Commit Graph
242 Commits
Author SHA1 Message Date
Niels Lohmann 97f3e1b9a5 Merge branch 'develop' into claude/basic-json-template-assumptions-tyc76m
develop rewrote serializer.hpp's dump() to be iterative (indent_string /
o->write_characters() replaced by put_indent()/put_literal()/dump_internal()/
dump_iteratively()), which conflicted with this branch's now-superseded hunks
touching the old recursive-descent code. Resolved by taking develop's
iterative implementation throughout.

The one substantive conflict was in binary-value dumping: this branch's
to_byte_value() cast a binary byte to std::uint8_t before dumping so that a
BinaryType whose value_type isn't uint8_t (e.g. std::byte) still dumps
correctly, while develop's dump_byte() dispatcher lost that cast in its
false_type (not-already-uint8_t) overload. Ported the to_byte_value() cast
into that overload so both the recursive and iterative binary-dump call sites
convert exotic BinaryTypes correctly.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-11 09:52:41 +02:00
Niels Lohmann 44f8ec30e9 Bound UBJSON optimized arrays of a valueless type (#5504)
* Bound UBJSON optimized arrays 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 UBJSON array of one of those has no
payload: reading an element consumes no input at all. Its declared count is
therefore the only thing that decides how much is allocated, and nothing
bounded it. "[$Z#l" and a four-byte count is nine bytes of input describing
two billion values; #2793 reports 35 GB and 150 seconds from ten bytes, and
OSS-Fuzz has an out-of-memory and a timeout report for the same shape.

Every other type costs at least one byte per element, so the end of the input
bounds it. 'N' (no-op) is already skipped rather than stored. Objects are not
affected either: each element is preceded by its key, which costs bytes. And
BJData already refuses these markers as an optimized type, so this is a plain
UBJSON matter.

Reject a count above 1,048,576 elements for those three types with
out_of_range.408, the code this reader already uses for a declared size it
will not honour. The check runs before the SAX start event, so no container
is opened and then abandoned.

Rejecting on the read side alone would break the guarantee that anything
to_ubjson() writes can be read back, and would trip the round-trip assertion
in fuzzer-parse_ubjson.cpp. So the writer falls back to the unoptimized
encoding, one byte per element, for arrays of these types above the same
limit. Its decision depends only on the array's size, which is identical for
a value and for anything parsed back from it, so the round trip is stable.

No existing test changes: the largest such count in the test suite is 65,793.
The excessive-size test that already used this shape still passes, now
rejected a little earlier than by the max_size() check it used to reach.

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

* Note the 1,048,576 valueless-array limit as (1 << 20) in the docs

Addresses review feedback from @gregmarr on PR #5504: spell out the
binary/hex form next to the decimal count so it reads as the round
power-of-two it is, matching how include/nlohmann/detail/input/binary_reader.hpp
defines max_valueless_container_size. Applied in both docs/exceptions.md
and ubjson.md, as requested.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-11 08:34:42 +02:00
Niels LohmannandClaude Opus 4.8 4a93aa4e2f Speed up parsing of contiguous input (numbers, strings, UTF-8) (#5283)
* Speed up number parsing in the lexer (fast paths from the fast_float/simdjson world)

The number scanner converted its already-validated digit buffer with
std::strtoull/std::strtoll/std::strtod. Those pull in locale and errno
machinery and dominate number-heavy parsing (strtod runs at ~6 M/s).

Replace them with dedicated parsers over the validated buffer:

- parse_integer_unsigned / parse_integer_signed: accumulate digits with
  overflow detection, falling back to the float path on overflow exactly
  as the strtoull/strtoll round-trip check did. Overflow behavior is
  unchanged for narrower or wider custom number types.

- parse_float_fast: Clinger's exact fast path for `double` (<=19 significant
  digits, |exp10| <= 22, significand < 2^53), where significand * 10^exp is
  exact under IEEE round-to-nearest. This is the same fast path used by
  fast_float/simdjson. It is bit-identical to strtod on this subset and
  declines (falling back to strtod) otherwise. Only `double` uses it; float
  and long double keep std::strtof/std::strtold via a templated overload.

Measured on representative data (g++ 13, -O3):
  - integers:  DOM parse +11%, SAX +25-34%
  - floats:    DOM parse +37%, SAX +70%  (clang: float DOM ~1.9x)

No dependencies added; header-only and C++11-clean. Existing parser,
lexer, conversion and deserialization unit tests pass unchanged; a
3M-value random-double fuzz matches strtod bit-for-bit.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Add SWAR bulk string scanning for contiguous input (simdjson-style)

scan_string() read the input one character at a time through the input
adapter and classified every byte with a large switch. For contiguous
byte buffers we can instead scan 8 bytes at a time with a SWAR word test
that finds the first byte needing individual handling (the closing quote,
an escape, a control character, or a non-ASCII UTF-8 byte) and bulk-append
the ordinary run in one go.

- input adapters expose supports_bulk_scan / bulk_data / bulk_remaining /
  bulk_skip for provably-contiguous, same-type, 1-byte iterator ranges
  (raw pointers in every standard; std::string/std::vector/std::array and
  friends additionally in C++20 via std::contiguous_iterator).
- the lexer gains a bulk_scan capability (gated on lazy_token_string so
  bypassing the per-character capture cannot lose error diagnostics) and a
  scan_string_bulk() fast path; streaming/wide/user adapters are unchanged
  and keep the byte-at-a-time scanner.

The run contains no newline (all bytes < 0x20 are treated as special), so
position bookkeeping stays exact, and error tokens are still reconstructed
lazily from the consumed byte range. The SWAR special-byte test is pure
uint64_t arithmetic - no intrinsics, no runtime dispatch, C++11-clean.

Measured on representative data, pointer input, g++ 13 -O3
(string values discarded by accept() see the largest gains):

  long ASCII strings:  DOM +4.5x,  SAX +14x,   accept +17x  (to ~2 GB/s)
  short strings:       DOM +15%,   SAX +62%,   accept +85%
  escape-heavy:        DOM +31%,   SAX +26%,   accept +28%

Same-input parity verified: 200k randomized documents (escapes, multibyte
UTF-8, surrogate pairs) accept/parse identically via the contiguous SWAR
path and the streaming byte path; unit lexer/parser/diagnostic-position/
deserialization/conversions suites pass unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Validate UTF-8 in the bulk string scanner (portable ~2-3x on non-ASCII text)

The SWAR bulk string path stopped at the first non-ASCII byte and handed
every multibyte character to the byte-at-a-time scanner, whose per-byte
get()/next_byte_in_range()/add() machinery runs at roughly half the speed
of validating straight from the buffer. As a result, dense non-ASCII text
(CJK, emoji, accented Latin) parsed ~10-15x slower than ASCII.

Fold well-formed UTF-8 into the bulk run: scan_string_bulk() now, on a
non-ASCII lead byte, validates one sequence with validate_one_utf8() -
which mirrors scan_string()'s per-byte switch ranges exactly (rejecting
overlong forms, surrogates, and out-of-range code points) - and appends it
in place, continuing until the closing quote, an escape, a control byte,
or an ill-formed sequence. All error handling still defers to the byte
path, so error messages and positions are byte-for-byte unchanged.

