Read CBOR containers and tags without recursing per nesting level

get_cbor_array() and get_cbor_object() read their elements by calling back
into the value reader, which called them again for a nested container, and a
tag was handled by reading the tagged value the same way. All three cost
native stack, and all three cost a single byte to encode: 0x9F opens an
indefinite-length array, 0x81 a one-element array, and 0xC2 is a tag. Half a
million of any of them crashes the process before the input runs out (#5104).

Apply the shape the MessagePack reader already uses: the open containers live
on the heap stack, parse_cbor_value() reads a single value and only opens a
container rather than reading it to its end, and parse_cbor_internal() loops,
resuming the innermost container after each element.

Two things are specific to CBOR. An indefinite-length container ends at a
break marker rather than at a count, and testing for that marker consumes a
byte which is the first byte of the next element when it is not one; the
frame's count is npos for those, and the driver tracks whether the next value
starts at a fresh byte. And a tag is not a value of its own: instead of
reading the tagged value by recursing, the value reader reports that a tag was
read and the driver reads on, so a chain of tags costs no stack at all.

The switch that decodes a value is unchanged apart from the twelve container
cases and the two tag sites. Verified against the previous commit over
definite and indefinite arrays and maps, all four counted forms, empty
containers, nesting of the forms inside each other, truncated inputs, and all
three tag handlers: identical values, error codes, messages and byte offsets.
500,000 levels of each of the three vectors now report parse_error.110 instead
of crashing, and a well-formed 200,000-level value is read to completion.

On performance: the driver does per element what a counted loop used to do
per container, and CBOR pays for it more than MessagePack because the value
reader also has to be told whether to fetch a byte. Parsing 60,000 small
objects and one array of a million integers is 3 to 4 % slower than the
recursive reader, measured over five alternating runs. Against develop the
same two inputs are about 44 % faster, because the entry point no longer
copies the value it parsed; the earlier commit in this series is what pays
for that.

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

.github/CONTRIBUTING.md

@@ -108,7 +108,9 @@ The tests are located in [`tests/src/unit-*.cpp`](https://github.com/nlohmann/js
 are structured along the features of the library or the nature of the tests. Usually, it should be clear from the
 context which existing file needs to be extended, and only very few cases require creating new test files.
 
-When fixing a bug, edit `unit-regression2.cpp` and add a section referencing the fixed issue.
+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 one of them.
 
 #### Exceptions
 

docs/mkdocs/docs/api/basic_json/patch.md

@@ -34,10 +34,6 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
   ("add", "remove", "move")
 - Throws [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) if an "add" operation's target
   location has a parent that is neither an object nor an array.
-- Throws [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) if a "remove" operation's target
-  location has a parent that is neither an object nor an array.
-- Throws [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) if a "move" operation's "from"
-  location is a proper prefix of its "path" location.
 - Throws [`other_error.501`](../../home/exceptions.md#jsonexceptionother_error501) if "test" operation was
   unsuccessful.
 
@@ -79,7 +75,3 @@ is thrown. In any case, the original value is not changed: the patch is applied
 - Added in version 2.0.0.
 - Added [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) and stopped relying on an internal assertion when an "add" operation's
   target location has a non-object/non-array parent in version 3.13.0.
-- Added [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) and stopped silently ignoring a "remove" operation whose target
-  location has a non-object/non-array parent in version 3.13.0.
-- Added [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) and rejected a "move" operation whose "from" location is a proper
-  prefix of its "path" location instead of silently producing a corrupted result in version 3.13.0.

docs/mkdocs/docs/api/basic_json/patch_inplace.md

@@ -30,10 +30,6 @@ No guarantees, value may be corrupted by an unsuccessful patch operation.
   ("add", "remove", "move")
 - Throws [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) if an "add" operation's target
   location has a parent that is neither an object nor an array.
-- Throws [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) if a "remove" operation's target
-  location has a parent that is neither an object nor an array.
-- Throws [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) if a "move" operation's "from"
-  location is a proper prefix of its "path" location.
 - Throws [`other_error.501`](../../home/exceptions.md#jsonexceptionother_error501) if "test" operation was
   unsuccessful.
 
@@ -76,7 +72,3 @@ function throws an exception.
 - Added in version 3.11.0.
 - Added [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) and stopped relying on an internal assertion when an "add" operation's
   target location has a non-object/non-array parent in version 3.13.0.
-- Added [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) and stopped silently ignoring a "remove" operation whose target
-  location has a non-object/non-array parent in version 3.13.0.
-- Added [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) and rejected a "move" operation whose "from" location is a proper
-  prefix of its "path" location instead of silently producing a corrupted result in version 3.13.0.

docs/mkdocs/docs/features/binary_formats/ubjson.md

@@ -69,6 +69,12 @@ The library uses the following mapping from JSON values types to UBJSON types ac
     Note that `use_size = true` alone may result in larger representations - the benefit of this parameter is that the
     receiving side is immediately informed on the number of elements of the container.
 
+    An array whose type marker is `Z` (null), `T` (true) or `F` (false) stores no payload at all, because the marker
+    already is the value. Its declared count is therefore the only thing that decides how much memory the receiving side
+    allocates, and a handful of bytes can describe billions of elements. `from_ubjson` rejects such an array with
+    [`out_of_range.408`](../../home/exceptions.md#jsonexceptionout_of_range408) when the count exceeds 1,048,576, and
+    `to_ubjson` writes longer arrays of these types without the annotation, so any value it produces can be read back.
+
 !!! info "Binary values"
 
     If the JSON data contains the binary type, the value stored is a list of integers, as suggested by the UBJSON

docs/mkdocs/docs/home/exceptions.md

@@ -868,6 +868,12 @@ The size of an array or object in a [binary format](../features/binary_formats/i
 the size following `#` for [UBJSON](../features/binary_formats/ubjson.md)/[BJData](../features/binary_formats/bjdata.md),
 or the encoded length for [CBOR](../features/binary_formats/cbor.md).
 
+The exception is also thrown for a [UBJSON](../features/binary_formats/ubjson.md) array of a type that is encoded by its
+marker alone (`Z`, `T` or `F`) whose declared count exceeds 1,048,576. Such an array has no payload, so its count alone
+decides how much memory is allocated, and a handful of bytes would otherwise describe billions of values.
+[`to_ubjson`](../api/basic_json/to_ubjson.md) writes longer arrays of these types without the size and type annotation,
+so any value it produces can still be read back.
+
 !!! failure "Example messages"
 
     ```
@@ -879,6 +885,9 @@ or the encoded length for [CBOR](../features/binary_formats/cbor.md).
     ```
     [json.exception.out_of_range.408] syntax error while parsing CBOR size: excessive map size
     ```
+    ```
+    [json.exception.out_of_range.408] syntax error while parsing UBJSON size: excessive array size
+    ```
 
 ### json.exception.out_of_range.409
 
@@ -933,34 +942,6 @@ BSON stores the length of documents, arrays, strings, and binary values in a sig
     [`to_bson`](../api/basic_json/to_bson.md) produced documents with negative length prefixes that
     [`from_bson`](../api/basic_json/from_bson.md) rejected.
 
-### json.exception.out_of_range.413
-
-A JSON Patch `remove` operation cannot be applied because the target location's parent is neither an object nor an array. Per [RFC 6902](https://datatracker.ietf.org/doc/html/rfc6902), a `remove` target must reference a member of an existing object or an element of an existing array; a primitive value (string, number, boolean, etc.) or `null` has no members or elements to remove.
-
-!!! failure "Example message"
-
-    ```
-    cannot remove value: the JSON Patch 'remove' target's parent is of type number, but must be an object or array
-    ```
-
-!!! note
-
-    This exception was added in version 3.13.0. Before that, this situation was silently ignored (the `remove` operation had no effect).
-
-### json.exception.out_of_range.414
-
-A JSON Patch `move` operation's `"from"` location is a proper prefix of its `"path"` location. Per [RFC 6902](https://datatracker.ietf.org/doc/html/rfc6902) (section 4.4), a location cannot be moved into one of its own children.
-
-!!! failure "Example message"
-
-    ```
-    cannot move value: 'from' path '/0' is a proper prefix of 'path' '/0/0'
-    ```
-
-!!! note
-
-    This exception was added in version 3.13.0. Before that, this situation could succeed with a corrupted result: for an array target, removing the "from" element before the "add" step shifted subsequent indices, so "path" silently re-resolved to a different element than intended.
-
 ## Further exceptions
 
 This exception is thrown in case of errors that cannot be classified with the

include/nlohmann/detail/input/binary_reader.hpp

@@ -58,6 +58,26 @@ inline bool little_endianness(int num = 1) noexcept
     return *reinterpret_cast<char*>(&num) == 1;
 }
 
+/*!
+@brief largest element count accepted for a UBJSON container of a valueless type
+
+An element of type 'Z' (null), 'T' (true) or 'F' (false) is encoded by its
+type marker alone, so an optimized container of one of those types has no
+payload at all and its declared count is the only thing that decides how much
+is allocated: `[$Z#L` followed by a large count turns some ten bytes of input
+into that many values (see #2793, which reports 35 GB and 150 seconds). Every
+other type costs at least one byte per element and is bounded by the end of
+the input.
+
+This is a sanity bound rather than a security boundary, and it is far above
+any container met in practice. @ref binary_writer falls back to the
+unoptimized encoding for longer containers, so that a value serialized by
+this library can always be read back.
+
+@sa https://github.com/nlohmann/json/issues/2793
+*/
+JSON_INLINE_VARIABLE constexpr std::size_t max_valueless_container_size = 1 << 20;
+
 ///////////////////
 // binary reader //
 ///////////////////
@@ -110,6 +130,7 @@ class binary_reader
                    const cbor_tag_handler_t tag_handler = cbor_tag_handler_t::error)
     {
         sax = sax_;
+        container_stack.clear();
         bool result = false;
 
         switch (format)
@@ -159,6 +180,69 @@ class binary_reader
     }
 
   private:
+    ////////////////////////
+    // nested containers  //
+    ////////////////////////
+
+    /*!
+    @brief a container that has been opened and not closed yet
+
+    The binary readers do not call themselves once per nesting level. Like
+    @ref parser::sax_parse_internal, which does the same for JSON text, they
+    keep the containers they are inside of on a heap-allocated stack, so that
+    the native call stack does not grow with the nesting depth of the input
+    and a deeply nested value is bounded by memory rather than by the stack
+    (see #5104).
+
+    The members are ordered by decreasing alignment, which is the ordering that
+    keeps a struct from growing as members are added to it.
+    */
+    struct container_frame
+    {
+        container_frame(const std::size_t remaining_, const bool is_object_) noexcept
+            : remaining(remaining_), is_object(is_object_) {}
+
+        /// number of elements that have not been read yet
+        std::size_t remaining;
+        /// whether to close this container with end_object() or end_array()
+        bool is_object;
+    };
+
+    /*!
+    @brief open a nested array or object
+
+    Emits the SAX start event and records the container. This is the only
+    place the binary readers start a container, so a check that rejects one
+    can be made here and is then guaranteed to run before the start event.
+
+    @param[in] is_object  whether an object (true) or an array (false) begins
+    @param[in] len        number of elements the container declares
+
+    @return whether the SAX parser accepted the start event
+    */
+    bool enter_container(const bool is_object, const std::size_t len)
+    {
+        if (JSON_HEDLEY_UNLIKELY(is_object ? !sax->start_object(len) : !sax->start_array(len)))
+        {
+            return false;
+        }
+
+        container_stack.emplace_back(len, is_object);
+        return true;
+    }
+
+    /// @copydoc enter_container
+    bool enter_array(const std::size_t len)
+    {
+        return enter_container(/*is_object*/false, len);
+    }
+
+    /// @copydoc enter_container
+    bool enter_object(const std::size_t len)
+    {
+        return enter_container(/*is_object*/true, len);
+    }
+
     //////////
     // BSON //
     //////////
@@ -491,9 +575,12 @@ class binary_reader
 
     @return whether a valid CBOR value was passed to the SAX parser
     */
-    bool parse_cbor_internal(const bool get_char,
+    bool parse_cbor_value(const bool get_char,
-                             const cbor_tag_handler_t tag_handler)
+                          const cbor_tag_handler_t tag_handler,
+                          bool& tag_pending)
     {
+        tag_pending = false;
+
         switch (get_char ? get() : current)
         {
             // EOF
@@ -685,37 +772,36 @@ class binary_reader
             case 0x95:
             case 0x96:
             case 0x97:
-                return get_cbor_array(
+                return enter_array(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x1Fu));
-                           conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x1Fu), tag_handler);
 
             case 0x98: // array (one-byte uint8_t for n follows)
             {
                 std::uint8_t len{};
-                return get_number(input_format_t::cbor, len) && get_cbor_array(static_cast<std::size_t>(len), tag_handler);
+                return get_number(input_format_t::cbor, len) && enter_array(static_cast<std::size_t>(len));
             }
 
             case 0x99: // array (two-byte uint16_t for n follow)
             {
                 std::uint16_t len{};
-                return get_number(input_format_t::cbor, len) && get_cbor_array(static_cast<std::size_t>(len), tag_handler);
+                return get_number(input_format_t::cbor, len) && enter_array(static_cast<std::size_t>(len));
             }
 
             case 0x9A: // array (four-byte uint32_t for n follow)
             {
                 std::uint32_t len{};
                 std::size_t size{};
-                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "array") && get_cbor_array(size, tag_handler);
+                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "array") && enter_array(size);
             }
 
             case 0x9B: // array (eight-byte uint64_t for n follow)
             {
                 std::uint64_t len{};
                 std::size_t size{};
-                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "array") && get_cbor_array(size, tag_handler);
+                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "array") && enter_array(size);
             }
 
             case 0x9F: // array (indefinite length)
-                return get_cbor_array(detail::unknown_size(), tag_handler);
+                return enter_array(detail::unknown_size());
 
             // map (0x00..0x17 pairs of data items follow)
             case 0xA0:
@@ -742,36 +828,36 @@ class binary_reader
             case 0xB5:
             case 0xB6:
             case 0xB7:
-                return get_cbor_object(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x1Fu), tag_handler);
+                return enter_object(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x1Fu));
 
             case 0xB8: // map (one-byte uint8_t for n follows)
             {
                 std::uint8_t len{};
-                return get_number(input_format_t::cbor, len) && get_cbor_object(static_cast<std::size_t>(len), tag_handler);
+                return get_number(input_format_t::cbor, len) && enter_object(static_cast<std::size_t>(len));
             }
 
             case 0xB9: // map (two-byte uint16_t for n follow)
             {
                 std::uint16_t len{};
-                return get_number(input_format_t::cbor, len) && get_cbor_object(static_cast<std::size_t>(len), tag_handler);
+                return get_number(input_format_t::cbor, len) && enter_object(static_cast<std::size_t>(len));
             }
 
             case 0xBA: // map (four-byte uint32_t for n follow)
             {
                 std::uint32_t len{};
                 std::size_t size{};
-                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "map") && get_cbor_object(size, tag_handler);
+                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "map") && enter_object(size);
             }
 
             case 0xBB: // map (eight-byte uint64_t for n follow)
             {
                 std::uint64_t len{};
                 std::size_t size{};
-                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "map") && get_cbor_object(size, tag_handler);
+                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "map") && enter_object(size);
             }
 
             case 0xBF: // map (indefinite length)
-                return get_cbor_object(detail::unknown_size(), tag_handler);
+                return enter_object(detail::unknown_size());
 
             case 0xC0: // tagged item
             case 0xC1:
@@ -855,7 +941,10 @@ class binary_reader
                             default:
                                 break;
                         }
-                        return parse_cbor_internal(true, tag_handler);
+                        // the tagged value follows; it is read by the loop in
+                        // parse_cbor_internal() rather than by recursing here
+                        tag_pending = true;
+                        return true;
                     }
 
                     case cbor_tag_handler_t::store:
@@ -905,7 +994,11 @@ class binary_reader
                                 break;
                             }
                             default:
-                                return parse_cbor_internal(true, tag_handler);
+                            {
+                                // as above, the tagged value is read by the caller
+                                tag_pending = true;
+                                return true;
+                            }
                         }
                         get();
                         return get_cbor_binary(b) && sax->binary(b);
@@ -996,23 +1089,21 @@ class binary_reader
     }
 
     /*!
-    @brief reads a CBOR string
+    @brief reads a definite-length CBOR string
 
-    This function first reads starting bytes to determine the expected
+    Reads everything @ref get_cbor_string accepts except the indefinite-length
-    string length and then copies this number of bytes into a string.
+    form, which that function handles itself. The bytes are appended to @a
-    Additionally, CBOR's strings with indefinite lengths are supported.
+    result, so consecutive chunks of an indefinite-length string can be read
+    into the same string.
 
