/) noexcept
+    {
+        return {};
+    }
+
+    /// @copydoc recover_missing_value
+    template<typename SAX>
+    JSON_INTERNAL_ALWAYS_INLINE
+    static std::false_type recover_missing_value(SAX* /*sax*/, const std::vector<bool>& /*states*/, std::false_type /*allow_recovery*/) noexcept
+    {
+        return {};
+    }
+
+    /// pass the end events of all open containers
+    template<typename SAX>
+    bool close_containers(SAX* sax, std::vector<bool>& states, std::true_type /*allow_recovery*/)
+    {
+        while (!states.empty())
+        {
+            const bool is_array = states.back();
+            states.pop_back();
+            if (JSON_HEDLEY_UNLIKELY(is_array ? !sax->end_array() : !sax->end_object()))
+            {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    /// @copydoc close_containers
+    template<typename SAX>
+    JSON_INTERNAL_ALWAYS_INLINE
+    static std::false_type close_containers(SAX* /*sax*/, std::vector<bool>& /*states*/, std::false_type /*allow_recovery*/) noexcept
+    {
+        return {};
+    }
+
+    /*!
+    @brief read tokens until one begins a value, skipping everything before
+           the top-level value
+    @return whether a value begins with last_token
+    */
+    bool skip_to_value(std::true_type /*allow_recovery*/)
+    {
+        while (true)
+        {
+            switch (get_token())
+            {
+                case token_type::begin_array:
+                case token_type::begin_object:
+                case token_type::literal_false:
+                case token_type::literal_null:
+                case token_type::literal_true:
+                case token_type::value_float:
+                case token_type::value_integer:
+                case token_type::value_string:
+                case token_type::value_unsigned:
+                    return true;
+
+                case token_type::end_of_input:
+                    return false;
+
+                case token_type::parse_error:
+                    recover_token();
+                    if (last_token != token_type::uninitialized)
+                    {
+                        return true;
+                    }
+                    break;
+
+                case token_type::uninitialized:
+                case token_type::end_array:
+                case token_type::end_object:
+                case token_type::name_separator:
+                case token_type::value_separator:
+                case token_type::literal_or_value:
+                default:
+                    break;
+            }
+        }
+    }
+
+    /*!
+    @brief skip the rest of an object member that cannot be read
+
+    Reads tokens, beginning with last_token, until a ',', '}', or ']' that is
+    not inside a container that begins in the skipped tokens, or the end of
+    the input.
+    */
+    void skip_member()
+    {
+        std::size_t depth = 0;
+        while (true)
+        {
+            switch (last_token)
+            {
+                case token_type::begin_array:
+                case token_type::begin_object:
+                    ++depth;
+                    break;
+
+                case token_type::end_array:
+                case token_type::end_object:
+                    if (depth == 0)
+                    {
+                        return;
+                    }
+                    --depth;
+                    break;
+
+                case token_type::value_separator:
+                    if (depth == 0)
+                    {
+                        return;
+                    }
+                    break;
+
+                case token_type::end_of_input:
+                    return;
+
+                case token_type::parse_error:
+                    recover_token();
+                    break;
+
+                case token_type::uninitialized:
+                case token_type::literal_true:
+                case token_type::literal_false:
+                case token_type::literal_null:
+                case token_type::value_string:
+                case token_type::value_unsigned:
+                case token_type::value_integer:
+                case token_type::value_float:
+                case token_type::name_separator:
+                case token_type::literal_or_value:
+                default:
+                    break;
+            }
+            get_token();
+        }
+    }
+
+    /*!
+    @brief pass a value where it is missing
+
+    last_token is ',', ']', '}', or the end of the input, where a value was
+    expected. In an object, the key gets null; in an array, a ',' where a
+    value is missing stands for null (as in JavaScript), while an array that
+    ends there just ends.
+    */
+    template<typename SAX>
+    bool recover_missing_value(SAX* sax, const std::vector<bool>& states, std::true_type /*allow_recovery*/)
+    {
+        JSON_ASSERT(!states.empty());
+        if (!states.back() || last_token == token_type::value_separator)
+        {
+            return sax->null();
+        }
+        return true;
+    }
+
+    /// recover from a missing key; last_token is where it was expected
+    template<typename SAX>
+    next_step recover_key(SAX* sax)
+    {
+        switch (last_token)
+        {
+            case token_type::value_separator:
+            case token_type::end_object:
+            case token_type::end_array:
+            case token_type::end_of_input:
+                // no member: the object's state handles the token
+                return next_step::evaluate_state;
+
+            case token_type::parse_error:
+                recover_token();
+                if (last_token == token_type::value_string)
+                {
+                    // a key that could be repaired
+                    return parse_key(sax);
+                }
+                skip_member();
+                return next_step::evaluate_state;
+
+            case token_type::uninitialized:
+            case token_type::literal_true:
+            case token_type::literal_false:
+            case token_type::literal_null:
+            case token_type::value_string:
+            case token_type::value_unsigned:
+            case token_type::value_integer:
+            case token_type::value_float:
+            case token_type::begin_array:
+            case token_type::begin_object:
+            case token_type::name_separator:
+            case token_type::literal_or_value:
+            default:
+                // a member without a key
+                skip_member();
+                return next_step::evaluate_state;
+        }
+    }
+
+    /// recover from a missing name separator (:) after the key; last_token
+    /// is where it was expected
+    template<typename SAX>
+    next_step recover_name_separator(SAX* sax)
+    {
+        switch (last_token)
+        {
+            case token_type::value_separator:
+            case token_type::end_object:
+            case token_type::end_array:
+            case token_type::end_of_input:
+                // the value is missing as well
+                return sax->null() ? next_step::evaluate_state : next_step::stop;
+
+            case token_type::uninitialized:
+            case token_type::literal_true:
+            case token_type::literal_false:
+            case token_type::literal_null:
+            case token_type::value_string:
+            case token_type::value_unsigned:
+            case token_type::value_integer:
+            case token_type::value_float:
+            case token_type::begin_array:
+            case token_type::begin_object:
+            case token_type::name_separator:
+            case token_type::parse_error:
+            case token_type::literal_or_value:
+            default:
+                // a missing ':'; the value begins here
+                return next_step::parse_value;
+        }
+    }
+
+    /// recover from a token after an object member that is neither ',' nor
+    /// '}' (nor ']' or the end of the input, which the caller handles)
+    template<typename SAX>
+    next_step recover_member(SAX* sax, std::true_type /*allow_recovery*/)
+    {
+        if (last_token == token_type::parse_error)
+        {
+            recover_token();
+        }
+        if (last_token == token_type::value_string)
+        {
+            // a missing ','; the next key begins here
+            return parse_key(sax);
+        }
+        skip_member();
+        return next_step::evaluate_state;
+    }
+
+    /// the parser for parse() and accept() never recovers (and does not come
+    /// here, as report_error() returned false)
+    template<typename SAX>
+    JSON_INTERNAL_ALWAYS_INLINE
+    std::false_type recover_member(SAX* /*sax*/, std::false_type /*allow_recovery*/) const noexcept
+    {
+        return {};
+    }
+
     /// get next token from lexer
     token_type get_token()
     {
@@ -598,6 +1262,12 @@ class parser
     const bool allow_exceptions = true;
     /// whether trailing commas in objects and arrays should be ignored (true) or signaled as errors (false)
     const bool ignore_trailing_commas = false;
+    /// whether an error was reported to the SAX parser
+    bool error_reported = false;
+    /// the position of the last reported error
+    std::size_t last_error_position = 0;
+    /// the token of the last reported error
+    token_type last_error_token = token_type::uninitialized;
 };
 
 }  // namespace detail

include/nlohmann/detail/input/simd_scan.hpp

@@ -1,314 +0,0 @@
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-FileCopyrightText: 2018-2025 The simdjson authors <https://github.com/simdjson/simdjson>
-// SPDX-License-Identifier: MIT
-
-#pragma once
-
-#include <array> // array
-#include <atomic> // atomic
-#include <cstddef> // size_t
-#include <cstdint> // uint8_t, uint64_t
-
-#include <nlohmann/detail/bit_ops.hpp>
-#include <nlohmann/detail/macro_scope.hpp>
-
-// Vector code for runs of string bytes, used by the lexer for contiguous input
-// (see string_bulk_run()). NEON (AArch64) and SSE2 (x86-64) belong to the
-// baseline instruction sets and are used by default. The vector UTF-8 check
-// needs NEON or SSSE3. SSSE3 is not part of x86-64, and the code must not
-// depend on the flags of a translation unit (two translation units with
-// different flags would have different definitions of the same inline
-// functions): the check is compiled for SSSE3 with a function attribute and
-// used where the CPU has SSSE3 (all x86-64 CPUs since about 2011), else the
-// portable check. Code compiled for SSSE3 anyway (-mssse3 or more) skips the
-// CPU check. JSON_NO_SIMD selects the portable code everywhere.
-// NLOHMANN_JSON_NO_TARGET_ATTRIBUTE (for compilers that ignore the target
-// attribute and then reject the SSSE3 intrinsics) keeps the check portable
-// without disabling the SSE2 code.
-#if !defined(JSON_NO_SIMD) && defined(__aarch64__) && (defined(__GNUC__) || defined(__clang__)) && defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-    #include <arm_neon.h>
-    #define JSON_SCAN_NEON 1
-#else
-    #define JSON_SCAN_NEON 0
-#endif
-// (x86 only: other targets can define __SSE2__ as well, e.g., WebAssembly with -msse2, but have no <cpuid.h>)
-#if !defined(JSON_NO_SIMD) && !JSON_SCAN_NEON && (defined(__x86_64__) || defined(__i386__) || defined(_M_X64) || defined(_M_IX86)) && !defined(_M_ARM64EC) && (defined(__SSE2__) || defined(_M_X64) || (defined(_M_IX86_FP) && _M_IX86_FP >= 2))
-    #include <emmintrin.h>
-    #define JSON_SCAN_SSE2 1
-#else
-    #define JSON_SCAN_SSE2 0
-#endif
-#if JSON_SCAN_SSE2 && defined(__SSSE3__)
-    #include <tmmintrin.h>
-    #define JSON_SCAN_SSSE3 1 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
-#else
-    #define JSON_SCAN_SSSE3 0 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
-#endif
-#if JSON_SCAN_SSE2 && !JSON_SCAN_SSSE3 && !defined(NLOHMANN_JSON_NO_TARGET_ATTRIBUTE) && ((defined(__clang__) && __clang_major__ >= 4) || (defined(__GNUC__) && !defined(__clang__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9))))
-    // (GCC before 4.9 has no SSSE3 intrinsics without -mssse3)
-    #include <cpuid.h>
-    #include <tmmintrin.h>
-    #define JSON_SCAN_SSSE3_DISPATCH 1 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
-    #define JSON_SCAN_SSSE3_TARGET __attribute__((target("ssse3")))
-#elif JSON_SCAN_SSE2 && !JSON_SCAN_SSSE3 && defined(_MSC_VER)
-    // (MSVC compiles intrinsics of any instruction set)
-    #include <intrin.h>
-    #include <tmmintrin.h>
-    #define JSON_SCAN_SSSE3_DISPATCH 1 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
-    #define JSON_SCAN_SSSE3_TARGET
-#else
-    #define JSON_SCAN_SSSE3_DISPATCH 0 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
-    #define JSON_SCAN_SSSE3_TARGET
-#endif
-#define JSON_SCAN_VECTOR (JSON_SCAN_NEON || JSON_SCAN_SSE2)
-#define JSON_SCAN_VECTOR_UTF8 (JSON_SCAN_NEON || JSON_SCAN_SSSE3 || JSON_SCAN_SSSE3_DISPATCH)
-
-NLOHMANN_JSON_NAMESPACE_BEGIN
-namespace detail
-{
-
-#if JSON_SCAN_VECTOR
-/*!
-@brief the first byte of a string run that is a quote, a backslash, a control
-character, or not ASCII, 16 bytes per step
-
-Stops at such a byte, or where fewer than 16 bytes are left (the caller tells
-the two apart). A signed compare with 0x20 finds control characters and
-non-ASCII bytes at once.
-*/
-JSON_HEDLEY_ALWAYS_INLINE const unsigned char* vector_plain_run(const unsigned char* p, const unsigned char* e) noexcept
-{
-    while (e - p >= 16)
-    {
-#if JSON_SCAN_NEON
-        const uint8x16_t in = vld1q_u8(p);
-        const uint8x16_t special = vorrq_u8(vorrq_u8(vceqq_u8(in, vdupq_n_u8('"')), vceqq_u8(in, vdupq_n_u8('\\'))),
-                                            vcltq_s8(vreinterpretq_s8_u8(in), vdupq_n_s8(0x20)));
-        // one nibble per byte (the usual NEON replacement of x86's movemask, see
-        // D. Kutenin, "Porting x86 vector bitmask optimizations to Arm NEON", 2022)
-        const std::uint64_t bits = vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(special), 4)), 0);
-        if (bits != 0)
-        {
-            return p + (count_trailing_zeros(bits) >> 2u);
-        }
-#else
-        const __m128i in = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(p))); // NOLINT(bugprone-casting-through-void)
-        const __m128i special = _mm_or_si128(_mm_or_si128(_mm_cmpeq_epi8(in, _mm_set1_epi8('"')), _mm_cmpeq_epi8(in, _mm_set1_epi8('\\'))),
-                                             _mm_cmplt_epi8(in, _mm_set1_epi8(0x20)));
-        const auto bits = static_cast<std::uint64_t>(static_cast<unsigned>(_mm_movemask_epi8(special)));
-        if (bits != 0)
-        {
-            return p + count_trailing_zeros(bits);
-        }
-#endif
-        p += 16;
-    }
-    return p;
-}
-#endif
-
-#if JSON_SCAN_VECTOR
-/// vector_plain_run() for runs that are already longer than a few words:
-/// inline with SSE2, out of line with NEON, where a larger string loop slows
-/// down the rest of the lexer
-#if JSON_SCAN_NEON
-    JSON_HEDLEY_NEVER_INLINE inline
-#else
-    JSON_HEDLEY_ALWAYS_INLINE
-#endif
-const unsigned char* vector_plain_run_long(const unsigned char* p, const unsigned char* e) noexcept
-{
-    return vector_plain_run(p, e);
-}
-#endif
-
-#if JSON_SCAN_SSSE3_DISPATCH
-/// whether the CPU has SSSE3 (CPUID leaf 1, ECX bit 9)
-inline bool cpu_ssse3() noexcept
-{
-#if defined(_MSC_VER) && !defined(__clang__)
-    std::array<int, 4> regs {{}};
-    __cpuid(regs.data(), 1);
-    return (static_cast<unsigned>(regs[2]) & (1u << 9u)) != 0;
-#else
-    unsigned eax = 0;
-    unsigned ebx = 0;
-    unsigned ecx = 0;
-    unsigned edx = 0;
-    return __get_cpuid(1, &eax, &ebx, &ecx, &edx) != 0 && (ecx & (1u << 9u)) != 0;
-#endif
-}
-
-/// whether the CPU has SSSE3, asked once: the answer is kept in an atomic
-/// that is initialized at compile time, so that neither a guard of a local
-/// static nor a global constructor is needed (threads that ask at the same
-/// time all store the same answer)
-JSON_HEDLEY_ALWAYS_INLINE bool cpu_has_ssse3() noexcept
-{
-    static std::atomic<int> known{0}; // 0: not asked yet, 1: no, 2: yes
-    int state = known.load(std::memory_order_relaxed);
-    if (JSON_HEDLEY_UNLIKELY(state == 0))
-    {
-        state = cpu_ssse3() ? 2 : 1;
-        known.store(state, std::memory_order_relaxed);
-    }
-    return state == 2;
-}
-#endif
-
-#if JSON_SCAN_VECTOR_UTF8
-/// Tables of the UTF-8 check of J. Keiser and D. Lemire, "Validating UTF-8 In
-/// Less Than One Instruction Per Byte" (2021), as in simdjson ("lookup4"): each
-/// maps a nibble (high and low nibble of the previous byte, high nibble of the
-/// current byte) to the errors it allows; a byte pair is ill-formed if all
-/// three have an error bit in common.
-template<typename Dummy = void>
-struct utf8_lookup4
-{
-    static constexpr std::uint8_t too_short = 1u << 0u, too_long = 1u << 1u, overlong_3 = 1u << 2u, too_large = 1u << 3u;
-    static constexpr std::uint8_t surrogate = 1u << 4u, overlong_2 = 1u << 5u, too_large_1000 = 1u << 6u, overlong_4 = 1u << 6u;
-    static constexpr std::uint8_t two_conts = 1u << 7u, carry = too_short | too_long | two_conts;
-    static const std::array<std::uint8_t, 16> byte_1_high;
-    static const std::array<std::uint8_t, 16> byte_1_low;
-    static const std::array<std::uint8_t, 16> byte_2_high;
-};
-
-template<typename Dummy>
-const std::array<std::uint8_t, 16> utf8_lookup4<Dummy>::byte_1_high =
-{
-    {
-        too_long, too_long, too_long, too_long, too_long, too_long, too_long, too_long,
-        two_conts, two_conts, two_conts, two_conts,
-        too_short | overlong_2, too_short, too_short | overlong_3 | surrogate, too_short | too_large | too_large_1000 | overlong_4
-    }
-};
-
-template<typename Dummy>
-const std::array<std::uint8_t, 16> utf8_lookup4<Dummy>::byte_1_low =
-{
-    {
-        carry | overlong_3 | overlong_2 | overlong_4, carry | overlong_2, carry, carry,
-        carry | too_large, carry | too_large | too_large_1000, carry | too_large | too_large_1000, carry | too_large | too_large_1000,
-        carry | too_large | too_large_1000, carry | too_large | too_large_1000, carry | too_large | too_large_1000, carry | too_large | too_large_1000,
-        carry | too_large | too_large_1000, carry | too_large | too_large_1000 | surrogate, carry | too_large | too_large_1000, carry | too_large | too_large_1000
-    }
-};
-
-template<typename Dummy>
-const std::array<std::uint8_t, 16> utf8_lookup4<Dummy>::byte_2_high =
-{
-    {
-        too_short, too_short, too_short, too_short, too_short, too_short, too_short, too_short,
-        static_cast<std::uint8_t>(too_long | overlong_2 | two_conts | overlong_3 | too_large_1000 | overlong_4),
-        static_cast<std::uint8_t>(too_long | overlong_2 | two_conts | overlong_3 | too_large),
-        static_cast<std::uint8_t>(too_long | overlong_2 | two_conts | surrogate | too_large),
-        static_cast<std::uint8_t>(too_long | overlong_2 | two_conts | surrogate | too_large),
-        too_short, too_short, too_short, too_short
-    }
-};
-
-/*!
-@brief the run of plain string bytes and well-formed UTF-8 at p (a character
-       boundary), 16 bytes per step
-
-The first quote, backslash, or control character is found with vector
-compares, and the UTF-8 check of J. Keiser and D. Lemire covers the bytes up
-to it. Returns true with @a block at that byte; returns false with @a block at
-the start of the 16 bytes where the check found ill-formed UTF-8 or where
-fewer than 16 bytes are left, for the caller to finish one sequence at a time.
-Out of line, so that no constants of the check occupy registers in the
-caller's loop. On x86-64, it is compiled for SSSE3 (see cpu_has_ssse3()).
-*/
-JSON_SCAN_SSSE3_TARGET JSON_HEDLEY_NEVER_INLINE inline bool vector_utf8_run(const unsigned char* p, const unsigned char* e, const unsigned char*& block_out) noexcept
-{
-    using lookup = utf8_lookup4<>;
-    const unsigned char* block = p;
-#if JSON_SCAN_NEON
-    const uint8x16_t t1h = vld1q_u8(lookup::byte_1_high.data());
-    const uint8x16_t t1l = vld1q_u8(lookup::byte_1_low.data());
-    const uint8x16_t t2h = vld1q_u8(lookup::byte_2_high.data());
-    uint8x16_t prev = vdupq_n_u8(0);
-    while (e - block >= 16)
-    {
-        const uint8x16_t in = vld1q_u8(block);
-        const uint8x16_t special = vorrq_u8(vorrq_u8(vceqq_u8(in, vdupq_n_u8('"')), vceqq_u8(in, vdupq_n_u8('\\'))), vcltq_u8(in, vdupq_n_u8(0x20)));
-        const uint8x16_t prev1 = vextq_u8(prev, in, 15);
-        const uint8x16_t sc = vandq_u8(vandq_u8(vqtbl1q_u8(t1h, vshrq_n_u8(prev1, 4)), vqtbl1q_u8(t1l, vandq_u8(prev1, vdupq_n_u8(0x0F)))), vqtbl1q_u8(t2h, vshrq_n_u8(in, 4)));
-        const uint8x16_t must23 = vorrq_u8(vqsubq_u8(vextq_u8(prev, in, 14), vdupq_n_u8(0xE0 - 0x80)), vqsubq_u8(vextq_u8(prev, in, 13), vdupq_n_u8(0xF0 - 0x80)));
-        const uint8x16_t err = veorq_u8(vandq_u8(must23, vdupq_n_u8(0x80)), sc);
-        const std::uint64_t special_bits = vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(special), 4)), 0);
-        const std::uint64_t err_bits = vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(vtstq_u8(err, err)), 4)), 0);
-        if (special_bits != 0)
-        {
-            // errors up to the special byte count (an incomplete sequence
-            // before a quote shows at the quote); the bytes after it do not
-            const unsigned k = static_cast<unsigned>(count_trailing_zeros(special_bits)) >> 2u;
-            const std::uint64_t upto = k == 15 ? ~std::uint64_t{0} :
-                                       (std::uint64_t{1} << (4u * (k + 1u))) - 1u;
-            if ((err_bits & upto) == 0)
-            {
-                block_out = block + k;
-                return true;
-            }
-            break;
-        }
-        if (err_bits != 0)
-        {
-            break;
-        }
-        prev = in;
-        block += 16;
-    }
-#else
-    // the same with SSSE3 (pshufb for the table lookups; nibbles from 16-bit
-    // shifts, as there are no byte shifts)
-    const __m128i t1h = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(lookup::byte_1_high.data()))); // NOLINT(bugprone-casting-through-void)
-    const __m128i t1l = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(lookup::byte_1_low.data()))); // NOLINT(bugprone-casting-through-void)
-    const __m128i t2h = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(lookup::byte_2_high.data()))); // NOLINT(bugprone-casting-through-void)
-    const __m128i nibble = _mm_set1_epi8(0x0F);
-    const __m128i zero = _mm_setzero_si128();
-    __m128i prev = zero;
-    while (e - block >= 16)
-    {
-        const __m128i in = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(block))); // NOLINT(bugprone-casting-through-void)
-        const __m128i special = _mm_or_si128(_mm_or_si128(_mm_cmpeq_epi8(in, _mm_set1_epi8('"')), _mm_cmpeq_epi8(in, _mm_set1_epi8('\\'))),
-                                             _mm_cmpeq_epi8(_mm_subs_epu8(in, _mm_set1_epi8(0x1F)), zero)); // in < 0x20
-        const __m128i prev1 = _mm_alignr_epi8(in, prev, 15);
-        const __m128i sc = _mm_and_si128(_mm_and_si128(_mm_shuffle_epi8(t1h, _mm_and_si128(_mm_srli_epi16(prev1, 4), nibble)),
-                                         _mm_shuffle_epi8(t1l, _mm_and_si128(prev1, nibble))),
-                                         _mm_shuffle_epi8(t2h, _mm_and_si128(_mm_srli_epi16(in, 4), nibble)));
-        const __m128i must23 = _mm_or_si128(_mm_subs_epu8(_mm_alignr_epi8(in, prev, 14), _mm_set1_epi8(0xE0 - 0x80)),
-                                            _mm_subs_epu8(_mm_alignr_epi8(in, prev, 13), _mm_set1_epi8(0xF0 - 0x80)));
-        const __m128i err = _mm_xor_si128(_mm_and_si128(must23, _mm_set1_epi8(static_cast<char>(-128))), sc);
-        const auto special_bits = static_cast<unsigned>(_mm_movemask_epi8(special));
-        const auto err_bits = ~static_cast<unsigned>(_mm_movemask_epi8(_mm_cmpeq_epi8(err, zero))) & 0xFFFFu;
-        if (special_bits != 0)
-        {
-            const auto k = static_cast<unsigned>(count_trailing_zeros(static_cast<std::uint64_t>(special_bits)));
-            if ((err_bits & ((2u << k) - 1u)) == 0)
-            {
-                block_out = block + k;
-                return true;
-            }
-            break;
-        }
-        if (err_bits != 0)
-        {
-            break;
-        }
-        prev = in;
-        block += 16;
-    }
-#endif
-    block_out = block;
-    return false;
-}
-#endif
-
-}  // namespace detail
-NLOHMANN_JSON_NAMESPACE_END