Because only well-formed content is fast-pathed and every rejection falls
through to the existing scanner, behavior is identical; the win is purely
throughput. Measured on pointer input (accept, string values discarded):

  content        g++ 13         clang 18
  dense CJK      277 -> 648     ~605  MB/s   (~2.3x)
  dense emoji    299 -> 857     ~702  MB/s   (~2.6-2.9x)
  mixed 90% ASCII 246 -> 331    ~334  MB/s   (~1.35x)
  pure ASCII     unchanged (~3.2 / 4.1 GB/s)

Verified: 2,000,000 randomized documents built from arbitrary bytes
(overlong, surrogate, truncated, out-of-range sequences) accept/reject and
parse identically via the contiguous path and the streaming byte path;
lexer/parser/diagnostic-position/deserialization/conversions suites pass
unchanged. Pure C++11, no intrinsics.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Route contiguous byte containers through the pointer adapter (fast paths in C++11)

json::parse(std::string) - the most common entry point - did not benefit
from the contiguous fast paths (bulk string scanning, UTF-8 bulk
validation, memcpy for binary formats) in C++11..17: std::string::iterator
is a library wrapper, not a raw pointer, and pre-C++20 there is no portable
way to prove it contiguous, so supports_bulk_scan was false. Only raw
pointers, string literals, and C-arrays (and, in C++20, anything modelling
std::contiguous_iterator) took the fast path.

Detect contiguous single-byte containers (std::string, std::vector<char>,
std::vector<std::uint8_t>, std::string_view, ...) via is_contiguous_byte_
container and route them through an iterator_input_adapter built from
data()/data()+size(). The generic iterator-based container overload is
constrained to exclude these, so the two overloads are disjoint and there
is no ambiguity (a plain competing overload loses to the greedy
forwarding-reference container overload on reference binding, and a factory
partial-specialization is ambiguous - both were tried and rejected).

The pointer keeps the container's own element type, so char_type - and
therefore all parsing behavior - is byte-for-byte identical to the iterator
path (const char* for std::string, const std::uint8_t* for
std::vector<std::uint8_t>); only the raw pointer additionally turns on the
fast paths. Lifetimes are unchanged: the container outlives the adapter for
the full parse expression, exactly as the iterators it replaces did.

Measured, C++11, json::parse/accept(std::string), g++ 13:

  long ASCII strings:  accept 201 -> 3200 MB/s  (~16x),  parse 174 -> 1444
  dense CJK:           accept 263 ->  697 MB/s  (~2.6x)
  short strings:       accept 163 ->  243 MB/s  (~1.5x)

Verified: char_type preserved for std::string (char) and
std::vector<std::uint8_t> (uint8_t); CBOR/MsgPack round-trips from
std::vector<std::uint8_t> unchanged; 1,000,000 randomized documents accept
and parse identically via std::string and via std::istream;
deserialization/user-defined-input/parser/lexer/conversions/diagnostic-
position suites pass (20,480 assertions); warning-clean on g++ and clang in
C++11/17/20.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Add optional simdutf backend for bulk UTF-8 validation (JSON_USE_SIMDUTF)

The bulk string scanner validates UTF-8 straight from a contiguous buffer.
The scalar validator caps at ~0.3-0.7 GB/s on non-ASCII text; a SIMD
validator reaches several GB/s. Rather than hand-rolling SIMD UTF-8
validation (easy to get subtly wrong - a from-scratch SSE attempt rejected
valid CJK), wire in the vetted simdutf library behind an opt-in switch.

simdutf is not header-only (it ships simdutf.cpp and uses runtime CPU
dispatch), so it is not vendored: defining JSON_USE_SIMDUTF includes
<simdutf.h> and routes the bulk validator through simdutf::validate_utf8;
the project supplies and links simdutf. Undefined (the default), nothing
external is included and the portable C++11 scalar path is used, so the
library stays header-only and its baseline behavior is unchanged.

Design keeps behavior identical either way:
- scan_string_bulk() now finds the run up to the next quote/escape/control
  byte (non-ASCII allowed) and validates it in one shot; on the rare
  validation failure it recomputes the exact valid prefix with the scalar
  helper, so ill-formed input still falls through to the byte path and is
  reported at the same position with the same message.
- the per-sequence scalar path is factored into scalar_string_bulk_run()
  and is the default backend; the refactor is behavior-preserving and does
  not change scalar throughput.

Verified: default and JSON_USE_SIMDUTF builds accept/reject/parse
identically across 2,000,000 arbitrary-byte documents and 1,000,000
mixed-escape/UTF-8 documents (differential fuzz vs the streaming byte
path); lexer/parser/diagnostic-position/deserialization suites pass under
both configurations (20,188 assertions with the backend enabled);
warning-clean on g++ and clang, C++11 and C++20, both configurations.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Add a contiguous fast path for scanning numbers

scan_number() reads a number one character at a time through the input
adapter (get()) and appends each byte to token_buffer (add()) before
converting. For contiguous input, the per-character get()/add() overhead
dominates: it is roughly two thirds of the time spent on number-heavy
parsing, far more than the value conversion itself.

Add scan_number_bulk_contiguous(), which parses the whole number token
straight from the input buffer: it validates and classifies the extent
with the same grammar as scan_number()'s state machine, materializes
token_buffer in one copy (substituting the locale decimal point exactly as
scan_number() does), advances the adapter, and reuses the shared
convert_number() tail. On anything it does not recognize as a well-formed
number it makes no state change and returns token_type::uninitialized, so
the caller falls back to scan_number(), which then produces the exact
diagnostic. Errors and their positions are therefore unchanged.

The conversion tail is factored out of scan_number() into convert_number()
so both scanners share it; the fast path is selected by tag dispatch on the
existing bulk_scan capability, so streaming/wide/user adapters are
unaffected.

Measured on pointer input, g++ 13 -O3:
  - integers: parse +65%, accept +98%
  - floats:   parse +39%, accept +70%

Verified: 2,000,000 randomized number documents (including overflow-range
integers, long digit strings and %.17g doubles) parse identically via the
contiguous path and the streaming byte path, matching value, type and
round-trip text; the locale suite and existing parser/lexer/conversions/
deserialization tests pass; a new "lexer number fast path" test checks
contiguous-vs-streaming parity, token classification, and that malformed
numbers are rejected identically. Pure C++11, no intrinsics.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Move byte-level scan/parse helpers out of lexer.hpp

lexer.hpp had grown by ~600 lines of byte-level helpers that have no
dependency on the lexer's template parameters and clutter the state
machine. Move them, unchanged, into two focused headers as free functions
in namespace detail:

- number_parse.hpp: parse_integer_unsigned/parse_integer_signed (now
  templated on the number type) and parse_float_fast (Clinger's exact
  double fast path, with the decimal point passed as an argument instead of
  read from a lexer member).
- string_scan.hpp: the SWAR string helpers (is_string_special,
  swar_string_special, find_string_special, validate_one_utf8,
  scalar_string_bulk_run) and the backend-dispatched string_bulk_run,
  including the optional simdutf include and find_string_delimiter.

lexer.hpp now includes these and calls the free functions; the methods that
touch lexer state (scan_string, scan_number, scan_string_bulk,
scan_number_bulk_contiguous, convert_number) stay put. This is a pure code
move with no behavior change: lexer.hpp drops from 2357 to 1934 lines, the
now-unused <cstdint>/<cstring>/<limits> includes are removed, and the
free-function form makes the SWAR helpers reusable elsewhere (e.g. the
serializer's string escaping).

Verified: default and JSON_USE_SIMDUTF builds compile; 2,000,000 number and
2,000,000 arbitrary-byte-string differential-fuzz documents parse
identically to before; lexer/parser/conversions/deserialization/locale/
diagnostic-position suites pass (20,576 assertions); warning-clean on g++
and clang in C++11/17/20; the amalgamation regenerates and passes
check-amalgamation.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix clang-tidy findings and document JSON_USE_SIMDUTF in the nav

- number_parse.hpp: use std::array for the powers-of-ten table
  (avoid-c-arrays) and `auto` for the cast-initialized result
  (modernize-use-auto), matching the codebase style (cf. the serializer's
  utf8d table). Indexing casts keep the -Wsign-conversion build clean.
- add JSON_USE_SIMDUTF to the mkdocs navigation so the macro page is
  reachable.