-    @param[out] result  created string
+    @param[out] result  string the bytes are appended to
 
     @return whether string creation completed
-    */
-    bool get_cbor_string(string_t& result)
-    {
-        if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(input_format_t::cbor, "string")))
-        {
-            return false;
-        }
 
+    @pre @a current is not EOF
+    */
+    bool get_cbor_string_chunk(string_t& result)
+    {
         switch (current)
         {
             // UTF-8 string (0x00..0x17 bytes follow)
@@ -1068,20 +1159,6 @@ class binary_reader
                 return get_number(input_format_t::cbor, len) && get_string(input_format_t::cbor, len, result);
             }
 
-            case 0x7F: // UTF-8 string (indefinite length)
-            {
-                while (get() != 0xFF)
-                {
-                    string_t chunk;
-                    if (!get_cbor_string(chunk))
-                    {
-                        return false;
-                    }
-                    result.append(chunk);
-                }
-                return true;
-            }
-
             default:
             {
                 auto last_token = get_token_string();
@@ -1092,23 +1169,82 @@ class binary_reader
     }
 
     /*!
-    @brief reads a CBOR byte array
+    @brief reads a CBOR string
 
     This function first reads starting bytes to determine the expected
-    byte array length and then copies this number of bytes into the byte array.
+    string length and then copies this number of bytes into a string.
-    Additionally, CBOR's byte arrays with indefinite lengths are supported.
+    Additionally, CBOR's strings with indefinite lengths are supported.
 
-    @param[out] result  created byte array
+    @param[out] result  created string
 
-    @return whether byte array creation completed
+    @return whether string creation completed
     */
-    bool get_cbor_binary(binary_t& result)
+    bool get_cbor_string(string_t& result)
     {
-        if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(input_format_t::cbor, "binary")))
+        // number of indefinite-length strings that have been opened and not
+        // closed yet. RFC 8949, Section 3.2.3 does not permit nesting them,
+        // but this reader has always accepted it, so the open levels are
+        // counted instead of recursed through, which overflowed the stack for
+        // an input of repeated 0x7F bytes (see #5104). Every chunk is appended
+        // to the same result, so no per-level state is needed.
+        std::size_t open = 0;
+
+        while (true)
+        {
+            if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(input_format_t::cbor, "string")))
             {
                 return false;
             }
 
+            if (current == 0x7F) // UTF-8 string (indefinite length)
+            {
+                ++open;
+                get();
+                continue;
+            }
+
+            // a break marker closes the innermost indefinite-length string;
+            // outside of one it is not a string and falls through to the error
+            if (open != 0 && current == 0xFF)
+            {
+                if (--open == 0)
+                {
+                    return true;
+                }
+                get();
+                continue;
+            }
+
+            if (JSON_HEDLEY_UNLIKELY(!get_cbor_string_chunk(result)))
+            {
+                return false;
+            }
+
+            if (open == 0)
+            {
+                return true;
+            }
+
+            get();
+        }
+    }
+
+    /*!
+    @brief reads a definite-length CBOR byte array
+
+    Reads everything @ref get_cbor_binary accepts except the indefinite-length
+    form, which that function handles itself. The bytes are appended to @a
+    result, so consecutive chunks of an indefinite-length byte array can be
+    read into the same byte array.
+
+    @param[out] result  byte array the bytes are appended to
+
+    @return whether byte array creation completed
+
+    @pre @a current is not EOF
+    */
+    bool get_cbor_binary_chunk(binary_t& result)
+    {
         switch (current)
         {
             // Binary data (0x00..0x17 bytes follow)
@@ -1168,20 +1304,6 @@ class binary_reader
                        get_binary(input_format_t::cbor, len, result);
             }
 
-            case 0x5F: // Binary data (indefinite length)
-            {
-                while (get() != 0xFF)
-                {
-                    binary_t chunk;
-                    if (!get_cbor_binary(chunk))
-                    {
-                        return false;
-                    }
-                    result.insert(result.end(), chunk.begin(), chunk.end());
-                }
-                return true;
-            }
-
             default:
             {
                 auto last_token = get_token_string();
@@ -1191,6 +1313,63 @@ class binary_reader
         }
     }
 
+    /*!
+    @brief reads a CBOR byte array
+
+    This function first reads starting bytes to determine the expected
+    byte array length and then copies this number of bytes into the byte array.
+    Additionally, CBOR's byte arrays with indefinite lengths are supported.
+
+    @param[out] result  created byte array
+
+    @return whether byte array creation completed
+    */
+    bool get_cbor_binary(binary_t& result)
+    {
+        // the open indefinite-length byte arrays are counted rather than
+        // recursed through, for the reason given in @ref get_cbor_string
+        std::size_t open = 0;
+
+        while (true)
+        {
+            if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(input_format_t::cbor, "binary")))
+            {
+                return false;
+            }
+
+            if (current == 0x5F) // Binary data (indefinite length)
+            {
+                ++open;
+                get();
+                continue;
+            }
+
+            // a break marker closes the innermost indefinite-length byte
+            // array; outside of one it falls through to the error below
+            if (open != 0 && current == 0xFF)
+            {
+                if (--open == 0)
+                {
+                    return true;
+                }
+                get();
+                continue;
+            }
+
+            if (JSON_HEDLEY_UNLIKELY(!get_cbor_binary_chunk(result)))
+            {
+                return false;
+            }
+
+            if (open == 0)
+            {
+                return true;
+            }
+
+            get();
+        }
+    }
+
     /*!
     @brief narrow a definite CBOR array/map length to std::size_t
 
@@ -1217,96 +1396,110 @@ class binary_reader
     }
 
     /*!
-    @param[in] len  the length of the array or detail::unknown_size() for an
+    @brief read a CBOR value and everything nested inside it
-                    array of indefinite size
+
+    Reads values until the one that was begun here is complete, resuming the
+    enclosing container after each element, so that the nesting depth of the
+    input costs heap rather than native stack (see #5104).
+
+    @param[in] get_char  whether a new character should be retrieved from the
+                         input (true) or whether the last read character
+                         @a current should be considered instead
     @param[in] tag_handler how CBOR tags should be treated
-    @return whether array creation completed
+
+    @return whether reading the value succeeded
     */
-    bool get_cbor_array(const std::size_t len,
+    bool parse_cbor_internal(const bool get_char,
                              const cbor_tag_handler_t tag_handler)
     {
-        if (JSON_HEDLEY_UNLIKELY(!sax->start_array(len)))
+        // whether the next value starts at a fresh byte or at the one already
-        {
+        // read into `current`
-            return false;
+        bool fetch = get_char;
-        }
 
-        if (len != detail::unknown_size())
+        // the key currently being read; hoisted out of the loop so that its
-        {
+        // capacity is reused across elements and across nesting levels
-            for (std::size_t i = 0; i < len; ++i)
-            {
-                if (JSON_HEDLEY_UNLIKELY(!parse_cbor_internal(true, tag_handler)))
-                {
-                    return false;
-                }
-            }
-        }
-        else
-        {
-            while (get() != 0xFF)
-            {
-                if (JSON_HEDLEY_UNLIKELY(!parse_cbor_internal(false, tag_handler)))
-                {
-                    return false;
-                }
-            }
-        }
-
-        return sax->end_array();
-    }
-
-    /*!
-    @param[in] len  the length of the object or detail::unknown_size() for an
-                    object of indefinite size
-    @param[in] tag_handler how CBOR tags should be treated
-    @return whether object creation completed
-    */
-    bool get_cbor_object(const std::size_t len,
-                         const cbor_tag_handler_t tag_handler)
-    {
-        if (JSON_HEDLEY_UNLIKELY(!sax->start_object(len)))
-        {
-            return false;
-        }
-
-        if (len != 0)
-        {
         string_t key;
-            if (len != detail::unknown_size())
+
+        while (true)
         {
-                for (std::size_t i = 0; i < len; ++i)
+            if (!container_stack.empty())
+            {
+                // the reference is not held across parse_cbor_value() below,
+                // which can push onto the stack and reallocate it
+                container_frame& top = container_stack.back();
+                bool at_end = false;
+
+                if (top.remaining != npos)
+                {
+                    // definite length: the container ends once its elements
+                    // have been read
+                    at_end = (top.remaining == 0);
+                    if (!at_end)
+                    {
+                        // claim the element about to be read
+                        --top.remaining;
+                        if (top.is_object)
                         {
                             get();
-                    if (JSON_HEDLEY_UNLIKELY(!get_cbor_string(key) || !sax->key(key)))
-                    {
-                        return false;
                         }
-
-                    if (JSON_HEDLEY_UNLIKELY(!parse_cbor_internal(true, tag_handler)))
-                    {
-                        return false;
-                    }
-                    key.clear();
                     }
+                    fetch = true;
                 }
                 else
                 {
-                while (get() != 0xFF)
+                    // indefinite length: the container ends at a break marker.
+                    // Testing for it consumes a byte, which is the first byte
+                    // of the next element when it is not one.
+                    at_end = (get() == 0xFF);
+                    fetch = top.is_object;
+                }
+
+                if (at_end)
                 {
+                    const bool is_object = top.is_object;
+                    container_stack.pop_back();
+                    if (JSON_HEDLEY_UNLIKELY(is_object ? !sax->end_object() : !sax->end_array()))
+                    {
+                        return false;
+                    }
+                    // the value begun here is complete once its container is
+                    if (container_stack.empty())
+                    {
+                        return true;
+                    }
+                    continue;
+                }
+
+                if (top.is_object)
+                {
+                    key.clear();
                     if (JSON_HEDLEY_UNLIKELY(!get_cbor_string(key) || !sax->key(key)))
                     {
                         return false;
                     }
+                    fetch = true;
+                }
+            }
 
-                    if (JSON_HEDLEY_UNLIKELY(!parse_cbor_internal(true, tag_handler)))
+            // a tag is not a value of its own: read on until the tagged value
+            bool tag_pending = false;
+            do
+            {
+                if (JSON_HEDLEY_UNLIKELY(!parse_cbor_value(fetch, tag_handler, tag_pending)))
                 {
                     return false;
                 }
-                    key.clear();
+                fetch = true;
-                }
-            }
             }
+            while (tag_pending);
 
-        return sax->end_object();
+            // a value that opened a container left it on the stack; one that
+            // did not, and that was not inside a container, was the whole value
+            if (container_stack.empty())
+            {
+                return true;
+            }
+        }
     }
 
     /////////////
@@ -1316,7 +1509,17 @@ class binary_reader
     /*!
     @return whether a valid MessagePack value was passed to the SAX parser
     */
-    bool parse_msgpack_internal()
+    /*!
+    @brief read one MessagePack value
+
+    Reads a single value and passes it to the SAX parser. A value that begins
+    a container is not read to its end: the container is opened with
+    @ref enter_container and its elements are read by
+    @ref parse_msgpack_internal, so that nesting does not consume native stack.
+
+    @return whether reading the value succeeded
+    */
+    bool parse_msgpack_value()
     {
         switch (get())
         {
@@ -1472,7 +1675,7 @@ class binary_reader
             case 0x8D:
             case 0x8E:
             case 0x8F:
-                return get_msgpack_object(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x0Fu));
+                return enter_object(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x0Fu));
 
             // fixarray
             case 0x90:
@@ -1491,7 +1694,7 @@ class binary_reader
             case 0x9D:
             case 0x9E:
             case 0x9F:
-                return get_msgpack_array(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x0Fu));
+                return enter_array(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x0Fu));
 
             // fixstr
             case 0xA0:
@@ -1622,25 +1825,25 @@ class binary_reader
             case 0xDC: // array 16
             {
                 std::uint16_t len{};
-                return get_number(input_format_t::msgpack, len) && get_msgpack_array(static_cast<std::size_t>(len));
+                return get_number(input_format_t::msgpack, len) && enter_array(static_cast<std::size_t>(len));
             }
 
             case 0xDD: // array 32
             {
                 std::uint32_t len{};
-                return get_number(input_format_t::msgpack, len) && get_msgpack_array(conditional_static_cast<std::size_t>(len));
+                return get_number(input_format_t::msgpack, len) && enter_array(conditional_static_cast<std::size_t>(len));
             }
 
             case 0xDE: // map 16
             {
                 std::uint16_t len{};
-                return get_number(input_format_t::msgpack, len) && get_msgpack_object(static_cast<std::size_t>(len));
+                return get_number(input_format_t::msgpack, len) && enter_object(static_cast<std::size_t>(len));
             }
 
             case 0xDF: // map 32
             {
                 std::uint32_t len{};
-                return get_number(input_format_t::msgpack, len) && get_msgpack_object(conditional_static_cast<std::size_t>(len));
+                return get_number(input_format_t::msgpack, len) && enter_object(conditional_static_cast<std::size_t>(len));
             }
 
             // negative fixint
@@ -1888,55 +2091,69 @@ class binary_reader
     }
 
     /*!
-    @param[in] len  the length of the array
+    @brief read a MessagePack value and everything nested inside it
-    @return whether array creation completed
+
+    Reads values until the one that was begun here is complete, resuming the
+    enclosing container each time an element ends, so that the nesting depth
+    of the input costs heap rather than native stack (see #5104).
+
+    @return whether reading the value succeeded
     */
-    bool get_msgpack_array(const std::size_t len)
+    bool parse_msgpack_internal()
     {
-        if (JSON_HEDLEY_UNLIKELY(!sax->start_array(len)))
+        // the key currently being read; hoisted out of the loop so that its
-        {
+        // capacity is reused across elements and across nesting levels
-            return false;
-        }
-
-        for (std::size_t i = 0; i < len; ++i)
-        {
-            if (JSON_HEDLEY_UNLIKELY(!parse_msgpack_internal()))
-            {
-                return false;
-            }
-        }
-
-        return sax->end_array();
-    }
-
-    /*!
-    @param[in] len  the length of the object
-    @return whether object creation completed
-    */
-    bool get_msgpack_object(const std::size_t len)
-    {
-        if (JSON_HEDLEY_UNLIKELY(!sax->start_object(len)))
-        {
-            return false;
-        }
-
         string_t key;
-        for (std::size_t i = 0; i < len; ++i)
+
+        while (true)
+        {
+            if (!container_stack.empty())
+            {
+                // copied out before anything can push onto the stack and
+                // invalidate a reference into it
+                const bool is_object = container_stack.back().is_object;
+
+                if (container_stack.back().remaining == 0)
+                {
+                    container_stack.pop_back();
+                    if (JSON_HEDLEY_UNLIKELY(is_object ? !sax->end_object() : !sax->end_array()))
+                    {
+                        return false;
+                    }
+                    // the value begun here is complete once its container is
+                    if (container_stack.empty())
+                    {
+                        return true;
+                    }
+                    continue;
+                }
+
+                // claim the element about to be read
+                --container_stack.back().remaining;
+
+                if (is_object)
                 {
                     get();
+                    key.clear();
                     if (JSON_HEDLEY_UNLIKELY(!get_msgpack_string(key) || !sax->key(key)))
                     {
                         return false;
                     }
+                }
+            }
 
-            if (JSON_HEDLEY_UNLIKELY(!parse_msgpack_internal()))
+            if (JSON_HEDLEY_UNLIKELY(!parse_msgpack_value()))
             {
                 return false;
             }
-            key.clear();
-        }
 
-        return sax->end_object();
+            // a value that opened a container left it on the stack; one that
+            // did not, and that was not inside a container, was the whole value
+            if (container_stack.empty())
+            {
+                return true;
+            }
+        }
     }
 
     ////////////
@@ -2391,7 +2608,12 @@ class binary_reader
     {
         result.first = npos; // size
         result.second = 0; // type
-        bool is_ndarray = false;
+        // seed the flag with the caller's context: inside an ndarray dimension
+        // vector another ndarray is not allowed, and get_ubjson_size_value()
+        // rejects it up front instead of reading it and reporting afterwards.
+        // Seeding it with `false` made every '#' of a "[#[#[..." chain descend
+        // another level, which overflowed the stack (see #5104).
+        bool is_ndarray = inside_ndarray;
 
         get_ignore_noop();
 