include/nlohmann/detail/input/string_scan.hpp

@@ -14,7 +14,6 @@
 #include <cstring> // memcpy
 
 #include <nlohmann/detail/bit_ops.hpp>
-#include <nlohmann/detail/input/simd_scan.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 
 // Optional SIMD backend for bulk UTF-8 validation. This is an opt-in external
@@ -67,7 +66,7 @@ inline std::uint64_t swar_string_special(std::uint64_t v) noexcept
 
 // return the index of the first is_string_special() byte in [data, data+n), or
 // n if every byte is ordinary; scans 8 bytes at a time
-JSON_HEDLEY_ALWAYS_INLINE std::size_t find_string_special(const unsigned char* data, std::size_t n) noexcept
+inline std::size_t find_string_special(const unsigned char* data, std::size_t n) noexcept
 {
     std::size_t i = 0;
     for (; i + 8 <= n; i += 8)
@@ -236,136 +235,35 @@ inline std::size_t valid_utf8_prefix(const unsigned char* data, std::size_t n) n
     return pos;
 }
 
-#if JSON_SCAN_VECTOR_UTF8
-/// the end of scan_string_vector from block, where the vector loop stopped
-/// (ill-formed UTF-8, or fewer than 16 bytes left): one byte or sequence at a
-/// time, from the start of a sequence that crosses into the block
-inline const unsigned char* scan_string_finish(const unsigned char* p, const unsigned char* block, const unsigned char* e) noexcept
-{
-    for (int i = 1; i <= 3 && block - i >= p; ++i)
-    {
-        const unsigned char c = block[-i];
-        if (c < 0x80)
-        {
-            break;
-        }
-        if (c >= 0xC0)
-        {
-            const int len = 2 + static_cast<int>(c >= 0xE0) + static_cast<int>(c >= 0xF0);
-            if (len > i)
-            {
-                block -= i;
-            }
-            break;
-        }
-    }
-    for (p = block; p != e;)
-    {
-        if (*p < 0x80)
-        {
-            if (is_string_special(*p))
-            {
-                return p;
-            }
-            ++p;
-            continue;
-        }
-        const std::size_t n = validate_one_utf8(p, static_cast<std::size_t>(e - p));
-        if (n == 0)
-        {
-            return p;
-        }
-        p += n;
-    }
-    return p;
-}
-
-/// the rest of a string from p (a character boundary), with the vector UTF-8
-/// check and the scalar check for the end of the block where it stopped
-inline const unsigned char* scan_string_vector(const unsigned char* p, const unsigned char* e) noexcept
-{
-    const unsigned char* block = p;
-    if (vector_utf8_run(p, e, block))
-    {
-        return block;
-    }
-    return scan_string_finish(p, block, e);
-}
-#endif
-
-#if JSON_SCAN_VECTOR
-/// the end of the run of plain string characters at @a p: the first quote,
-/// backslash, control character, or non-ASCII byte, or @a e. The first words
-/// are checked with SWAR (one; four with NEON, where the vector mask costs
-/// more), as most keys and short values end there; longer runs continue 16
-/// bytes at a time.
-JSON_HEDLEY_ALWAYS_INLINE const unsigned char* plain_run_end(const unsigned char* p, const unsigned char* e) noexcept
-{
-    constexpr int prefix_words = JSON_SCAN_NEON ? 4 : 1;
-    for (int words = prefix_words; words > 0 && e - p >= 8; --words)
-    {
-        const std::uint64_t special = swar_string_special(read_eight_bytes(p));
-        if (special != 0)
-        {
-            return p + (static_cast<std::size_t>(count_trailing_zeros(special)) / 8);
-        }
-        p += 8;
-    }
-    p = vector_plain_run_long(p, e);
-    if (e - p < 16) // else the vector loop stopped at a special byte
-    {
-        p += find_string_special(p, static_cast<std::size_t>(e - p));
-    }
-    return p;
-}
-#endif
-
-// Computation of the bulk run length: the number of leading bytes in
-// [data, data+n) that are ordinary ASCII or complete well-formed UTF-8
+// Scalar (C++11) computation of the bulk run length: the number of leading
+// bytes in [data, data+n) that are ordinary ASCII or complete well-formed UTF-8
 // sequences, stopping before the first byte that needs individual handling (the
 // closing quote, an escape, a control character, or an ill-formed/truncated
-// sequence). ASCII is skipped 16 bytes at a time with SSE2 and 8 bytes at a
-// time otherwise; runs of non-ASCII text use the vector UTF-8 check where
-// available.
-JSON_HEDLEY_ALWAYS_INLINE std::size_t scalar_string_bulk_run(const unsigned char* data, std::size_t n) noexcept
+// sequence). ASCII is skipped 8 bytes at a time.
+inline std::size_t scalar_string_bulk_run(const unsigned char* data, std::size_t n) noexcept
 {
-    const unsigned char* const e = data + n;
-    const unsigned char* p = data;
-    while (p != e)
+    std::size_t pos = 0;
+    while (pos < n)
     {
-#if JSON_SCAN_VECTOR
-        p = plain_run_end(p, e);
-#else
-        p += find_string_special(p, static_cast<std::size_t>(e - p));
-#endif
-        if (p == e || *p < 0x80u)
+        pos += find_string_special(data + pos, n - pos);
+        if (pos >= n || data[pos] < 0x80u)
         {
             break; // end of buffer, or a quote/escape/control byte
         }
-#if JSON_SCAN_VECTOR_UTF8
-#if JSON_SCAN_SSSE3_DISPATCH
-        if (JSON_HEDLEY_LIKELY(cpu_has_ssse3()))
-#endif
-        {
-            return static_cast<std::size_t>(scan_string_vector(p, e) - data);
-        }
-#endif
-#if !JSON_SCAN_VECTOR_UTF8 || JSON_SCAN_SSSE3_DISPATCH
         // a run of multi-byte sequences (e.g. CJK text) is validated sequence
         // by sequence without searching for the next special byte in between
         do
         {
-            const std::size_t seq = validate_one_utf8(p, static_cast<std::size_t>(e - p));
+            const std::size_t seq = validate_one_utf8(data + pos, n - pos);
             if (seq == 0)
             {
-                return static_cast<std::size_t>(p - data); // ill-formed or truncated: let the byte path diagnose it
+                return pos; // ill-formed or truncated: let the byte path diagnose it
             }
-            p += seq;
+            pos += seq;
         }
-        while (p != e && *p >= 0x80u);
-#endif
+        while (pos < n && data[pos] >= 0x80u);
     }
-    return static_cast<std::size_t>(p - data);
+    return pos;
 }
 
 #if defined(JSON_USE_SIMDUTF) && defined(JSON_HAS_CPP_17)
@@ -406,7 +304,7 @@ inline std::size_t find_string_delimiter(const unsigned char* data, std::size_t
 // next delimiter is validated in one shot by simdutf; on the rare failure the
 // scalar helper recomputes the exact valid prefix so the byte path still
 // produces the precise diagnostic. Without it, the pure scalar path is used.
-JSON_HEDLEY_ALWAYS_INLINE std::size_t string_bulk_run(const unsigned char* data, std::size_t n) noexcept
+inline std::size_t string_bulk_run(const unsigned char* data, std::size_t n) noexcept
 {
 #if defined(JSON_USE_SIMDUTF) && defined(JSON_HAS_CPP_17)
     const std::size_t run = find_string_delimiter(data, n);

include/nlohmann/detail/macro_scope.hpp

@@ -199,6 +199,17 @@
     #define JSON_NO_UNIQUE_ADDRESS
 #endif
 
+// Inlines small functions even in unoptimized builds, so that they are not
+// emitted. The parsers for parse(), accept(), and from_*() use it for the
+// functions that stand in for the code recovering from errors (see #3989).
+// MSVC is left to decide, as it warns (C4714) where it does not inline a
+// __forceinline function.
+#if defined(_MSC_VER) && !defined(__clang__)
+    #define JSON_INTERNAL_ALWAYS_INLINE
+#else
+    #define JSON_INTERNAL_ALWAYS_INLINE JSON_HEDLEY_ALWAYS_INLINE
+#endif
+
 // Clang targeting MinGW does not survive the thread_local storage the copy
 // constructor uses to bound its descent: every test that copies a value
 // segfaults with clang 11.0.1 and clang 18.1.8, while the same tests pass with
@@ -895,11 +906,3 @@
 #ifndef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
     #define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION 0
 #endif
-
-#ifndef JSON_DISABLE_STREAM_BULK_SCAN
-    #define JSON_DISABLE_STREAM_BULK_SCAN 0
-#endif
-
-#ifndef JSON_DISABLE_UNLOCKED_FILE_IO
-    #define JSON_DISABLE_UNLOCKED_FILE_IO 0
-#endif

include/nlohmann/detail/macro_unscope.hpp

@@ -19,20 +19,11 @@
 #undef NLOHMANN_CAN_CALL_STD_FUNC_IMPL
 #undef JSON_INLINE_VARIABLE
 #undef JSON_NO_UNIQUE_ADDRESS
+#undef JSON_INTERNAL_ALWAYS_INLINE
 #undef JSON_DISABLE_ENUM_SERIALIZATION
 #undef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
-#undef JSON_DISABLE_STREAM_BULK_SCAN
-#undef JSON_DISABLE_UNLOCKED_FILE_IO
-#undef JSON_UNLOCKED_FILE_IO
 #undef JSON_DTOA_SSE2
 #undef JSON_DTOA_NEON
-#undef JSON_SCAN_NEON
-#undef JSON_SCAN_SSE2
-#undef JSON_SCAN_SSSE3
-#undef JSON_SCAN_SSSE3_DISPATCH
-#undef JSON_SCAN_SSSE3_TARGET
-#undef JSON_SCAN_VECTOR
-#undef JSON_SCAN_VECTOR_UTF8
 
 #ifndef JSON_TEST_KEEP_MACROS
     #undef JSON_CATCH

include/nlohmann/detail/string_utils.hpp

@@ -13,6 +13,7 @@
 #include <cstddef> // size_t
 #include <cstdint> // uint8_t, uint32_t
 #include <string> // string, to_string
+#include <utility> // move
 
 #include <nlohmann/detail/abi_macros.hpp>
 #include <nlohmann/detail/macro_scope.hpp>

include/nlohmann/json.hpp

@@ -154,7 +154,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     friend class ::nlohmann::detail::iter_impl;
     template<typename BasicJsonType, typename CharType, typename OutputSinkType>
     friend class ::nlohmann::detail::binary_writer;
-    template<typename BasicJsonType, typename InputType, typename SAX>
+    template<typename BasicJsonType, typename InputType, typename SAX, bool AllowRecovery>
     friend class ::nlohmann::detail::binary_reader;
     template<typename BasicJsonType, typename InputAdapterType>
     friend class ::nlohmann::detail::json_sax_dom_parser;
@@ -6112,7 +6112,7 @@ public:
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         return format == input_format_t::json
                ? parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict)
-               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(sax, strict, tag_handler);
+               : detail::binary_reader<basic_json, decltype(ia), SAX, true>(std::move(ia), format).sax_parse(sax, strict, tag_handler);
     }
 
     /// @brief generate SAX events (iterator pair, or iterator+sentinel pair for C++20 ranges support)
@@ -6130,7 +6130,7 @@ public:
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         return format == input_format_t::json
                ? parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict)
-               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(sax, strict, tag_handler);
+               : detail::binary_reader<basic_json, decltype(ia), SAX, true>(std::move(ia), format).sax_parse(sax, strict, tag_handler);
     }
 
     /// @brief generate SAX events
@@ -6169,7 +6169,7 @@ public:
                // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
                ? parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict)
                // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(sax, strict, tag_handler);
+               : detail::binary_reader<basic_json, decltype(ia), SAX, true>(std::move(ia), format).sax_parse(sax, strict, tag_handler);
     }
 #endif
 #if defined(__clang__)

src/modules/json.cppm

@@ -47,6 +47,7 @@ inline namespace json_literals
 namespace detail
 {
     using NLOHMANN_JSON_NAMESPACE::detail::json_sax_dom_callback_parser;
+    using NLOHMANN_JSON_NAMESPACE::detail::json_sax_dom_parser;
     using NLOHMANN_JSON_NAMESPACE::detail::unknown_size;
 } // namespace detail
 

tests/CMakeLists.txt

@@ -285,10 +285,6 @@ if (JSON_TestSimdutf)
     endif()
 endif()
 
-# test-file_input checks from a second thread that parsing from a FILE* releases the file's lock
-find_package(Threads REQUIRED)
-json_test_set_test_options("test-file_input;test-file_input_unlocked_io_disabled" LINK_LIBRARIES Threads::Threads)
-
 # *DO* use json_test_set_test_options() above this line
 
 json_test_should_build_32bit_test(json_32bit_test json_32bit_test_only "${JSON_32bitTest}")
@@ -373,52 +369,6 @@ json_test_add_test_for(src/unit-diagnostic-positions.cpp
     MAIN test_main CXX_STANDARDS ${test_cxx_standards} ${test_force}
 )
 
-# the lexer again with the portable string scanning instead of SSE2/NEON, and on
-# x86-64 with SSSE3 compiled in (no check of the CPU)
-json_test_set_test_options(test-class_lexer_no_simd
-    COMPILE_DEFINITIONS JSON_NO_SIMD
-)
-json_test_add_test_for(src/unit-class_lexer.cpp
-    NAME test-class_lexer_no_simd
-    MAIN test_main CXX_STANDARDS ${test_cxx_standards} ${test_force}
-)
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "^(x86_64|AMD64|amd64)$" AND NOT MSVC)
-    json_test_set_test_options(test-class_lexer_ssse3
-        COMPILE_OPTIONS -mssse3
-    )
-    json_test_add_test_for(src/unit-class_lexer.cpp
-        NAME test-class_lexer_ssse3
-        MAIN test_main CXX_STANDARDS ${test_cxx_standards} ${test_force}
-    )
-endif()
-
-# test reading from a std::istream again without scanning the get area in bulk
-json_test_set_test_options(test-stream-bulk-scan_disabled
-    COMPILE_DEFINITIONS JSON_DISABLE_STREAM_BULK_SCAN=1
-)
-json_test_add_test_for(src/unit-stream-bulk-scan.cpp
-    NAME test-stream-bulk-scan_disabled
-    MAIN test_main CXX_STANDARDS ${test_cxx_standards} ${test_force}
-)
-
-# test reading from a std::istream again with JSON_PRECISE_STREAM_POSITION
-json_test_set_test_options(test-stream-bulk-scan_precise
-    COMPILE_DEFINITIONS JSON_PRECISE_STREAM_POSITION=1
-)
-json_test_add_test_for(src/unit-stream-bulk-scan.cpp
-    NAME test-stream-bulk-scan_precise
-    MAIN test_main CXX_STANDARDS ${test_cxx_standards} ${test_force}
-)
-
-# test reading from a FILE* again with the locking stdio functions
-json_test_set_test_options(test-file_input_unlocked_io_disabled
-    COMPILE_DEFINITIONS JSON_DISABLE_UNLOCKED_FILE_IO=1
-)
-json_test_add_test_for(src/unit-file_input.cpp
-    NAME test-file_input_unlocked_io_disabled
-    MAIN test_main CXX_STANDARDS ${test_cxx_standards} ${test_force}
-)
-
 endif()
 
 # *DO NOT* use json_test_set_test_options() below this line

tests/benchmarks/src/benchmarks.cpp

@@ -8,13 +8,11 @@
 
 #include <benchmark/benchmark.h>
 #include <nlohmann/json.hpp>
-#include <array>
-#include <cstdio>
-#include <deque>
 #include <fstream>
+#include <array>
+#include <deque>
 #include <numeric>
 #include <set>
-#include <sstream>
 #include <vector>
 #include <test_data.hpp>
 
@@ -53,65 +51,6 @@ BENCHMARK_CAPTURE(ParseFile, signed_ints,       TEST_DATA_DIRECTORY "/regression
 BENCHMARK_CAPTURE(ParseFile, unsigned_ints,     TEST_DATA_DIRECTORY "/regression/unsigned_ints.json");
 BENCHMARK_CAPTURE(ParseFile, small_signed_ints, TEST_DATA_DIRECTORY "/regression/small_signed_ints.json");
 
-//////////////////////////////////////////////////////////////////////////////
-// parse JSON from a FILE*
-//////////////////////////////////////////////////////////////////////////////
-
-static void ParseFILE(benchmark::State& state, const char* filename)
-{
-    while (state.KeepRunning())
-    {
-        state.PauseTiming();
-        std::FILE* f = std::fopen(filename, "rb");
-        auto* j = new json();
-        state.ResumeTiming();
-
-        *j = json::parse(f);
-
-        state.PauseTiming();
-        std::fclose(f);
-        delete j;
-        state.ResumeTiming();
-    }
-
-    std::ifstream file(filename, std::ios::binary | std::ios::ate);
-    state.SetBytesProcessed(state.iterations() * file.tellg());
-}
-BENCHMARK_CAPTURE(ParseFILE, canada,       TEST_DATA_DIRECTORY "/nativejson-benchmark/canada.json");
-BENCHMARK_CAPTURE(ParseFILE, citm_catalog, TEST_DATA_DIRECTORY "/nativejson-benchmark/citm_catalog.json");
-BENCHMARK_CAPTURE(ParseFILE, twitter,      TEST_DATA_DIRECTORY "/nativejson-benchmark/twitter.json");
-
-//////////////////////////////////////////////////////////////////////////////
-// read many small values from one stream (NDJSON)
-//////////////////////////////////////////////////////////////////////////////
-
-static void ParseStreamValues(benchmark::State& state, bool numbers)
-{
-    std::string input;
-    for (int i = 0; i < 10000; ++i)
-    {
-        input += numbers ? std::to_string(i * 7919) + " "
-                 : R"({"id":)" + std::to_string(i) + R"(,"name":"user)" + std::to_string(i) + R"(","active":true,"score":)" + std::to_string(i * 0.25) + "}\n";
-    }
-
-    for (auto _ : state)
-    {
-        std::istringstream is(input);
-        json j;
-        std::size_t count = 0;
-        while (!(is >> std::ws).eof())
-        {
-            is >> j;
-            ++count;
-        }
-        benchmark::DoNotOptimize(count);
-    }
-
-    state.SetBytesProcessed(static_cast<int64_t>(state.iterations() * input.size()));
-}
-BENCHMARK_CAPTURE(ParseStreamValues, ndjson,  false);
-BENCHMARK_CAPTURE(ParseStreamValues, numbers, true);
-
 //////////////////////////////////////////////////////////////////////////////
 // parse JSON from string
 //////////////////////////////////////////////////////////////////////////////

tests/src/fuzzer-parse_bjdata.cpp

@@ -47,6 +47,10 @@ dumps is stable under exactly the same values that break operator==.
 The unit tests run the same checks on a fixed corpus (see the "BJData round-trip
 invariants" test case), so keep both in sync.
 