No behavior change; clang-tidy is clean on the new headers and the
amalgamation is regenerated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix number fast path for custom string types without assign()

The contiguous number fast path materialized token_buffer with
token_buffer.assign(data, len), but string_t is only required to provide
the minimal interface the rest of the lexer uses (push_back, append,
clear, operator[], ...). Custom string types such as the test's alt_string
do not implement assign(), so scan_number_bulk_contiguous() failed to
compile for them (unit-alt-string), breaking the gcc/clang standards and
old-compiler CI jobs.

reset() already clears token_buffer, so fill it with append() - which
alt_string and std::string both provide and which the string fast path
already relies on - instead of assign().

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Satisfy clang-tidy: parenthesize math and drop unused forwarding reference

The CI clang-tidy (newer than the locally available version) reported two
additional checks on the new code:

- readability-math-missing-parentheses: parenthesize the (a * b) + c digit
  accumulations in number_parse.hpp.
- cppcoreguidelines-missing-std-forward: the contiguous-byte-container
  input_adapter overload took a forwarding reference but only reads
  data()/size() and never forwards it. It is already disjoint from the
  generic container overload via SFINAE, so a plain const& is correct and
  clearer (and keeps the container alive for the whole parse just as before).

No behavior change; char_type and routing are unchanged (std::string and
std::vector<std::uint8_t> still take the pointer adapter with char/uint8_t
char_type), CBOR/MsgPack round-trips and the 2M number fuzz still pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Use std::from_chars (Eisel-Lemire) for float conversion when available

The Clinger fast path is exact only for the "easy" subset (<=19 significant
digits, |exp10| <= 22); high-precision and scientific floats fall through to
strtod, where the failed Clinger attempt actually makes parsing a net loss.
std::from_chars implements the Eisel-Lemire algorithm in modern standard
libraries: locale-independent, correctly rounded, and fast over the whole
value range.

convert_number() now tries parse_float_from_chars() first (guarded by
__cpp_lib_to_chars, so C++11 and libc++-without-float-support keep the
Clinger + strtod path unchanged), then Clinger, then strtof. from_chars is
used only when it consumes the entire token; a partial parse means a non-'.'
locale decimal point, and an under-/overflow (result_out_of_range) also
declines - in both cases the existing strtod fallback supplies the exact
value and the well-defined +/-inf/0 the parser expects, side-stepping the
P4168 divergence between implementations. float and long double now get the
fast path too (Clinger was double-only).

Measured, C++17, g++ 13 -O3, json::parse/accept:
  - canada-style floats: ~unchanged (Clinger already covered them)
  - high-precision (17 digits):  parse 2.1x, accept 2.5x
  - scientific (17 digits + exp): parse 3.6x, accept 4.1x

Verified: C++11 (Clinger/strtod) and C++17 (from_chars) parse every value -
including subnormals, boundary values, and 1e9999/1e-9999 over-/underflow -
to bit-identical results; 2M number-fuzz clean; conversions/deserialization/
locale/number-fast-path suites pass in both C++11 and C++17; clang-tidy
clean; warning-clean on g++ and clang in C++11/17/20.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Guard from_chars use on JSON_HAS_CPP_17, not just __cpp_lib_to_chars

libstdc++ 15 defines __cpp_lib_to_chars even in C++14 mode (via
bits/version.h pulled in by other headers), but <charconv> is only included
under JSON_HAS_CPP_17. That made parse_float_from_chars() reference
std::from_chars without the header in C++14 builds, breaking gcc-latest,
icpx, and the offline-testdata jobs.

Gate the use on JSON_HAS_CPP_17 && __cpp_lib_to_chars so it matches the
include condition exactly; C++11/14 always take the scalar fallback.
Verified by forcing __cpp_lib_to_chars in a C++14 build: the guard
suppresses std::from_chars and it compiles. C++17 behavior is unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Disable Clinger float fast path under extended FP precision (x87)

The contiguous number fast path uses a Clinger-style exact algorithm
(significand * 10^scale in double arithmetic), which is only correctly
rounded when double operations are evaluated in true 53-bit precision.
On the x87 FPU used by 32-bit x86 (FLT_EVAL_METHOD == 2) the single
multiply/divide is computed in 80-bit and then double-rounded to double,
so a small fraction of values land 1 ULP off.

This surfaced as test-cbor_cpp11 and test-msgpack_cpp11 failing on the
mingw (x86) job for regression/floats.json: the C++17 builds pass because
they take the correctly-rounded std::from_chars path, while C++11 falls
back to parse_float_fast(). A 5M-sample check over shortest round-trip
decimals reproduces it: 0 divergences with 53-bit doubles, ~1 in 25 000
with 80-bit intermediates; declining to std::strtod fixes all of them.

Guard parse_float_fast() on FLT_EVAL_METHOD so it declines whenever the
platform evaluates doubles in extended precision, letting the caller use
the correctly-rounded std::from_chars / std::strtod path instead. On
mainstream x86-64/ARM64 (FLT_EVAL_METHOD == 0) the fast path is unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Guard <charconv> include with __has_include for GCC 7

GCC 7 sets __cplusplus to the C++17 value under -std=gnu++1z, so
JSON_HAS_CPP_17 is defined, but its libstdc++ ships no <charconv> header
(added in GCC 8; floating-point from_chars in GCC 11). The unconditional
"#if defined(JSON_HAS_CPP_17) #include <charconv>" therefore failed to
compile there: "fatal error: charconv: No such file or directory" in the
ci_test_compilers_gcc (7) job.

Wrap the include in __has_include(<charconv>), mirroring the library's
existing handling of <version> and <filesystem> in macro_scope.hpp. When
the header is absent, __cpp_lib_to_chars stays undefined and
parse_float_from_chars() takes its scalar fallback, so the from_chars use
site (already gated on __cpp_lib_to_chars) is never reached. GCC 8-10,
which have <charconv> but no floating-point from_chars, are unaffected:
they include the header but still take the fallback. GCC 11+ is unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Restore the column when ungetting a newline

The contiguous number fast path never reads the character that terminates
a number token, while scan_number() reads it and then ungets it. When that
character is a newline, get() has already cleared chars_read_current_line,
and unget() could only restore lines_read - leaving the column at 0. The
two paths therefore reported different columns for the same document:

    json::parse("[01\n]")      -> line 1, column 3
    json::parse(stringstream)  -> line 1, column 0

Remember the column the newline was read at so unget() can restore it.
Both paths now report the position the offending token actually starts at,
which also fixes the pre-existing column-0 artifact for streaming input.

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

* Extend the bulk scan fast paths to sized sentinels

supports_bulk_scan required IteratorType and SentinelType to be the same
type, which excluded std::counted_iterator paired with std::default_sentinel_t
- the combination #5268 had already enabled for the memcpy fast path. Such
input fell back to the byte-at-a-time scanner even though it is contiguous
and its remaining length is computable in O(1).

Factor the "distance is computable in O(1)" test into sentinel_is_sized and
use it for iterator_is_contiguous, supports_seek, and supports_bulk_scan
alike, and share the std::ranges::distance/std::distance dispatch through a
remaining_count() helper.

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

* Document JSON_USE_SIMDUTF on the macro overview page

The macro was only listed in the API macro index; add it to the supported
macros overview alongside the other JSON_USE_* macros, and note that it
selects between two definitions of the same inline function and so must be
defined identically in every translation unit.