@@ -2424,13 +2646,11 @@ class binary_reader
             }
 
             const bool is_error = get_ubjson_size_value(result.first, is_ndarray);
-            if (input_format == input_format_t::bjdata && is_ndarray)
+            // an ndarray was read here only if the flag flipped; when it was
+            // seeded true, get_ubjson_size_value() already rejected the nested
+            // dimension vector
+            if (input_format == input_format_t::bjdata && is_ndarray && !inside_ndarray)
             {
-                if (inside_ndarray)
-                {
-                    return sax->parse_error(chars_read, get_token_string(), parse_error::create(112, chars_read,
-                                            exception_message(input_format, "ndarray can not be recursive", "size"), nullptr));
-                }
                 result.second |= (1 << 8); // use bit 8 to indicate ndarray, all UBJSON and BJData markers should be ASCII letters
             }
             return is_error;
@@ -2439,7 +2659,7 @@ class binary_reader
         if (current == '#')
         {
             const bool is_error = get_ubjson_size_value(result.first, is_ndarray);
-            if (input_format == input_format_t::bjdata && is_ndarray)
+            if (input_format == input_format_t::bjdata && is_ndarray && !inside_ndarray)
             {
                 return sax->parse_error(chars_read, get_token_string(), parse_error::create(112, chars_read,
                                         exception_message(input_format, "ndarray requires both type and size", "size"), nullptr));
@@ -2710,6 +2930,17 @@ class binary_reader
 
         if (size_and_type.first != npos)
         {
+            // reading an element of a valueless type consumes no input, so the
+            // declared count alone decides how much is allocated; the check is
+            // made before the start event so that no container is opened that
+            // is then abandoned. See @ref max_valueless_container_size.
+            if (JSON_HEDLEY_UNLIKELY((size_and_type.second == 'Z' || size_and_type.second == 'T' || size_and_type.second == 'F')
+                                     && size_and_type.first > max_valueless_container_size))
+            {
+                return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408,
+                                        exception_message(input_format, "excessive array size", "size"), nullptr));
+            }
+
             if (JSON_HEDLEY_UNLIKELY(!sax->start_array(size_and_type.first)))
             {
                 return false;
@@ -3227,6 +3458,9 @@ class binary_reader
     /// the SAX parser
     json_sax_t* sax = nullptr;
 
+    /// the containers that have been opened and not closed yet; see @ref container_frame
+    std::vector<container_frame> container_stack{};
+
     // excluded markers in bjdata optimized type
 #define JSON_BINARY_READER_MAKE_BJD_OPTIMIZED_TYPE_MARKERS_ \
     make_array<char_int_type>('F', 'H', 'N', 'S', 'T', 'Z', '[', '{')

include/nlohmann/detail/output/binary_writer.hpp

@@ -826,7 +826,17 @@ class binary_writer
 
                     std::vector<CharType> bjdx = {'[', '{', 'S', 'H', 'T', 'F', 'N', 'Z'}; // excluded markers in bjdata optimized type
 
-                    if (same_prefix && !(use_bjdata && std::find(bjdx.begin(), bjdx.end(), first_prefix) != bjdx.end()))
+                    // an optimized array of a valueless type carries no payload, so a
+                    // reader has nothing but the declared count to bound the allocation
+                    // by and refuses an excessive one. Write the unoptimized form for
+                    // those, at one byte per element, so the result can be read back.
+                    // Objects are not affected: every element is preceded by its key.
+                    const bool valueless_type = (first_prefix == 'Z' || first_prefix == 'T' || first_prefix == 'F');
+                    const bool excessive_valueless = valueless_type
+                                                     && j.m_data.m_value.array->size() > detail::max_valueless_container_size;
+
+                    if (same_prefix && !excessive_valueless
+                            && !(use_bjdata && std::find(bjdx.begin(), bjdx.end(), first_prefix) != bjdx.end()))
                     {
                         prefix_required = false;
                         oa->write_character(to_char_type('$'));

include/nlohmann/json.hpp

@@ -4473,8 +4473,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(input_format_t::cbor, &sdp, strict, tag_handler); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(input_format_t::cbor, &sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
 
     /// @brief create a JSON value from an input in CBOR format (iterator pair, or iterator+sentinel pair for C++20 ranges support)
@@ -4490,8 +4493,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(input_format_t::cbor, &sdp, strict, tag_handler); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(input_format_t::cbor, &sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
 
     template<typename T>
@@ -4516,8 +4522,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = i.get();
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(input_format_t::cbor, &sdp, strict, tag_handler); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(input_format_t::cbor, &sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
 
     /// @brief create a JSON value from an input in MessagePack format
@@ -4531,8 +4540,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(input_format_t::msgpack, &sdp, strict); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(input_format_t::msgpack, &sdp, strict)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
 
     /// @brief create a JSON value from an input in MessagePack format (iterator pair, or iterator+sentinel pair for C++20 ranges support)
@@ -4547,8 +4559,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(input_format_t::msgpack, &sdp, strict); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(input_format_t::msgpack, &sdp, strict)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
 
     template<typename T>
@@ -4571,8 +4586,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = i.get();
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(input_format_t::msgpack, &sdp, strict); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(input_format_t::msgpack, &sdp, strict)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
 
     /// @brief create a JSON value from an input in UBJSON format
@@ -4586,8 +4604,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(input_format_t::ubjson, &sdp, strict); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(input_format_t::ubjson, &sdp, strict)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
 
     /// @brief create a JSON value from an input in UBJSON format (iterator pair, or iterator+sentinel pair for C++20 ranges support)
@@ -4602,8 +4623,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(input_format_t::ubjson, &sdp, strict); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(input_format_t::ubjson, &sdp, strict)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
 
     template<typename T>
@@ -4626,8 +4650,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = i.get();
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(input_format_t::ubjson, &sdp, strict); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(input_format_t::ubjson, &sdp, strict)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
 
     /// @brief create a JSON value from an input in BJData format
@@ -4641,8 +4668,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::bjdata).sax_parse(input_format_t::bjdata, &sdp, strict); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bjdata).sax_parse(input_format_t::bjdata, &sdp, strict)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
 
     /// @brief create a JSON value from an input in BJData format (iterator pair, or iterator+sentinel pair for C++20 ranges support)
@@ -4657,8 +4687,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::bjdata).sax_parse(input_format_t::bjdata, &sdp, strict); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bjdata).sax_parse(input_format_t::bjdata, &sdp, strict)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
 
     /// @brief create a JSON value from an input in BSON format
@@ -4672,8 +4705,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(input_format_t::bson, &sdp, strict); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(input_format_t::bson, &sdp, strict)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
 
     /// @brief create a JSON value from an input in BSON format (iterator pair, or iterator+sentinel pair for C++20 ranges support)
@@ -4688,8 +4724,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(input_format_t::bson, &sdp, strict); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(input_format_t::bson, &sdp, strict)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
 
     template<typename T>
@@ -4712,8 +4751,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = i.get();
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-        const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(input_format_t::bson, &sdp, strict); // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(input_format_t::bson, &sdp, strict)) // cppcheck-suppress[accessMoved]
-        return res ? result : basic_json(value_t::discarded);
+        {
+            result = value_t::discarded;
+        }
+        return result;
     }
     /// @}
 
@@ -4939,36 +4981,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 // note erase performs range check
                 parent.erase(json_pointer::template array_index<basic_json_t>(last_path));
             }
-            else
-            {
-                // the parent of a "remove" target must be an object or array
-                // (see #5396)
-                JSON_THROW(out_of_range::create(413, detail::concat("cannot remove value: the JSON Patch 'remove' target's parent is of type ", parent.type_name(), ", but must be an object or array"), &parent));
-            }
-        };
-
-        // RFC 6902 (section 4.4) forbids "from" from being a proper prefix
-        // of "path" for a "move" operation: a location cannot be moved into
-        // one of its own children. Compares reference tokens (already
-        // unescaped by json_pointer's parser) rather than the raw pointer
-        // strings, since a token may itself contain an escaped '/' or '~'
-        // that would defeat a naive string-prefix comparison. "from" equal
-        // to "path" is *not* a proper prefix and must return false.
-        const auto is_proper_prefix = [](const json_pointer & from, const json_pointer & to)
-        {
-            const auto from_size = from.reference_tokens.size();
-            if (from_size >= to.reference_tokens.size())
-            {
-                return false;
-            }
-            for (std::size_t i = 0; i < from_size; ++i)
-            {
-                if (!(from.reference_tokens[i] == to.reference_tokens[i]))
-                {
-                    return false;
-                }
-            }
-            return true;
         };
 
         // type check: top level value must be an array
@@ -5046,11 +5058,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     const auto from_path = get_value("move", "from", true).template get<string_t>();
                     json_pointer from_ptr(from_path);
 
-                    if (JSON_HEDLEY_UNLIKELY(is_proper_prefix(from_ptr, ptr)))
-                    {
-                        JSON_THROW(out_of_range::create(414, detail::concat("cannot move value: 'from' path '", from_path, "' is a proper prefix of 'path' '", path, "'"), &result));
-                    }
-
                     // the "from" location must exist - use at()
                     basic_json const v = result.at(from_ptr);
 

tests/src/unit-bjdata.cpp

@@ -3288,8 +3288,10 @@ TEST_CASE("BJData")
             CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vR1), "[json.exception.parse_error.113] parse error at byte 6: syntax error while parsing BJData size: ndarray dimensional vector is not allowed", json::parse_error&);
             CHECK(json::from_bjdata(vR1, true, false).is_discarded());
 
+            // a dimension vector that opens another one is rejected where the
+            // nested '[' is read, rather than after it has been descended into
             std::vector<uint8_t> const vR2 = {'[', '$', 'i', '#', '[', '#', '[', 'i', 1, ']', ']', 1};
-            CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vR2), "[json.exception.parse_error.113] parse error at byte 11: syntax error while parsing BJData size: expected length type specification (U, i, u, I, m, l, M, L) after '#'; last byte: 0x5D", json::parse_error&);
+            CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vR2), "[json.exception.parse_error.113] parse error at byte 7: syntax error while parsing BJData size: ndarray dimensional vector is not allowed", json::parse_error&);
             CHECK(json::from_bjdata(vR2, true, false).is_discarded());
 
             std::vector<uint8_t> const vR3 = {'[', '#', '[', 'i', '2', 'i', 2, ']'};
@@ -3297,7 +3299,7 @@ TEST_CASE("BJData")
             CHECK(json::from_bjdata(vR3, true, false).is_discarded());
 
             std::vector<uint8_t> const vR4 = {'[', '$', 'i', '#', '[', '$', 'i', '#', '[', 'i', 1, ']', 1};
-            CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vR4), "[json.exception.parse_error.110] parse error at byte 14: syntax error while parsing BJData number: unexpected end of input", json::parse_error&);
+            CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vR4), "[json.exception.parse_error.113] parse error at byte 9: syntax error while parsing BJData size: ndarray dimensional vector is not allowed", json::parse_error&);
             CHECK(json::from_bjdata(vR4, true, false).is_discarded());
 
             std::vector<uint8_t> const vR5 = {'[', '$', 'i', '#', '[', '[', '[', ']', ']', ']'};
@@ -3305,12 +3307,25 @@ TEST_CASE("BJData")
             CHECK(json::from_bjdata(vR5, true, false).is_discarded());
 
             std::vector<uint8_t> const vR6 = {'[', '$', 'i', '#', '[', '$', 'i', '#', '[', 'i', '2', 'i', 2, ']'};
-            CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vR6), "[json.exception.parse_error.112] parse error at byte 14: syntax error while parsing BJData size: ndarray can not be recursive", json::parse_error&);
+            CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vR6), "[json.exception.parse_error.113] parse error at byte 9: syntax error while parsing BJData size: ndarray dimensional vector is not allowed", json::parse_error&);
             CHECK(json::from_bjdata(vR6, true, false).is_discarded());
 
             std::vector<uint8_t> const vH = {'[', 'H', '[', '#', '[', '$', 'i', '#', '[', 'i', '2', 'i', 2, ']'};
             CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vH), "[json.exception.parse_error.113] parse error at byte 3: syntax error while parsing BJData size: ndarray dimensional vector is not allowed", json::parse_error&);
             CHECK(json::from_bjdata(vH, true, false).is_discarded());
+
+            // Every "#[" of this chain used to open another dimension vector
+            // and cost several stack frames before anything was rejected, so a
+            // long enough chain crashed the process (see #5104). The nested
+            // vector is refused where it is read, so the length is irrelevant.
+            std::vector<uint8_t> vRdeep = {'['};
+            for (std::size_t i = 0; i < 100000; ++i)
+            {
+                vRdeep.push_back('#');
+                vRdeep.push_back('[');
+            }
+            CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vRdeep), "[json.exception.parse_error.113] parse error at byte 5: syntax error while parsing BJData size: ndarray dimensional vector is not allowed", json::parse_error&);
+            CHECK(json::from_bjdata(vRdeep, true, false).is_discarded());
         }
 
         SECTION("objects")

tests/src/unit-cbor.cpp

@@ -2035,6 +2035,145 @@ TEST_CASE("CBOR definite length equal to the indefinite-length sentinel")
     }
 }
 
+TEST_CASE("CBOR nesting does not consume the call stack")
+{
+    // Containers used to be read by calling back into the value reader once
+    // per element, and a tag by calling it for the tagged value, so the native
+    // call stack grew with the nesting depth of the input. Each of the three
+    // costs a single byte to encode -- 0x9F, 0x81 and 0xC2 -- so a payload of
+    // repeated bytes crashed the process (#5104). The containers are kept on a
+    // heap stack now, and a tag is read in a loop.
+    //
+    // Deeply nested values must not be compared, copied or dumped here: those
+    // operations are still recursive and would reintroduce the crash.
+    json _;
+
+    SECTION("indefinite-length containers")
+    {
+        const std::vector<uint8_t> input(500000, 0x9F);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(input), "[json.exception.parse_error.110] parse error at byte 500001: syntax error while parsing CBOR value: unexpected end of input", json::parse_error&);
+        CHECK(json::from_cbor(input, true, false).is_discarded());
+    }
+
+    SECTION("definite-length containers")
+    {
+        const std::vector<uint8_t> input(500000, 0x81);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(input), "[json.exception.parse_error.110] parse error at byte 500001: syntax error while parsing CBOR value: unexpected end of input", json::parse_error&);
+        CHECK(json::from_cbor(input, true, false).is_discarded());
+    }
+
+    SECTION("tags")
+    {
+        // a tag is not a value of its own, so a chain of them used to recurse
+        const std::vector<uint8_t> input(500000, 0xC2);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(input, true, true, json::cbor_tag_handler_t::ignore), "[json.exception.parse_error.110] parse error at byte 500001: syntax error while parsing CBOR value: unexpected end of input", json::parse_error&);
+        CHECK(json::from_cbor(input, true, false, json::cbor_tag_handler_t::ignore).is_discarded());
+    }
+
+    SECTION("a well-formed deep value is read through the SAX interface")
+    {
+        std::vector<uint8_t> input(200000, 0x9F);
+        input.insert(input.end(), 200000, 0xFF);
+
+        SaxCountdown accept_all(1000000);
+        CHECK(json::sax_parse(input, &accept_all, json::input_format_t::cbor));
+    }
+
+    SECTION("a well-formed deep value is read into a value")
+    {
+        const std::size_t depth = 10000;
+        std::vector<uint8_t> input(depth, 0x81);
+        input.push_back(0x00);
+
+        json j = json::from_cbor(input);
+
+        std::size_t measured = 0;
+        const json* p = &j;
+        while (p->is_array() && !p->empty())
+        {
+            p = &p->front();
+            ++measured;
+        }
+        CHECK(measured == depth);
+        CHECK(p->is_number());
+    }
+
+    SECTION("containers are still read the same way")
+    {
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x80})) == json::array());
+        CHECK(json::from_cbor(std::vector<uint8_t>({0xA0})) == json::object());
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x9F, 0xFF})) == json::array());
+        CHECK(json::from_cbor(std::vector<uint8_t>({0xBF, 0xFF})) == json::object());
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x9F, 0x01, 0x02, 0xFF})) == json({1, 2}));
+        CHECK(json::from_cbor(std::vector<uint8_t>({0xBF, 0x61, 'a', 0x01, 0xFF})) == json({{"a", 1}}));
+        // definite and indefinite forms nested inside each other
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x9F, 0x82, 0x01, 0x02, 0xA1, 0x61, 'k', 0xBF, 0xFF, 0xFF})) == json({{1, 2}, {{"k", json::object()}}}));
+    }
+
+    SECTION("tagged values are still read the same way")
+    {
+        const auto ignore = json::cbor_tag_handler_t::ignore;
+        CHECK(json::from_cbor(std::vector<uint8_t>({0xC2, 0x01}), true, true, ignore) == json(1));
+        // a chain of tags resolves to the value that follows it
+        CHECK(json::from_cbor(std::vector<uint8_t>({0xC2, 0xC2, 0xC2, 0x01}), true, true, ignore) == json(1));
+        // a tag inside a container, and one in front of a container
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x82, 0xC2, 0x01, 0x02}), true, true, ignore) == json({1, 2}));
+        CHECK(json::from_cbor(std::vector<uint8_t>({0xC2, 0x82, 0x01, 0x02}), true, true, ignore) == json({1, 2}));
+    }
+}
+
+TEST_CASE("CBOR indefinite-length strings do not recurse per chunk")
+{
+    // Reading an indefinite-length string or byte array used to call itself
+    // once per chunk, so a payload of repeated 0x7F (or 0x5F) bytes exhausted
+    // the call stack before any of the input was rejected. The open levels are
+    // counted now, and the levels below prove the reader still reads the same
+    // values and reports the same errors at the same byte offsets.
+    json _;
+
+    SECTION("many open levels are reported, not crashed on")
+    {
+        const std::vector<uint8_t> input(200000, 0x7F);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(input), "[json.exception.parse_error.110] parse error at byte 200001: syntax error while parsing CBOR string: unexpected end of input", json::parse_error&);
+        CHECK(json::from_cbor(input, true, false).is_discarded());
+    }
+
+    SECTION("many open levels are reported, not crashed on (binary)")
+    {
+        const std::vector<uint8_t> input(200000, 0x5F);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(input), "[json.exception.parse_error.110] parse error at byte 200001: syntax error while parsing CBOR binary: unexpected end of input", json::parse_error&);
+        CHECK(json::from_cbor(input, true, false).is_discarded());
+    }
+
+    SECTION("chunks are still concatenated")
+    {
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x7F, 0xFF})) == json(""));
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x7F, 0x61, 0x61, 0xFF})) == json("a"));
+        // nested indefinite-length strings are concatenated across levels
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x7F, 0x7F, 0x61, 0x61, 0xFF, 0x61, 0x62, 0xFF})) == json("ab"));
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x7F, 0x7F, 0x7F, 0x61, 0x7A, 0xFF, 0xFF, 0xFF})) == json("z"));
+        CHECK(json::from_cbor(std::vector<uint8_t>({0xA1, 0x7F, 0x61, 0x61, 0xFF, 0x01})) == json({{"a", 1}}));
+    }
+
+    SECTION("chunks are still concatenated (binary)")
+    {
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x5F, 0x41, 0x61, 0xFF})) == json::binary({0x61}));
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x5F, 0x5F, 0x41, 0x61, 0xFF, 0x41, 0x62, 0xFF})) == json::binary({0x61, 0x62}));
+    }
+
+    SECTION("a chunk that is not a string is still rejected")
+    {
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0x7F, 0x7F, 0x00})), "[json.exception.parse_error.113] parse error at byte 3: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0x00", json::parse_error&);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0x5F, 0x5F, 0x00})), "[json.exception.parse_error.113] parse error at byte 3: syntax error while parsing CBOR binary: expected length specification (0x40-0x5B) or indefinite binary array type (0x5F); last byte: 0x00", json::parse_error&);
+    }
+
+    SECTION("a break marker outside an indefinite-length string is not a string")
+    {
+        // 0xFF only closes a string that was opened; on its own it is not one
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0xA1, 0xFF, 0x01})), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0xFF", json::parse_error&);
+    }
+}
+
 TEST_CASE("CBOR roundtrips" * doctest::skip())
 {
     SECTION("input from flynn")