+Furthermore, it reads data with a SAX parser that recovers from every error
+and checks that the events are balanced, that reading ends, and that it
+reports an error exactly when from_bjdata() fails (see #3989).
+
 Finally, it reads the data from a stream, a non-contiguous iterator range, and
 a FILE*, which read byte by byte, and checks that each gives the same value or
 error (id, message, byte position) as the pointer range, which takes the bulk
@@ -57,6 +61,7 @@ drivers.
 */
 
 #include "fuzzer_common.hpp"
+#include "fuzzer-recovering_checker.hpp"
 
 namespace
 {
@@ -81,6 +86,9 @@ static bool is_value_stable(const json& lhs, const json& rhs)
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    // recover from all errors, reading from memory and from a stream
+    const bool recovered_without_errors = check_recovering_parse(data, size, json::input_format_t::bjdata).errors == 0;
+
     std::vector<uint8_t> const vec1(data, data + size);
 
     // step 0: parse input without exceptions
@@ -99,6 +107,9 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
         // without exceptions, the same input must give the same value
         assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
 
+        // the recovering parser must not have reported an error either
+        assert(recovered_without_errors);
+
         try
         {
             // step 2.1: round trip without adding size annotations to container types
@@ -132,6 +143,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     {
         // parse errors are ok, because input may be random bytes
         assert(parsed || noexcept_threw || j_noexcept.is_discarded());
+        assert(parsed || !recovered_without_errors);
     }
     catch (const json::type_error&)
     {
@@ -142,6 +154,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     {
         // out of range errors may happen if provided sizes are excessive
         assert(parsed || noexcept_threw || j_noexcept.is_discarded());
+        assert(parsed || !recovered_without_errors);
     }
 
     // step 3: the other input adapters must read the data alike

tests/src/fuzzer-parse_bon8.cpp

@@ -17,6 +17,10 @@ array data, it performs the following steps:
 - j2 = from_bon8(vec)
 - assert(to_bon8(j2) == vec)
 
+Furthermore, it reads data with a SAX parser that recovers from every error
+and checks that the events are balanced, that reading ends, and that it
+reports an error exactly when from_bon8() fails (see #3989).
+
 Finally, it reads the data from a stream, a non-contiguous iterator range, and
 a FILE*, which read byte by byte, and checks that each gives the same value or
 error (id, message, byte position) as the pointer range, which takes the bulk
@@ -27,6 +31,7 @@ drivers.
 */
 
 #include "fuzzer_common.hpp"
+#include "fuzzer-recovering_checker.hpp"
 
 namespace
 {
@@ -44,6 +49,9 @@ struct read_bon8
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    // recover from all errors, reading from memory and from a stream
+    const bool recovered_without_errors = check_recovering_parse(data, size, json::input_format_t::bon8).errors == 0;
+
     std::vector<uint8_t> const vec1(data, data + size);
 
     // step 0: parse input without exceptions
@@ -62,6 +70,9 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
         // without exceptions, the same input must give the same value
         assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
 
+        // the recovering parser must not have reported an error either
+        assert(recovered_without_errors);
+
         try
         {
             // step 2: round trip
@@ -83,6 +94,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     {
         // parse errors are ok, because input may be random bytes
         assert(parsed || noexcept_threw || j_noexcept.is_discarded());
+        assert(parsed || !recovered_without_errors);
     }
     catch (const json::type_error&)
     {
@@ -93,6 +105,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     {
         // out of range errors may happen if provided sizes are excessive
         assert(parsed || noexcept_threw || j_noexcept.is_discarded());
+        assert(parsed || !recovered_without_errors);
     }
 
     // step 3: the other input adapters must read the data alike

tests/src/fuzzer-parse_bson.cpp

@@ -17,6 +17,10 @@ array data, it performs the following steps:
 - j2 = from_bson(vec)
 - assert(to_bson(j2) == vec)
 
+Furthermore, it reads data with a SAX parser that recovers from every error
+and checks that the events are balanced, that reading ends, and that it
+reports an error exactly when from_bson() fails (see #3989).
+
 Finally, it reads the data from a stream, a non-contiguous iterator range, and
 a FILE*, which read byte by byte, and checks that each gives the same value or
 error (id, message, byte position) as the pointer range, which takes the bulk
@@ -27,6 +31,7 @@ drivers.
 */
 
 #include "fuzzer_common.hpp"
+#include "fuzzer-recovering_checker.hpp"
 
 namespace
 {
@@ -44,6 +49,9 @@ struct read_bson
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    // recover from all errors, reading from memory and from a stream
+    const bool recovered_without_errors = check_recovering_parse(data, size, json::input_format_t::bson).errors == 0;
+
     std::vector<uint8_t> const vec1(data, data + size);
 
     // step 0: parse input without exceptions
@@ -62,6 +70,9 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
         // without exceptions, the same input must give the same value
         assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
 
+        // the recovering parser must not have reported an error either
+        assert(recovered_without_errors);
+
         try
         {
             // step 2: round trip
@@ -83,6 +94,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     {
         // parse errors are ok, because input may be random bytes
         assert(parsed || noexcept_threw || j_noexcept.is_discarded());
+        assert(parsed || !recovered_without_errors);
     }
     catch (const json::type_error&)
     {
@@ -93,6 +105,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     {
         // out of range errors can occur during parsing, too
         assert(parsed || noexcept_threw || j_noexcept.is_discarded());
+        assert(parsed || !recovered_without_errors);
     }
 
     // step 3: the other input adapters must read the data alike

tests/src/fuzzer-parse_cbor.cpp

@@ -17,6 +17,10 @@ array data, it performs the following steps:
 - j2 = from_cbor(vec)
 - assert(to_cbor(j2) == vec)
 
+Furthermore, it reads data with a SAX parser that recovers from every error
+and checks that the events are balanced, that reading ends, and that it
+reports an error exactly when from_cbor() fails (see #3989).
+
 Finally, it reads the data from a stream, a non-contiguous iterator range, and
 a FILE*, which read byte by byte, and checks that each gives the same value or
 error (id, message, byte position) as the pointer range, which takes the bulk
@@ -27,6 +31,7 @@ drivers.
 */
 
 #include "fuzzer_common.hpp"
+#include "fuzzer-recovering_checker.hpp"
 
 namespace
 {
@@ -44,6 +49,9 @@ struct read_cbor
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    // recover from all errors, reading from memory and from a stream
+    const bool recovered_without_errors = check_recovering_parse(data, size, json::input_format_t::cbor).errors == 0;
+
     std::vector<uint8_t> const vec1(data, data + size);
 
     // step 0: parse input without exceptions
@@ -62,6 +70,9 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
         // without exceptions, the same input must give the same value
         assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
 
+        // the recovering parser must not have reported an error either
+        assert(recovered_without_errors);
+
         try
         {
             // step 2: round trip
@@ -83,6 +94,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     {
         // parse errors are ok, because input may be random bytes
         assert(parsed || noexcept_threw || j_noexcept.is_discarded());
+        assert(parsed || !recovered_without_errors);
     }
     catch (const json::type_error&)
     {
@@ -93,6 +105,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     {
         // out of range errors can occur during parsing, too
         assert(parsed || noexcept_threw || j_noexcept.is_discarded());
+        assert(parsed || !recovered_without_errors);
     }
 
     // step 3: the other input adapters must read the data alike

tests/src/fuzzer-parse_json.cpp

@@ -24,11 +24,16 @@ array data, it performs the following steps:
 The pointer range takes the bulk fast paths, the other input adapters read byte
 by byte; see check_input_adapters().
 
+Furthermore, it parses data with a SAX parser that recovers from every error
+and checks that the events are balanced, that parsing ends, and that valid
+input is parsed without errors (see #3989).
+
 The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
 #include "fuzzer_common.hpp"
+#include "fuzzer-recovering_checker.hpp"
 
 namespace
 {
@@ -59,6 +64,13 @@ struct accept_json
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    // recover from all errors, reading from memory and from a stream
+    {
+        const auto checker = check_recovering_parse(data, size, json::input_format_t::json);
+        assert(checker.events <= (4 * size) + 4);
+        assert((checker.errors == 0) == json::accept(data, data + size));
+    }
+
     // step 0: parse input without exceptions
     bool noexcept_threw = false;
     json const j_noexcept = parse_without_exceptions([&] { return json::parse(data, data + size, nullptr, false); }, noexcept_threw);

tests/src/fuzzer-parse_msgpack.cpp

@@ -17,6 +17,10 @@ array data, it performs the following steps:
 - j2 = from_msgpack(vec)
 - assert(to_msgpack(j2) == vec)
 
+Furthermore, it reads data with a SAX parser that recovers from every error
+and checks that the events are balanced, that reading ends, and that it
+reports an error exactly when from_msgpack() fails (see #3989).
+
 Finally, it reads the data from a stream, a non-contiguous iterator range, and
 a FILE*, which read byte by byte, and checks that each gives the same value or
 error (id, message, byte position) as the pointer range, which takes the bulk
@@ -27,6 +31,7 @@ drivers.
 */
 
 #include "fuzzer_common.hpp"
+#include "fuzzer-recovering_checker.hpp"
 
 namespace
 {
@@ -44,6 +49,9 @@ struct read_msgpack
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    // recover from all errors, reading from memory and from a stream
+    const bool recovered_without_errors = check_recovering_parse(data, size, json::input_format_t::msgpack).errors == 0;
+
     std::vector<uint8_t> const vec1(data, data + size);
 
     // step 0: parse input without exceptions
@@ -62,6 +70,9 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
         // without exceptions, the same input must give the same value
         assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
 
+        // the recovering parser must not have reported an error either
+        assert(recovered_without_errors);
+
         try
         {
             // step 2: round trip
@@ -83,6 +94,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     {
         // parse errors are ok, because input may be random bytes
         assert(parsed || noexcept_threw || j_noexcept.is_discarded());
+        assert(parsed || !recovered_without_errors);
     }
     catch (const json::type_error&)
     {
@@ -93,6 +105,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     {
         // out of range errors may happen if provided sizes are excessive
         assert(parsed || noexcept_threw || j_noexcept.is_discarded());
+        assert(parsed || !recovered_without_errors);
     }
 
     // step 3: the other input adapters must read the data alike

tests/src/fuzzer-parse_ubjson.cpp

@@ -26,6 +26,10 @@ array data, it performs the following steps:
 The unit tests run the same checks on a fixed corpus (see the "UBJSON round-trip
 invariants" test case), so keep both in sync.
 
+Furthermore, it reads data with a SAX parser that recovers from every error
+and checks that the events are balanced, that reading ends, and that it
+reports an error exactly when from_ubjson() fails (see #3989).
+
 Finally, it reads the data from a stream, a non-contiguous iterator range, and
 a FILE*, which read byte by byte, and checks that each gives the same value or
 error (id, message, byte position) as the pointer range, which takes the bulk
@@ -36,6 +40,7 @@ drivers.
 */
 
 #include "fuzzer_common.hpp"
+#include "fuzzer-recovering_checker.hpp"
 
 namespace
 {
@@ -53,6 +58,9 @@ struct read_ubjson
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    // recover from all errors, reading from memory and from a stream
+    const bool recovered_without_errors = check_recovering_parse(data, size, json::input_format_t::ubjson).errors == 0;
+
     std::vector<uint8_t> const vec1(data, data + size);
 
     // step 0: parse input without exceptions
@@ -71,6 +79,9 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
         // without exceptions, the same input must give the same value
         assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
 
+        // the recovering parser must not have reported an error either
+        assert(recovered_without_errors);
+
         try
         {
             // step 2.1: round trip without adding size annotations to container types
@@ -102,6 +113,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     {
         // parse errors are ok, because input may be random bytes
         assert(parsed || noexcept_threw || j_noexcept.is_discarded());
+        assert(parsed || !recovered_without_errors);
     }
     catch (const json::type_error&)
     {
@@ -112,6 +124,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     {
         // out of range errors may happen if provided sizes are excessive
         assert(parsed || noexcept_threw || j_noexcept.is_discarded());
+        assert(parsed || !recovered_without_errors);
     }
 
     // step 3: the other input adapters must read the data alike

tests/src/fuzzer-recovering_checker.hpp

@@ -0,0 +1,154 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <sstream>
+#include <string>
+#include <vector>
+#include <nlohmann/json.hpp>
+
+namespace
+{
+// a SAX parser that recovers from every error and checks that the events are
+// balanced and that every key is followed by exactly one value
+class recovering_checker : public nlohmann::json_sax<nlohmann::json>
+{
+  public:
+    bool null() override
+    {
+        return value();
+    }
+
+    bool boolean(bool /*val*/) override
+    {
+        return value();
+    }
+
+    bool number_integer(number_integer_t /*val*/) override
+    {
+        return value();
+    }
+
+    bool number_unsigned(number_unsigned_t /*val*/) override
+    {
+        return value();
+    }
+
+    bool number_float(number_float_t /*val*/, const string_t& /*s*/) override
+    {
+        return value();
+    }
+
+    bool string(string_t& /*val*/) override
+    {
+        return value();
+    }
+
+    bool binary(binary_t& /*val*/) override
+    {
+        return value();
+    }
+
+    bool start_object(std::size_t /*elements*/) override
+    {
+        value();
+        stack.push_back('o');
+        return true;
+    }
+
+    bool key(string_t& /*val*/) override
+    {
+        ++events;
+        assert(!stack.empty() && stack.back() == 'o');
+        stack.back() = 'v';
+        return true;
+    }
+
+    bool end_object() override
+    {
+        ++events;
+        assert(!stack.empty() && stack.back() == 'o');
+        stack.pop_back();
+        return true;
+    }
+
+    bool start_array(std::size_t /*elements*/) override
+    {
+        value();
+        stack.push_back('a');
+        return true;
+    }
+
+    bool end_array() override
+    {
+        ++events;
+        assert(!stack.empty() && stack.back() == 'a');
+        stack.pop_back();
+        return true;
+    }
+
+    bool parse_error(std::size_t /*position*/, const std::string& /*last_token*/, const nlohmann::detail::exception& /*ex*/) override
+    {
+        ++errors;
+        return true;
+    }
+
+    bool complete() const
+    {
+        return stack.empty();
+    }
+
+    std::size_t events = 0;
+    std::size_t errors = 0;
+
+  private:
+    bool value()
+    {
+        ++events;
+        if (!stack.empty())
+        {
+            // an array element, or the value of a key
+            assert(stack.back() != 'o');
+            if (stack.back() == 'v')
+            {
+                stack.back() = 'o';
+            }
+        }
+        return true;
+    }
+
+    // 'a' for an array, 'o' for an object that expects a key, 'v' for an
+    // object that expects the value of a key
+    std::vector<char> stack {}; // NOLINT(readability-redundant-member-init)
+};
+
+/// parses @a data with a recovering_checker from memory and from a stream,
+/// checks that both see the same, that the events are balanced, and that the
+/// number of errors is bounded, and returns the checker (see #3989)
+inline recovering_checker check_recovering_parse(const std::uint8_t* data, const std::size_t size, const nlohmann::json::input_format_t format)
+{
+    recovering_checker checker;
+    const bool ok = nlohmann::json::sax_parse(data, data + size, &checker, format);
+    assert(checker.complete());
+    assert(checker.errors <= size + 1);
+    assert(ok == (checker.errors == 0));
+
+    std::istringstream stream(std::string(reinterpret_cast<const char*>(data), size));
+    recovering_checker stream_checker;
+    assert(nlohmann::json::sax_parse(stream, &stream_checker, format) == ok);
+    assert(stream_checker.complete());
+    assert(stream_checker.events == checker.events);
+    assert(stream_checker.errors == checker.errors);
+
+    return checker;
+}
+} // namespace

tests/src/sax_event_loggers.hpp

@@ -131,11 +131,13 @@ struct SaxEventLogger : public nlohmann::json_sax<nlohmann::json>
     {
         errored = true;
         events.push_back("parse_error(" + std::to_string(position) + ")");
-        return false;
+        return recover;
     }
 
     std::vector<std::string> events {}; // NOLINT(readability-redundant-member-init)
     bool errored = false;
+    /// whether parse_error() asks the parser to recover from the error (see #3989)
+    bool recover = false;
 };
 
 struct SaxEventLoggerExitAfterStartObject : public SaxEventLogger

tests/src/unit-alt-string.cpp

@@ -415,6 +415,46 @@ TEST_CASE("alternative string type")
         CHECK(j2.dump() == R"({"/foo/0":"bar","/foo/1":"baz"})");
     }
 
+    SECTION("error recovery")
+    {
+        // a SAX parser that recovers from every error (see #3989)
+        struct recovering_parser : nlohmann::detail::json_sax_dom_parser<alt_json>
+        {
+            explicit recovering_parser(alt_json& j)
+                : nlohmann::detail::json_sax_dom_parser<alt_json>(j, false)
+            {}
+
+            // sax_parse() calls the SAX parser's own parse_error(), so hiding
+            // the one of the base class is what recovering takes
+            // NOLINTNEXTLINE(bugprone-derived-method-shadowing-base-method)
+            bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/, const nlohmann::detail::exception& /*unused*/)
+            {
+                ++errors;
+                return true;
+            }
+
+            std::size_t errors = 0;
+        };
+
+        alt_json j;
+        recovering_parser sax(j);
+        // not inside CHECK(): MSVC reads the escape in a stringized raw string
+        const std::string input = R"([1., "a\qb", tru, {"k" 2}])";
+        CHECK(!alt_json::sax_parse(input, &sax));
+        CHECK(sax.errors == 4);
+        CHECK(j.dump() == R"([1,"aqb",null,{"k":2}])");
+
+        // a UBJSON high-precision number, a CBOR key that is not a string
+        alt_json u;
+        recovering_parser ubjson_sax(u);
+        CHECK(!alt_json::sax_parse(std::vector<std::uint8_t> {'[', 'H', 'i', 2, '1', '.', ']'}, &ubjson_sax, alt_json::input_format_t::ubjson));
+        CHECK(u.dump() == "[1]");
+        alt_json c;
+        recovering_parser cbor_sax(c);
+        CHECK(!alt_json::sax_parse(std::vector<std::uint8_t> {0xA2, 0x01, 0x02, 0x61, 'a', 0x03}, &cbor_sax, alt_json::input_format_t::cbor));
+        CHECK(c.dump() == R"({"a":3})");
+    }
+
     SECTION("conversion between basic_json specializations (#2649)")
     {
         // explicit conversions are always possible

tests/src/unit-class_lexer.cpp

@@ -13,15 +13,11 @@
 using nlohmann::json;
 