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

* Amalgamate source code

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

* Cover the counted-iterator bulk scan paths

Sized sentinels newly reach the bulk string/number scanners and the
seek-based token reconstruction, so exercise both:

- diagnostics that quote the offending token, which are rebuilt from the
  consumed input via copy_consumed_range()
- inputs whose count ends before the underlying buffer does, including a
  closing quote that exists only behind the count, a cut inside an 8-byte
  SWAR stride, and a cut inside a UTF-8 sequence

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

* Fix the SentinelType example on iterator_input_adapter

The comment offered "a C++20 sentinel or counted_iterator" as examples of a
SentinelType, but std::counted_iterator is the IteratorType - the sentinel it
pairs with is std::default_sentinel_t. #5268 corrected the same wording in the
API documentation and left the code comment behind.

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

* Do not discard the parse result in the error position check

json::parse is declared warn_unused_result, and CHECK_THROWS_WITH_AS
evaluates its expression as a discarded statement, so the assertion broke
the -Werror builds (GCC -Werror=unused-result, MSVC C4834 under /WX).
Compare against the helper that already captures the message instead.

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

* Lock the two number grammars together with a parity test

The JSON number grammar is encoded twice: as the scan_number() state machine
and as the contiguous fast path. The fast path declining on anything it does
not recognize keeps most divergence harmless, but if it ever accepted
something the state machine rejects the result would be a silent correctness
bug, and the existing test only pinned a hand-written list of numbers.

Enumerate every string of length 1..4 over "01.eE+-" (2800 tokens) and
require both paths to agree on the parsed value and on the exact error
message. Verified to fail if the fast path's grammar is perturbed.

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

* Skip token_buffer for integers on the contiguous path

An integer token does not need token_buffer: the number_integer and
number_unsigned SAX callbacks take only the value, and the overflow
diagnostic rebuilds the text from the input via get_token_string(). Convert
straight from the input buffer and materialize the token only for the
floating-point tail, which still needs a NUL-terminated buffer for strtod.

JSON_DIAGNOSTIC_POSITIONS derives a number's start position from
get_string().size(), so the copy is kept when that is enabled.

The integer dispatch is factored into convert_integer() and shared with
convert_number(), so both scanners keep using one implementation.

Integer-heavy input, 400k values, -O3:

              parse    accept
  gcc 16      +14%     +23%
  clang       +15%     +22%

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

* Amalgamate source code

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

* Cover the bulk string and UTF-8 scanners

These paths had no dedicated tests and rested on differential fuzzing only.
Add three sections, all comparing the contiguous scanner against the
byte-at-a-time one on the parsed value and on the exact error message:

- every string of length 1..3 over an alphabet of ordinary ASCII, both
  specials, a control byte, escape characters, UTF-8 lead and continuation
  bytes, and a byte that is never valid - each at offset 0 and offset 9, so
  the bulk scanner sees them with and without a run behind them
- every kind of run-ending byte at each offset across two 8-byte SWAR words,
  so multibyte sequences also straddle the word boundary
- the boundaries of every range validate_one_utf8() recognizes: shortest and
  longest encodings, overlongs, both ends of the surrogate block, U+10FFFF
  and just past it, and truncated sequences

Verified to fail if the bulk validator accepts surrogates, and if the SWAR
word test stops detecting control characters.

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

* Format the new string fast path test with astyle

The pinned astyle expands a braced-init-list used as a range-for range onto
several lines; hoist the two offsets into a named vector instead, which reads
better and leaves nothing for astyle to reformat.

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

* Fix shadowed locals and guard the exception-dependent tests

Two problems in the tests added for the bulk scanners, both found by CI:

- the inner `const json j` in the counted-iterator diagnostics shadowed the
  one declared at test-case scope, which -Wshadow rejects on GCC and clang
  and C4456 rejects on MSVC under /WX; rename them
- the new parity checks parse deliberately invalid input, which calls
  std::abort() rather than throwing when JSON_NOEXCEPTION is defined, so
  they would have crashed the no-exception build; guard them the way the
  other tests do

json::accept() does not abort, so the UTF-8 range assertions stay compiled
without exceptions and keep covering validate_one_utf8() there.

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

* Gate the C++20 iterator classification on JSON_HAS_RANGES

Making supports_bulk_scan depend on iterator_is_contiguous meant the trait
is now instantiated for every adapter, not only when get_elements() is
called. On standard libraries with an incomplete <ranges> that is fatal:
libstdc++ 10 evaluates std::contiguous_iterator<std::counted_iterator<T*>>
by calling std::to_address, which needs an operator-> its counted_iterator
does not have, so satisfaction checking is a hard error rather than false.
Reported by clang 14 + libstdc++ 10.

JSON_HAS_RANGES already encodes exactly this ("libstdc++ < 11 has incomplete
C++20 ranges", #4440), so require it for the C++20 branch. Affected
toolchains fall back to the pointer-only test and the byte-at-a-time
scanner, which parses identically, just without the bulk fast paths.

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

* Amalgamate source code

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

* Satisfy clang-tidy in the new bulk scanner tests

- give the helper lambdas an explicit std::string return type and return
  braced initializer lists (modernize-return-braced-init-list)
- replace the C-style array of test cases with a std::vector
  (modernize-avoid-c-arrays)
- silence pro-type-member-init on the two brace-initialized aggregates;
  default member initializers would stop them being aggregates in C++11

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

* Avoid escaped literals in the counted-iterator diagnostics list

clang-tidy reads "[\"\\ud834\"]" as a literal better written raw, and the
two literals written next to each other in "[\"a\x01""b\"]" as a missing
comma. The concatenation was there to stop the hex escape swallowing the
following character; build those documents from explicit bytes instead and
use raw strings elsewhere. The byte sequences are unchanged.

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

* Reattach convert_number's documentation

@gregmarr spotted that convert_integer() was inserted between convert_number()
and its doc block, leaving convert_integer() with two stacked blocks and
convert_number() with none. Comment only; no code change.

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

* Address review comments on the simdutf backend

string_bulk_run() had the same `return scalar_string_bulk_run(...)` in both
arms of the `#if`. The simdutf arm already falls through when validation
fails, so a single return after the `#endif` says the same thing.

The JSON_USE_SIMDUTF example showed `#include <simdutf.h>`, which
string_scan.hpp already does under the same guard; users only have to put the
header on the include path and link the library, not include it themselves.

Set the version history entry to 3.13.0, matching the other macro pages
documenting unreleased features.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MXDi7NTMKAmoArUZSKMc4T
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Pin the number error position against a non-newline terminator

The comment claimed the reported column is the one the offending token starts
at. It is the column reached after the token's last character - which is the
actual point of the unget() change: a number terminated by a newline now
reports what the same number terminated by a space always did.

Assert that equality directly, and add a multi-character token where the start
and end columns differ, so the invariant cannot be read off a single-character
example.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MXDi7NTMKAmoArUZSKMc4T
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Do not repeat the integer conversion that just failed

scan_number_bulk_contiguous() converts an integer token straight from the input
buffer. When the value does not fit, it materializes token_buffer and calls
convert_number(), which tried the very same integer conversion again before
falling back to floating point.

Recording the outcome in number_type skips the second attempt. The resulting
token type and value are unchanged: convert_number() reached the float tail
either way.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MXDi7NTMKAmoArUZSKMc4T
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Require a container's value_type to match what data() points at

is_contiguous_byte_container accepted any type with a data() returning a
pointer to a single-byte integral plus a size(). That is duck typing: the two
members say nothing about size() counting the units data() points at.