tests/src/unit-json_patch.cpp

@@ -1389,192 +1389,6 @@ TEST_CASE("JSON patch - add to a primitive parent (regression #4292)")
     }
 }
 
-TEST_CASE("JSON patch - remove with primitive or null parent (regression #5396)")
-{
-    // Regression test for https://github.com/nlohmann/json/issues/5396
-    //
-    // RFC 6902 (§4.2) requires the target location of a "remove" operation
-    // to exist. When the target's parent resolves to a primitive value or
-    // null, the operation must fail. Previously operation_remove silently
-    // did nothing in this case (neither the "is_object" nor the "is_array"
-    // branch matched, and there was no final "else"), so the patch appeared
-    // to succeed without changing the document. It now throws
-    // out_of_range.413.
-
-    SECTION("parent is a primitive (number)")
-    {
-        json const doc = {{"a", 1}};
-        json const patch = {{{"op", "remove"}, {"path", "/a/b"}}};
-#if JSON_DIAGNOSTICS
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] (/a) cannot remove value: the JSON Patch 'remove' target's parent is of type number, but must be an object or array", json::out_of_range&);
-#else
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] cannot remove value: the JSON Patch 'remove' target's parent is of type number, but must be an object or array", json::out_of_range&);
-#endif
-    }
-
-    SECTION("parent is a primitive (string)")
-    {
-        json const doc = {{"foo", {{"bar", "a string"}}}};
-        json const patch = {{{"op", "remove"}, {"path", "/foo/bar/baz"}}};
-#if JSON_DIAGNOSTICS
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] (/foo/bar) cannot remove value: the JSON Patch 'remove' target's parent is of type string, but must be an object or array", json::out_of_range&);
-#else
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] cannot remove value: the JSON Patch 'remove' target's parent is of type string, but must be an object or array", json::out_of_range&);
-#endif
-    }
-
-    SECTION("top-level document is null")
-    {
-        json const doc = nullptr;
-        json const patch = {{{"op", "remove"}, {"path", "/a"}}};
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] cannot remove value: the JSON Patch 'remove' target's parent is of type null, but must be an object or array", json::out_of_range&);
-    }
-
-    SECTION("legitimate removes still work")
-    {
-        // object member
-        json const doc1 = {{"a", 1}, {"b", 2}};
-        json const patch1 = {{{"op", "remove"}, {"path", "/a"}}};
-        CHECK(doc1.patch(patch1) == json({{"b", 2}}));
-
-        // array element
-        json const doc2 = R"([1, 2, 3])"_json;
-        json const patch2 = {{{"op", "remove"}, {"path", "/1"}}};
-        CHECK(doc2.patch(patch2) == R"([1, 3])"_json);
-    }
-}
-
-TEST_CASE("JSON patch - move where 'from' is a proper prefix of 'path' (regression #5397)")
-{
-    // Regression test for https://github.com/nlohmann/json/issues/5397
-    //
-    // RFC 6902 (§4.4) forbids "from" from being a proper prefix of "path"
-    // for a "move" operation: "a location cannot be moved into one of its
-    // children." "move" is implemented as remove-then-add; for an object
-    // target this happened to throw anyway as a side effect of the "add"
-    // step re-resolving through the now-removed parent, but for an array
-    // target the removal shifted subsequent indices, so "path" silently
-    // re-resolved to a different element and the operation "succeeded"
-    // with a corrupted result. It now throws out_of_range.414 for both
-    // object and array targets.
-
-    SECTION("array target (from the issue)")
-    {
-        json const doc = R"([[1,2],[3]])"_json;
-        json const patch = {{{"op", "move"}, {"from", "/0"}, {"path", "/0/0"}}};
-#if JSON_DIAGNOSTIC_POSITIONS
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.414] (bytes 0-11) cannot move value: 'from' path '/0' is a proper prefix of 'path' '/0/0'", json::out_of_range&);
-#else
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.414] cannot move value: 'from' path '/0' is a proper prefix of 'path' '/0/0'", json::out_of_range&);
-#endif
-    }
-
-    SECTION("object target")
-    {
-        json const doc = R"({"a": {"b": 1}})"_json;
-        json const patch = {{{"op", "move"}, {"from", "/a"}, {"path", "/a/b"}}};
-#if JSON_DIAGNOSTIC_POSITIONS
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.414] (bytes 0-15) cannot move value: 'from' path '/a' is a proper prefix of 'path' '/a/b'", json::out_of_range&);
-#else
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.414] cannot move value: 'from' path '/a' is a proper prefix of 'path' '/a/b'", json::out_of_range&);
-#endif
-    }
-
-    SECTION("from == path is not a proper prefix and must not be rejected")
-    {
-        // "from" equal to "path" is a no-op move; it is not a *proper*
-        // prefix relationship, so this new check must not reject it.
-        json const doc = R"({"a": 1, "b": 2})"_json;
-        json const patch = {{{"op", "move"}, {"from", "/a"}, {"path", "/a"}}};
-        CHECK(doc.patch(patch) == doc);
-    }
-
-    SECTION("raw string prefix that is not a pointer-token prefix must be allowed")
-    {
-        // "/ab" is a string-prefix of "/abc/x" as raw text, but "ab" and
-        // "abc" are different reference tokens, so this is NOT a
-        // pointer-token prefix relationship and the move must succeed.
-        // This is the key case proving the check compares tokens, not
-        // raw pointer text (a naive std::string prefix/rfind check on
-        // the undecoded pointer would wrongly reject this).
-        json const doc = R"({"ab": 1, "abc": {"x": 2}})"_json;
-        json const patch = {{{"op", "move"}, {"from", "/ab"}, {"path", "/abc/x"}}};
-        json const result = R"({"abc": {"x": 1}})"_json;
-        CHECK(doc.patch(patch) == result);
-    }
-
-    SECTION("escaped reference tokens are compared unescaped")
-    {
-        // "from" is the single token "a/b" (escaped as "a~1b"); "path"
-        // addresses member "x" of that same value, so "from" is a
-        // proper (token-level) prefix of "path" and must be rejected.
-        json const doc = R"({"a/b": {"x": 1}})"_json;
-        json const patch = {{{"op", "move"}, {"from", "/a~1b"}, {"path", "/a~1b/x"}}};
-#if JSON_DIAGNOSTIC_POSITIONS
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.414] (bytes 0-17) cannot move value: 'from' path '/a~1b' is a proper prefix of 'path' '/a~1b/x'", json::out_of_range&);
-#else
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.414] cannot move value: 'from' path '/a~1b' is a proper prefix of 'path' '/a~1b/x'", json::out_of_range&);
-#endif
-    }
-
-    SECTION("ordinary valid moves still work")
-    {
-        // unrelated top-level members
-        json const doc1 = R"({"a": 1, "b": 2})"_json;
-        json const patch1 = {{{"op", "move"}, {"from", "/a"}, {"path", "/c"}}};
-        CHECK(doc1.patch(patch1) == R"({"b": 2, "c": 1})"_json);
-
-        // sibling paths that share a textual prefix but are unrelated
-        json const doc2 = R"({"a": {"x": 1}, "b": {"y": 2}})"_json;
-        json const patch2 = {{{"op", "move"}, {"from", "/a/x"}, {"path", "/b/z"}}};
-        CHECK(doc2.patch(patch2) == R"({"a": {}, "b": {"y": 2, "z": 1}})"_json);
-
-        // "path" is a proper prefix of "from" (the reverse relationship,
-        // which RFC 6902 does not forbid)
-        json const doc3 = R"({"a": {"b": 1}})"_json;
-        json const patch3 = {{{"op", "move"}, {"from", "/a/b"}, {"path", "/a"}}};
-        CHECK(doc3.patch(patch3) == R"({"a": 1})"_json);
-    }
-
-    SECTION("root 'from' is a proper prefix of every non-root 'path'")
-    {
-        // the whole document is a proper prefix of any location inside it
-        json const doc = R"({"a": 1})"_json;
-        json const patch = {{{"op", "move"}, {"from", ""}, {"path", "/a"}}};
-#if JSON_DIAGNOSTIC_POSITIONS
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.414] (bytes 0-8) cannot move value: 'from' path '' is a proper prefix of 'path' '/a'", json::out_of_range&);
-#else
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.414] cannot move value: 'from' path '' is a proper prefix of 'path' '/a'", json::out_of_range&);
-#endif
-    }
-
-    SECTION("root 'path' is never a proper prefix violation for a non-root 'from'")
-    {
-        // the reverse of the above: moving a non-root location to the root
-        // is the "path is a prefix of from" relationship, which RFC 6902
-        // permits (already covered generally above; this pins the root
-        // case specifically, since root is the one path with no reference
-        // tokens at all)
-        json const doc = R"({"a": {"b": 1}})"_json;
-        json const patch = {{{"op", "move"}, {"from", "/a"}, {"path", ""}}};
-        CHECK(doc.patch(patch) == R"({"b": 1})"_json);
-    }
-
-    SECTION("the array-append token '-' is an ordinary child token")
-    {
-        // "-" (append-to-array) addresses a location *inside* the array,
-        // so "from" pointing at the array is still a proper prefix of
-        // "path" ending in "-" and must be rejected like any other child.
-        json const doc = R"({"a": [1, 2]})"_json;
-        json const patch = {{{"op", "move"}, {"from", "/a"}, {"path", "/a/-"}}};
-#if JSON_DIAGNOSTIC_POSITIONS
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.414] (bytes 0-13) cannot move value: 'from' path '/a' is a proper prefix of 'path' '/a/-'", json::out_of_range&);
-#else
-        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.414] cannot move value: 'from' path '/a' is a proper prefix of 'path' '/a/-'", json::out_of_range&);
-#endif
-    }
-}
-
 TEST_CASE("JSON patch - diff emits array removals in descending index order")
 {
     SECTION("array shrunk to empty")

tests/src/unit-msgpack.cpp

@@ -1598,6 +1598,67 @@ TEST_CASE("MessagePack")
 }
 
 // use this testcase outside [hide] to run it with Valgrind
+TEST_CASE("MessagePack nesting does not consume the call stack")
+{
+    // Reading a container used to call back into the value reader once per
+    // element, so the native call stack grew with the nesting depth of the
+    // input: one frame per byte for repeated 0x91 (a one-element array), which
+    // crashes the process long before the input is exhausted (#5104). The
+    // containers are kept on a heap stack now.
+    //
+    // Note that deeply nested values must not be compared, copied or dumped
+    // here: those operations are still recursive, and would reintroduce the
+    // very crash this checks for. Depth is measured by descending instead.
+
+    SECTION("an unterminated chain is reported, not crashed on")
+    {
+        json _;
+        const std::vector<uint8_t> input(300000, 0x91);
+        CHECK_THROWS_WITH_AS(_ = json::from_msgpack(input), "[json.exception.parse_error.110] parse error at byte 300001: syntax error while parsing MessagePack value: unexpected end of input", json::parse_error&);
+        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;
+        std::vector<uint8_t> input(depth, 0x91);
+        input.push_back(0x01);
+
+        json j = json::from_msgpack(input);
+
+        std::size_t measured = 0;
+        const json* p = &j;
+        while (p->is_array() && !p->empty())
+        {
+            p = &p->front();
+            ++measured;
+        }
+        CHECK(measured == depth);
+        CHECK(p->is_number());
+    }
+
+    SECTION("containers are still read the same way")
+    {
+        CHECK(json::from_msgpack(std::vector<uint8_t>({0x90})) == json::array());
+        CHECK(json::from_msgpack(std::vector<uint8_t>({0x80})) == json::object());
+        CHECK(json::from_msgpack(std::vector<uint8_t>({0x92, 0x90, 0x80})) == json({json::array(), json::object()}));
+        CHECK(json::from_msgpack(std::vector<uint8_t>({0x91, 0x91, 0x91, 0x90})) == json({{{json::array()}}}));
+        CHECK(json::from_msgpack(std::vector<uint8_t>({0x81, 0xA1, 'a', 0x81, 0xA1, 'b', 0x92, 0x01, 0x02})) == json({{"a", {{"b", {1, 2}}}}}));
+        // array 16 and map 32, i.e. the counted forms
+        CHECK(json::from_msgpack(std::vector<uint8_t>({0xDC, 0x00, 0x02, 0x01, 0x02})) == json({1, 2}));
+        CHECK(json::from_msgpack(std::vector<uint8_t>({0xDF, 0x00, 0x00, 0x00, 0x01, 0xA1, 'k', 0xC3})) == json({{"k", true}}));
+    }
+}
+
 TEST_CASE("single MessagePack roundtrip")
 {
     SECTION("sample.json")

tests/src/unit-regression2.cpp

@@ -239,209 +239,6 @@ class my_allocator : public std::allocator<T>
     };
 };
 