 #include <array> // array
-#include <cctype> // toupper
 #include <cstdint> // uint32_t, uint64_t
 #include <cstdio> // snprintf
-#include <cmath> // isfinite
 #include <cstdlib> // strtod
 #include <cstring> // memcpy
 #include <limits> // numeric_limits
-#include <initializer_list> // initializer_list
-#include <list> // list
 #include <map> // map
 #include <random> // mt19937
 #include <sstream> // stringstream
@@ -336,109 +332,6 @@ TEST_CASE("lexer number fast path")
         }
     }
 
-    SECTION("digits accumulated while scanning")
-    {
-        // The fast path accumulates the digits while it validates them, eight
-        // at a time where possible, and converts tokens with at most 19
-        // digits (floats) or 18 digits (integers) from that value. Every digit
-        // count from 1 to 25, in the integer and in the fraction part, with
-        // and without sign and exponent, must give the byte path's result. A
-        // std::list has no contiguous storage, so parsing it takes the byte
-        // path.
-        // type and value, or the error (values beyond the range of double
-        // are rejected with out_of_range.406 on both paths)
-        const auto outcome = [](const std::string & doc, bool byte_path) -> std::string
-        {
-            JSON_TRY
-            {
-                const std::list<char> chars(doc.begin(), doc.end());
-                const json j = byte_path ? json::parse(chars.begin(), chars.end()) : json::parse(doc);
-                return std::string(j[0].type_name()) + '|' + j.dump();
-            }
-            JSON_CATCH (const json::exception & e)
-            {
-                return e.what();
-            }
-        };
-
-        // the concatenation of @a parts
-        const auto join = [](std::initializer_list<std::string> parts)
-        {
-            std::string result;
-            for (const auto& part : parts)
-            {
-                result += part;
-            }
-            return result;
-        };
-
-        std::vector<std::string> numbers;
-        for (std::size_t digits = 1; digits <= 25; ++digits)
-        {
-            std::string run;
-            for (std::size_t i = 0; i < digits; ++i)
-            {
-                run += static_cast<char>('1' + static_cast<char>((i * 7) % 9));
-            }
-            const std::string nines(digits, '9');
-            for (const char* sign_text :
-                    {"", "-"
-                    })
-            {
-                const std::string sign = sign_text;
-                numbers.push_back(join({sign, run}));
-                numbers.push_back(join({sign, nines}));
-                numbers.push_back(join({sign, "1", std::string(digits - 1, '0')}));
-                numbers.push_back(join({sign, "0.", run}));
-                numbers.push_back(join({sign, "0.", std::string(digits, '0'), "1"}));
-                numbers.push_back(join({sign, run, ".", run}));
-                numbers.push_back(join({sign, run, "e-", std::to_string(digits)}));
-                numbers.push_back(join({sign, "1.", run, "E+", std::to_string(digits * 13)}));
-            }
-        }
-        // exponents beyond every range, and zeros
-        numbers.insert(numbers.end(), {"1e400", "1e-400", "-1e99999999999999999999", "1e-99999999999999999999",
-                                       "0e99999999999999999999", "0.0e-5", "-0.000", "123456789e-0000000000000000000000330"
-                                      });
-
-        for (const auto& n : numbers)
-        {
-            CAPTURE(n)
-            const std::string doc = "[" + n + "]";
-            const std::string a = outcome(doc, false);
-            CHECK(a == outcome(doc, true));
-            const double expected = std::strtod(n.c_str(), nullptr);
-            if (a.compare(0, 6, "number") == 0 && std::isfinite(expected) && n.find_first_of(".eE") != std::string::npos)
-            {
-                CHECK(json::parse(doc)[0].get<double>() == expected);
-            }
-        }
-    }
-
-    SECTION("integers that do not fit a narrower type become floats")
-    {
-        // up to 18 digits, the fast path stores the accumulated value without
-        // an overflow check; a narrower number_integer_t/number_unsigned_t
-        // must still see the value rejected and converted as a float
-        using json32 = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int32_t, std::uint32_t, float>;
-        for (const char* n :
-                {"4294967295", "4294967296", "2147483647", "-2147483648", "-2147483649", "99999999999", "-99999999999"
-                })
-        {
-            CAPTURE(n)
-            const std::string doc = std::string("[") + n + "]";
-            const std::list<char> chars(doc.begin(), doc.end());
-            const json32 a = json32::parse(doc);
-            const json32 b = json32::parse(chars.begin(), chars.end());
-            CHECK(a[0].type() == b[0].type());
-            CHECK(a == b);
-        }
-        CHECK(json32::parse("[4294967295]")[0].is_number_unsigned());
-        CHECK(json32::parse("[4294967296]")[0].is_number_float());
-        CHECK(json32::parse("[-2147483648]")[0].is_number_integer());
-        CHECK(json32::parse("[-2147483649]")[0].is_number_float());
-    }
-
     SECTION("token type classification")
     {
         CHECK((scan_string("0") == json::lexer::token_type::value_unsigned));
@@ -597,63 +490,6 @@ TEST_CASE("lexer number fast path")
 #endif
 }
 
-TEST_CASE("lexer literal fast path")
-{
-    // For contiguous input, the rest of a literal is compared at once, and a
-    // mismatch is left to the byte path, which reports the error at the
-    // character that differs. Every truncation and every wrong character of
-    // each literal, at the end of the input or followed by more text, must
-    // give the byte path's result (a std::list is read one character at a
-    // time).
-    const auto outcome = [](const std::string & doc, bool byte_path) -> std::string
-    {
-        JSON_TRY
-        {
-            const std::list<char> chars(doc.begin(), doc.end());
-            return (byte_path ? json::parse(chars.begin(), chars.end()) : json::parse(doc)).dump();
-        }
-        JSON_CATCH (const json::exception & e)
-        {
-            return e.what();
-        }
-    };
-
-    std::vector<std::string> mismatches;
-    for (const std::string literal :
-            {"true", "false", "null"
-            })
-    {
-        std::vector<std::string> variants;
-        for (std::size_t length = 1; length <= literal.size(); ++length)
-        {
-            variants.push_back(literal.substr(0, length));
-        }
-        for (std::size_t i = 1; i < literal.size(); ++i)
-        {
-            std::string changed = literal;
-            changed[i] = 'X';
-            variants.push_back(changed);
-            changed[i] = static_cast<char>(std::toupper(static_cast<unsigned char>(literal[i])));
-            variants.push_back(changed);
-        }
-        for (const auto& variant : variants)
-        {
-            for (const std::string& doc :
-                    {
-                        variant, "[" + variant + "]", "[" + variant, variant + " ", variant + "1", "{\"k\":" + variant + "}"
-                    })
-            {
-                if (outcome(doc, false) != outcome(doc, true))
-                {
-                    mismatches.push_back(doc);
-                }
-            }
-        }
-    }
-    CAPTURE(mismatches)
-    CHECK(mismatches.empty());
-}
-
 TEST_CASE("lexer string fast path")
 {
     // Build a byte string from explicit values: a hex escape in a string
@@ -774,73 +610,6 @@ TEST_CASE("lexer string fast path")
         CAPTURE(mismatches)
         CHECK(mismatches.empty());
     }
-
-    SECTION("special bytes at every offset of the vector blocks")
-    {
-        // With SSE2 or NEON, runs are scanned 16 bytes at a time (after one
-        // SWAR word, or four with NEON), and runs of non-ASCII text are
-        // checked 16 bytes at a time as well. Place every kind of byte that
-        // ends a run at each offset across several blocks, after ASCII and
-        // after CJK text, so sequences also straddle the block boundaries.
-        // The reference is a std::list, which has no contiguous storage and
-        // is therefore read one character at a time.
-        const auto byte_path = [](const std::string & doc) -> std::string
-        {
-            const std::list<char> chars(doc.begin(), doc.end());
-            JSON_TRY
-            {
-                return json::parse(chars.begin(), chars.end()).dump();
-            }
-            JSON_CATCH (const json::exception & e)
-            {
-                return e.what();
-            }
-        };
-        const std::vector<std::string> specials =
-        {
-            "\"", "\\", "\\u00e9", bytes({0x01}), bytes({0x1F}), bytes({0x7F}),
-            bytes({0xC3, 0xA9}), bytes({0xE4, 0xB8, 0xAD}), bytes({0xF0, 0x9F, 0x98, 0x80}),
-            bytes({0xFF}), bytes({0xC3}), bytes({0xE4, 0xB8}), bytes({0xED, 0xA0, 0x80}), bytes({0xC0, 0x80})
-        };
-        const std::string cjk = bytes({0xE4, 0xB8, 0xAD}); // U+4E2D
-
-        std::vector<std::string> mismatches;
-        for (std::size_t offset = 0; offset <= 80; ++offset)
-        {
-            std::string text;
-            while (text.size() < offset)
-            {
-                text += cjk;
-            }
-            for (const auto& prefix :
-                    {
-                        std::string(offset, 'a'), text
-                    })
-            {
-                for (const auto& special : specials)
-                {
-                    // the closing quote right behind, or in a later block
-                    for (const int tail :
-                            {
-                                0, 1, 3, 20
-                            })
-                    {
-                        std::string doc = "[\"";
-                        doc += prefix;
-                        doc += special;
-                        doc.append(static_cast<std::size_t>(tail), 'b');
-                        doc += "\"]";
-                        if (outcome(doc, false) != byte_path(doc))
-                        {
-                            mismatches.push_back(doc);
-                        }
-                    }
-                }
-            }
-        }
-        CAPTURE(mismatches)
-        CHECK(mismatches.empty());
-    }
 #endif
 
     // json::accept() never throws, so the ranges stay covered without exceptions

tests/src/unit-class_parser.cpp

@@ -30,9 +30,7 @@ using nlohmann::json;
 #include <valarray>
 #include <algorithm>
 #include <cstdio>
-#include <cstdint>
 #include <fstream>
-#include <iterator>
 #include <list>
 #include <sstream>
 #include <string>
@@ -2452,79 +2450,6 @@ std::string parse_error_message_range(IteratorType first, IteratorType last)
 }
 } // namespace
 