A type where it does not - fixed-size records, say - was routed to the
pointer-based adapter and parsed as [data(), data() + size()) bytes, silently
truncating input the iterator-based adapter had read in full:

    struct record_buffer {
        using value_type = std::array<char, 4>;
        std::string bytes;
        const char* data() const;                        // raw bytes
        std::size_t size() const;                        // in records
        const char* begin() const; const char* end() const;
    };
    json::parse(record_buffer{"[1,2,3,4,5]"});           // parse error at column 3

Requiring the container's own value_type to be that same element type ties the
two together. Every contiguous standard container satisfies it, so std::string,
std::vector<char>, std::array<char, N> and std::string_view keep the fast path;
anything else falls back to the iterator-based adapter, which is always correct.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MXDi7NTMKAmoArUZSKMc4T
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Only compile the simdutf backend from C++17 on

simdutf.h rejects anything below C++17 with an #error, so defining
JSON_USE_SIMDUTF in a C++11 or C++14 translation unit did not fail with a
message about simdutf being unavailable - it failed to compile at all, taking
the library's C++11 support with it. Nothing caught this because no build ever
compiled that path.

Gate the include and both uses on JSON_HAS_CPP_17, the same way number_parse.hpp
gates std::from_chars. Below C++17 the macro now has no effect and the scalar
validator runs; it accepts and rejects exactly the same input, so the macro is
safe to set project-wide even when some translation units use an older standard.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MXDi7NTMKAmoArUZSKMc4T
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Test the simdutf backend in CI

JSON_USE_SIMDUTF was documented and shipped but never compiled by anything in
the repository, so nothing held the backend to the behavior the docs promise.

Add JSON_TestSimdutf (OFF by default), which fetches simdutf and defines
JSON_USE_SIMDUTF for every test target, and a ci_test_simdutf target that runs
the whole suite in that configuration. Because simdutf needs C++17, the suite is
built at C++11 as well, so one job covers both the scalar fallback with the
macro defined and simdutf itself.

The dependency hangs off test_main, whose usage requirements every test target
inherits. The library target and the installed CMake package are deliberately
untouched: making nlohmann_json link simdutf would put a find_dependency() in
the exported package, which is a separate decision.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MXDi7NTMKAmoArUZSKMc4T
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Warn when JSON_TestSimdutf cannot reach the simdutf backend

simdutf needs C++17: without it the dependency does not even compile, and with
a C++17 compiler but no C++17-or-later standard under test it builds and then
goes unused. Either way the option silently did nothing useful, or broke the
configure step outright.

Resolve the tested standards first, then check them: when none of them can
reach simdutf, skip the dependency and say so, naming which of the two reasons
applies and how to fix it. The tests then run against the scalar validator,
which is what would have happened anyway.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MXDi7NTMKAmoArUZSKMc4T
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Use record_buffer::data() so clang does not flag it unneeded

The record_buffer test type declares data() and size() so the
is_contiguous_byte_container trait can see both and still reject the
type on its value_type. data() was never called, so clang's
-Wunneeded-member-function (under -Weverything -Werror) failed the
C++20 build. Assert that data() points at the underlying bytes: it
ODR-uses the member and documents the property the type is meant to
demonstrate.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XAYM1qhSA2FDaDcGfPW3fG
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Skip the float fast path when it cannot succeed

parse_float_fast() (Clinger) needs a significand below 2^53, so it always
declines once the mantissa has 17 or more significant digits. convert_number()
called it unconditionally, so those numbers were walked an extra time before
strtod had to run anyway. On streaming input, where scanning is byte-at-a-time
and there is no compensating win, that made canada.json about 6% slower than
develop.

Derive the significant-digit count from token_buffer indices - the digits are
not scanned again - and skip the call when it is guaranteed to decline. Both
scanners pass the offset where the mantissa ends; the count only has to be
corrected for a leading "0", which the JSON grammar admits nowhere else. The
integer path returns before the check, so integer-heavy input is unaffected.

Values are unchanged: this only avoids an attempt that would have failed.
Verified bit-exact against develop over every number in canada.json,
floats.json, signed_ints.json, unsigned_ints.json, small_signed_ints.json,
citm_catalog.json and twitter.json, for both the contiguous and the streaming
scanner.

  parse, streaming     develop    before     after
  canada.json           19.4ms    20.5ms    19.3ms
  floats.json          135.9ms   131.8ms   128.0ms

  parse, contiguous    develop    before     after
  canada.json           15.5ms    12.9ms    11.7ms
  floats.json           98.6ms    69.8ms    66.7ms

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
2026-09-10 17:20:48 +02:00
Niels Lohmann b17c272f46 Reserve capacity in from_json() object conversion when the target container supports it (#5472)
* Reserve capacity in from_json() object conversion when supported

The object-to-container from_json() overload filled the target
container one element at a time without reserving capacity, even
when the target type supports reserve() (e.g. std::unordered_map)
and the number of elements is already known. This caused unnecessary
rehashing while parsing large objects into such containers.

Add a reserve-detecting overload (from_json_object_impl), mirroring
the priority_tag-based SFINAE technique already used by the array
conversion path (from_json_array_impl), so that reserve(size()) is
called up front when available and the loop falls back unchanged
otherwise (e.g. for std::map).

Fixes #5406

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

* Update doc example outputs for new object-conversion iteration order

Reserving capacity in from_json()'s object-conversion path before
inserting elements changes libstdc++'s std::unordered_map bucket
layout, which changes the iteration order used by
get__ValueType_const.cpp, get_to.cpp and operator__ValueType.cpp to
print the elements of a converted std::unordered_map<std::string,
json>. Verified against a clean develop checkout (built with the
same GCC/libstdc++ used in CI) that the old order was produced
without this PR's change and the new order is produced with it, and
that the three affected examples now match their updated expected
output byte-for-byte.

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

* Factor out a reserve-dispatch helper instead of duplicating the object from_json loop

Addresses review feedback from @gregmarr on PR #5472: the emplace loop no
longer needs to exist twice for the reserve/no-reserve cases. A small
from_json_object_reserve() overload pair (SFINAE-dispatched on whether
reserve() exists, mirroring the priority_tag technique used elsewhere)
either calls reserve() or is a no-op; from_json_object_impl() calls it once.

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

* Inline from_json_object_impl into from_json now that it is called only once

Addresses review feedback from @gregmarr on PR #5472: with the reserve
loop de-duplicated, from_json_object_impl no longer needs to be a
separate function that from_json immediately delegates to.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-09 09:54:12 +02:00
Niels Lohmann 8c38e270b5 Reject JSON Patch move when from is a proper prefix of path (#5497)
* Reject JSON Patch move when from is a proper prefix of path

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 children." "move" is implemented as remove-then-add with no
check for this. For object targets, the subsequent "add" happened to
throw as a side effect of resolving through the now-removed parent,
but for array targets, removing the "from" element shifts subsequent
indices, so "path" silently re-resolves to a different element and
the operation "succeeds" with a silently corrupted document.

Add a check, before performing the remove/add, for whether "from" is
a proper prefix of "path" at the reference-token level. This compares
json_pointer's already-unescaped reference_tokens vectors (basic_json
is a friend of json_pointer) rather than the raw pointer strings, so
that tokens containing escaped '/' or '~' characters are compared
correctly, and a token that merely looks like a string prefix (e.g.
"/ab" vs "/abc/x") is not mistaken for a pointer-token prefix. When
"from" is a proper prefix of "path", throw out_of_range.414.

Fixes #5397.

Stacked on top of the fix for #5396 (branch
issue-5396-patch-remove-primitive-parent), since both touch the same
patch_inplace move/remove handling in include/nlohmann/json.hpp.

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

* Add root-pointer and array-append-token edge case tests for the move prefix check

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

* Replace std::equal with an explicitly-bounded loop in the move prefix check

The three-iterator std::equal(first1, last1, first2) form has no
explicit end iterator for the second range, which a static analyzer
(Flawfinder, CWE-126) flags as a potential over-read even though the
preceding size comparison already guarantees the second range is long
enough. Rather than argue the point, make the bound visible in the code
itself via an explicit loop -- every access to ptr.reference_tokens is
now guarded by the same index the loop condition bounds against
from_size.