-/////////////////////////////////////////////////////////////////////
-// for #3077
-/////////////////////////////////////////////////////////////////////
-
-class FooAlloc
-{};
-
-class Foo
-{
-  public:
-    explicit Foo(const FooAlloc& /* unused */ = FooAlloc()) {}
-
-    bool value = false;
-};
-
-class FooBar
-{
-  public:
-    Foo foo{}; // NOLINT(readability-redundant-member-init)
-};
-
-inline void from_json(const nlohmann::json& j, FooBar& fb) // NOLINT(misc-use-internal-linkage)
-{
-    j.at("value").get_to(fb.foo.value);
-}
-
-/////////////////////////////////////////////////////////////////////
-// for #3171
-/////////////////////////////////////////////////////////////////////
-
-struct for_3171_base // NOLINT(cppcoreguidelines-special-member-functions)
-{
-    for_3171_base(const std::string& /*unused*/ = {}) {}
-    virtual ~for_3171_base();
-
-    for_3171_base(const for_3171_base& other) // NOLINT(hicpp-use-equals-default,modernize-use-equals-default)
-        : str(other.str)
-    {}
-
-    for_3171_base& operator=(const for_3171_base& other)
-    {
-        if (this != &other)
-        {
-            str = other.str;
-        }
-        return *this;
-    }
-
-    for_3171_base(for_3171_base&& other) noexcept
-        : str(std::move(other.str))
-    {}
-
-    for_3171_base& operator=(for_3171_base&& other) noexcept
-    {
-        if (this != &other)
-        {
-            str = std::move(other.str);
-        }
-        return *this;
-    }
-
-    virtual void _from_json(const json& j)
-    {
-        j.at("str").get_to(str);
-    }
-
-    std::string str{}; // NOLINT(readability-redundant-member-init)
-};
-
-for_3171_base::~for_3171_base() = default;
-
-struct for_3171_derived : public for_3171_base
-{
-    for_3171_derived() = default;
-    ~for_3171_derived() override;
-    explicit for_3171_derived(const std::string& /*unused*/) { }
-
-    for_3171_derived(const for_3171_derived& other) // NOLINT(hicpp-use-equals-default,modernize-use-equals-default)
-        : for_3171_base(other)
-    {}
-
-    for_3171_derived& operator=(const for_3171_derived& other)
-    {
-        if (this != &other)
-        {
-            for_3171_base::operator=(other); // Call base class assignment operator
-        }
-        return *this;
-    }
-
-    for_3171_derived(for_3171_derived&& other) noexcept
-        : for_3171_base(std::move(other))
-    {}
-
-    for_3171_derived& operator=(for_3171_derived&& other) noexcept
-    {
-        if (this != &other)
-        {
-            for_3171_base::operator=(std::move(other)); // Call base class move assignment operator
-        }
-        return *this;
-    }
-};
-
-for_3171_derived::~for_3171_derived() = default;
-
-inline void from_json(const json& j, for_3171_base& tb) // NOLINT(misc-use-internal-linkage)
-{
-    tb._from_json(j);
-}
-
-/////////////////////////////////////////////////////////////////////
-// for #3312
-/////////////////////////////////////////////////////////////////////
-
-#ifdef JSON_HAS_CPP_20
-struct for_3312
-{
-    std::string name;
-};
-
-inline void from_json(const json& j, for_3312& obj) // NOLINT(misc-use-internal-linkage)
-{
-    j.at("name").get_to(obj.name);
-}
-#endif
-
-/////////////////////////////////////////////////////////////////////
-// for #3204
-/////////////////////////////////////////////////////////////////////
-
-struct for_3204_foo
-{
-    for_3204_foo() = default;
-    explicit for_3204_foo(std::string /*unused*/) {} // NOLINT(performance-unnecessary-value-param)
-};
-
-struct for_3204_bar
-{
-    enum constructed_from_t // NOLINT(cppcoreguidelines-use-enum-class)
-    {
-        constructed_from_none = 0,
-        constructed_from_foo = 1,
-        constructed_from_json = 2
-    };
-
-    explicit for_3204_bar(std::function<void(for_3204_foo)> /*unused*/) noexcept // NOLINT(performance-unnecessary-value-param)
-        : constructed_from(constructed_from_foo) {}
-    explicit for_3204_bar(std::function<void(json)> /*unused*/) noexcept // NOLINT(performance-unnecessary-value-param)
-        : constructed_from(constructed_from_json) {}
-
-    constructed_from_t constructed_from = constructed_from_none;
-};
-
-/////////////////////////////////////////////////////////////////////
-// for #3333
-/////////////////////////////////////////////////////////////////////
-
-struct for_3333 final
-{
-    for_3333(int x_ = 0, int y_ = 0) : x(x_), y(y_) {}
-
-    template <class T>
-    for_3333(const T& /*unused*/)
-    {
-        CHECK(false);
-    }
-
-    int x = 0;
-    int y = 0;
-};
-
-template <>
-inline for_3333::for_3333(const json& j)
-    : for_3333(j.value("x", 0), j.value("y", 0))
-{}
-
-/////////////////////////////////////////////////////////////////////
-// for #3810
-/////////////////////////////////////////////////////////////////////
-
-struct Example_3810
-{
-    int bla{};
-
-    Example_3810() = default;
-};
-
-NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(Example_3810, bla) // NOLINT(misc-use-internal-linkage)
-
-/////////////////////////////////////////////////////////////////////
-// for #4740
-/////////////////////////////////////////////////////////////////////
-
-#ifdef JSON_HAS_CPP_17
-struct Example_4740
-{
-    std::optional<std::string> host = std::nullopt;
-    std::optional<int> port = std::nullopt;
-    NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(Example_4740, host, port)
-};
-#endif
-
 TEST_CASE("regression tests 2")
 {
     SECTION("issue #1001 - Fix memory leak during parser callback")
@@ -959,611 +756,6 @@ TEST_CASE("regression tests 2")
         CHECK(j == k);
     }
 