-TEST_CASE("text of float tokens")
-{
-    // For contiguous input, the lexer copies the text of a float token into
-    // its buffer only when a SAX handler asks for it (the library's own
-    // handlers do not). A user handler must still see the exact text, for
-    // every input adapter and in every position of a document.
-    const std::string doc = R"([1.5, -0.0, 0.1, 1e5, -2.5E-4, 12345678901234567890.5, 0.12345678901234567890123,
-                              {"a": 3.25, "b": [6.02e23, 1]}, "x", true, 7e-1])";
-    const std::vector<std::string> expected_floats =
-    {
-        "number_float(1.5)", "number_float(-0.0)", "number_float(0.1)", "number_float(1e5)", "number_float(-2.5E-4)",
-        "number_float(12345678901234567890.5)", "number_float(0.12345678901234567890123)", "number_float(3.25)",
-        "number_float(6.02e23)", "number_float(7e-1)"
-    };
-
-    const auto floats = [](const std::vector<std::string>& events)
-    {
-        std::vector<std::string> result;
-        std::copy_if(events.begin(), events.end(), std::back_inserter(result), [](const std::string & e)
-        {
-            return e.compare(0, 13, "number_float(") == 0;
-        });
-        return result;
-    };
-
-    SECTION("contiguous input")
-    {
-        SaxEventLogger l;
-        CHECK(json::sax_parse(doc, &l));
-        CHECK(floats(l.events) == expected_floats);
-    }
-
-    SECTION("byte input")
-    {
-        const std::vector<std::uint8_t> bytes(doc.begin(), doc.end());
-        SaxEventLogger l;
-        CHECK(json::sax_parse(bytes, &l));
-        CHECK(floats(l.events) == expected_floats);
-    }
-
-    SECTION("stream input")
-    {
-        std::istringstream is(doc);
-        SaxEventLogger l;
-        CHECK(json::sax_parse(is, &l));
-        CHECK(floats(l.events) == expected_floats);
-    }
-
-    SECTION("non-contiguous iterators")
-    {
-        const std::list<char> chars(doc.begin(), doc.end());
-        SaxEventLogger l;
-        CHECK(json::sax_parse(chars.begin(), chars.end(), &l));
-        CHECK(floats(l.events) == expected_floats);
-    }
-
-    SECTION("the library's own handlers do not need the text")
-    {
-        using lexer_adapter = nlohmann::detail::iterator_input_adapter<const char*>;
-        CHECK(nlohmann::detail::sax_ignores_number_text<nlohmann::detail::json_sax_dom_parser<json, lexer_adapter>>::value);
-        CHECK(nlohmann::detail::sax_ignores_number_text<nlohmann::detail::json_sax_dom_callback_parser<json, lexer_adapter>>::value);
-        CHECK(nlohmann::detail::sax_ignores_number_text<nlohmann::detail::json_sax_acceptor<json>>::value);
-        CHECK_FALSE(nlohmann::detail::sax_ignores_number_text<SaxEventLogger>::value);
-
-        // and the values are the same as when the text is read
-        const json j = json::parse(doc);
-        CHECK(j[0] == 1.5);
-        CHECK(j[5].get<double>() == 12345678901234567890.5);
-        CHECK(j[7]["b"][0] == 6.02e23);
-        CHECK(json::accept(doc));
-    }
-}
-
 TEST_CASE("last-read diagnostics are identical across input adapters")
 {
     // The lexer reconstructs the "last read" token lazily for seekable adapters
@@ -2922,3 +2847,648 @@ TEST_CASE("diagnostic positions: value lifetime, input adapters, and SAX")
     }
 }
 #endif
+
+namespace
+{
+/// builds a value like json::parse(), but asks the parser to recover from
+/// errors (see #3989), and checks that the events it receives are balanced
+class RecoveringDomParser
+{
+  public:
+    explicit RecoveringDomParser(json& j, std::size_t max_errors_ = static_cast<std::size_t>(-1))
+        : dom(j, false)
+        , max_errors(max_errors_)
+    {}
+
+    bool null()
+    {
+        value();
+        return dom.null();
+    }
+
+    bool boolean(bool val)
+    {
+        value();
+        return dom.boolean(val);
+    }
+
+    bool number_integer(json::number_integer_t val)
+    {
+        value();
+        return dom.number_integer(val);
+    }
+
+    bool number_unsigned(json::number_unsigned_t val)
+    {
+        value();
+        return dom.number_unsigned(val);
+    }
+
+    bool number_float(json::number_float_t val, const std::string& s)
+    {
+        value();
+        return dom.number_float(val, s);
+    }
+
+    bool string(std::string& val)
+    {
+        value();
+        return dom.string(val);
+    }
+
+    bool binary(json::binary_t& val)
+    {
+        value();
+        return dom.binary(val);
+    }
+
+    bool start_object(std::size_t elements)
+    {
+        value();
+        stack.push_back('o');
+        return dom.start_object(elements);
+    }
+
+    bool key(std::string& val)
+    {
+        ++events;
+        if (stack.empty() || stack.back() != 'o')
+        {
+            well_formed = false;
+            return false;
+        }
+        stack.back() = 'v';
+        return dom.key(val);
+    }
+
+    bool end_object()
+    {
+        ++events;
+        if (stack.empty() || stack.back() != 'o')
+        {
+            well_formed = false;
+            return false;
+        }
+        stack.pop_back();
+        return dom.end_object();
+    }
+
+    bool start_array(std::size_t elements)
+    {
+        value();
+        stack.push_back('a');
+        return dom.start_array(elements);
+    }
+
+    bool end_array()
+    {
+        ++events;
+        if (stack.empty() || stack.back() != 'a')
+        {
+            well_formed = false;
+            return false;
+        }
+        stack.pop_back();
+        return dom.end_array();
+    }
+
+    bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/, const json::exception& ex)
+    {
+        errors.emplace_back(ex.what());
+        return errors.size() < max_errors;
+    }
+
+    /// whether the events were balanced and every key was followed by a value
+    bool balanced() const
+    {
+        return well_formed && stack.empty();
+    }
+
+    /// builds the value
+    nlohmann::detail::json_sax_dom_parser<json> dom;
+    std::vector<std::string> errors {}; // NOLINT(readability-redundant-member-init)
+    std::size_t events = 0;
+    /// the open containers: 'a' for an array, 'o' for an object that expects
+    /// a key, 'v' for an object that expects the value of a key
+    std::vector<char> stack {}; // NOLINT(readability-redundant-member-init)
+    bool well_formed = true;
+    std::size_t max_errors;
+
+  private:
+    /// a value is passed: it is an array element, or the value of a key
+    void value()
+    {
+        ++events;
+        if (!stack.empty())
+        {
+            if (stack.back() == 'v')
+            {
+                stack.back() = 'o';
+            }
+            else if (stack.back() == 'o')
+            {
+                // a value without a key
+                well_formed = false;
+            }
+        }
+    }
+
+};
+
+struct RecoveryResult
+{
+    json value;
+    std::vector<std::string> errors;
+    std::size_t events;
+    bool ok;
+    bool balanced;
+};
+
+template<typename InputType>
+RecoveryResult parse_recovering(InputType&& input, const bool strict = true,
+                                const bool ignore_comments = false, const bool ignore_trailing_commas = false)
+{
+    json j;
+    RecoveringDomParser sax(j);
+    const bool ok = json::sax_parse(std::forward<InputType>(input), &sax, json::input_format_t::json,
+                                    strict, ignore_comments, ignore_trailing_commas);
+    return {j, sax.errors, sax.events, ok, sax.balanced()};
+}
+
+/// stops after a number of events, but recovers from errors
+class RecoveringCountdown
+{
+  public:
+    explicit RecoveringCountdown(const int count)
+        : countdown(count)
+    {}
+
+    bool null()
+    {
+        return countdown.null();
+    }
+
+    bool boolean(bool val)
+    {
+        return countdown.boolean(val);
+    }
+
+    bool number_integer(json::number_integer_t val)
+    {
+        return countdown.number_integer(val);
+    }
+
+    bool number_unsigned(json::number_unsigned_t val)
+    {
+        return countdown.number_unsigned(val);
+    }
+
+    bool number_float(json::number_float_t val, const std::string& s)
+    {
+        return countdown.number_float(val, s);
+    }
+
+    bool string(std::string& val)
+    {
+        return countdown.string(val);
+    }
+
+    bool binary(json::binary_t& val)
+    {
+        return countdown.binary(val);
+    }
+
+    bool start_object(std::size_t elements)
+    {
+        return countdown.start_object(elements);
+    }
+
+    bool key(std::string& val)
+    {
+        return countdown.key(val);
+    }
+
+    bool end_object()
+    {
+        return countdown.end_object();
+    }
+
+    bool start_array(std::size_t elements)
+    {
+        return countdown.start_array(elements);
+    }
+
+    bool end_array()
+    {
+        return countdown.end_array();
+    }
+
+    bool parse_error(std::size_t /*position*/, const std::string& /*last_token*/, const json::exception& /*ex*/) // NOLINT(readability-convert-member-functions-to-static)
+    {
+        return true;
+    }
+
+  private:
+    SaxCountdown countdown;
+};
+
+/// a repaired input: the value it is repaired to, and the number of errors
+struct Repair
+{
+    const char* input;
+    const char* expected;
+    std::size_t errors;
+};
+} // namespace
+
+TEST_CASE("parser error recovery (#3989)")
+{
+    SECTION("repairs")
+    {
+        const std::vector<Repair> repairs =
+        {
+            // a missing separator is inserted
+            {"[1 2]", "[1,2]", 1},
+            {R"({"a":1 "b":2})", R"({"a":1,"b":2})", 1},
+            {R"({"a" 1})", R"({"a":1})", 1},
+            {"[1 tru 2]", "[1,null,2]", 2},
+            {R"({"a" "b": 1})", R"({"a":"b"})", 2},
+
+            // a missing value is null in an object; in an array, a ',' stands
+            // for null, while an array that ends there just ends
+            {R"({"a":})", R"({"a":null})", 1},
+            {R"({"a"})", R"({"a":null})", 1},
+            {R"({"a","b":1})", R"({"a":null,"b":1})", 1},
+            {"[1,,2]", "[1,null,2]", 1},
+            {"[,1]", "[null,1]", 1},
+            {"[1,]", "[1]", 1},
+            {"[1,2,3,]", "[1,2,3]", 1},
+            {R"({"a":1,})", R"({"a":1})", 1},
+
+            // a broken string keeps what can be read
+            {R"(["a\qb"])", R"(["aqb"])", 1},
+            {R"({"na\me":1})", R"({"name":1})", 1},
+            {"[\"\xFF\"]", R"(["\uFFFD"])", 1},
+            {"[\"a\xC3(\"]", R"(["a\uFFFD("])", 1},
+            {"[\"\xE2\x82\"]", R"(["\uFFFD"])", 1},
+            {"[\"\xC3\\\\\", 1]", R"(["\uFFFD\\",1])", 1},
+            {R"(["\u12"])", R"(["\uFFFD"])", 1},
+            {R"(["\u12G4"])", R"(["\uFFFDG4"])", 1},
+            {R"(["\uDC00x"])", R"(["\uFFFDx"])", 1},
+            {R"(["\uD800x"])", R"(["\uFFFDx"])", 1},
+            {R"(["\uD800\u0041"])", R"(["\uFFFDA"])", 1},
+            {R"(["\uD800\uD800\uDC00"])", R"(["\uFFFD\uD800\uDC00"])", 1},
+            {R"(["\uD800\uD800\uD800x"])", R"(["\uFFFD\uFFFD\uFFFDx"])", 1},
+            {
+                R"(["\uD800\"x", 1])", R"(["\uFFFD\"x",1])", 1
+            },
+            {R"(["\uD800\q"])", R"(["\uFFFDq"])", 1},
+            {"[\"a\tb\"]", R"(["a\tb"])", 1},
+            {R"(["a\qb\u0041\x"])", R"(["aqbAx"])", 1},
+
+            // a broken number keeps its longest valid prefix
+            {"[1.]", "[1]", 1},
+            {"[-2.]", "[-2]", 1},
+            {"[1.5e]", "[1.5]", 1},
+            {"[1e+]", "[1]", 1},
+            {"[1.x2, 3]", "[1,3]", 1},
+
+            // what cannot be read at all is null
+            {"[1,NaN,3]", "[1,null,3]", 1},
+            {"[tru]", "[null]", 1},
+            {"[-]", "[null]", 1},
+            {R"({"a":Infinity})", R"({"a":null})", 1},
+
+            // a stray token is dropped
+            {"[:1]", "[1]", 1},
+            {R"(["a":1])", R"(["a",1])", 1},
+            {R"({"a"::1})", R"({"a":1})", 1},
+
+            // a member that cannot be read is skipped
+            {R"({1:2,"b":3})", R"({"b":3})", 1},
+            {R"({"a":1 2})", R"({"a":1})", 1},
+            {R"({,"a":1})", R"({"a":1})", 1},
+            {R"({"a":1,,"b":2})", R"({"a":1,"b":2})", 1},
+            {"{a:1}", "{}", 1},
+            {R"({"a":1 [1,{"b":2}], "c":3})", R"({"a":1,"c":3})", 1},
+            {R"([{1}, "a"])", R"([{},"a"])", 1},
+
+            // a wrong closing bracket closes the innermost container
+            {R"({"a":[1,2}, "b":3})", R"({"a":[1,2],"b":3})", 1},
+            {R"([{"a":1], 2])", R"([{"a":1},2])", 1},
+            {"{]", "{}", 1},
+            {"[}", "[]", 1},
+
+            // the end of the input closes all containers
+            {R"({"a":[1,2)", R"({"a":[1,2]})", 1},
+            {"[", "[]", 1},
+            {"{", "{}", 1},
+            {R"({"a")", R"({"a":null})", 1},
+            {R"({"a":)", R"({"a":null})", 1},
+            {"[1,", "[1]", 1},
+            {"[[[1", "[[[1]]]", 1},
+            {
+                R"(["abc)", R"(["abc"])", 2
+            },
+            {"[1,tr", "[1,null]", 2},
+            {"\"abc", "\"abc\"", 1},
+            {"[\"ab\ncd\"]", R"(["ab",null,"]"])", 4},
+
+            // what comes before the top-level value is skipped
+            {")]}'\n{\"a\":1}", R"({"a":1})", 1},
+            {R"(data: {"a":1})", R"({"a":1})", 1},
+            {"\xEF\xBB[1]", "[1]", 1},
+
+            // what comes after it is an error that ends parsing
+            {R"({"a":1}})", R"({"a":1})", 1},
+            {"[1}]", "[1]", 2},
+            {"[1] [2]", "[1]", 1},
+        };
+
+        for (const auto& repair : repairs)
+        {
+            CAPTURE(repair.input)
+            const auto result = parse_recovering(std::string(repair.input));
+            CHECK(!result.ok);
+            CHECK(result.balanced);
+            CHECK(result.value == json::parse(repair.expected));
+            CHECK(result.errors.size() == repair.errors);
+        }
+    }
+
+    SECTION("number overflow")
+    {
+        const auto result = parse_recovering(std::string("[1e999,-1e999]"));
+        CHECK(!result.ok);
+        CHECK(result.balanced);
+        CHECK(result.errors.size() == 2);
+        CHECK(result.errors[0] == "[json.exception.out_of_range.406] number overflow parsing '1e999'");
+        REQUIRE(result.value.size() == 2);
+        CHECK(result.value[0].is_number_float());
+        CHECK(result.value[0].get<double>() == std::numeric_limits<double>::infinity());
+        CHECK(result.value[1].get<double>() == -std::numeric_limits<double>::infinity());
+
+        // the SAX parser gets the number's text
+        SaxEventLogger logger;
+        logger.recover = true;
+        CHECK(!json::sax_parse("1e999", &logger));
+        CHECK(logger.events == std::vector<std::string>({"parse_error(5)", "number_float(1e999)"}));
+    }
+
+    SECTION("nothing to recover")
+    {
+        for (const std::string s :
+                {
+                    "", "   ", "]", "tru", "NaN", ",:", "/* comment"
+                })
+        {
+            CAPTURE(s)
+            const auto result = parse_recovering(s, true, true);
+            CHECK(!result.ok);
+            CHECK(result.balanced);
+            CHECK(result.events == 0);
+            CHECK(result.value == nullptr);
+            CHECK(result.errors.size() == 1);
+        }
+    }
+
+    SECTION("error messages")
+    {
+        // the first error is reported as without recovery
+        for (const std::string s :
+                {
+                    "[1 2]", R"({"a":1 "b":2})", R"({"a" 1})", R"({"a":})", "[1,]", "[1.]",
+                    R"(["a\qb"])", "[1e999]", "{1:2}", R"({"a":[1,2}})", "[1,", "[1] [2]", "{a:1}"
+                })
+        {
+            CAPTURE(s)
+            const auto result = parse_recovering(s);
+            REQUIRE(!result.errors.empty());
+            json _;
+            CHECK_THROWS_WITH_STD_STR(_ = json::parse(s), result.errors.front());
+        }
+
+        // the token of an error begins where the previous error was
+        const auto result = parse_recovering(std::string("[tru, fals, nul]"));
+        CHECK(result.errors == std::vector<std::string>(
+        {
+            "[json.exception.parse_error.101] parse error at line 1, column 5: syntax error while parsing value - invalid literal; last read: '[tru,'",
+            "[json.exception.parse_error.101] parse error at line 1, column 11: syntax error while parsing value - invalid literal; last read: ', fals,'",
+            "[json.exception.parse_error.101] parse error at line 1, column 16: syntax error while parsing value - invalid literal; last read: ', nul]'"
+        }));
+        CHECK(result.value == json::parse("[null,null,null]"));
+    }
+
+    SECTION("events")
+    {
+        // see #4522
+        SaxEventLogger logger;
+        logger.recover = true;
+        CHECK(!json::sax_parse(R"([{1}, "a"])", &logger));
+        CHECK(logger.events == std::vector<std::string>(
+        {
+            "start_array()", "start_object()", "parse_error(3)", "end_object()", "string(a)", "end_array()"
+        }));
+    }
+
+    SECTION("options")
+    {
+        SECTION("strict")
+        {
+            const auto result = parse_recovering(std::string("[1 2] [3]"), false);
+            CHECK(!result.ok);
+            CHECK(result.value == json::parse("[1,2]"));
+            CHECK(result.errors.size() == 1);
+        }
+
+        SECTION("ignore_trailing_commas")
+        {
+            for (const std::string s :
+                    {
+                        "[1,]", R"({"a":1,})", "[[1,],]"
+                    })
+            {
+                CAPTURE(s)
+                const auto result = parse_recovering(s, true, false, true);
+                CHECK(result.ok);
+                CHECK(result.errors.empty());
+            }
+
+            auto result = parse_recovering(std::string("[1,,]"), true, false, true);
+            CHECK(result.value == json::parse("[1,null]"));
+            CHECK(result.errors.size() == 1);
+
+            result = parse_recovering(std::string(R"({"a":1,,})"), true, false, true);
+            CHECK(result.value == json::parse(R"({"a":1})"));
+            CHECK(result.errors.size() == 1);
+        }
+
+        SECTION("ignore_comments")
+        {
+            auto result = parse_recovering(std::string("[1 /* one */ 2]"), true, true);
+            CHECK(result.value == json::parse("[1,2]"));
+            CHECK(result.errors.size() == 1);
+
+            // a comment that is not closed runs to the end of the input, which
+            // is not reported again
+            result = parse_recovering(std::string("[1, 2 /* unterminated"), true, true);
+            CHECK(result.balanced);
+            CHECK(result.value == json::parse("[1,2]"));
+            CHECK(result.errors.size() == 1);
+
+            // a '/' that does not begin a comment is garbage
+            result = parse_recovering(std::string("[1, /x, 2]"), true, true);
+            CHECK(result.balanced);
+            CHECK(result.value == json::parse("[1,null,2]"));
+            CHECK(result.errors.size() == 1);
+        }
+    }
+
+    SECTION("null bytes")
+    {
+        // a null byte ends the input, unless JSON_STRICT_NUL_HANDLING is set
+        const auto result = parse_recovering(std::string("[1,\0x", 5));
+        CHECK(result.balanced);
+        CHECK(!result.ok);
+#ifdef JSON_TEST_STRICT_NUL_HANDLING_ENABLED
+        CHECK(result.value == json::parse("[1,null]"));
+#else
+        CHECK(result.value == json::parse("[1]"));
+        CHECK(result.errors.size() == 1);
+#endif
+
+        const auto in_string = parse_recovering(std::string("[\"a\0b\"]", 7));
+        CHECK(in_string.balanced);
+#ifdef JSON_TEST_STRICT_NUL_HANDLING_ENABLED
+        CHECK(in_string.value == json::array({std::string("a\0b", 3)}));
+#else
+        CHECK(in_string.value == json::parse(R"(["a"])"));
+#endif
+    }
+
+    SECTION("the SAX parser stops recovering")
+    {
+        json j;
+        RecoveringDomParser sax(j, 2);
+        CHECK(!json::sax_parse("[1 2 3 4 5]", &sax));
+        CHECK(sax.errors.size() == 2);
+
+        // an error at a delimiter that an invalid token consumed is reported
+        // to the SAX parser, too
+        json j2;
+        RecoveringDomParser sax2(j2, 2);
+        CHECK(!json::sax_parse("[tru}, 1]", &sax2));
+        CHECK(sax2.errors.size() == 2);
+    }
+
+    SECTION("an event stops parsing during a repair")
+    {
+        // start_object() and key() are passed, then null() for the missing
+        // value returns false
+        RecoveringCountdown countdown(2);
+        CHECK(!json::sax_parse(R"({"a":})", &countdown));
+
+        // the end of the input: end_array() for the second array returns false
+        RecoveringCountdown countdown2(4);
+        CHECK(!json::sax_parse("[[1", &countdown2));
+    }
+
+    SECTION("input adapters")
+    {
+        // the lexer reads contiguous and streaming input differently, and it
+        // puts back a character that ended an invalid token
+        for (const std::string s :
+                {
+                    "[1 2]", "[tru}, 1]", R"({"a" "b\q", "c":[1.x, 2}})", "[\"\xFF\xC3(\", -, 1e+]", "{a:1,\"b\":2", ")]}' [1]"
+                })
+        {
+            CAPTURE(s)
+            const auto reference = parse_recovering(s);
+            CHECK(reference.balanced);
+
+            const auto from_c_string = parse_recovering(s.c_str());
+            CHECK(from_c_string.value == reference.value);
+            CHECK(from_c_string.errors == reference.errors);
+
+            const std::list<char> l(s.begin(), s.end());
+            json j;
+            RecoveringDomParser sax(j);
+            CHECK(!json::sax_parse(l.begin(), l.end(), &sax));
+            CHECK(j == reference.value);
+            CHECK(sax.errors == reference.errors);
+
+            std::istringstream ss(s);
+            const auto from_stream = parse_recovering(ss);
+            CHECK(from_stream.value == reference.value);
+            CHECK(from_stream.errors == reference.errors);
+        }
+    }
+
+    SECTION("long runs of errors")
+    {
+        // no error may copy all the input read before it
+        const auto closing = parse_recovering("[" + std::string(100000, '}'));
+        CHECK(closing.balanced);
+        CHECK(closing.value == json::array());
+
+        const auto garbage = parse_recovering("[" + std::string(100000, 'x') + "]");
+        CHECK(garbage.balanced);
+        CHECK(garbage.errors.size() == 1);
+
+        const auto commas = parse_recovering("{" + std::string(100000, ',') + "}");
+        CHECK(commas.balanced);
+        CHECK(commas.value == json::object());
+    }
+
+    SECTION("mutations of valid input")
+    {
+        // whatever the input, the events are balanced, every error is reported
+        // at most once, and valid input is parsed as usual
+        const std::vector<std::string> documents =
+        {
+            R"({"name": "value", "list": [1, -2.5, true, null, {"x": [[]]}], "e": "\u00e9"})",
+            R"([{"a": [1, 2, {"b": "c"}]}, [], {}, "\ud83d\ude00", 1e10])",
+            "{\"\xC3\xA9\": \"\xF0\x9F\x98\x80\"}",
+            R"(  {"k" : [ "v" , 0 ] }  )",
+        };
+        // each character that can be inserted, including a null byte
+        const std::string insertions("[]{},:\"x\\\0\xFF", 11);
+
+        std::vector<std::string> inputs;
+        for (const auto& doc : documents)
+        {
+            for (std::size_t i = 0; i <= doc.size(); ++i)
+            {
+                inputs.push_back(doc.substr(0, i));
+                if (i < doc.size())
+                {
+                    inputs.push_back(doc.substr(0, i) + doc.substr(i + 1));
+                }
+                for (const char c : insertions)
+                {
+                    inputs.push_back(doc.substr(0, i) + c + doc.substr(i));
+                }
+            }
+        }
+
+        for (const auto& s : inputs)
+        {
+            CAPTURE(s)
+            const auto result = parse_recovering(s);
+            CHECK(result.balanced);
+            CHECK(result.errors.size() <= s.size() + 1);
+            CHECK(result.events <= (4 * s.size()) + 4);
+            if (json::accept(s))
+            {
+                CHECK(result.ok);
+                CHECK(result.errors.empty());
+                CHECK(result.value == json::parse(s));
+            }
+            else
+            {
+                CHECK(!result.ok);
+                CHECK(!result.errors.empty());
+            }
+        }
+    }
+}

tests/src/unit-file_input.cpp

@@ -1,236 +0,0 @@
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-#include "doctest_compatibility.h"
-
-#include <nlohmann/json.hpp>
-using nlohmann::json;
-
-#include <array>
-#include <cstdint>
-#include <cstdio>
-#include <fstream>
-#include <memory>
-#include <random>
-#include <string>
-#include <thread>
-#include <vector>
-
-// Parsing from a FILE* locks the file once and reads it with the unlocked
-// stdio functions (see JSON_DISABLE_UNLOCKED_FILE_IO). These tests pin that
-// this is not observable: the results are the same, the file is unlocked
-// again when parsing ends - also with an exception - and the same thread can
-// keep using the file while it is locked, e.g., from a SAX callback.
-
-namespace
-{
-// a file name of its own for every run: the test runs for several C++
-// standards and configurations at the same time, in the same directory
-std::string temp_file_name()
-{
-    std::random_device rd;
-    return "unit-file_input-" + std::to_string(rd()) + ".tmp";
-}
-
-using file_ptr = std::unique_ptr<std::FILE, int (*)(std::FILE*)>;
-
-// write @a content to the file @a name and open it for reading
-file_ptr open_with(const char* name, const std::string& content)
-{
-    {
-        std::ofstream file(name, std::ios::binary);
-        file << content;
-    }
-    return {std::fopen(name, "rb"), &std::fclose};
-}
-
-// The stdio lock is recursive, so whether parsing released it can only be
-// seen from another thread: ftrylockfile() fails there while this thread
-// holds the lock. ftrylockfile() is POSIX; elsewhere, the check is skipped.
-#if defined(__GLIBC__) || defined(__APPLE__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__)
-void check_unlocked(std::FILE* f)
-{
-    int result = -1;
-    std::thread other([f, &result]
-    {
-        result = ftrylockfile(f);
-        if (result == 0)
-        {
-            funlockfile(f);
-        }
-    });
-    other.join();
-    CHECK(result == 0);
-}
-#else
-void check_unlocked(std::FILE* /*f*/) {}
-#endif
-
-// SAX consumer that also reads the position of the file it is parsing, which
-// takes the file's lock again on the same thread
-class position_reading_sax : public nlohmann::json_sax<json>
-{
-  public:
-    explicit position_reading_sax(std::FILE* f) : m_file(f) {}
-    position_reading_sax(const position_reading_sax&) = delete;
-    position_reading_sax(position_reading_sax&&) = delete;
-    position_reading_sax& operator=(const position_reading_sax&) = delete;
-    position_reading_sax& operator=(position_reading_sax&&) = delete;
-    ~position_reading_sax() override = default;
-
-    bool null() override
-    {
-        return record();
-    }
-    bool boolean(bool /*val*/) override
-    {
-        return record();
-    }
-    bool number_integer(number_integer_t /*val*/) override
-    {
-        return record();
-    }
-    bool number_unsigned(number_unsigned_t /*val*/) override
-    {
-        return record();
-    }
-    bool number_float(number_float_t /*val*/, const string_t& /*s*/) override
-    {
-        return record();
-    }
-    bool string(string_t& /*val*/) override
-    {
-        return record();
-    }
-    bool binary(binary_t& /*val*/) override
-    {
-        return record();
-    }
-    bool start_object(std::size_t /*elements*/) override
-    {
-        return record();
-    }
-    bool key(string_t& /*val*/) override
-    {
-        return record();
-    }
-    bool end_object() override
-    {
-        return record();
-    }
-    bool start_array(std::size_t /*elements*/) override
-    {
-        return record();
-    }
-    bool end_array() override
-    {
-        return record();
-    }
-    bool parse_error(std::size_t /*position*/, const std::string& /*last_token*/, const nlohmann::detail::exception& /*ex*/) override
-    {
-        return false;
-    }
-
-    const std::vector<long>& positions() const
-    {
-        return m_positions;
-    }
-
-  private:
-    bool record()
-    {
-        m_positions.push_back(std::ftell(m_file));
-        return true;
-    }
-
-    std::FILE* m_file;
-    std::vector<long> m_positions{}; // NOLINT(readability-redundant-member-init)
-};
-}  // namespace
-
-TEST_CASE("parsing from a FILE*")
-{
-    const std::string temp_name = temp_file_name();
-    const char* const name = temp_name.c_str();
-    const std::string input = "{\"a\": [1, -2.5, \"three\", true, null], \"b\": {\"c\": \"caf\xc3\xa9\"}}";
-
-    SECTION("values are the same as when parsing from a string")
-    {
-        const file_ptr f = open_with(name, input);
-        REQUIRE(f != nullptr);
-        CHECK(json::parse(f.get()) == json::parse(input));
-        // the whole input was consumed
-        std::array<char, 8> rest{};
-        CHECK(std::fgets(rest.data(), static_cast<int>(rest.size()), f.get()) == nullptr);
-        check_unlocked(f.get());
-    }
-
-    SECTION("the file is unlocked after a parse error")
-    {
-        const file_ptr f = open_with(name, "[1, 2, x]");
-        REQUIRE(f != nullptr);
-        json _;
-        CHECK_THROWS_WITH_AS(_ = json::parse(f.get()),
-                             "[json.exception.parse_error.101] parse error at line 1, column 8: syntax error while parsing value - invalid literal; last read: '2, x'",
-                             json::parse_error&);
-        check_unlocked(f.get());
-
-        // the file is still usable: the rest of the input is there
-        std::array<char, 8> rest{};
-        CHECK(std::fgets(rest.data(), static_cast<int>(rest.size()), f.get()) != nullptr);
-        CHECK(std::string(rest.data()) == "]");
-    }
-
-    SECTION("the file can be parsed again and read with stdio afterwards")
-    {
-        const file_ptr f = open_with(name, "[1] [2] tail");
-        REQUIRE(f != nullptr);
-
-        // sax_parse with strict == false stops after the first value; an array
-        // ends with its closing bracket, so the space after it is not read
-        json j;
-        nlohmann::detail::json_sax_dom_parser<json, nlohmann::detail::string_input_adapter_type> sax1(j);
-        CHECK(json::sax_parse(f.get(), &sax1, json::input_format_t::json, false));
-        CHECK(j == json({1}));
-        check_unlocked(f.get());
-
-        json k;
-        nlohmann::detail::json_sax_dom_parser<json, nlohmann::detail::string_input_adapter_type> sax2(k);
-        CHECK(json::sax_parse(f.get(), &sax2, json::input_format_t::json, false));
-        CHECK(k == json({2}));
-        check_unlocked(f.get());
-
-        std::array<char, 8> rest{};
-        CHECK(std::fgets(rest.data(), static_cast<int>(rest.size()), f.get()) != nullptr);
-        CHECK(std::string(rest.data()) == " tail");
-    }
-
-    SECTION("the same thread can use the file while it is parsed")
-    {
-        const file_ptr f = open_with(name, "[10, 20, 30]");
-        REQUIRE(f != nullptr);
-        position_reading_sax sax(f.get());
-        CHECK(json::sax_parse(f.get(), &sax));
-        // start_array, three numbers, end_array
-        CHECK(sax.positions().size() == 5);
-        CHECK(sax.positions().front() == 1);
-        check_unlocked(f.get());
-    }
-
-    SECTION("binary formats read from a FILE*")
-    {
-        const json j = {{"string", std::string(300, 'x')}, {"array", {1, 2, 3}}, {"number", 1.5}};
-        const std::vector<std::uint8_t> cbor = json::to_cbor(j);
-        const file_ptr f = open_with(name, std::string(reinterpret_cast<const char*>(cbor.data()), cbor.size()));
-        REQUIRE(f != nullptr);
-        CHECK(json::from_cbor(f.get()) == j);
-        check_unlocked(f.get());
-    }
-
-    static_cast<void>(std::remove(name));
-}