(The C++14 four-iterator std::equal(first1, last1, first2, last2) form
was tried first as a more minimal fix, but this codebase targets C++11
and that overload is not safely usable under -std=c++11 with all
supported standard library implementations.)

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

* Extract the move prefix check into a named helper lambda

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

* Account for JSON_DIAGNOSTIC_POSITIONS in the move-prefix-check error messages

out_of_range::create() includes a "(bytes X-Y)" position annotation when
JSON_DIAGNOSTIC_POSITIONS is enabled, which the ci_test_diagnostic_positions
CI job builds the whole suite with. The five new out_of_range.414
assertions only checked the annotation-free message. Confirmed
JSON_DIAGNOSTICS produces the same (annotation-free) message as the
default build for this particular throw site (its path-based annotation
is empty at the root, where &result always points here), so only two
message variants are needed, not three.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-09 09:49:12 +02:00
Niels Lohmann c9477ccf91 Throw when JSON Patch remove's target path resolves through a primitive or null parent (#5496)
RFC 6902 (section 4.2) requires the target location of a "remove"
operation to exist. operation_remove handled parent.is_object() and
parent.is_array(), but had no final else branch: when the resolved
parent was a primitive value or null, neither branch matched and the
operation silently did nothing instead of failing.

Add the missing else branch, throwing out_of_range.413 with wording
that matches the existing out_of_range.411 thrown by the analogous
"add" case (operation_add) for the same kind of invalid parent.

Fixes #5396.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-09 09:49:12 +02:00
Qatadaha Bin Matloob 09b6b6b5ba Fix to_bjdata() emitting unparsable output when _ArraySize_ is not an array (#5455)
* Fix to_bjdata() emitting unparsable output when _ArraySize_ is not an array

write_bjdata_ndarray() never checked that _ArraySize_ is an array. The shape
is written verbatim as the header length, so a null shape emitted 'Z' and an
object shape emitted '{' after the '#', neither of which from_bjdata()
accepts, and the round-trip guarantee in the BJData docs was broken.

Both slipped through the existing validation: for null, empty() is true so
the element count starts at 0 and the per-dimension loop never runs, and for
an object the loop walks its values, which can satisfy the non-negative
integer check. When _ArrayData_ then matched that count, the writer took the
ndarray path.

Require the shape to be an array, so anything else falls back to a plain
object encoding that round-trips, as the fallback rule in the docs already
specifies.

Signed-off-by: qatcod <79017227+qatcod@users.noreply.github.com>

* Document that _ArraySize_ must be an array in the ndarray requirements

The list at bjdata.md is the exhaustive set of conditions for the ndarray
encoding, but it only implied this one through 'every entry of'.

Signed-off-by: qatcod <79017227+qatcod@users.noreply.github.com>

---------

Signed-off-by: qatcod <79017227+qatcod@users.noreply.github.com>
2026-09-05 20:30:22 +02:00
Niels Lohmann dd26d3ff07 docs: add 41 customers and rebuild the overview image (#5463)
* docs: add 89 customers and sort all sections

Extend the customers page from 136 to 225 entries. New entries were
found by searching vendor open-source notices and by inspecting
dependency manifests in public repositories.

Every added entry was verified to link either to a page that credits
the library, or to an open source repository where its use is directly
visible (a vendored copy, a build manifest, or an include). Candidates
whose only evidence was a transitive dependency (via ICU or
KDDockWidgets), packaging metadata, or an unused vendored file were
dropped rather than listed.

Also sort every section alphabetically ignoring case, and keep the
Peregrine lunar lander first under "Space Exploration".

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

* docs: add 41 customers and rebuild the overview image

The list was assembled by searching for names one at a time, which is why it
had plateaued. These additions come from enumerating instead: a public code
search returning every repository that references the library, and the reverse
build-dependencies of the Debian and Ubuntu source indices.

Every addition cites a first-party call site rather than a repository root,
and every evidence URL was checked to resolve. Several prominent candidates
were rejected on exactly that test:

  - Node.js reaches the library only through deps/icu-small, the inherited
    attribution ICU carries into everything that ships it.
  - Visual Studio Code's only hits are copies of the library's own headers
    used as sample C++ in the Copilot extension's test fixtures.
  - OSS-Fuzz fuzzes the library rather than calling it; projects/json/ is the
    library's own OSS-Fuzz integration.
  - libuv matched only its AUTHORS file, which lists a contributor by name.
  - simdjson and LLVM matched only benchmarks and a mangled-symbol test.

Two entries were already present under a different name and are merged rather
than duplicated: PrestoDB, and DB Browser for SQLite under its repository name.
GitHub CodeQL's citation moves from the repository root to shared/cpp/Diagnostics.h,
which includes the header directly.

The image is rebuilt with 236 logos over 17 rows. It is smaller than the one it
replaces, 1.02 MB against 1.35 MB, despite carrying 100 more marks.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-05 11:27:57 +02:00
Niels Lohmann b38c4cc937 docs: add compiled reference implementations for the container template parameters
Each of ObjectType, ArrayType, StringType, and BinaryType now links to a
minimal, self-contained header (docs/mkdocs/docs/examples/custom_*_type.hpp)
that wraps the corresponding standard container by composition and satisfies
every "Always required" member listed on that page. Unlike the prose
requirement lists, these are real code: each header has a companion .cpp that
instantiates a basic_json specialization with it and is compiled and run by
the existing ci_test_examples check (docs/Makefile's check_output_portable),
so the reference implementations cannot silently drift from what the library
actually requires. The .output files were generated with that same target.

StringType's existing pointer to tests/src/unit-alt-string.cpp's alt_string
is kept alongside the new header as a more thorough, battle-tested example.

Verified locally: astyle (pinned 3.4.13, project .astylerc) on the new files;
clang++/g++ under C++11/17/20 for each example against the amalgamated
header; `make check_output_portable` in docs/; `mkdocs build --strict` and
scripts/check_structure.py for the page itself.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-02 09:31:19 +02:00
dependabot[bot] c864bb36da Bump mkdocs-git-revision-date-localized-plugin in /docs/mkdocs (#5444)
Bumps [mkdocs-git-revision-date-localized-plugin](https://github.com/timvink/mkdocs-git-revision-date-localized-plugin) from 1.5.3 to 1.5.4.
- [Release notes](https://github.com/timvink/mkdocs-git-revision-date-localized-plugin/releases)
- [Commits](https://github.com/timvink/mkdocs-git-revision-date-localized-plugin/compare/v1.5.3...v1.5.4)

---
updated-dependencies:
- dependency-name: mkdocs-git-revision-date-localized-plugin
  dependency-version: 1.5.4
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
2026-08-31 23:06:13 +02:00
Niels Lohmann e024fe5fb6 Align the template parameter tables and record what is now diagnosed
Every table in the page is reformatted so each column is exactly as wide as
its widest cell, which is what the review asked for in a dozen places: the
separator rows that ran two dashes long, the stray spaces, and the columns
padded well past their content.

The row listing six containers that require a complete mapped type is split
in two so that one cell no longer sets the width of the whole table.

Content changes: NumberUnsignedType is described as any unsigned integer type
at least as wide as NumberIntegerType rather than any unsigned integer type;
the two requirements that are now static_asserts move out of the list of
violations that are not caught at compile time; and the two places that
require a non-const operator[] say why data() will not do (std::string has no
non-const data() before C++17).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-31 19:52:26 +00:00
Niels Lohmann 43afb5bebc Do not instantiate a hash map with an incomplete basic_json in the tests
object_t is probed for key_compare inside the definition of basic_json, so
it is instantiated while basic_json is still incomplete. Whether a hash map
survives that depends on the standard library: libstdc++ 9 needs the size of
the mapped type to instantiate std::unordered_map's node type and rejects
the adapter, which broke the GCC 9 builds.