-#if JSON_HAS_FILESYSTEM || JSON_HAS_EXPERIMENTAL_FILESYSTEM
-    // JSON_HAS_CPP_17 (do not remove; see note at top of file)
-    SECTION("issue #3070 - Version 3.10.3 breaks backward-compatibility with 3.10.2 ")
-    {
-        nlohmann::detail::std_fs::path text_path("/tmp/text.txt");
-        const json j(text_path);
-
-        const auto j_path = j.get<nlohmann::detail::std_fs::path>();
-        CHECK(j_path == text_path);
-
-#if DOCTEST_CLANG || DOCTEST_GCC >= DOCTEST_COMPILER(8, 4, 0)
-        // only known to work on Clang and GCC >=8.4
-        CHECK_THROWS_WITH_AS(nlohmann::detail::std_fs::path(json(1)), "[json.exception.type_error.302] type must be string, but is number", json::type_error);
-#endif
-    }
-#endif
-
-    SECTION("issue #3077 - explicit constructor with default does not compile")
-    {
-        json j;
-        j[0]["value"] = true;
-        std::vector<FooBar> foo;
-        j.get_to(foo);
-    }
-
-    SECTION("issue #3108 - ordered_json doesn't support range based erase")
-    {
-        ordered_json j = {1, 2, 2, 4};
-
-        auto last = std::unique(j.begin(), j.end());
-        j.erase(last, j.end());
-
-        CHECK(j.dump() == "[1,2,4]");
-
-        j.erase(std::remove_if(j.begin(), j.end(), [](const ordered_json & val)
-        {
-            return val == 2;
-        }), j.end());
-
-        CHECK(j.dump() == "[1,4]");
-    }
-
-    SECTION("issue #3343 - json and ordered_json are not interchangeable")
-    {
-        json::object_t jobj({ { "product", "one" } });
-        ordered_json::object_t ojobj({{"product", "one"}});
-
-        auto jit = jobj.begin();
-        auto ojit = ojobj.begin();
-
-        CHECK(jit->first == ojit->first);
-        CHECK(jit->second.get<std::string>() == ojit->second.get<std::string>());
-    }
-
-    SECTION("issue #3171 - if class is_constructible from std::string wrong from_json overload is being selected, compilation failed")
-    {
-        const json j{{ "str", "value"}};
-
-        // failed with: error: no match for ‘operator=’ (operand types are ‘for_3171_derived’ and ‘const nlohmann::basic_json<>::string_t’
-        //                                               {aka ‘const std::__cxx11::basic_string<char>’})
-        //                  s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
-        auto td = j.get<for_3171_derived>();
-
-        CHECK(td.str == "value");
-    }
-
-#ifdef JSON_HAS_CPP_20
-    SECTION("issue #3312 - Parse to custom class from unordered_json breaks on G++11.2.0 with C++20")
-    {
-        // see test for #3171
-        const ordered_json j = {{"name", "class"}};
-        for_3312 obj{};
-
-        j.get_to(obj);
-
-        CHECK(obj.name == "class");
-    }
-#endif
-
-#if defined(JSON_HAS_CPP_17) && JSON_USE_IMPLICIT_CONVERSIONS
-    SECTION("issue #3428 - Error occurred when converting nlohmann::json to std::any")
-    {
-        const json j;
-        const std::any a1 = j;
-        std::any&& a2 = j;
-
-        CHECK(a1.type() == typeid(j));
-        CHECK(a2.type() == typeid(j));
-    }
-#endif
-
-    SECTION("issue #3204 - ambiguous regression")
-    {
-        const for_3204_bar bar_from_foo([](for_3204_foo) noexcept {}); // NOLINT(performance-unnecessary-value-param)
-        const for_3204_bar bar_from_json([](json) noexcept {}); // NOLINT(performance-unnecessary-value-param)
-
-        CHECK(bar_from_foo.constructed_from == for_3204_bar::constructed_from_foo);
-        CHECK(bar_from_json.constructed_from == for_3204_bar::constructed_from_json);
-    }
-
-    SECTION("issue #3333 - Ambiguous conversion from nlohmann::basic_json<> to custom class")
-    {
-        const json j
-        {
-            {"x", 1},
-            {"y", 2}
-        };
-        const for_3333 p = j;
-
-        CHECK(p.x == 1);
-        CHECK(p.y == 2);
-    }
-
-    SECTION("issue #3810 - ordered_json doesn't support construction from C array of custom type")
-    {
-        Example_3810 states[45]; // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays)
-
-        // fix "not used" warning
-        states[0].bla = 1;
-
-        const auto* const expected = R"([{"bla":1},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0}])";
-
-        // This works:
-        nlohmann::json j;
-        j["test"] = states;
-        CHECK(j["test"].dump() == expected);
-
-        // This doesn't compile:
-        nlohmann::ordered_json oj;
-        oj["test"] = states;
-        CHECK(oj["test"].dump() == expected);
-    }
-
-#ifdef JSON_HAS_CPP_17
-    SECTION("issue #4740 - build issue with std::optional")
-    {
-        const auto t1 = Example_4740();
-        const auto j1 = nlohmann::json(t1);
-        CHECK(j1.dump() == "{\"host\":null,\"port\":null}");
-        const auto t2 = j1.get<Example_4740>();
-        CHECK(!t2.host.has_value());
-        CHECK(!t2.port.has_value());
-
-        // improve coverage
-        auto t3 = Example_4740();
-        t3.port = 80;
-        t3.host = "example.com";
-        const auto j2 = nlohmann::json(t3);
-        CHECK(j2.dump() == "{\"host\":\"example.com\",\"port\":80}");
-        const auto t4 = j2.get<Example_4740>();
-        CHECK(t4.host.has_value());
-        CHECK(t4.port.has_value());
-    }
-#endif
-
-#if !defined(_MSVC_LANG)
-    // MSVC returns garbage on invalid enum values, so this test is excluded
-    // there.
-    SECTION("issue #4762 - json exception 302 with unhelpful explanation : type must be number, but is number")
-    {
-        // In #4762, the main issue was that a json object with an invalid type
-        // returned "number" as type_name(), because this was the default case.
-        // This test makes sure we now return "invalid" instead.
-        json j;
-        j.m_data.m_type = static_cast<json::value_t>(100); // NOLINT(clang-analyzer-optin.core.EnumCastOutOfRange)
-        CHECK(j.type_name() == "invalid");
-    }
-#endif
-
-#ifdef JSON_HAS_CPP_17
-    SECTION("issue #4804: from_cbor incompatible with std::vector<std::byte> as binary_t")
-    {
-        const std::vector<std::uint8_t> data = {0x80};
-        const auto decoded = json_4804::from_cbor(data);
-        CHECK((decoded == json_4804::array()));
-    }
-
-    SECTION("discussion #4209 - custom BinaryType direct assignment and round-tripping")
-    {
-        // Test that assigning a custom BinaryType directly creates a binary value, not an array
-        const std::vector<std::byte> original{std::byte{1}, std::byte{2}, std::byte{3}};
-        const json_4804 j = original;
-        CHECK(j.is_binary());
-        CHECK(!j.is_array());
-
-        // Test round-tripping: extracting the binary value back as the custom container type
-        const auto extracted = j.get<std::vector<std::byte>>();
-        CHECK(extracted == original);
-
-        // Test that the default json alias behavior is unchanged: std::vector<uint8_t> -> array
-        const json default_json = std::vector<std::uint8_t> {1, 2, 3};
-        CHECK(default_json.is_array());
-        CHECK(!default_json.is_binary());
-    }
-
-    SECTION("discussion #4209 - custom BinaryType extraction from parsed array")
-    {
-        // Test that extracting a custom BinaryType from a parsed JSON array still works
-        // (not just from a binary-typed node)
-        const auto j = json_4804::parse("[1,2,3]");
-        CHECK(j.is_array());
-        CHECK(!j.is_binary());
-
-        // Extracting as custom BinaryType should work from arrays
-        const auto extracted = j.get<std::vector<std::byte>>();
-        CHECK(extracted.size() == 3);
-        CHECK(extracted[0] == std::byte{1});
-        CHECK(extracted[1] == std::byte{2});
-        CHECK(extracted[2] == std::byte{3});
-    }
-
-    SECTION("issue #5046 - implicit conversion of return json to std::optional no longer implicit")
-    {
-        const json jval{};
-        auto GetValue = [](const json & valRoot) -> std::optional<json>
-        {
-            if (valRoot.contains("default"))
-            {
-                return valRoot.at("default");
-            }
-            return std::nullopt;
-        };
-        auto result = GetValue(jval);
-        CHECK(!result.has_value());
-    }
-#endif
-
-#if JSON_HAS_RANGES == 1
-    SECTION("issue #4440 - assert when using std::views::filter and GCC 10")
-    {
-        auto noOpFilter = std::views::filter([](auto&&) noexcept
-        {
-            return true;
-        });
-        json j = {1, 2, 3};
-        auto filtered = j | noOpFilter;
-        CHECK(*filtered.begin() == 1);
-    }
-#endif
-
-#if JSON_HAS_RANGES && !defined(__MINGW32__)
-    SECTION("issue #4916 - constructing array from C++20 ranges view does not work")
-    {
-        std::vector<int> nums{1, 2, 37, 42, 21};
-        auto filteredNums = nums | std::views::filter([](int i)
-        {
-            return i > 10;
-        });
-        json const j(filteredNums);
-        CHECK(j.type() == json::value_t::array);
-        CHECK(j == json({37, 42, 21}));
-    }
-#endif
-
-    // owning_view is not available in libstdc++ < 12
-#if JSON_HAS_RANGES && !defined(__MINGW32__) && !(defined(__GLIBCXX__) && _GLIBCXX_RELEASE < 12)
-    SECTION("issue #4916 - constructing array from prvalue C++20 ranges view (owning_view)")
-    {
-        json const j(std::vector<int> {1, 2, 37, 42, 21} | std::views::filter([](int i)
-        {
-            return i > 10;
-        }));
-        CHECK(j.type() == json::value_t::array);
-        CHECK(j == json({37, 42, 21}));
-    }
-#endif
-
-#if JSON_HAS_RANGES && !defined(__MINGW32__)
-    SECTION("issue #4916 - constructing array from C++20 transform view (prvalue elements)")
-    {
-        std::vector<int> nums{1, 2, 3};
-        auto t = nums | std::views::transform([](int i) noexcept
-        {
-            return i * 2;
-        });
-        json const j(t);
-        CHECK(j.type() == json::value_t::array);
-        CHECK(j == json({2, 4, 6}));
-    }
-#endif
-}
-
-TEST_CASE_TEMPLATE("issue #4798 - nlohmann::json::to_msgpack() encode float NaN as double", T, double, float) // NOLINT(readability-math-missing-parentheses, bugprone-throwing-static-initialization)
-{
-    // With issue #4798, we encode NaN, infinity, and -infinity as float instead
-    // of double to allow for smaller encodings.
-    const json jx = std::numeric_limits<T>::quiet_NaN();
-    const json jy = std::numeric_limits<T>::infinity();
-    const json jz = -std::numeric_limits<T>::infinity();
-
-    /////////////////////////////////////////////////////////////////////////
-    // MessagePack
-    /////////////////////////////////////////////////////////////////////////
-
-    // expected MessagePack values
-    const std::vector<std::uint8_t> msgpack_x = {{0xCA, 0x7F, 0xC0, 0x00, 0x00}};
-    const std::vector<std::uint8_t> msgpack_y = {{0xCA, 0x7F, 0x80, 0x00, 0x00}};
-    const std::vector<std::uint8_t> msgpack_z = {{0xCA, 0xFF, 0x80, 0x00, 0x00}};
-
-    CHECK(json::to_msgpack(jx) == msgpack_x);
-    CHECK(json::to_msgpack(jy) == msgpack_y);
-    CHECK(json::to_msgpack(jz) == msgpack_z);
-
-    CHECK(std::isnan(json::from_msgpack(msgpack_x).get<T>()));
-    CHECK(json::from_msgpack(msgpack_y).get<T>() == std::numeric_limits<T>::infinity());
-    CHECK(json::from_msgpack(msgpack_z).get<T>() == -std::numeric_limits<T>::infinity());
-
-    // Make sure the other MessagePakc encodings for NaN, infinity, and
-    // -infinity are still supported.
-    const std::vector<std::uint8_t> msgpack_x_2 = {{0xCB, 0x7F, 0xF8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}};
-    const std::vector<std::uint8_t> msgpack_y_2 = {{0xCB, 0x7F, 0xF0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}};
-    const std::vector<std::uint8_t> msgpack_z_2 = {{0xCB, 0xFF, 0xF0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}};
-    CHECK(std::isnan(json::from_msgpack(msgpack_x_2).get<T>()));
-    CHECK(json::from_msgpack(msgpack_y_2).get<T>() == std::numeric_limits<T>::infinity());
-    CHECK(json::from_msgpack(msgpack_z_2).get<T>() == -std::numeric_limits<T>::infinity());
-
-    /////////////////////////////////////////////////////////////////////////
-    // CBOR
-    /////////////////////////////////////////////////////////////////////////
-
-    // expected CBOR values
-    const std::vector<std::uint8_t> cbor_x = {{0xF9, 0x7E, 0x00}};
-    const std::vector<std::uint8_t> cbor_y = {{0xF9, 0x7C, 0x00}};
-    const std::vector<std::uint8_t> cbor_z = {{0xF9, 0xfC, 0x00}};
-
-    CHECK(json::to_cbor(jx) == cbor_x);
-    CHECK(json::to_cbor(jy) == cbor_y);
-    CHECK(json::to_cbor(jz) == cbor_z);
-
-    CHECK(std::isnan(json::from_cbor(cbor_x).get<T>()));
-    CHECK(json::from_cbor(cbor_y).get<T>() == std::numeric_limits<T>::infinity());
-    CHECK(json::from_cbor(cbor_z).get<T>() == -std::numeric_limits<T>::infinity());
-
-    // Make sure the other CBOR encodings for NaN, infinity, and -infinity are
-    // still supported.
-    const std::vector<std::uint8_t> cbor_x_2 = {{0xFA, 0x7F, 0xC0, 0x00, 0x00}};
-    const std::vector<std::uint8_t> cbor_y_2 = {{0xFA, 0x7F, 0x80, 0x00, 0x00}};
-    const std::vector<std::uint8_t> cbor_z_2 = {{0xFA, 0xFF, 0x80, 0x00, 0x00}};
-    const std::vector<std::uint8_t> cbor_x_3 = {{0xFB, 0x7F, 0xF8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}};
-    const std::vector<std::uint8_t> cbor_y_3 = {{0xFB, 0x7F, 0xF0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}};
-    const std::vector<std::uint8_t> cbor_z_3 = {{0xFB, 0xFF, 0xF0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}};
-    CHECK(std::isnan(json::from_cbor(cbor_x_2).get<T>()));
-    CHECK(json::from_cbor(cbor_y_2).get<T>() == std::numeric_limits<T>::infinity());
-    CHECK(json::from_cbor(cbor_z_2).get<T>() == -std::numeric_limits<T>::infinity());
-    CHECK(std::isnan(json::from_cbor(cbor_x_3).get<T>()));
-    CHECK(json::from_cbor(cbor_y_3).get<T>() == std::numeric_limits<T>::infinity());
-    CHECK(json::from_cbor(cbor_z_3).get<T>() == -std::numeric_limits<T>::infinity());
-}
-
-TEST_CASE("regression test #5074 - portable workaround for single-element brace init")
-{
-    json const j_obj = {{"key", "value"}};
-
-    json const j = json::array({j_obj});
-    CHECK(j.is_array());
-    CHECK(j.size() == 1);
-    CHECK(j[0] == j_obj);
-}
-
-#if defined(JSON_BRACE_INIT_COPY_SEMANTICS) && (JSON_BRACE_INIT_COPY_SEMANTICS == 1)
-TEST_CASE("regression test #5074 - single-element brace init with JSON_BRACE_INIT_COPY_SEMANTICS")
-{
-    // with JSON_BRACE_INIT_COPY_SEMANTICS: single-element brace init copies/moves
-    json const j_obj = {{"key", "value"}, {"num", 42}};
-    json const j_arr = {1, 2, 3};
-
-    // object: brace init copies instead of wrapping
-    json const j1{j_obj};
-    CHECK(j1.is_object());
-    CHECK(j1 == j_obj);
-
-    // array: brace init copies instead of wrapping
-    json const j2{j_arr};
-    CHECK(j2.is_array());
-    CHECK(j2.size() == 3);
-    CHECK(j2 == j_arr);
-
-    // primitives still work as initializer lists
-    json const j3{true};
-    CHECK(j3.is_boolean());
-
-    json const j4{42};
-    CHECK(j4.is_number_integer());
-}
-#endif
-
-struct Example_5122
-{
-    float b = 2;
-    nlohmann::ordered_map<std::string, std::string> c{}; // NOLINT(readability-redundant-member-init): needed for GCC -Weffc++
-    int a = 1;
-    NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(Example_5122, b, c, a)
-};
-
-TEST_CASE("regression test #5122 - from_json into types holding nlohmann::ordered_map")
-{
-    Example_5122 src;
-    src.c.emplace("first", "1");
-    src.c.emplace("second", "2");
-
-    ordered_json const j = src;
-    Example_5122 const dst = j.get<Example_5122>();
-
-    CHECK(dst.b == src.b);
-    CHECK(dst.a == src.a);
-    REQUIRE(dst.c.size() == src.c.size());
-    auto src_it = src.c.begin();
-    auto dst_it = dst.c.begin();
-    for (; src_it != src.c.end(); ++src_it, ++dst_it)
-    {
-        CHECK(dst_it->first == src_it->first);
-        CHECK(dst_it->second == src_it->second);
-    }
-}
-
-// -Wself-assign-overloaded was introduced in Clang 7. Gate the pragma on
-// __has_warning so older Clang versions do not error with "unknown warning
-// group". The __has_warning check has to stay inside the __clang__ branch
-// because GCC does not provide it and would tokenize-error on the argument.
-#if defined(__clang__) && defined(__has_warning)
-    #if __has_warning("-Wself-assign-overloaded")
-        DOCTEST_CLANG_SUPPRESS_WARNING_PUSH
-        DOCTEST_CLANG_SUPPRESS_WARNING("-Wself-assign-overloaded")
-    #endif
-#endif
-
-TEST_CASE("regression test #5122 - nlohmann::ordered_map copy-assignment is self-assignment safe")
-{
-    nlohmann::ordered_map<std::string, std::string> m;
-    m.emplace("first", "1");
-    m.emplace("second", "2");
-
-    // Insertion order is preserved by ordered_map, so we can check it directly.
-    m = m;
-
-    REQUIRE(m.size() == 2);
-    auto it = m.begin();
-    CHECK(it->first == "first");
-    CHECK(it->second == "1");
-    ++it;
-    CHECK(it->first == "second");
-    CHECK(it->second == "2");
-}
-
-#if defined(__clang__) && defined(__has_warning)
-    #if __has_warning("-Wself-assign-overloaded")
-        DOCTEST_CLANG_SUPPRESS_WARNING_POP
-    #endif
-#endif
-
-TEST_CASE("regression test #5122 - nlohmann::ordered_map move-assignment transfers contents")
-{
-    nlohmann::ordered_map<std::string, std::string> src;
-    src.emplace("first", "1");
-    src.emplace("second", "2");
-
-    nlohmann::ordered_map<std::string, std::string> dst;
-    dst.emplace("stale", "x");
-    dst = std::move(src);
-
-    REQUIRE(dst.size() == 2);
-    auto it = dst.begin();
-    CHECK(it->first == "first");
-    CHECK(it->second == "1");
-    ++it;
-    CHECK(it->first == "second");
-    CHECK(it->second == "2");
-
-    // Re-assigning into the moved-from object must leave it in a usable state.
-    src = nlohmann::ordered_map<std::string, std::string> {};
-    src.emplace("after-move", "3");
-    REQUIRE(src.size() == 1);
-    CHECK(src.begin()->first == "after-move");
-}
-
-// Stand-in for a third-party library (e.g., Eigen as of 3.4, which added
-// STL-compatible begin()/end() to its vector types), living in its own
-// namespace with its own to_json overload for its vector type.
-namespace issue_4320_eigen
-{
-// "array-compatible" from the library's point of view (it has begin()/end()),
-// but for which this (fake) third-party namespace provides its own to_json.
-struct vector3
-{
-    double v[3]; // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays,cppcoreguidelines-use-default-member-init,modernize-use-default-member-init)
-    vector3(double x, double y, double z) : v{x, y, z} {} // NOLINT(hicpp-member-init,cppcoreguidelines-pro-type-member-init)
-    double x() const
-    {
-        return v[0];
-    }
-    double y() const
-    {
-        return v[1];
-    }
-    double z() const
-    {
-        return v[2];
-    }
-    double* begin()
-    {
-        return v;
-    }
-    double* end()
-    {
-        return v + 3;
-    }
-    const double* begin() const
-    {
-        return v;
-    }
-    const double* end() const
-    {
-        return v + 3;
-    }
-};
-
-inline void to_json(json& j, const vector3& v) // NOLINT(misc-use-internal-linkage)
-{
-    j = {{"x", v.x()}, {"y", v.y()}, {"z", v.z()}};
-}
-} // namespace issue_4320_eigen
-
-// The user's own namespace, using the (fake) Eigen type as an implementation
-// detail behind a payload type that has nothing to do with vectors/arrays.
-namespace issue_4320
-{
-// Publicly derives from issue_4320_eigen::vector3 but does *not* define its
-// own to_json - it is only ever used as a temporary to reach the base
-// class's to_json via ADL.
-struct vector3_wrapper : issue_4320_eigen::vector3
-{
-    using issue_4320_eigen::vector3::vector3;
-};
-
-struct payload
-{
-    double x, y, z;
-};
-
-inline vector3_wrapper to_eigen(const payload& p) // NOLINT(misc-use-internal-linkage)
-{
-    return {p.x, p.y, p.z};
-}
-
-inline void to_json(json& j, const payload& p) // NOLINT(misc-use-internal-linkage)
-{
-    // Unqualified call, passing a *derived* vector3_wrapper: relies on ADL
-    // finding issue_4320_eigen::to_json(json&, const vector3&) through the
-    // vector3 base class, via a derived-to-base conversion. Must NOT resolve
-    // to the library's own generic array-compatible to_json (an exact-match
-    // template for vector3_wrapper, since it also has begin()/end()), which
-    // would serialize this as [x, y, z] instead of {"x":x, "y":y, "z":z}.
-    to_json(j, to_eigen(p));
-}
-} // namespace issue_4320
-
-TEST_CASE("issue #4320 - custom base class must not leak nlohmann::detail into ADL")
-{
-    // Before the fix, basic_json unconditionally derived from a type living in
-    // nlohmann::detail (json_default_base), which made nlohmann::detail an
-    // associated namespace of every basic_json for ADL purposes. That leaked
-    // the library's internal generic-array to_json overload into unqualified
-    // to_json() calls made from user code, silently bypassing user-defined
-    // to_json overloads reached via a derived-to-base conversion.
-    const issue_4320::payload p{1.0, 2.0, 3.0};
-
-    json j;
-    to_json(j, p);
-    CHECK(j == json({{"x", 1.0}, {"y", 2.0}, {"z", 3.0}}));
-}
-
-TEST_CASE("issue #5338 - truncated CBOR tagged binary subtype is rejected")
-{
-    const std::vector<std::vector<std::uint8_t>> truncated_tags =
-    {
-        {0xD8},
-        {0xD9, 0x00},
-        {0xDA, 0x00, 0x00, 0x00},
-        {0xDB, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}
-    };
-
-    for (const auto& data : truncated_tags)
-    {
-        CAPTURE(data);
-        for (const auto tag_handler :
-                {
-                    json::cbor_tag_handler_t::ignore, json::cbor_tag_handler_t::store
-                })
-        {
-            CAPTURE(tag_handler);
-            const auto result = json::from_cbor(data, true, false, tag_handler);
-            CHECK(result.is_discarded());
-        }
-    }
-}
-
-TEST_CASE("issue #5402 - update(merge_objects=true) overwrites a primitive with an object")
-{
-    json t = {{"k", 1}};
-    t.update(json{{"k", {{"x", 2}}}}, true);
-    CHECK(t == json({{"k", {{"x", 2}}}}));
-
-    json mixed = {{"keep", {{"a", 1}}}, {"replace", 1}};
-    mixed.update(json{{"keep", {{"b", 2}}}, {"replace", {{"x", 2}}}}, true);
-    CHECK(mixed == json({{"keep", {{"a", 1}, {"b", 2}}}, {"replace", {{"x", 2}}}}));
 }
 