tests/src/unit-msgpack.cpp

@@ -31,8 +31,6 @@ using nlohmann::json;
 #include "make_test_data_available.hpp"
 #include "round_trip_corpus.hpp"
 #include "test_utils.hpp"
-#include "sax_countdown.hpp"
-using utils::SaxCountdown;
 
 
 TEST_CASE("MessagePack")
@@ -1645,30 +1643,6 @@ TEST_CASE("MessagePack")
             }
         }
     }
-
-    SECTION("SAX aborts")
-    {
-        SECTION("start_array(len)")
-        {
-            std::vector<uint8_t> const v = {0x93, 0x01, 0x02, 0x03};
-            SaxCountdown scp(0);
-            CHECK(!json::sax_parse(v, &scp, json::input_format_t::msgpack));
-        }
-
-        SECTION("start_object(len)")
-        {
-            std::vector<uint8_t> const v = {0x81, 0xa3, 0x66, 0x6F, 0x6F, 0xc2};
-            SaxCountdown scp(0);
-            CHECK(!json::sax_parse(v, &scp, json::input_format_t::msgpack));
-        }
-
-        SECTION("key()")
-        {
-            std::vector<uint8_t> const v = {0x81, 0xa3, 0x66, 0x6F, 0x6F, 0xc2};
-            SaxCountdown scp(1);
-            CHECK(!json::sax_parse(v, &scp, json::input_format_t::msgpack));
-        }
-    }
 }
 
 TEST_CASE("issue #5405 - array reserve for definite-length MessagePack arrays")
@@ -1739,21 +1713,6 @@ TEST_CASE("issue #5405 - array reserve for definite-length MessagePack arrays")
             CHECK(json::from_msgpack(packed) == j);
         }
     }
-
-    SECTION("a user-defined SAX consumer is unaffected by the internal DOM reserve optimization")
-    {
-        // the reserve() call is local to json_sax_dom_parser / json_sax_dom_callback_parser;
-        // a custom SAX consumer that does not touch a DOM array sees identical events
-        json j = json::array();
-        for (int i = 0; i < 100; ++i)
-        {
-            j.push_back(i);
-        }
-        const auto packed = json::to_msgpack(j);
-
-        SaxCountdown scp(1000000); // large enough to never trigger an abort
-        CHECK(json::sax_parse(packed, &scp, json::input_format_t::msgpack));
-    }
 }
 
 TEST_CASE("regression test - MessagePack ext type rejects a subtype that doesn't fit a single byte")
@@ -1792,15 +1751,6 @@ TEST_CASE("MessagePack nesting does not consume the call stack")
         CHECK(json::from_msgpack(input, true, false).is_discarded());
     }
 
-    SECTION("a well-formed deep value is read through the SAX interface")
-    {
-        std::vector<uint8_t> input(300000, 0x91);
-        input.push_back(0x01); // innermost value
-
-        SaxCountdown accept_all(600001);
-        CHECK(json::sax_parse(input, &accept_all, json::input_format_t::msgpack));
-    }
-
     SECTION("a well-formed deep value is read into a value")
     {
         const std::size_t depth = 10000;
@@ -1848,31 +1798,6 @@ TEST_CASE("MessagePack input that cannot be read is discarded by every overload"
 #endif
 }
 
-TEST_CASE("MessagePack SAX parsing stops at every event")
-{
-    // Containers are opened and closed by the loop that reads them; a SAX
-    // handler that rejects any event - including the end of a nested
-    // container - must stop the parse right there.
-    const auto count_events = [](const std::vector<std::uint8_t>& input)
-    {
-        int events = 0;
-        while (true)
-        {
-            SaxCountdown scp(events);
-            if (json::sax_parse(input, &scp, json::input_format_t::msgpack))
-            {
-                return events;
-            }
-            ++events;
-            REQUIRE(events < 1000);
-        }
-    };
-
-    // 20 events: every container kind closes inside another one
-    const json j = json::parse(R"({"a": [1, {"b": []}], "c": {"d": [[2]]}})");
-    CHECK(count_events(json::to_msgpack(j)) == 20);
-}
-
 TEST_CASE("single MessagePack roundtrip")
 {
     SECTION("sample.json")

tests/src/unit-precise-stream-position.cpp

@@ -20,7 +20,6 @@
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 
-#include <algorithm>
 #include <cstddef>
 #include <sstream>
 #include <streambuf>
@@ -73,40 +72,6 @@ class no_putback_streambuf : public std::streambuf
     std::size_t m_pos = 0;
 };
 
-// A streambuf that serves its input in get areas of a fixed size, so that the
-// end of a number falls on every possible offset of a get area. The lexer scans
-// the get area directly; the stream position must not depend on its size.
-class chunked_streambuf : public std::streambuf
-{
-  public:
-    chunked_streambuf(std::string s, std::size_t chunk_size)
-        : m_data(std::move(s)), m_chunk_size(chunk_size)
-    {}
-
-  protected:
-    int_type underflow() override
-    {
-        if (gptr() < egptr())
-        {
-            return traits_type::to_int_type(*gptr());
-        }
-        m_pos += static_cast<std::size_t>(egptr() - eback());
-        if (m_pos >= m_data.size())
-        {
-            setg(nullptr, nullptr, nullptr);
-            return traits_type::eof();
-        }
-        char* const begin = &m_data[m_pos];
-        setg(begin, begin, begin + (std::min)(m_chunk_size, m_data.size() - m_pos));
-        return traits_type::to_int_type(*gptr());
-    }
-
-  private:
-    std::string m_data;
-    std::size_t m_pos = 0;
-    std::size_t m_chunk_size;
-};
-
 // read the characters that are left in a stream
 std::string remaining(std::istream& is)
 {
@@ -298,26 +263,4 @@ TEST_CASE("JSON_PRECISE_STREAM_POSITION")
         json _;
         CHECK_THROWS_WITH_AS(_ = json::parse(is), "[json.exception.parse_error.101] parse error: attempting to parse an empty input; check that your input string or stream contains the expected JSON", json::parse_error&);
     }
-
-    SECTION("the position does not depend on the get area of the streambuf")
-    {
-        const std::vector<std::size_t> chunk_sizes = {1, 2, 3, 4, 5, 7, 8, 13, 4096};
-        for (const std::size_t chunk_size : chunk_sizes)
-        {
-            CAPTURE(chunk_size)
-            chunked_streambuf buf("12345678901234567890true\"a long string value\"-1.25e+3,[1,2]42", chunk_size);
-            std::istream input(&buf);
-            json j;
-
-            input >> j;
-            CHECK(j == 12345678901234567890u);
-            input >> j;
-            CHECK(j == true);
-            input >> j;
-            CHECK(j == "a long string value");
-            input >> j;
-            CHECK(j == -1250.0);
-            CHECK(remaining(input) == ",[1,2]42");
-        }
-    }
 }

tests/src/unit-regression3.cpp

@@ -22,14 +22,6 @@
 // scoped enum, so get<std::byte>() (needed below to get<std::vector<std::byte>>()
 // from a plain JSON array, not just from an already-binary value) relies on
 // enum serialization being enabled
-// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
-// line *before* including json.hpp, since the library #undefs it once the header
-// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
-// tests of deprecated functions are skipped if these functions are deleted
-#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
-    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-#endif
-
 #if defined(JSON_DISABLE_ENUM_SERIALIZATION) && (JSON_DISABLE_ENUM_SERIALIZATION == 1)
     #define SKIP_TESTS_FOR_ENUM_SERIALIZATION
 #endif
@@ -811,50 +803,6 @@ TEST_CASE("issue #5338 - truncated CBOR tagged binary subtype is rejected")
     }
 }
 
-TEST_CASE("issue #5676 - SAX parsing of CBOR tags")
-{
-    const json expected = json::binary({1, 2, 3}, 42);
-    const auto cbor = json::to_cbor(expected);
-
-    nlohmann::detail::json_sax_acceptor<json> acceptor;
-    CHECK_FALSE(json::sax_parse(cbor, &acceptor, json::input_format_t::cbor));
-    CHECK_FALSE(json::sax_parse(cbor, &acceptor, json::input_format_t::cbor,
-                                true, false, false, json::cbor_tag_handler_t::error));
-
-    CHECK(json::sax_parse(cbor, &acceptor, json::input_format_t::cbor,
-                          true, false, false, json::cbor_tag_handler_t::ignore));
-
-    json parsed;
-    nlohmann::detail::json_sax_dom_parser<json, nlohmann::detail::string_input_adapter_type> sax(parsed);
-    CHECK(json::sax_parse(cbor, &sax, json::input_format_t::cbor,
-                          true, false, false, json::cbor_tag_handler_t::store));
-    CHECK(parsed == expected);
-
-    json iterator_parsed;
-    nlohmann::detail::json_sax_dom_parser<json, nlohmann::detail::string_input_adapter_type> iterator_sax(iterator_parsed);
-    CHECK(json::sax_parse(cbor.begin(), cbor.end(), &iterator_sax, json::input_format_t::cbor,
-                          true, false, false, json::cbor_tag_handler_t::store));
-    CHECK(iterator_parsed == expected);
-
-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-    json span_parsed;
-    nlohmann::detail::json_sax_dom_parser<json, nlohmann::detail::string_input_adapter_type> span_sax(span_parsed);
-    CHECK(json::sax_parse(nlohmann::detail::span_input_adapter(cbor.data(), cbor.size()), &span_sax,
-                          json::input_format_t::cbor, true, false, false, json::cbor_tag_handler_t::store));
-    CHECK(span_parsed == expected);
-#endif
-
-    const std::string text = "null";
-    CHECK(json::sax_parse(text, &acceptor, json::input_format_t::json,
-                          true, false, false, json::cbor_tag_handler_t::store));
-    CHECK(json::sax_parse(text.begin(), text.end(), &acceptor, json::input_format_t::json,
-                          true, false, false, json::cbor_tag_handler_t::store));
-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-    CHECK(json::sax_parse(nlohmann::detail::span_input_adapter(text.data(), text.size()), &acceptor,
-                          json::input_format_t::json, true, false, false, json::cbor_tag_handler_t::store));
-#endif
-}
-
 TEST_CASE("issue #5402 - update(merge_objects=true) overwrites a primitive with an object")
 {
     json t = {{"k", 1}};