The test now derives its no-key_compare object type from std::map -- which
does cope -- and shadows the inherited key_compare member type with an
entity that is not a type, so the library's probe finds none, exactly as for
a hash map. The unflatten() order-independence checks in unit-json_pointer
already cover the behaviour that the unordered object type was there for.
The limitation is documented for std::unordered_map.

Also address two Clang-Tidy findings the earlier commits introduced:
erase_from_object() declares its iterator with auto, and at(size_type) checks
the type first and then falls through to the return instead of throwing from
an else branch.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 18:17:15 +00:00
Niels Lohmann 0e4ad2e8da docs: record the reduced string_t and array_t requirements
Drop c_str(), back(), find(str, pos), replace(), and substr() from the
StringType requirements and at(size_type) from the ArrayType ones, and
note the string assignment the JSON pointer code performs. Streaming a
json_pointer no longer needs assignability from a std::string.

Add the non-null-terminated data() to the list of violations that are not
diagnosed at compile time -- it was described in the StringType section
but missing from the summary at the top -- and correct the QString row,
which no longer fails for the c_str() it lacks.

JSON_CATCH_USER no longer wraps a catch of std::out_of_range: the last one
went away with array_t::at(). Describe what the library actually catches.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 17:38:58 +00:00
Niels Lohmann 26b10a7b18 docs: correct the template parameter requirements after independent verification
Every claim on the page was re-checked by compiling and running it, including
the rows that say a type cannot be used, which were checked to fail for the
documented reason and not merely to fail. Twenty-four claims were wrong.

The most consequential: the incomplete-type constraint applies to ObjectType
only. object_t is instantiated inside the class definition, because it is
probed for key_compare; array_t is only named there and is not instantiated
until basic_json is complete. So eastl::vector, QList and QVector are not
excluded by incomplete types at all -- they simply have no max_size() -- and
absl::InlinedVector is excluded for a subtler reason of its own.

Further corrections: ObjectType does not need erase(key), which has a fallback,
but does need at(key) for UBJSON output; only == and < are used, or == and <=>
under C++20, not all six; the documented adapter does not fit ankerl or
robin_hood. ArrayType needs no initializer-list insert, and value_type, the
(count, value) constructor and swappability are per-function, not always.
BinaryType needs a range insert for CBOR indefinite-length byte strings and
does not need push_back. StringType needs append(const StringType&)
unconditionally, and does not need operator!= or operator== against const
char*; empty(), resize(n) and reserve(n) are per-subsystem; int_to_string is
needed by diff, items and std::hash rather than by JSON Pointer or flatten.
BooleanType must be implicitly convertible from bool, and JSONSerializer's
second parameter need not carry a default.

std::pmr::string was wrong in the other direction this time: a moved-in string
does keep its memory resource, and later growth allocates from it. Only copies
land on the default resource.

Five requirement violations are not caught at compile time rather than the two
the page claimed; they are now listed together up front. Split every
compatibility table into what works and what does not, as the reasons in the
second half are the useful part.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 17:38:58 +00:00
Niels Lohmann 690c3be01d docs: remove a duplicated StringType compatibility section
The StringType section carried two 'Compatible types' tables and two copies of
the reference-implementation tip. The second table was a stale copy from before
the binary format string fixes and still listed std::pmr::string and
std::basic_string with a custom allocator as unusable, contradicting the
corrected table a few lines above it, and it dragged along the old explanation
that blamed int_to_string.

Drop the stale copy and put the surviving table before the notes, so the
'see below' in the std::pmr::string row points forwards.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 17:38:57 +00:00
Niels Lohmann ca47dd539d docs: qualify the std::pmr::string support claim
Listing std::pmr::string as fully supported was an overclaim: it was only ever
checked with the default memory resource, which is not what PMR is for.

basic_json cannot be given an allocator or a memory resource, so a pmr string
inside a value always allocates from std::pmr::get_default_resource(), and
assigning an arena-backed string into a value silently drops its resource,
because polymorphic_allocator does not propagate on copy construction. Passing
polymorphic_allocator as AllocatorType does not compile either. Only the
process-global set_default_resource() redirects these allocations.

Say so, and separate the row from std::basic_string with a custom stateless
allocator, which is unaffected.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 17:38:57 +00:00
Niels Lohmann 681fb07eb2 docs: cover fifo_map, gtl, folly::sorted_vector_map, and Qt
nlohmann::fifo_map works through the adapter that has always been documented
for it, and preserves the insertion order. Restore its mention in the object
order page, which was dropped together with the tsl::ordered_map one: unlike
ordered_map it keeps a lookup index, so it is the insertion-ordered option
without the quadratic cost.

gtl::flat_hash_map and folly::sorted_vector_map work as well, the latter
through an alias that drops the allocator, whose value type it disagrees on.
gtl::btree_map does not, for the same reason as the other btree containers.

None of the Qt containers can be used, each for its own reason: QMap has no
value_type, QHash iterators yield the mapped value rather than a pair, QList
has no max_size(), QByteArray spells empty() as isEmpty(), and QString is
UTF-16.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 17:38:57 +00:00
Niels Lohmann a02741fd28 docs: record Folly and the remaining vector replacements
Folly works, with the caveat that its headers need C++20: folly::fbstring as
StringType, folly::fbvector and folly::small_vector as ArrayType,
folly::fbvector<std::uint8_t> as BinaryType, and folly::F14NodeMap as
ObjectType through the usual argument-order adapter. folly::F14FastMap is the
exception and requires a complete value type.

For ArrayType, boost::container::devector, boost::container::static_vector
(within its fixed capacity), and std::pmr::vector work as well.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 17:38:57 +00:00
Niels Lohmann b8482ed7f4 docs: record compatibility for the common header-only hash maps
ankerl::unordered_dense (map and segmented_map), phmap (flat_hash_map and
node_hash_map), and robin_hood::unordered_flat_map all work as ObjectType
through the same adapter as Abseil's and Boost's hash maps, which only has to
restore the template argument order.

phmap::btree_map and robin_hood::unordered_node_map do not: like the other
btree containers they require a complete value type.

Note that none of these hash maps defines key_compare, so every one of them
depends on object_comparator_t falling back to default_object_comparator_t.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 17:38:56 +00:00
Niels Lohmann d386e0aa52 Do not require string_t to be convertible from std::string
Three places built a std::string and handed it to something expecting a
string_t: the UBJSON high-precision number reader, which every binary reader
instantiates, and the BSON writer's array element size calculation and write.
That silently required string_t to be implicitly convertible from std::string,
which std::string itself and types with a string_view conversion satisfy, but
many string types do not.

Construct the string_t explicitly from the data and size, which the
requirements already cover. This makes boost::container::string, eastl::string,
std::pmr::string, and std::basic_string with a custom allocator work as
StringType, none of which could previously be used with any binary format.

Add binary format coverage to the alt_string test, which had none, including a
UBJSON high-precision number -- the case that goes through the reader path.
BSON stays uncovered there: it additionally needs string_t::find(value_type),
which alt_string does not provide.

Also record which containers from Boost, Abseil, and EASTL work for each
template parameter, and correct two claims: std::pmr::string is usable after
this change, and tsl::ordered_map is not usable at all, because its iterators
expose the mapped value as const while basic_json modifies it in place.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 17:38:56 +00:00
Niels LohmannandClaude Opus 5 5d93f35463 Relax the ArrayType and ObjectType requirements
Two requirements forced users of otherwise suitable containers to write a
wrapper, and neither was load-bearing.

array_t::capacity() was read in push_back(), emplace_back(), operator+=(), and
operator[](size_type), but set_parent() only looks at the value under
JSON_DIAGNOSTICS; without diagnostics it was computed and discarded. Read it
through array_capacity(), which reports unknown_size() when diagnostics are off
or when the array type has no capacity() at all, and treat an unknown capacity
as "the elements may have moved" so the parent pointers are refreshed
conservatively. std::deque now works as ArrayType, in both builds, and
capacity() is no longer named at all in a default build. Since the capacity is
now only meaningful for array insertions, it moves out of set_parent() into
set_parent_after_array_insert().

basic_json::erase(iterator) assigned the object's erase() return value, which
requires the container to return the following iterator. Abseil's hash maps
return void to avoid computing a successor the caller may not need. Detect that
and compute the successor before erasing; containers that return an iterator,
including the vector-backed ordered_map where a precomputed successor would be
wrong, keep the existing path.