 DOCTEST_CLANG_SUPPRESS_WARNING_POP

tests/src/unit-regression3.cpp

@@ -0,0 +1,899 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  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
+
+// cmake/test.cmake selects the C++ standard versions with which to build a
+// unit test based on the presence of JSON_HAS_CPP_<VERSION> macros.
+// When using macros that are only defined for particular versions of the standard
+// (e.g., JSON_HAS_FILESYSTEM for C++17 and up), please mention the corresponding
+// version macro in a comment close by, like this:
+// JSON_HAS_CPP_<VERSION> (do not remove; see note at top of file)
+
+#include "doctest_compatibility.h"
+
+// for some reason including this after the json header leads to linker errors with VS 2017...
+#include <locale>
+
+#define JSON_TESTS_PRIVATE
+#include <nlohmann/json.hpp>
+using json = nlohmann::json;
+using ordered_json = nlohmann::ordered_json;
+#ifdef JSON_TEST_NO_GLOBAL_UDLS
+    using namespace nlohmann::literals; // NOLINT(google-build-using-namespace)
+#endif
+
+#include <cstdio>
+#include <list>
+#include <type_traits>
+#include <utility>
+
+#ifdef JSON_HAS_CPP_17
+    #include <any>
+    #include <variant>
+#endif
+
+#ifdef JSON_HAS_CPP_17
+    #if __has_include(<optional>)
+        #include <optional>
+    #elif __has_include(<experimental/optional>)
+    #endif
+
+    /////////////////////////////////////////////////////////////////////
+    // for #4804
+    /////////////////////////////////////////////////////////////////////
+    using json_4804 = nlohmann::basic_json<std::map,        // ObjectType
+    std::vector,     // ArrayType
+    std::string,     // StringType
+    bool,            // BooleanType
+    std::int64_t,    // NumberIntegerType
+    std::uint64_t,   // NumberUnsignedType
+    double,          // NumberFloatType
+    std::allocator,  // AllocatorType
+    nlohmann::adl_serializer,  // JSONSerializer
+    std::vector<std::byte>,    // BinaryType
+    void                       // CustomBaseClass
+    >;
+#endif
+
+#ifdef JSON_HAS_CPP_20
+    #if __has_include(<span>)
+        #include <span>
+    #endif
+#endif
+
+/////////////////////////////////////////////////////////////////////
+// for #4825 - explicitly instantiating basic_json must compile; this
+// forces instantiation of binary_writer::write_bjdata_ndarray, whose
+// static_cast<string_t> was ambiguous under explicit instantiation on
+// C++17. Merely compiling this translation unit is the regression test.
+/////////////////////////////////////////////////////////////////////
+template class nlohmann::basic_json<>;
+
+/////////////////////////////////////////////////////////////////////
+// for #4440
+/////////////////////////////////////////////////////////////////////
+#if JSON_HAS_RANGES == 1
+    #include <ranges>
+#endif
+
+// NLOHMANN_JSON_SERIALIZE_ENUM uses a static std::pair
+DOCTEST_CLANG_SUPPRESS_WARNING_PUSH
+DOCTEST_CLANG_SUPPRESS_WARNING("-Wexit-time-destructors")
+/////////////////////////////////////////////////////////////////////
+// for #3077
+/////////////////////////////////////////////////////////////////////
+
+class FooAlloc
+{};
+
+class Foo
+{
+  public:
+    explicit Foo(const FooAlloc& /* unused */ = FooAlloc()) {}
+
+    bool value = false;
+};
+
+class FooBar
+{
+  public:
+    Foo foo{}; // NOLINT(readability-redundant-member-init)
+};
+
+inline void from_json(const nlohmann::json& j, FooBar& fb) // NOLINT(misc-use-internal-linkage)
+{
+    j.at("value").get_to(fb.foo.value);
+}
+
+/////////////////////////////////////////////////////////////////////
+// for #3171
+/////////////////////////////////////////////////////////////////////
+
+struct for_3171_base // NOLINT(cppcoreguidelines-special-member-functions)
+{
+    for_3171_base(const std::string& /*unused*/ = {}) {}
+    virtual ~for_3171_base();
+
+    for_3171_base(const for_3171_base& other) // NOLINT(hicpp-use-equals-default,modernize-use-equals-default)
+        : str(other.str)
+    {}
+
+    for_3171_base& operator=(const for_3171_base& other)
+    {
+        if (this != &other)
+        {
+            str = other.str;
+        }
+        return *this;
+    }
+
+    for_3171_base(for_3171_base&& other) noexcept
+        : str(std::move(other.str))
+    {}
+
+    for_3171_base& operator=(for_3171_base&& other) noexcept
+    {
+        if (this != &other)
+        {
+            str = std::move(other.str);
+        }
+        return *this;
+    }
+
+    virtual void _from_json(const json& j)
+    {
+        j.at("str").get_to(str);
+    }
+
+    std::string str{}; // NOLINT(readability-redundant-member-init)
+};
+
+for_3171_base::~for_3171_base() = default;
+
+struct for_3171_derived : public for_3171_base
+{
+    for_3171_derived() = default;
+    ~for_3171_derived() override;
+    explicit for_3171_derived(const std::string& /*unused*/) { }
+
+    for_3171_derived(const for_3171_derived& other) // NOLINT(hicpp-use-equals-default,modernize-use-equals-default)
+        : for_3171_base(other)
+    {}
+
+    for_3171_derived& operator=(const for_3171_derived& other)
+    {
+        if (this != &other)
+        {
+            for_3171_base::operator=(other); // Call base class assignment operator
+        }
+        return *this;
+    }
+
+    for_3171_derived(for_3171_derived&& other) noexcept
+        : for_3171_base(std::move(other))
+    {}
+
+    for_3171_derived& operator=(for_3171_derived&& other) noexcept
+    {
+        if (this != &other)
+        {
+            for_3171_base::operator=(std::move(other)); // Call base class move assignment operator
+        }
+        return *this;
+    }
+};
+
+for_3171_derived::~for_3171_derived() = default;
+
+inline void from_json(const json& j, for_3171_base& tb) // NOLINT(misc-use-internal-linkage)
+{
+    tb._from_json(j);
+}
+
+/////////////////////////////////////////////////////////////////////
+// for #3312
+/////////////////////////////////////////////////////////////////////
+
+#ifdef JSON_HAS_CPP_20
+struct for_3312
+{
+    std::string name;
+};
+
+inline void from_json(const json& j, for_3312& obj) // NOLINT(misc-use-internal-linkage)
+{
+    j.at("name").get_to(obj.name);
+}
+#endif
+
+/////////////////////////////////////////////////////////////////////
+// for #3204
+/////////////////////////////////////////////////////////////////////
+
+struct for_3204_foo
+{
+    for_3204_foo() = default;
+    explicit for_3204_foo(std::string /*unused*/) {} // NOLINT(performance-unnecessary-value-param)
+};
+
+struct for_3204_bar
+{
+    enum constructed_from_t // NOLINT(cppcoreguidelines-use-enum-class)
+    {
+        constructed_from_none = 0,
+        constructed_from_foo = 1,
+        constructed_from_json = 2
+    };
+
+    explicit for_3204_bar(std::function<void(for_3204_foo)> /*unused*/) noexcept // NOLINT(performance-unnecessary-value-param)
+        : constructed_from(constructed_from_foo) {}
+    explicit for_3204_bar(std::function<void(json)> /*unused*/) noexcept // NOLINT(performance-unnecessary-value-param)
+        : constructed_from(constructed_from_json) {}
+
+    constructed_from_t constructed_from = constructed_from_none;
+};
+
+/////////////////////////////////////////////////////////////////////
+// for #3333
+/////////////////////////////////////////////////////////////////////
+
+struct for_3333 final
+{
+    for_3333(int x_ = 0, int y_ = 0) : x(x_), y(y_) {}
+
+    template <class T>
+    for_3333(const T& /*unused*/)
+    {
+        CHECK(false);
+    }
+
+    int x = 0;
+    int y = 0;
+};
+
+template <>
+inline for_3333::for_3333(const json& j)
+    : for_3333(j.value("x", 0), j.value("y", 0))
+{}
+
+/////////////////////////////////////////////////////////////////////
+// for #3810
+/////////////////////////////////////////////////////////////////////
+
+struct Example_3810
+{
+    int bla{};
+
+    Example_3810() = default;
+};
+
+NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(Example_3810, bla) // NOLINT(misc-use-internal-linkage)
+
+/////////////////////////////////////////////////////////////////////
+// for #4740
+/////////////////////////////////////////////////////////////////////
+
+#ifdef JSON_HAS_CPP_17
+struct Example_4740
+{
+    std::optional<std::string> host = std::nullopt;
+    std::optional<int> port = std::nullopt;
+    NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(Example_4740, host, port)
+};
+#endif
+
+TEST_CASE("regression tests 3")
+{
+#if JSON_HAS_FILESYSTEM || JSON_HAS_EXPERIMENTAL_FILESYSTEM
+    // JSON_HAS_CPP_17 (do not remove; see note at top of file)
+    SECTION("issue #3070 - Version 3.10.3 breaks backward-compatibility with 3.10.2 ")
+    {
+        nlohmann::detail::std_fs::path text_path("/tmp/text.txt");
+        const json j(text_path);
+
+        const auto j_path = j.get<nlohmann::detail::std_fs::path>();
+        CHECK(j_path == text_path);
+
+#if DOCTEST_CLANG || DOCTEST_GCC >= DOCTEST_COMPILER(8, 4, 0)
+        // only known to work on Clang and GCC >=8.4
+        CHECK_THROWS_WITH_AS(nlohmann::detail::std_fs::path(json(1)), "[json.exception.type_error.302] type must be string, but is number", json::type_error);
+#endif
+    }
+#endif
+
+    SECTION("issue #3077 - explicit constructor with default does not compile")
+    {
+        json j;
+        j[0]["value"] = true;
+        std::vector<FooBar> foo;
+        j.get_to(foo);
+    }
+
+    SECTION("issue #3108 - ordered_json doesn't support range based erase")
+    {
+        ordered_json j = {1, 2, 2, 4};
+
+        auto last = std::unique(j.begin(), j.end());
+        j.erase(last, j.end());
+
+        CHECK(j.dump() == "[1,2,4]");
+
+        j.erase(std::remove_if(j.begin(), j.end(), [](const ordered_json & val)
+        {
+            return val == 2;
+        }), j.end());
+
+        CHECK(j.dump() == "[1,4]");
+    }
+
+    SECTION("issue #3343 - json and ordered_json are not interchangeable")
+    {
+        json::object_t jobj({ { "product", "one" } });
+        ordered_json::object_t ojobj({{"product", "one"}});
+
+        auto jit = jobj.begin();
+        auto ojit = ojobj.begin();
+
+        CHECK(jit->first == ojit->first);
+        CHECK(jit->second.get<std::string>() == ojit->second.get<std::string>());
+    }
+
+    SECTION("issue #3171 - if class is_constructible from std::string wrong from_json overload is being selected, compilation failed")
+    {
+        const json j{{ "str", "value"}};
+
+        // failed with: error: no match for ‘operator=’ (operand types are ‘for_3171_derived’ and ‘const nlohmann::basic_json<>::string_t’
+        //                                               {aka ‘const std::__cxx11::basic_string<char>’})
+        //                  s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
+        auto td = j.get<for_3171_derived>();
+
+        CHECK(td.str == "value");
+    }
+
+#ifdef JSON_HAS_CPP_20
+    SECTION("issue #3312 - Parse to custom class from unordered_json breaks on G++11.2.0 with C++20")
+    {
+        // see test for #3171
+        const ordered_json j = {{"name", "class"}};
+        for_3312 obj{};
+
+        j.get_to(obj);
+
+        CHECK(obj.name == "class");
+    }
+#endif
+
+#if defined(JSON_HAS_CPP_17) && JSON_USE_IMPLICIT_CONVERSIONS
+    SECTION("issue #3428 - Error occurred when converting nlohmann::json to std::any")
+    {
+        const json j;
+        const std::any a1 = j;
+        std::any&& a2 = j;
+
+        CHECK(a1.type() == typeid(j));
+        CHECK(a2.type() == typeid(j));
+    }
+#endif
+
+    SECTION("issue #3204 - ambiguous regression")
+    {
+        const for_3204_bar bar_from_foo([](for_3204_foo) noexcept {}); // NOLINT(performance-unnecessary-value-param)
+        const for_3204_bar bar_from_json([](json) noexcept {}); // NOLINT(performance-unnecessary-value-param)
+
+        CHECK(bar_from_foo.constructed_from == for_3204_bar::constructed_from_foo);
+        CHECK(bar_from_json.constructed_from == for_3204_bar::constructed_from_json);
+    }
+
+    SECTION("issue #3333 - Ambiguous conversion from nlohmann::basic_json<> to custom class")
+    {
+        const json j
+        {
+            {"x", 1},
+            {"y", 2}
+        };
+        const for_3333 p = j;
+
+        CHECK(p.x == 1);
+        CHECK(p.y == 2);
+    }
+
+    SECTION("issue #3810 - ordered_json doesn't support construction from C array of custom type")
+    {
+        Example_3810 states[45]; // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays)
+
+        // fix "not used" warning
+        states[0].bla = 1;
+
+        const auto* const expected = R"([{"bla":1},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0},{"bla":0}])";
+
+        // This works:
+        nlohmann::json j;
+        j["test"] = states;
+        CHECK(j["test"].dump() == expected);
+
+        // This doesn't compile:
+        nlohmann::ordered_json oj;
+        oj["test"] = states;
+        CHECK(oj["test"].dump() == expected);
+    }
+
+#ifdef JSON_HAS_CPP_17
+    SECTION("issue #4740 - build issue with std::optional")
+    {
+        const auto t1 = Example_4740();
+        const auto j1 = nlohmann::json(t1);
+        CHECK(j1.dump() == "{\"host\":null,\"port\":null}");
+        const auto t2 = j1.get<Example_4740>();
+        CHECK(!t2.host.has_value());
+        CHECK(!t2.port.has_value());
+
+        // improve coverage
+        auto t3 = Example_4740();
+        t3.port = 80;
+        t3.host = "example.com";
+        const auto j2 = nlohmann::json(t3);
+        CHECK(j2.dump() == "{\"host\":\"example.com\",\"port\":80}");
+        const auto t4 = j2.get<Example_4740>();
+        CHECK(t4.host.has_value());
+        CHECK(t4.port.has_value());
+    }
+#endif
+
+#if !defined(_MSVC_LANG)
+    // MSVC returns garbage on invalid enum values, so this test is excluded
+    // there.
+    SECTION("issue #4762 - json exception 302 with unhelpful explanation : type must be number, but is number")
+    {
+        // In #4762, the main issue was that a json object with an invalid type
+        // returned "number" as type_name(), because this was the default case.
+        // This test makes sure we now return "invalid" instead.
+        json j;
+        j.m_data.m_type = static_cast<json::value_t>(100); // NOLINT(clang-analyzer-optin.core.EnumCastOutOfRange)
+        CHECK(j.type_name() == "invalid");
+    }
+#endif
+
+#ifdef JSON_HAS_CPP_17
+    SECTION("issue #4804: from_cbor incompatible with std::vector<std::byte> as binary_t")
+    {
+        const std::vector<std::uint8_t> data = {0x80};
+        const auto decoded = json_4804::from_cbor(data);
+        CHECK((decoded == json_4804::array()));
+    }
+
+    SECTION("discussion #4209 - custom BinaryType direct assignment and round-tripping")
+    {
+        // Test that assigning a custom BinaryType directly creates a binary value, not an array
+        const std::vector<std::byte> original{std::byte{1}, std::byte{2}, std::byte{3}};
+        const json_4804 j = original;
+        CHECK(j.is_binary());
+        CHECK(!j.is_array());
+
+        // Test round-tripping: extracting the binary value back as the custom container type
+        const auto extracted = j.get<std::vector<std::byte>>();
+        CHECK(extracted == original);
+
+        // Test that the default json alias behavior is unchanged: std::vector<uint8_t> -> array
+        const json default_json = std::vector<std::uint8_t> {1, 2, 3};
+        CHECK(default_json.is_array());
+        CHECK(!default_json.is_binary());
+    }
+
+    SECTION("discussion #4209 - custom BinaryType extraction from parsed array")
+    {
+        // Test that extracting a custom BinaryType from a parsed JSON array still works
+        // (not just from a binary-typed node)
+        const auto j = json_4804::parse("[1,2,3]");
+        CHECK(j.is_array());
+        CHECK(!j.is_binary());
+
+        // Extracting as custom BinaryType should work from arrays
+        const auto extracted = j.get<std::vector<std::byte>>();
+        CHECK(extracted.size() == 3);
+        CHECK(extracted[0] == std::byte{1});
+        CHECK(extracted[1] == std::byte{2});
+        CHECK(extracted[2] == std::byte{3});
+    }
+
+    SECTION("issue #5046 - implicit conversion of return json to std::optional no longer implicit")
+    {
+        const json jval{};
+        auto GetValue = [](const json & valRoot) -> std::optional<json>
+        {
+            if (valRoot.contains("default"))
+            {
+                return valRoot.at("default");
+            }
+            return std::nullopt;
+        };
+        auto result = GetValue(jval);
+        CHECK(!result.has_value());
+    }
+#endif
+
+#if JSON_HAS_RANGES == 1
+    SECTION("issue #4440 - assert when using std::views::filter and GCC 10")
+    {
+        auto noOpFilter = std::views::filter([](auto&&) noexcept
+        {
+            return true;
+        });
+        json j = {1, 2, 3};
+        auto filtered = j | noOpFilter;
+        CHECK(*filtered.begin() == 1);
+    }
+#endif
+
+#if JSON_HAS_RANGES && !defined(__MINGW32__)
+    SECTION("issue #4916 - constructing array from C++20 ranges view does not work")
+    {
+        std::vector<int> nums{1, 2, 37, 42, 21};
+        auto filteredNums = nums | std::views::filter([](int i)
+        {
+            return i > 10;
+        });
+        json const j(filteredNums);
+        CHECK(j.type() == json::value_t::array);
+        CHECK(j == json({37, 42, 21}));
+    }
+#endif
+
+    // owning_view is not available in libstdc++ < 12
+#if JSON_HAS_RANGES && !defined(__MINGW32__) && !(defined(__GLIBCXX__) && _GLIBCXX_RELEASE < 12)
+    SECTION("issue #4916 - constructing array from prvalue C++20 ranges view (owning_view)")
+    {
+        json const j(std::vector<int> {1, 2, 37, 42, 21} | std::views::filter([](int i)
+        {
+            return i > 10;
+        }));
+        CHECK(j.type() == json::value_t::array);
+        CHECK(j == json({37, 42, 21}));
+    }
+#endif
+
+#if JSON_HAS_RANGES && !defined(__MINGW32__)
+    SECTION("issue #4916 - constructing array from C++20 transform view (prvalue elements)")
+    {
+        std::vector<int> nums{1, 2, 3};
+        auto t = nums | std::views::transform([](int i) noexcept
+        {
+            return i * 2;
+        });
+        json const j(t);
+        CHECK(j.type() == json::value_t::array);
+        CHECK(j == json({2, 4, 6}));
+    }
+#endif
+}
+
+TEST_CASE_TEMPLATE("issue #4798 - nlohmann::json::to_msgpack() encode float NaN as double", T, double, float) // NOLINT(readability-math-missing-parentheses, bugprone-throwing-static-initialization)
+{
+    // With issue #4798, we encode NaN, infinity, and -infinity as float instead
+    // of double to allow for smaller encodings.
+    const json jx = std::numeric_limits<T>::quiet_NaN();
+    const json jy = std::numeric_limits<T>::infinity();
+    const json jz = -std::numeric_limits<T>::infinity();
+
+    /////////////////////////////////////////////////////////////////////////
+    // MessagePack
+    /////////////////////////////////////////////////////////////////////////
+
+    // expected MessagePack values
+    const std::vector<std::uint8_t> msgpack_x = {{0xCA, 0x7F, 0xC0, 0x00, 0x00}};
+    const std::vector<std::uint8_t> msgpack_y = {{0xCA, 0x7F, 0x80, 0x00, 0x00}};
+    const std::vector<std::uint8_t> msgpack_z = {{0xCA, 0xFF, 0x80, 0x00, 0x00}};
+
+    CHECK(json::to_msgpack(jx) == msgpack_x);
+    CHECK(json::to_msgpack(jy) == msgpack_y);
+    CHECK(json::to_msgpack(jz) == msgpack_z);
+
+    CHECK(std::isnan(json::from_msgpack(msgpack_x).get<T>()));
+    CHECK(json::from_msgpack(msgpack_y).get<T>() == std::numeric_limits<T>::infinity());
+    CHECK(json::from_msgpack(msgpack_z).get<T>() == -std::numeric_limits<T>::infinity());
+
+    // Make sure the other MessagePakc encodings for NaN, infinity, and
+    // -infinity are still supported.
+    const std::vector<std::uint8_t> msgpack_x_2 = {{0xCB, 0x7F, 0xF8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}};
+    const std::vector<std::uint8_t> msgpack_y_2 = {{0xCB, 0x7F, 0xF0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}};
+    const std::vector<std::uint8_t> msgpack_z_2 = {{0xCB, 0xFF, 0xF0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}};
+    CHECK(std::isnan(json::from_msgpack(msgpack_x_2).get<T>()));
+    CHECK(json::from_msgpack(msgpack_y_2).get<T>() == std::numeric_limits<T>::infinity());
+    CHECK(json::from_msgpack(msgpack_z_2).get<T>() == -std::numeric_limits<T>::infinity());
+
+    /////////////////////////////////////////////////////////////////////////
+    // CBOR
+    /////////////////////////////////////////////////////////////////////////
+
+    // expected CBOR values
+    const std::vector<std::uint8_t> cbor_x = {{0xF9, 0x7E, 0x00}};
+    const std::vector<std::uint8_t> cbor_y = {{0xF9, 0x7C, 0x00}};
+    const std::vector<std::uint8_t> cbor_z = {{0xF9, 0xfC, 0x00}};
+
+    CHECK(json::to_cbor(jx) == cbor_x);
+    CHECK(json::to_cbor(jy) == cbor_y);
+    CHECK(json::to_cbor(jz) == cbor_z);
+
+    CHECK(std::isnan(json::from_cbor(cbor_x).get<T>()));
+    CHECK(json::from_cbor(cbor_y).get<T>() == std::numeric_limits<T>::infinity());
+    CHECK(json::from_cbor(cbor_z).get<T>() == -std::numeric_limits<T>::infinity());
+
+    // Make sure the other CBOR encodings for NaN, infinity, and -infinity are
+    // still supported.
+    const std::vector<std::uint8_t> cbor_x_2 = {{0xFA, 0x7F, 0xC0, 0x00, 0x00}};
+    const std::vector<std::uint8_t> cbor_y_2 = {{0xFA, 0x7F, 0x80, 0x00, 0x00}};
+    const std::vector<std::uint8_t> cbor_z_2 = {{0xFA, 0xFF, 0x80, 0x00, 0x00}};
+    const std::vector<std::uint8_t> cbor_x_3 = {{0xFB, 0x7F, 0xF8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}};
+    const std::vector<std::uint8_t> cbor_y_3 = {{0xFB, 0x7F, 0xF0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}};
+    const std::vector<std::uint8_t> cbor_z_3 = {{0xFB, 0xFF, 0xF0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}};
+    CHECK(std::isnan(json::from_cbor(cbor_x_2).get<T>()));
+    CHECK(json::from_cbor(cbor_y_2).get<T>() == std::numeric_limits<T>::infinity());
+    CHECK(json::from_cbor(cbor_z_2).get<T>() == -std::numeric_limits<T>::infinity());
+    CHECK(std::isnan(json::from_cbor(cbor_x_3).get<T>()));
+    CHECK(json::from_cbor(cbor_y_3).get<T>() == std::numeric_limits<T>::infinity());
+    CHECK(json::from_cbor(cbor_z_3).get<T>() == -std::numeric_limits<T>::infinity());
+}
+
+TEST_CASE("regression test #5074 - portable workaround for single-element brace init")
+{
+    json const j_obj = {{"key", "value"}};
+
+    json const j = json::array({j_obj});
+    CHECK(j.is_array());
+    CHECK(j.size() == 1);
+    CHECK(j[0] == j_obj);
+}
+
+#if defined(JSON_BRACE_INIT_COPY_SEMANTICS) && (JSON_BRACE_INIT_COPY_SEMANTICS == 1)
+TEST_CASE("regression test #5074 - single-element brace init with JSON_BRACE_INIT_COPY_SEMANTICS")
+{
+    // with JSON_BRACE_INIT_COPY_SEMANTICS: single-element brace init copies/moves
+    json const j_obj = {{"key", "value"}, {"num", 42}};
+    json const j_arr = {1, 2, 3};
+
+    // object: brace init copies instead of wrapping
+    json const j1{j_obj};
+    CHECK(j1.is_object());
+    CHECK(j1 == j_obj);
+
+    // array: brace init copies instead of wrapping
+    json const j2{j_arr};
+    CHECK(j2.is_array());
+    CHECK(j2.size() == 3);
+    CHECK(j2 == j_arr);
+
+    // primitives still work as initializer lists
+    json const j3{true};
+    CHECK(j3.is_boolean());
+
+    json const j4{42};
+    CHECK(j4.is_number_integer());
+}
+#endif
+
+struct Example_5122
+{
+    float b = 2;
+    nlohmann::ordered_map<std::string, std::string> c{}; // NOLINT(readability-redundant-member-init): needed for GCC -Weffc++
+    int a = 1;
+    NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(Example_5122, b, c, a)
+};
+
+TEST_CASE("regression test #5122 - from_json into types holding nlohmann::ordered_map")
+{
+    Example_5122 src;
+    src.c.emplace("first", "1");
+    src.c.emplace("second", "2");
+
+    ordered_json const j = src;
+    Example_5122 const dst = j.get<Example_5122>();
+
+    CHECK(dst.b == src.b);
+    CHECK(dst.a == src.a);
+    REQUIRE(dst.c.size() == src.c.size());
+    auto src_it = src.c.begin();
+    auto dst_it = dst.c.begin();
+    for (; src_it != src.c.end(); ++src_it, ++dst_it)
+    {
+        CHECK(dst_it->first == src_it->first);
+        CHECK(dst_it->second == src_it->second);
+    }
+}
+
+// -Wself-assign-overloaded was introduced in Clang 7. Gate the pragma on
+// __has_warning so older Clang versions do not error with "unknown warning
+// group". The __has_warning check has to stay inside the __clang__ branch
+// because GCC does not provide it and would tokenize-error on the argument.
+#if defined(__clang__) && defined(__has_warning)
+    #if __has_warning("-Wself-assign-overloaded")
+        DOCTEST_CLANG_SUPPRESS_WARNING_PUSH
+        DOCTEST_CLANG_SUPPRESS_WARNING("-Wself-assign-overloaded")
+    #endif
+#endif
+
+TEST_CASE("regression test #5122 - nlohmann::ordered_map copy-assignment is self-assignment safe")
+{
+    nlohmann::ordered_map<std::string, std::string> m;
+    m.emplace("first", "1");
+    m.emplace("second", "2");
+
+    // Insertion order is preserved by ordered_map, so we can check it directly.
+    m = m;
+
+    REQUIRE(m.size() == 2);
+    auto it = m.begin();
+    CHECK(it->first == "first");
+    CHECK(it->second == "1");
+    ++it;
+    CHECK(it->first == "second");
+    CHECK(it->second == "2");
+}
+
+#if defined(__clang__) && defined(__has_warning)
+    #if __has_warning("-Wself-assign-overloaded")
+        DOCTEST_CLANG_SUPPRESS_WARNING_POP
+    #endif
+#endif
+
+TEST_CASE("regression test #5122 - nlohmann::ordered_map move-assignment transfers contents")
+{
+    nlohmann::ordered_map<std::string, std::string> src;
+    src.emplace("first", "1");
+    src.emplace("second", "2");
+
+    nlohmann::ordered_map<std::string, std::string> dst;
+    dst.emplace("stale", "x");
+    dst = std::move(src);
+
+    REQUIRE(dst.size() == 2);
+    auto it = dst.begin();
+    CHECK(it->first == "first");
+    CHECK(it->second == "1");
+    ++it;
+    CHECK(it->first == "second");
+    CHECK(it->second == "2");
+
+    // Re-assigning into the moved-from object must leave it in a usable state.
+    src = nlohmann::ordered_map<std::string, std::string> {};
+    src.emplace("after-move", "3");
+    REQUIRE(src.size() == 1);
+    CHECK(src.begin()->first == "after-move");
+}
+
+// Stand-in for a third-party library (e.g., Eigen as of 3.4, which added
+// STL-compatible begin()/end() to its vector types), living in its own
+// namespace with its own to_json overload for its vector type.
+namespace issue_4320_eigen
+{
+// "array-compatible" from the library's point of view (it has begin()/end()),
+// but for which this (fake) third-party namespace provides its own to_json.
+struct vector3
+{
+    double v[3]; // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays,cppcoreguidelines-use-default-member-init,modernize-use-default-member-init)
+    vector3(double x, double y, double z) : v{x, y, z} {} // NOLINT(hicpp-member-init,cppcoreguidelines-pro-type-member-init)
+    double x() const
+    {
+        return v[0];
+    }
+    double y() const
+    {
+        return v[1];
+    }
+    double z() const
+    {
+        return v[2];
+    }
+    double* begin()
+    {
+        return v;
+    }
+    double* end()
+    {
+        return v + 3;
+    }
+    const double* begin() const
+    {
+        return v;
+    }
+    const double* end() const
+    {
+        return v + 3;
+    }
+};
+
+inline void to_json(json& j, const vector3& v) // NOLINT(misc-use-internal-linkage)
+{
+    j = {{"x", v.x()}, {"y", v.y()}, {"z", v.z()}};
+}
+} // namespace issue_4320_eigen
+
+// The user's own namespace, using the (fake) Eigen type as an implementation
+// detail behind a payload type that has nothing to do with vectors/arrays.
+namespace issue_4320
+{
+// Publicly derives from issue_4320_eigen::vector3 but does *not* define its
+// own to_json - it is only ever used as a temporary to reach the base
+// class's to_json via ADL.
+struct vector3_wrapper : issue_4320_eigen::vector3
+{
+    using issue_4320_eigen::vector3::vector3;
+};
+
+struct payload
+{
+    double x, y, z;
+};
+
+inline vector3_wrapper to_eigen(const payload& p) // NOLINT(misc-use-internal-linkage)
+{
+    return {p.x, p.y, p.z};
+}
+
+inline void to_json(json& j, const payload& p) // NOLINT(misc-use-internal-linkage)
+{
+    // Unqualified call, passing a *derived* vector3_wrapper: relies on ADL
+    // finding issue_4320_eigen::to_json(json&, const vector3&) through the
+    // vector3 base class, via a derived-to-base conversion. Must NOT resolve
+    // to the library's own generic array-compatible to_json (an exact-match
+    // template for vector3_wrapper, since it also has begin()/end()), which
+    // would serialize this as [x, y, z] instead of {"x":x, "y":y, "z":z}.
+    to_json(j, to_eigen(p));
+}
+} // namespace issue_4320
+
+TEST_CASE("issue #4320 - custom base class must not leak nlohmann::detail into ADL")
+{
+    // Before the fix, basic_json unconditionally derived from a type living in
+    // nlohmann::detail (json_default_base), which made nlohmann::detail an
+    // associated namespace of every basic_json for ADL purposes. That leaked
+    // the library's internal generic-array to_json overload into unqualified
+    // to_json() calls made from user code, silently bypassing user-defined
+    // to_json overloads reached via a derived-to-base conversion.
+    const issue_4320::payload p{1.0, 2.0, 3.0};
+
+    json j;
+    to_json(j, p);
+    CHECK(j == json({{"x", 1.0}, {"y", 2.0}, {"z", 3.0}}));
+}
+
+TEST_CASE("issue #5338 - truncated CBOR tagged binary subtype is rejected")
+{
+    const std::vector<std::vector<std::uint8_t>> truncated_tags =
+    {
+        {0xD8},
+        {0xD9, 0x00},
+        {0xDA, 0x00, 0x00, 0x00},
+        {0xDB, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}
+    };
+
+    for (const auto& data : truncated_tags)
+    {
+        CAPTURE(data);
+        for (const auto tag_handler :
+                {
+                    json::cbor_tag_handler_t::ignore, json::cbor_tag_handler_t::store
+                })
+        {
+            CAPTURE(tag_handler);
+            const auto result = json::from_cbor(data, true, false, tag_handler);
+            CHECK(result.is_discarded());
+        }
+    }
+}
+
+TEST_CASE("issue #5402 - update(merge_objects=true) overwrites a primitive with an object")
+{
+    json t = {{"k", 1}};
+    t.update(json{{"k", {{"x", 2}}}}, true);
+    CHECK(t == json({{"k", {{"x", 2}}}}));
+
+    json mixed = {{"keep", {{"a", 1}}}, {"replace", 1}};
+    mixed.update(json{{"keep", {{"b", 2}}}, {"replace", {{"x", 2}}}}, true);
+    CHECK(mixed == json({{"keep", {{"a", 1}, {"b", 2}}}, {"replace", {{"x", 2}}}}));
+}
+
+
+DOCTEST_CLANG_SUPPRESS_WARNING_POP