tests/src/unit-sax_parse.cpp

@@ -0,0 +1,768 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+/////////////////////////////////////////////////////////////////////
+// Tests that call basic_json::sax_parse have a file of their own: every
+// sax_parse call instantiates the parser and binary reader that recover from
+// errors (see #3989), and in unit-regression2.cpp, unit-regression3.cpp, and
+// unit-msgpack.cpp this made the objects too large for the MinGW linker to
+// relocate (see #5511).
+/////////////////////////////////////////////////////////////////////
+
+#include "doctest_compatibility.h"
+
+// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
+// line *before* including json.hpp, since the library #undefs it once the header
+// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
+// tests of deprecated functions are skipped if these functions are deleted
+#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
+    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
+#endif
+
+#include <nlohmann/json.hpp>
+using json = nlohmann::json;
+
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <initializer_list>
+#include <map>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "sax_countdown.hpp"
+using utils::SaxCountdown;
+
+// a narrow number_float_t, so that a double read from binary input can
+// overflow it
+using float_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, float>;
+
+DOCTEST_CLANG_SUPPRESS_WARNING_PUSH
+DOCTEST_CLANG_SUPPRESS_WARNING("-Wexit-time-destructors")
+
+namespace
+{
+/// builds a value from SAX events, asks the parser to recover from its first
+/// 100 errors, and checks that the events are balanced (see #3989)
+template<typename BasicJsonType>
+class BasicRecoveringParser
+{
+  public:
+    explicit BasicRecoveringParser(BasicJsonType& j)
+        : dom(j, false)
+    {}
+
+    bool null()
+    {
+        value();
+        return dom.null();
+    }
+
+    bool boolean(bool val)
+    {
+        value();
+        return dom.boolean(val);
+    }
+
+    bool number_integer(typename BasicJsonType::number_integer_t val)
+    {
+        value();
+        return dom.number_integer(val);
+    }
+
+    bool number_unsigned(typename BasicJsonType::number_unsigned_t val)
+    {
+        value();
+        return dom.number_unsigned(val);
+    }
+
+    bool number_float(typename BasicJsonType::number_float_t val, const std::string& s)
+    {
+        value();
+        return dom.number_float(val, s);
+    }
+
+    bool string(std::string& val)
+    {
+        value();
+        return dom.string(val);
+    }
+
+    bool binary(typename BasicJsonType::binary_t& val)
+    {
+        value();
+        return dom.binary(val);
+    }
+
+    bool start_object(std::size_t elements)
+    {
+        value();
+        stack.push_back('o');
+        return dom.start_object(elements);
+    }
+
+    bool key(std::string& val)
+    {
+        if (stack.empty() || stack.back() != 'o')
+        {
+            well_formed = false;
+            return false;
+        }
+        stack.back() = 'v';
+        return dom.key(val);
+    }
+
+    bool end_object()
+    {
+        if (stack.empty() || stack.back() != 'o')
+        {
+            well_formed = false;
+            return false;
+        }
+        stack.pop_back();
+        return dom.end_object();
+    }
+
+    bool start_array(std::size_t elements)
+    {
+        value();
+        stack.push_back('a');
+        return dom.start_array(elements);
+    }
+
+    bool end_array()
+    {
+        if (stack.empty() || stack.back() != 'a')
+        {
+            well_formed = false;
+            return false;
+        }
+        stack.pop_back();
+        return dom.end_array();
+    }
+
+    bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/, const json::exception& ex)
+    {
+        messages.emplace_back(ex.what());
+        // a limit, so that a reader that does not stop fails the test
+        // instead of making it hang
+        return ++errors < 100;
+    }
+
+    /// whether the events were balanced and every key was followed by a value
+    bool balanced() const
+    {
+        return well_formed && stack.empty();
+    }
+
+    /// builds the value
+    nlohmann::detail::json_sax_dom_parser<BasicJsonType> dom;
+    std::size_t errors = 0;
+    std::vector<std::string> messages {}; // NOLINT(readability-redundant-member-init)
+    std::vector<char> stack {}; // NOLINT(readability-redundant-member-init)
+    bool well_formed = true;
+
+  private:
+    void value()
+    {
+        if (!stack.empty())
+        {
+            if (stack.back() == 'v')
+            {
+                stack.back() = 'o';
+            }
+            else if (stack.back() == 'o')
+            {
+                well_formed = false;
+            }
+        }
+    }
+
+};
+
+using RecoveringParser = BasicRecoveringParser<json>;
+
+struct BinaryParseResult
+{
+    json value;
+    std::size_t errors;
+    std::vector<std::string> messages;
+    bool ok;
+    bool balanced;
+};
+
+BinaryParseResult parse_binary_recovering(const std::vector<std::uint8_t>& input, const json::input_format_t format)
+{
+    json j;
+    RecoveringParser sax(j);
+    const bool ok = json::sax_parse(input, &sax, format);
+    return {j, sax.errors, sax.messages, ok, sax.balanced()};
+}
+
+#if !defined(JSON_NOEXCEPTION)
+/// the message of the exception that reading @a input into a JSON value
+/// throws, or an empty string if reading succeeds
+std::string binary_error_message(const std::vector<std::uint8_t>& input, const json::input_format_t format)
+{
+    try
+    {
+        json _;
+        switch (format)
+        {
+            case json::input_format_t::cbor:
+                _ = json::from_cbor(input);
+                break;
+            case json::input_format_t::msgpack:
+                _ = json::from_msgpack(input);
+                break;
+            case json::input_format_t::ubjson:
+                _ = json::from_ubjson(input);
+                break;
+            case json::input_format_t::bjdata:
+                _ = json::from_bjdata(input);
+                break;
+            case json::input_format_t::bson:
+                _ = json::from_bson(input);
+                break;
+            case json::input_format_t::bon8:
+                _ = json::from_bon8(input);
+                break;
+            case json::input_format_t::json:
+            default:
+                break;
+        }
+    }
+    catch (const json::exception& e)
+    {
+        return e.what();
+    }
+    return "";
+}
+#endif
+
+/// a BSON element: its type, its name, and its value
+std::vector<std::uint8_t> bson_element(const std::uint8_t type, const std::string& name, const std::vector<std::uint8_t>& value)
+{
+    std::vector<std::uint8_t> result = {type};
+    result.insert(result.end(), name.begin(), name.end());
+    result.push_back(0x00);
+    result.insert(result.end(), value.begin(), value.end());
+    return result;
+}
+
+/// a BSON document of the given elements; @a size_offset is added to the
+/// size it declares
+std::vector<std::uint8_t> bson_document(const std::vector<std::vector<std::uint8_t>>& elements, const int size_offset = 0)
+{
+    std::vector<std::uint8_t> body;
+    for (const auto& element : elements)
+    {
+        body.insert(body.end(), element.begin(), element.end());
+    }
+    const auto size = static_cast<std::uint32_t>(static_cast<int>(body.size()) + 5 + size_offset);
+    std::vector<std::uint8_t> result = {static_cast<std::uint8_t>(size & 0xFFu), static_cast<std::uint8_t>((size >> 8u) & 0xFFu),
+                                        static_cast<std::uint8_t>((size >> 16u) & 0xFFu), static_cast<std::uint8_t>((size >> 24u) & 0xFFu)
+                                       };
+    result.insert(result.end(), body.begin(), body.end());
+    result.push_back(0x00);
+    return result;
+}
+
+/// a BSON int32 value
+std::vector<std::uint8_t> bson_int32(const std::int32_t value)
+{
+    const auto u = static_cast<std::uint32_t>(value);
+    return {static_cast<std::uint8_t>(u & 0xFFu), static_cast<std::uint8_t>((u >> 8u) & 0xFFu),
+            static_cast<std::uint8_t>((u >> 16u) & 0xFFu), static_cast<std::uint8_t>((u >> 24u) & 0xFFu)};
+}
+
+/// a BSON string value, whose length is @a length_offset off
+std::vector<std::uint8_t> bson_string(const std::string& value, const std::int32_t length_offset = 0)
+{
+    auto result = bson_int32(static_cast<std::int32_t>(value.size() + 1) + length_offset);
+    result.insert(result.end(), value.begin(), value.end());
+    result.push_back(0x00);
+    return result;
+}
+
+/// @a count bytes of value 0xAB
+std::vector<std::uint8_t> bytes(const std::size_t count)
+{
+    return std::vector<std::uint8_t>(count, 0xAB);
+}
+
+/// the bytes of @a parts, one after the other
+std::vector<std::uint8_t> concatenated(std::initializer_list<std::vector<std::uint8_t>> parts)
+{
+    std::vector<std::uint8_t> result;
+    for (const auto& part : parts)
+    {
+        result.insert(result.end(), part.begin(), part.end());
+    }
+    return result;
+}
+
+/// U+FFFD REPLACEMENT CHARACTER
+std::string replacement_character()
+{
+    return "\xEF\xBF\xBD";
+}
+}  // namespace
+
+TEST_CASE("regression test - #3989 SAX parse_error() returning true")
+{
+    SECTION("binary formats complete what was read before the input ends")
+    {
+        const json j = {{"a", {1, -2, {{"b", "c"}}, json::array()}}, {"d", {{"e", nullptr}, {"f", true}}}, {"g", 1.5}, {"h", json::binary({1, 2, 3})}};
+
+        const std::vector<std::pair<json::input_format_t, std::vector<std::uint8_t>>> encodings =
+        {
+            {json::input_format_t::cbor, json::to_cbor(j)},
+            {json::input_format_t::msgpack, json::to_msgpack(j)},
+            {json::input_format_t::ubjson, json::to_ubjson(j)},
+            {json::input_format_t::ubjson, json::to_ubjson(j, true, true)},
+            {json::input_format_t::bjdata, json::to_bjdata(j)},
+            {json::input_format_t::bjdata, json::to_bjdata(j, true, true)},
+            {json::input_format_t::bson, json::to_bson(j)},
+            {json::input_format_t::bon8, json::to_bon8(j)},
+        };
+
+        for (const auto& encoding : encodings)
+        {
+            const auto format = encoding.first;
+            const auto& bytes = encoding.second;
+            CAPTURE(format)
+
+            // every prefix is truncated input
+            for (std::size_t length = 0; length < bytes.size(); ++length)
+            {
+                CAPTURE(length)
+                const auto result = parse_binary_recovering(std::vector<std::uint8_t>(bytes.begin(), bytes.begin() + static_cast<std::ptrdiff_t>(length)), format);
+                CHECK(!result.ok);
+                CHECK(result.errors == 1);
+                CHECK(result.balanced);
+            }
+
+            // the complete input is read as usual (binary values do not
+            // round-trip through every format, so compare with a plain parse)
+            json expected;
+            nlohmann::detail::json_sax_dom_parser<json> dom(expected);
+            CHECK(json::sax_parse(bytes, &dom, format));
+            const auto complete = parse_binary_recovering(bytes, format);
+            CHECK(complete.ok);
+            CHECK(complete.errors == 0);
+            CHECK(complete.value == expected);
+
+            // a byte after the value
+            auto trailing_bytes = bytes;
+            trailing_bytes.push_back(0x01);
+            const auto trailing = parse_binary_recovering(trailing_bytes, format);
+            CHECK(!trailing.ok);
+            CHECK(trailing.errors == 1);
+            CHECK(trailing.value == expected);
+        }
+    }
+
+    SECTION("containers without an end")
+    {
+        // these made the readers loop, or read on, after the error
+        const auto cbor_array = parse_binary_recovering({0x9F}, json::input_format_t::cbor);
+        CHECK(cbor_array.errors == 1);
+        CHECK(cbor_array.value == json::array());
+
+        const auto cbor_map = parse_binary_recovering({0xBF, 0x61, 'a'}, json::input_format_t::cbor);
+        CHECK(cbor_map.errors == 1);
+        CHECK(cbor_map.value == json({{"a", nullptr}}));
+
+        const auto msgpack_array = parse_binary_recovering({0xDD, 0xFF, 0xFF, 0xFF, 0xFF}, json::input_format_t::msgpack);
+        CHECK(msgpack_array.errors == 1);
+        CHECK(msgpack_array.value == json::array());
+
+        const auto msgpack_map = parse_binary_recovering({0x81, 0xA1, 'a', 0x92, 0x01}, json::input_format_t::msgpack);
+        CHECK(msgpack_map.errors == 1);
+        CHECK(msgpack_map.value == json({{"a", {1}}}));
+    }
+
+    SECTION("BJData ndarray")
+    {
+        // a 2x3 int8 array with two of its six elements; the annotated array
+        // format opens an object and two arrays of its own
+        const auto result = parse_binary_recovering({'[', '$', 'i', '#', '[', '$', 'i', '#', 'i', 2, 2, 3, 1, 2}, json::input_format_t::bjdata);
+        CHECK(result.errors == 1);
+        CHECK(result.balanced);
+        CHECK(result.value == json({{"_ArrayType_", "int8"}, {"_ArraySize_", {2, 3}}, {"_ArrayData_", {1, 2}}}));
+    }
+
+    SECTION("binary formats repair items whose end is known")
+    {
+        struct Repair
+        {
+            json::input_format_t format;
+            std::vector<std::uint8_t> input;
+            json expected;
+            std::size_t errors;
+        };
+
+        const std::vector<Repair> repairs =
+        {
+            // CBOR: tags are ignored (here tag 1 and the self-describe tag 55799)
+            {json::input_format_t::cbor, {0x82, 0xC1, 0x05, 0xD9, 0xD9, 0xF7, 0x06}, {5, 6}, 2},
+            // CBOR: undefined and other simple values become null
+            {json::input_format_t::cbor, {0x84, 0xF7, 0xE0, 0xF8, 0x20, 0x01}, {nullptr, nullptr, nullptr, 1}, 3},
+            // CBOR: members whose key is not a string are skipped, whatever their key and value
+            {json::input_format_t::cbor, {0xA4, 0x01, 0x02, 0x82, 0x01, 0x02, 0xA1, 0x61, 'x', 0x9F, 0xFF, 0xC1, 0x01, 0x5F, 0x41, 0x00, 0xFF, 0x61, 'a', 0x03}, {{"a", 3}}, 3},
+            {json::input_format_t::cbor, {0xBF, 0xF5, 0xBF, 0x61, 'x', 0x7F, 0x61, 'y', 0xFF, 0xFF, 0x61, 'a', 0x03, 0xFF}, {{"a", 3}}, 1},
+            // MessagePack: members whose key is not a string are skipped
+            {json::input_format_t::msgpack, {0x84, 0x01, 0x02, 0x81, 0xA1, 'x', 0x01, 0x92, 0x01, 0x02, 0xD4, 0x01, 0x02, 0xC0, 0xA1, 'a', 0x04}, {{"a", 4}}, 3},
+            // UBJSON: a char that is not ASCII becomes U+FFFD
+            {json::input_format_t::ubjson, {'[', 'C', 0x80, 'C', 'A', ']'}, {replacement_character(), "A"}, 1},
+            // UBJSON: the longest beginning of a high-precision number is kept
+            {json::input_format_t::ubjson, {'[', 'H', 'i', 5, '1', '2', 'a', 'b', 'c', 'H', 'i', 2, '1', '.', 'H', 'i', 3, 'a', 'b', 'c', 'H', 'i', 3, '4', '.', '5', ']'}, {12, 1, nullptr, 4.5}, 3},
+            // BJData, too
+            {json::input_format_t::bjdata, {'[', 'C', 0xFF, 'H', 'i', 2, '-', '1', 'H', 'i', 2, '-', 'x', ']'}, {replacement_character(), -1, nullptr}, 2},
+            // a NUL ends a high-precision number, as it ends JSON text
+            {json::input_format_t::ubjson, {'[', 'H', 'i', 4, '1', '2', 0, '9', 'H', 'i', 2, 0, '1', 'i', 3, ']'}, {12, nullptr, 3}, 2},
+            // BON8: members whose key is not a string are skipped
+            {json::input_format_t::bon8, {0x89, 0x91, 0x92, 0xC9, 0x40, 0x82, 0x91, 0x92, 0x61, 0x93}, {{"a", 3}}, 2},
+            {json::input_format_t::bon8, {0x8B, 0x91, 0x85, 0x91, 0xFE, 0xFA, 0x8B, 'x', 0x91, 0xFE, 0x61, 0x93, 0xFE}, {{"a", 3}}, 2},
+            // BSON: elements of types the library does not read become null
+            {
+                json::input_format_t::bson, bson_document(
+                {
+                    bson_element(0x07, "_id", bytes(12)),                         // ObjectId
+                    bson_element(0x09, "date", bytes(8)),                         // UTC datetime
+                    bson_element(0x13, "decimal", bytes(16)),                     // 128-bit decimal
+                    bson_element(0x0B, "regex", {'a', '+', 0, 'i', 0}),           // regular expression
+                    bson_element(0x0D, "code", bson_string("f()")),               // JavaScript code
+                    bson_element(0x0E, "symbol", bson_string("s")),               // symbol
+                    bson_element(0x0C, "pointer", concatenated({bson_string("c"), bytes(12)})), // DBPointer
+                    bson_element(0x0F, "scope", concatenated({bson_int32(15), bson_string("g"), bson_document({})})), // code with scope
+                    bson_element(0x06, "undefined", {}),                          // undefined
+                    bson_element(0xFF, "min", {}),                                // min key
+                    bson_element(0x7F, "max", {}),                                // max key
+                    bson_element(0x10, "z", bson_int32(7)),
+                }),
+                {{"_id", nullptr}, {"date", nullptr}, {"decimal", nullptr}, {"regex", nullptr}, {"code", nullptr}, {"symbol", nullptr}, {"pointer", nullptr}, {"scope", nullptr}, {"undefined", nullptr}, {"min", nullptr}, {"max", nullptr}, {"z", 7}},
+                11
+            },
+            // BSON: an element of an unknown type becomes null, and the rest of its document is skipped
+            {
+                json::input_format_t::bson, bson_document(
+                {
+                    bson_element(0x03, "inner", bson_document({bson_element(0x10, "a", bson_int32(1)), bson_element(0x42, "x", bytes(3)), bson_element(0x10, "b", bson_int32(2))})),
+                    bson_element(0x04, "array", bson_document({bson_element(0x10, "0", bson_int32(1)), bson_element(0x42, "1", bytes(3))})),
+                    bson_element(0x10, "after", bson_int32(3)),
+                }),
+                {{"inner", {{"a", 1}, {"x", nullptr}}}, {"array", {1, nullptr}}, {"after", 3}},
+                2
+            },
+            // BSON: so does a string or byte array whose length cannot be right
+            {
+                json::input_format_t::bson, bson_document(
+                {
+                    bson_element(0x03, "inner", bson_document({bson_element(0x02, "s", bson_string("abc", -10)), bson_element(0x10, "b", bson_int32(2))})),
+                    bson_element(0x03, "bin", bson_document({bson_element(0x05, "b", concatenated({bson_int32(-1), bytes(1)})), bson_element(0x10, "b", bson_int32(2))})),
+                    bson_element(0x10, "after", bson_int32(3)),
+                }),
+                {{"inner", {{"s", nullptr}}}, {"bin", {{"b", nullptr}}}, {"after", 3}},
+                2
+            },
+            // BSON: a string without its terminator, and a document whose size does not match, are kept
+            {
+                json::input_format_t::bson, bson_document(
+                {
+                    bson_element(0x02, "s", {2, 0, 0, 0, 'a', 'X'}),
+                    bson_element(0x03, "inner", bson_document({bson_element(0x10, "a", bson_int32(1))}, 1)),
+                }),
+                {{"s", "a"}, {"inner", {{"a", 1}}}},
+                2
+            },
+        };
+
+        for (const auto& repair : repairs)
+        {
+            CAPTURE(repair.format)
+            CAPTURE(repair.input)
+            const auto result = parse_binary_recovering(repair.input, repair.format);
+            CHECK(!result.ok);
+            CHECK(result.balanced);
+            CHECK(result.errors == repair.errors);
+            CHECK(result.value == repair.expected);
+            REQUIRE(!result.messages.empty());
+#if !defined(JSON_NOEXCEPTION)
+            // the first error is the one reported without recovering; under
+            // JSON_NOEXCEPTION, reading without recovering aborts instead of
+            // throwing, so there is no message to compare with
+            CHECK(result.messages.front() == binary_error_message(repair.input, repair.format));
+#endif
+        }
+    }
+
+    SECTION("binary formats repair numbers that are out of range")
+    {
+        // CBOR: a double too large for a float number_float_t
+        float_json cbor;
+        BasicRecoveringParser<float_json> sax(cbor);
+        const std::vector<std::uint8_t> cbor_input = {0x82, 0xFB, 0x7E, 0x37, 0xE4, 0x3C, 0x88, 0x00, 0x75, 0x9C, 0x01}; // [1e300, 1]
+        CHECK(!float_json::sax_parse(cbor_input, &sax, float_json::input_format_t::cbor));
+        CHECK(sax.errors == 1);
+        CHECK(sax.messages.front() == "[json.exception.out_of_range.406] syntax error while parsing CBOR value: number overflow");
+        REQUIRE(cbor.size() == 2);
+        CHECK(std::isinf(cbor[0].get<float>()));
+        CHECK(cbor[1] == 1);
+
+        // UBJSON: a high-precision number too large for number_float_t
+        const auto ubjson = parse_binary_recovering({'H', 'i', 5, '1', 'e', '9', '9', '9'}, json::input_format_t::ubjson);
+        CHECK(ubjson.errors == 1);
+        CHECK(ubjson.value.is_number_float());
+        CHECK(std::isinf(ubjson.value.get<double>()));
+    }
+
+    SECTION("binary formats stop where the end of an item is not known")
+    {
+        // a byte that begins no item
+        const auto cbor = parse_binary_recovering({0x82, 0x01, 0x1C, 0x02}, json::input_format_t::cbor);
+        CHECK(cbor.errors == 1);
+        CHECK(cbor.value == json({1}));
+
+        // a key that is no item: the unused MessagePack byte, a CBOR break
+        // in a map of known size, and the end of a BON8 container
+        const auto msgpack = parse_binary_recovering({0x82, 0xA1, 'a', 0x01, 0xC1, 0x02}, json::input_format_t::msgpack);
+        CHECK(msgpack.errors == 1);
+        CHECK(msgpack.value == json({{"a", 1}}));
+        const auto cbor_break = parse_binary_recovering({0xA2, 0x61, 'a', 0x01, 0xFF, 0x02}, json::input_format_t::cbor);
+        CHECK(cbor_break.errors == 1);
+        CHECK(cbor_break.value == json({{"a", 1}}));
+        const auto bon8 = parse_binary_recovering({0x88, 0x61, 0x91, 0xFE}, json::input_format_t::bon8);
+        CHECK(bon8.errors == 1);
+        CHECK(bon8.value == json({{"a", 1}}));
+
+        // an indefinite-length string inside an indefinite-length string
+        const auto nested = parse_binary_recovering({0x82, 0x01, 0x7F, 0x7F, 0x61, 'a', 0xFF, 0xFF}, json::input_format_t::cbor);
+        CHECK(nested.errors == 1);
+        CHECK(nested.value == json({1}));
+
+        // a BJData ndarray whose element type has no name: the object that
+        // holds the ndarray was already begun
+        const auto ndarray = parse_binary_recovering({'[', '$', 0x01, '#', '[', '$', 'i', '#', 'i', 2, 2, 3}, json::input_format_t::bjdata);
+        CHECK(ndarray.errors == 1);
+        CHECK(ndarray.balanced);
+        CHECK(ndarray.value == json::object());
+
+        // a skipped member that the input ends in
+        const auto truncated = parse_binary_recovering({0xA2, 0x01, 0x82, 0x01}, json::input_format_t::cbor);
+        CHECK(truncated.errors == 2);
+        CHECK(truncated.balanced);
+        CHECK(truncated.value == json::object());
+
+        // a BSON element of an unknown type in a document whose size cannot be right
+        const auto bson = parse_binary_recovering(bson_document({bson_element(0x10, "a", bson_int32(1)), bson_element(0x42, "x", bytes(3))}, -10), json::input_format_t::bson);
+        CHECK(bson.errors == 1);
+        CHECK(bson.value == json({{"a", 1}, {"x", nullptr}}));
+    }
+
+    SECTION("changed bytes in binary input")
+    {
+        const json j = {{"a", {1, -2, {{"b", "c"}}, json::array()}}, {"d", {{"e", nullptr}, {"f", true}}}, {"g", 1.5}, {"h", json::binary({1, 2, 3})}, {"i", "\xC3\xA4"}};
+
+        const std::vector<std::pair<json::input_format_t, std::vector<std::uint8_t>>> encodings =
+        {
+            {json::input_format_t::cbor, json::to_cbor(j)},
+            {json::input_format_t::msgpack, json::to_msgpack(j)},
+            {json::input_format_t::ubjson, json::to_ubjson(j)},
+            {json::input_format_t::ubjson, json::to_ubjson(j, true, true)},
+            {json::input_format_t::bjdata, json::to_bjdata(j)},
+            {json::input_format_t::bjdata, json::to_bjdata(j, true, true)},
+            {json::input_format_t::bson, json::to_bson(j)},
+            {json::input_format_t::bon8, json::to_bon8(j)},
+        };
+        const std::vector<std::uint8_t> replacements = {0x00, 0x01, 0x7F, 0x80, 0xC1, 0xD9, 0xE0, 0xF7, 0xFE, 0xFF};
+
+        for (const auto& encoding : encodings)
+        {
+            const auto format = encoding.first;
+            const auto& original = encoding.second;
+            CAPTURE(format)
+
+            std::vector<std::vector<std::uint8_t>> inputs;
+            for (std::size_t position = 0; position < original.size(); ++position)
+            {
+                for (const auto replacement : replacements)
+                {
+                    auto changed = original;
+                    changed[position] = replacement;
+                    inputs.push_back(changed);
+                }
+                auto removed = original;
+                removed.erase(removed.begin() + static_cast<std::ptrdiff_t>(position));
+                inputs.push_back(removed);
+            }
+
+            for (const auto& input : inputs)
+            {
+                CAPTURE(input)
+                const auto result = parse_binary_recovering(input, format);
+                CHECK(result.balanced);
+                CHECK(result.errors <= input.size() + 1);
+#if !defined(JSON_NOEXCEPTION)
+                // an error is reported exactly if reading into a JSON value
+                // fails, and the first one is the same (under JSON_NOEXCEPTION,
+                // that reading aborts instead of throwing)
+                const auto message = binary_error_message(input, format);
+                CHECK(result.ok == message.empty());
+                if (!result.ok && result.errors < 100)
+                {
+                    CHECK(result.messages.front() == message);
+                }
+#endif
+            }
+        }
+    }
+
+    SECTION("JSON text")
+    {
+        // the parser stopped, but reported success
+        json j;
+        RecoveringParser sax(j);
+        CHECK(!json::sax_parse("[1,2,3,]", &sax));
+        CHECK(sax.errors == 1);
+        CHECK(j == json({1, 2, 3}));
+    }
+
+    SECTION("the SAX parsers of the library stop")
+    {
+        json _;
+        CHECK(json::from_cbor(std::vector<std::uint8_t> {0x9F}, true, false).is_discarded());
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<std::uint8_t> {0x9F}), "[json.exception.parse_error.110] parse error at byte 2: syntax error while parsing CBOR value: unexpected end of input", json::parse_error&);
+        CHECK(json::parse("[1,2,3,]", nullptr, false).is_discarded());
+        CHECK(!json::accept("[1,2,3,]"));
+    }
+}
+
+
+TEST_CASE("issue #5676 - SAX parsing of CBOR tags")
+{
+    const json expected = json::binary({1, 2, 3}, 42);
+    const auto cbor = json::to_cbor(expected);
+
+    nlohmann::detail::json_sax_acceptor<json> acceptor;
+    CHECK_FALSE(json::sax_parse(cbor, &acceptor, json::input_format_t::cbor));
+    CHECK_FALSE(json::sax_parse(cbor, &acceptor, json::input_format_t::cbor,
+                                true, false, false, json::cbor_tag_handler_t::error));
+
+    CHECK(json::sax_parse(cbor, &acceptor, json::input_format_t::cbor,
+                          true, false, false, json::cbor_tag_handler_t::ignore));
+
+    json parsed;
+    nlohmann::detail::json_sax_dom_parser<json, nlohmann::detail::string_input_adapter_type> sax(parsed);
+    CHECK(json::sax_parse(cbor, &sax, json::input_format_t::cbor,
+                          true, false, false, json::cbor_tag_handler_t::store));
+    CHECK(parsed == expected);
+
+    json iterator_parsed;
+    nlohmann::detail::json_sax_dom_parser<json, nlohmann::detail::string_input_adapter_type> iterator_sax(iterator_parsed);
+    CHECK(json::sax_parse(cbor.begin(), cbor.end(), &iterator_sax, json::input_format_t::cbor,
+                          true, false, false, json::cbor_tag_handler_t::store));
+    CHECK(iterator_parsed == expected);
+
+#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
+    json span_parsed;
+    nlohmann::detail::json_sax_dom_parser<json, nlohmann::detail::string_input_adapter_type> span_sax(span_parsed);
+    CHECK(json::sax_parse(nlohmann::detail::span_input_adapter(cbor.data(), cbor.size()), &span_sax,
+                          json::input_format_t::cbor, true, false, false, json::cbor_tag_handler_t::store));
+    CHECK(span_parsed == expected);
+#endif
+
+    const std::string text = "null";
+    CHECK(json::sax_parse(text, &acceptor, json::input_format_t::json,
+                          true, false, false, json::cbor_tag_handler_t::store));
+    CHECK(json::sax_parse(text.begin(), text.end(), &acceptor, json::input_format_t::json,
+                          true, false, false, json::cbor_tag_handler_t::store));
+#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
+    CHECK(json::sax_parse(nlohmann::detail::span_input_adapter(text.data(), text.size()), &acceptor,
+                          json::input_format_t::json, true, false, false, json::cbor_tag_handler_t::store));
+#endif
+}
+
+
+TEST_CASE("MessagePack SAX aborts")
+{
+    SECTION("start_array(len)")
+    {
+        std::vector<uint8_t> const v = {0x93, 0x01, 0x02, 0x03};
+        SaxCountdown scp(0);
+        CHECK(!json::sax_parse(v, &scp, json::input_format_t::msgpack));
+    }
+
+    SECTION("start_object(len)")
+    {
+        std::vector<uint8_t> const v = {0x81, 0xa3, 0x66, 0x6F, 0x6F, 0xc2};
+        SaxCountdown scp(0);
+        CHECK(!json::sax_parse(v, &scp, json::input_format_t::msgpack));
+    }
+
+    SECTION("key()")
+    {
+        std::vector<uint8_t> const v = {0x81, 0xa3, 0x66, 0x6F, 0x6F, 0xc2};
+        SaxCountdown scp(1);
+        CHECK(!json::sax_parse(v, &scp, json::input_format_t::msgpack));
+    }
+}
+
+TEST_CASE("issue #5405 - a user-defined SAX consumer is unaffected by the internal DOM reserve optimization")
+{
+    // the reserve() call is local to json_sax_dom_parser / json_sax_dom_callback_parser;
+    // a custom SAX consumer that does not touch a DOM array sees identical events
+    json j = json::array();
+    for (int i = 0; i < 100; ++i)
+    {
+        j.push_back(i);
+    }
+    const auto packed = json::to_msgpack(j);
+
+    SaxCountdown scp(1000000); // large enough to never trigger an abort
+    CHECK(json::sax_parse(packed, &scp, json::input_format_t::msgpack));
+}
+
+TEST_CASE("MessagePack nesting does not consume the call stack - SAX interface")
+{
+    // see the test case of the same name in unit-msgpack.cpp (#5104)
+    std::vector<uint8_t> input(300000, 0x91);
+    input.push_back(0x01); // innermost value
+
+    SaxCountdown accept_all(600001);
+    CHECK(json::sax_parse(input, &accept_all, json::input_format_t::msgpack));
+}
+
+TEST_CASE("MessagePack SAX parsing stops at every event")
+{
+    // Containers are opened and closed by the loop that reads them; a SAX
+    // handler that rejects any event - including the end of a nested
+    // container - must stop the parse right there.
+    const auto count_events = [](const std::vector<std::uint8_t>& input)
+    {
+        int events = 0;
+        while (true)
+        {
+            SaxCountdown scp(events);
+            if (json::sax_parse(input, &scp, json::input_format_t::msgpack))
+            {
+                return events;
+            }
+            ++events;
+            REQUIRE(events < 1000);
+        }
+    };
+
+    // 20 events: every container kind closes inside another one
+    const json j = json::parse(R"({"a": [1, {"b": []}], "c": {"d": [[2]]}})");
+    CHECK(count_events(json::to_msgpack(j)) == 20);
+}
+
+DOCTEST_CLANG_SUPPRESS_WARNING_POP