tests/src/unit-ubjson.cpp

@@ -2149,6 +2149,67 @@ TEST_CASE("UBJSON")
     }
 }
 
+TEST_CASE("UBJSON optimized arrays of a valueless type are bounded")
+{
+    // An element of type 'Z', 'T' or 'F' is encoded by its marker alone, so an
+    // optimized array of one of those has no payload and the declared count is
+    // the only thing deciding how much is allocated. Ten bytes used to produce
+    // billions of values (#2793); every other type costs at least one byte per
+    // element and is bounded by the end of the input.
+    json _;
+
+    SECTION("an excessive count is rejected")
+    {
+        // 'l' is a big-endian int32: 0x7FFFFFFF elements, about 34 GB of value
+        for (const auto marker :
+                {'Z', 'T', 'F'
+                })
+        {
+            const std::vector<uint8_t> input = {'[', '$', static_cast<uint8_t>(marker), '#', 'l', 0x7F, 0xFF, 0xFF, 0xFF};
+            CHECK_THROWS_WITH_AS(_ = json::from_ubjson(input), "[json.exception.out_of_range.408] syntax error while parsing UBJSON size: excessive array size", json::out_of_range&);
+            CHECK(json::from_ubjson(input, true, false).is_discarded());
+        }
+    }
+
+    SECTION("ordinary counts are unaffected")
+    {
+        CHECK(json::from_ubjson(std::vector<uint8_t>({'[', '$', 'Z', '#', 'i', 3})) == json({nullptr, nullptr, nullptr}));
+        CHECK(json::from_ubjson(std::vector<uint8_t>({'[', '$', 'T', '#', 'i', 2})) == json({true, true}));
+        CHECK(json::from_ubjson(std::vector<uint8_t>({'[', '$', 'F', '#', 'i', 2})) == json({false, false}));
+        // 'N' is a no-op rather than a value, and still yields an empty array
+        CHECK(json::from_ubjson(std::vector<uint8_t>({'[', '$', 'N', '#', 'i', 2})) == json::array());
+    }
+
+    SECTION("a type with a payload is unaffected")
+    {
+        // A count past the limit is not rejected for 'U', which costs a byte
+        // per element and is bounded by the end of the input instead. The
+        // count is kept just past the limit rather than made huge, because a
+        // count that also exceeds the array's max_size() is reported as
+        // out_of_range before the input runs out, and max_size() depends on
+        // the width of std::size_t.
+        const std::vector<uint8_t> input = {'[', '$', 'U', '#', 'l', 0x00, 0x10, 0x00, 0x01};
+        CHECK_THROWS_WITH_AS(_ = json::from_ubjson(input), "[json.exception.parse_error.110] parse error at byte 10: syntax error while parsing UBJSON number: unexpected end of input", json::parse_error&);
+        CHECK(json::from_ubjson(input, true, false).is_discarded());
+    }
+
+    SECTION("the writer stays within what the reader accepts")
+    {
+        // below the limit the optimized form is used and is tiny; above it the
+        // writer falls back so that the result can still be read back
+        json const at_limit(1048576, nullptr);
+        const auto v_at_limit = json::to_ubjson(at_limit, true, true);
+        CHECK(v_at_limit.size() == 9);
+        CHECK(v_at_limit.at(1) == '$');
+        CHECK(json::from_ubjson(v_at_limit) == at_limit);
+
+        json const above_limit(1048577, nullptr);
+        const auto v_above_limit = json::to_ubjson(above_limit, true, true);
+        CHECK(v_above_limit.at(1) != '$');
+        CHECK(json::from_ubjson(v_above_limit) == above_limit);
+    }
+}
+
 TEST_CASE("Universal Binary JSON Specification Examples 1")
 {
     SECTION("Null Value")