tests/src/unit-stream-bulk-scan.cpp

@@ -1,418 +0,0 @@
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-#include "doctest_compatibility.h"
-
-// the library undefines its configuration macros at the end of the header
-#if defined(JSON_DISABLE_STREAM_BULK_SCAN) && JSON_DISABLE_STREAM_BULK_SCAN
-    #define TEST_STREAM_BULK_SCAN 0
-#else
-    #define TEST_STREAM_BULK_SCAN 1
-#endif
-
-#include <nlohmann/json.hpp>
-using nlohmann::json;
-
-#include <algorithm>
-#include <cstddef>
-#include <cstdint>
-#include <cstdio>
-#include <fstream>
-#include <istream>
-#include <random>
-#include <sstream>
-#include <streambuf>
-#include <string>
-#include <utility>
-#include <vector>
-
-// The lexer scans the characters in the get area of a std::istream's
-// streambuf directly instead of reading them one at a time. These tests pin
-// that this is not observable: for any get area size - including a streambuf
-// without a get area, which still takes the character-at-a-time path - the
-// parsed values, the exception messages (including the "last read" token),
-// the stream state, and the characters left in the stream are the same. See
-// unit-stream-bulk-scan-disabled.cpp for JSON_DISABLE_STREAM_BULK_SCAN.
-
-namespace
-{
-// A streambuf that serves its input in get areas of a fixed size, so that
-// tokens, numbers, UTF-8 sequences, and indentation cross the end of the get
-// area at every possible offset. With a size of 0, it keeps no get area at all
-// and serves every character from underflow()/uflow().
-class chunked_streambuf : public std::streambuf
-{
-  public:
-    chunked_streambuf(std::string s, std::size_t chunk_size)
-        : m_data(std::move(s)), m_chunk_size(chunk_size)
-    {}
-
-  protected:
-    int_type underflow() override
-    {
-        if (m_chunk_size == 0)
-        {
-            return m_pos < m_data.size() ? traits_type::to_int_type(m_data[m_pos]) : traits_type::eof();
-        }
-        if (gptr() < egptr())
-        {
-            return traits_type::to_int_type(*gptr());
-        }
-        // the previous get area has been consumed
-        m_pos += static_cast<std::size_t>(egptr() - eback());
-        if (m_pos >= m_data.size())
-        {
-            setg(nullptr, nullptr, nullptr);
-            return traits_type::eof();
-        }
-        char* const begin = &m_data[m_pos];
-        setg(begin, begin, begin + (std::min)(m_chunk_size, m_data.size() - m_pos));
-        return traits_type::to_int_type(*gptr());
-    }
-
-    int_type uflow() override
-    {
-        if (m_chunk_size == 0)
-        {
-            return m_pos < m_data.size() ? traits_type::to_int_type(m_data[m_pos++]) : traits_type::eof();
-        }
-        return std::streambuf::uflow();
-    }
-
-  private:
-    std::string m_data;
-    std::size_t m_pos = 0;
-    std::size_t m_chunk_size;
-};
-
-// how a test reads from the stream
-enum class read_mode
-{
-    extract,         // up to four times operator>>, as for concatenated values
-    parse,           // json::parse(stream)
-    parse_lenient,   // json::parse(stream) with comments
-};
-
-// Read @a input from a chunked_streambuf and describe everything observable:
-// the values or the exception, the stream state after each value, and the
-// characters left in the stream.
-std::string observe(const std::string& input, std::size_t chunk_size, read_mode mode)
-{
-    chunked_streambuf buf(input, chunk_size);
-    std::istream is(&buf);
-    std::string result;
-    for (int i = 0; i < 4; ++i)
-    {
-        json j;
-        try
-        {
-            if (mode == read_mode::extract)
-            {
-                is >> j;
-            }
-            else
-            {
-                j = json::parse(is, nullptr, true, mode == read_mode::parse_lenient);
-            }
-            result += "value " + j.dump() + "; state " + std::to_string(static_cast<unsigned int>(is.rdstate())) + "\n";
-        }
-        catch (const json::exception& e)
-        {
-            result += std::string("exception ") + e.what() + "\n";
-            break;
-        }
-        if (mode != read_mode::extract)
-        {
-            break;
-        }
-        is.clear();
-    }
-
-    is.clear();
-    result += "remaining ";
-    char c = 0;
-    while (is.get(c))
-    {
-        result += c;
-    }
-    return result;
-}
-
-// get area sizes that put every boundary everywhere in short inputs, plus one
-// that holds most inputs completely
-std::vector<std::size_t> chunk_sizes()
-{
-    return {1, 2, 3, 4, 5, 7, 8, 9, 13, 16, 64, 4096};
-}
-
-// valid and invalid inputs covering every token type and every bulk path:
-// strings (plain runs, escapes, UTF-8), numbers (all grammar parts, too large
-// for an integer), and indentation
-std::vector<std::string> corpus()
-{
-    return
-    {
-        // numbers, terminated in every way
-        "0", "-0", "123", "-123", "1.5", "-1.5e+10", "2E-3", "123456789012345678901234567890",
-        "18446744073709551615", "18446744073709551616", "-9223372036854775809",
-        "123 456", "123,456", "123]", "1true", "42\nfoo", "1.25e3}", "7\t8\r9",
-        // malformed numbers
-        "1.", "-", "1e", "1e+", "01", "-a", "1.x", "1ee5",
-        // strings
-        R"("")", R"("abc")", R"("a long string with a run of ordinary characters to scan in bulk")",
-        R"("escapes \" \\ \/ \b \f \n \r \t é 😀")",
-        "\"UTF-8: \xc3\xa9 \xe2\x82\xac \xf0\x9f\x98\x80 done\"",
-        // malformed strings
-        R"("unterminated)", "\"control\x01character\"", "\"ill-formed \xc3\x28 UTF-8\"", R"("bad \x escape")",
-        R"("\ud800 lone surrogate")",
-        // literals
-        "true", "false", "null", "tru", "nul", "falsey", "[true,false,null]", "nulL", "truex", "[fals e]", "t",
-        "true1", "null null", "[false]",
-        // structures
-        "[]", "{}", "[1,2,3]", R"({"a":1,"b":[true,false,null],"c":{"d":"e"}})", "[1,]", R"({"a" 1})", "[[[[[]]]]]",
-        // pretty-printed
-        "{\n    \"key\": [\n        1,\n        -2.5,\n        \"three\"\n    ]\n}",
-        "[\n                                \"deep\"\n                                ]",
-        "{\n    \"a\": 1,\n    \"b\": 2x\n}",
-        // concatenated values and whitespace
-        "1 2 3", R"("a""b")", "[1][2]", "{}{}", " \n\t 42 \n\t ", "",
-        // comments (only accepted by parse_lenient)
-        "/* comment */ 1", "// comment\n[1, /* c */ 2]",
-        // byte order mark
-        "\xef\xbb\xbf[1]",
-    };
-}
-}  // namespace
-
-TEST_CASE("parsing from a std::istream scans the get area in bulk")
-{
-    SECTION("results do not depend on the get area")
-    {
-        const std::vector<read_mode> read_modes = {read_mode::extract, read_mode::parse, read_mode::parse_lenient};
-        for (const auto& input : corpus())
-        {
-            for (const read_mode mode : read_modes)
-            {
-                // no get area: the character-at-a-time path
-                const std::string expected = observe(input, 0, mode);
-                for (const std::size_t chunk_size : chunk_sizes())
-                {
-                    CAPTURE(input)
-                    CAPTURE(chunk_size)
-                    CAPTURE(static_cast<int>(mode))
-                    CHECK(observe(input, chunk_size, mode) == expected);
-                }
-            }
-        }
-    }
-
-    SECTION("values are the same as when parsing from a string")
-    {
-        const std::string input = R"({"name": "nlohmann::json", "numbers": [1, -2, 3.5, 4e10, 18446744073709551615],)"
-                                  "\n    \"text\": \"caf\xc3\xa9 \\u00e9 \\\"quoted\\\"\", \"nested\": [[{}], [[]]], \"flags\": [true, false, null]}";
-        const json expected = json::parse(input);
-        for (const std::size_t chunk_size : chunk_sizes())
-        {
-            CAPTURE(chunk_size)
-            chunked_streambuf buf(input, chunk_size);
-            std::istream is(&buf);
-            CHECK(json::parse(is) == expected);
-        }
-
-        std::istringstream ss(input);
-        CHECK(json::parse(ss) == expected);
-    }
-
-    SECTION("a token that spans several get areas is reported completely")
-    {
-        // the error is found after the string has crossed many get areas; the
-        // token string holds everything since the start of the last token
-        const std::string input = R"(["this string is longer than every get area", tru])";
-        for (const std::size_t chunk_size : chunk_sizes())
-        {
-            CAPTURE(chunk_size)
-            chunked_streambuf buf(input, chunk_size);
-            std::istream is(&buf);
-            json j;
-            CHECK_THROWS_WITH_AS(is >> j,
-                                 "[json.exception.parse_error.101] parse error at line 1, column 50: syntax error while parsing value - invalid literal; last read: '\"this string is longer than every get area\", tru]'",
-                                 json::parse_error&);
-        }
-
-        const std::string unterminated = R"("this string is longer than every get area)";
-        for (const std::size_t chunk_size : chunk_sizes())
-        {
-            CAPTURE(chunk_size)
-            chunked_streambuf buf(unterminated, chunk_size);
-            std::istream is(&buf);
-            json j;
-            CHECK_THROWS_WITH_AS(is >> j,
-                                 "[json.exception.parse_error.101] parse error at line 1, column 43: syntax error while parsing value - invalid string: missing closing quote; last read: '\"this string is longer than every get area'",
-                                 json::parse_error&);
-        }
-    }
-
-    SECTION("an error before the first token reports everything read")
-    {
-        chunked_streambuf buf("  \n  x", 2);
-        std::istream is(&buf);
-        json j;
-        CHECK_THROWS_WITH_AS(is >> j,
-                             "[json.exception.parse_error.101] parse error at line 2, column 3: syntax error while parsing value - invalid literal; last read: '  <U+000A>  x'",
-                             json::parse_error&);
-    }
-
-    SECTION("lines and columns are counted across get areas")
-    {
-        const std::string input = "[\n    1,\n    \"two\",\n    3.0,\n    x\n]";
-        for (const std::size_t chunk_size : chunk_sizes())
-        {
-            CAPTURE(chunk_size)
-            chunked_streambuf buf(input, chunk_size);
-            std::istream is(&buf);
-            json j;
-            CHECK_THROWS_WITH_AS(is >> j,
-                                 "[json.exception.parse_error.101] parse error at line 5, column 5: syntax error while parsing value - invalid literal; last read: '3.0,<U+000A>    x'",
-                                 json::parse_error&);
-        }
-    }
-
-    SECTION("many values from one stream")
-    {
-        std::string input;
-        for (int i = 0; i < 200; ++i)
-        {
-            input += R"({"id":)" + std::to_string(i) + R"(,"name":"user)" + std::to_string(i) + R"(","score":)" + std::to_string(i) + ".5}\n";
-            input += std::to_string(i * 7919) + "\n";
-        }
-
-        for (const std::size_t chunk_size : chunk_sizes())
-        {
-            CAPTURE(chunk_size)
-            chunked_streambuf buf(input, chunk_size);
-            std::istream is(&buf);
-            json j;
-            int count = 0;
-            while (!(is >> std::ws).eof())
-            {
-                is >> j;
-                if (count % 2 == 0)
-                {
-                    CHECK(j["id"] == count / 2);
-                }
-                else
-                {
-                    CHECK(j == (count / 2) * 7919);
-                }
-                ++count;
-            }
-            CHECK(count == 400);
-        }
-    }
-
-    SECTION("the stream can be used after parsing")
-    {
-        for (const std::size_t chunk_size : chunk_sizes())
-        {
-            CAPTURE(chunk_size)
-            chunked_streambuf buf(R"({"a": "some text"} trailing words 42)", chunk_size);
-            std::istream is(&buf);
-            json j;
-            is >> j;
-            CHECK(j == json({{"a", "some text"}}));
-
-            std::string word;
-            int number = 0;
-            is >> word;
-            CHECK(word == "trailing");
-            is >> word >> number;
-            CHECK(word == "words");
-            CHECK(number == 42);
-        }
-    }
-
-    SECTION("std::stringstream and std::ifstream")
-    {
-        const std::string input = R"([1, 2.5, "three", {"four": [true, null]}] 5)";
-
-        std::stringstream ss(input);
-        json j1;
-        json j2;
-        ss >> j1 >> j2;
-        CHECK(j1 == json::parse(R"([1, 2.5, "three", {"four": [true, null]}])"));
-        CHECK(j2 == 5);
-        CHECK(ss.eof());
-
-        // a file name of its own for every run: the test runs for several C++
-        // standards and configurations at the same time, in the same directory
-        std::random_device rd;
-        const std::string temp_name = "unit-stream-bulk-scan-" + std::to_string(rd()) + ".tmp";
-        const char* const filename = temp_name.c_str();
-        {
-            std::ofstream file(filename);
-            file << input;
-        }
-        {
-            std::ifstream file(filename);
-            json k1;
-            json k2;
-            file >> k1 >> k2;
-            CHECK(k1 == j1);
-            CHECK(k2 == j2);
-        }
-        static_cast<void>(std::remove(filename));
-    }
-
-    SECTION("binary formats read from a stream")
-    {
-        const json j = {{"string", std::string(300, 'x')}, {"array", {1, 2, 3}}, {"number", 1.5}};
-        const std::vector<std::uint8_t> cbor = json::to_cbor(j);
-        const std::string bytes(reinterpret_cast<const char*>(cbor.data()), cbor.size());
-        for (const std::size_t chunk_size : chunk_sizes())
-        {
-            CAPTURE(chunk_size)
-            chunked_streambuf buf(bytes, chunk_size);
-            std::istream is(&buf);
-            CHECK(json::from_cbor(is) == j);
-        }
-    }
-
-#if TEST_STREAM_BULK_SCAN
-    SECTION("the adapter keeps no token unless the lexer starts one")
-    {
-        // the binary readers read through the same adapter, but never start a
-        // token; refilling the get area must then not collect the input
-        chunked_streambuf buf(std::string(1000, 'x'), 7);
-        std::istream is(&buf);
-        nlohmann::detail::input_stream_adapter ia(is);
-        for (int i = 0; i < 1000; ++i)
-        {
-            CHECK(ia.get_character() == 'x');
-        }
-
-        std::vector<char> token;
-        ia.copy_token(token, false);
-        CHECK(token.empty());
-    }
-#endif
-
-    SECTION("SAX parsing from a stream")
-    {
-        const std::string input = R"({"a": [1, "two", 3.5]} rest)";
-        for (const std::size_t chunk_size : chunk_sizes())
-        {
-            CAPTURE(chunk_size)
-            chunked_streambuf buf(input, chunk_size);
-            std::istream is(&buf);
-            json j;
-            nlohmann::detail::json_sax_dom_parser<json, nlohmann::detail::string_input_adapter_type> sax(j);
-            CHECK(json::sax_parse(is, &sax, json::input_format_t::json, false));
-            CHECK(j == json::parse(R"({"a": [1, "two", 3.5]})"));
-        }
-    }
-}