Together these leave an Abseil hash map needing only an alias that restores the
template argument order, and no adapter at all for std::deque.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018hxZxz8svM54c6ATEvXp5E
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 17:38:56 +00:00
Niels LohmannandClaude Opus 5 96806af2dc docs: note which Abseil containers can be used as template arguments
Checked against Abseil release 20250127.0 with the same workload as the other
entries on the page (DOM access, dump, parse, CBOR/MessagePack/UBJSON
round-trip, flatten, hash), with and without JSON_DIAGNOSTICS.

absl::flat_hash_map and absl::node_hash_map work as ObjectType through an
adapter that restores the template argument order and makes erase(iterator)
return the following iterator, which Abseil's returns as void. The page now
carries that adapter, and notes that absl::flat_hash_map does not keep
references to the mapped values valid across insertions while
absl::node_hash_map does. Both have a capacity() member, so JSON_DIAGNOSTICS
already refreshes the parent pointers conservatively for them.

absl::btree_map and absl::InlinedVector cannot be used at all: object_t and
array_t are formed while basic_json is still incomplete, and both inspect
their value type at class scope. std::map and std::vector are required by the
standard to tolerate this, third-party containers generally are not, so the
page states the constraint on its own rather than only per container.

absl::InlinedVector does work as BinaryType, where it is instantiated with a
complete type. absl::FixedArray and absl::Cord are not usable.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018hxZxz8svM54c6ATEvXp5E
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 17:38:56 +00:00
Niels LohmannandClaude Opus 5 7a37a27a67 Fix unflatten and binary dumping for non-default configurations
unflatten() decided between array and object by looking at the first reference
token it happened to see for a node: it started an array only when that token
was 0. With a sorted object type the token 0 always arrives first, so the
result was correct by accident; with an object type whose iteration order is
unspecified, {"/c/2":3,"/c/1":2,"/c/0":1} unflattened to an object with the
keys "0", "1", and "2" instead of an array.

Collect the pointer prefixes that have a reference token 0 among their children
before building the result, and let get_and_create() consult that set. The
outcome is now independent of the iteration order and matches, for every input,
what a sorted object type produced before: a value is restored as an array if
and only if one of its keys is 0. Iterating the flattened object in a different
order would have been simpler, but it would have changed the key order of the
result for insertion-ordered object types.

The serializer, std::hash, and the UBJSON writer converted the elements of a
binary value to an integer implicitly, which does not compile for a BinaryType
whose value type is std::byte, and which made dump() write the bytes of a
signed value type as negative numbers. Convert to std::uint8_t explicitly in
all three places, so every byte type dumps as 0..255. The default
std::vector<std::uint8_t> configuration is unaffected.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018hxZxz8svM54c6ATEvXp5E
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 17:38:55 +00:00
Niels LohmannandClaude Opus 5 06feaa8d04 docs: list the types that are known to work for each template parameter
Follow up on the template parameter requirements page: state, for every
template parameter, which concrete types work and where they stop working.
Each entry was verified by compiling and running a common workload (DOM
access, dump, parse, CBOR/MessagePack round-trip, flatten, hash) against that
instantiation.

Findings worth calling out:

- ObjectType no longer needs a key_compare member type, so the std::unordered_map
  adapter only has to restore the template argument order. A hash-ordered
  ObjectType works everywhere except unflatten(), which reconstructs an array
  only when it meets the reference token 0 before the other indices.
- ArrayType: std::deque works when wrapped to add capacity(); std::list does not.
- StringType: std::pmr::string and std::basic_string with a custom allocator
  compile for the DOM, dump, and parse, but not for the binary readers, flatten,
  or diff, because the library assigns std::string values to string_t and
  int_to_string cannot be overloaded for a type in namespace std.
- NumberFloatType: long double works for dump and parse but not for the binary
  formats, which have no encoding for it.
- BinaryType: std::vector<std::byte> supports assignment, get, and the binary
  formats, but neither dump nor std::hash<basic_json>.

Also record the object_comparator_t fix in its version history.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018hxZxz8svM54c6ATEvXp5E
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 17:38:55 +00:00
Niels LohmannandClaude Opus 5 599bb1b68c docs: document the implicit requirements on basic_json's template parameters
The requirements that basic_json places on its eleven template parameters
were only implied by how the library uses the resulting object_t, array_t,
string_t, etc. Consumers had to discover them by trial and error.

Add "Template Parameter Requirements" collecting them, split into what is
always required and what is only required when a particular part of the API
is instantiated. Notable findings that were previously undocumented:

- ObjectType must provide a key_compare member type (actual_object_comparator
  names object_t::key_compare in both arms of a std::conditional), and its
  third template parameter is used as a comparator, so std::unordered_map
  cannot be used without a wrapper.
- ArrayType must provide capacity() -- push_back(), emplace_back(),
  operator+=(), and operator[](size_type) call it unconditionally -- and
  needs random-access iterators, so std::deque and std::list do not work.
- StringType needs contiguous, null-terminated data(), a one-byte value_type,
  and either assignability from std::to_string or an ADL int_to_string().
- NumberFloatType must be float, double, or long double for parsing and
  serialization; the integer types must satisfy std::is_integral.
- AllocatorType must be stateless, support incomplete types, and use plain
  pointers.
- BooleanType and the number types are union members and must be trivial.

Link the new page from the basic_json overview, the types feature page, and
the individual type alias pages, and correct the container examples given for
ObjectType (std::unordered_map) and ArrayType (std::list), which do not work.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018hxZxz8svM54c6ATEvXp5E
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-28 17:38:55 +00:00
whn 1ac268d409 docs: correct to_bson complexity (#5334)
Signed-off-by: whn <142425816+Whning0513@users.noreply.github.com>
2026-08-28 13:27:18 +01:00
Niels LohmannandClaude 3fa93dac65 docs: document std::pair/std::tuple serializing as an object for string-keyed pairs (#5442)
A std::pair or std::tuple whose every element is itself a two-element array
with a string first element (e.g. std::pair<std::string, int>) serializes to
a JSON object instead of a JSON array, because to_json builds the value with a
brace initializer and the initializer-list object-detection rule fires. The
resulting object cannot be read back into the original type and collapses
duplicate keys. Document this quirk in the conversions guide, together with the
unaffected cases and the idiom to force an array.


Claude-Session: https://claude.ai/code/session_016cwQq8WQRFzQcGQtbJTtJg

Signed-off-by: Claude <noreply@anthropic.com>
Co-authored-by: Claude <noreply@anthropic.com>
2026-08-28 13:26:01 +01:00
whn 01853ed6bc docs: document lenient BSON input handling (#5333)
Signed-off-by: whn <142425816+Whning0513@users.noreply.github.com>
2026-08-25 07:18:50 +01:00
Krishnanand G 2f025f401e Throw other_error.502 when UBJSON use_type is set without use_size (#5380)
* Throw other_error.502 when UBJSON use_type is set without use_size

Fixes #5321

Signed-off-by: Krishnanand G <118352827+Krishnanand-G@users.noreply.github.com>

* Scope UBJSON use_type check to container branches and expand tests

Signed-off-by: Krishnanand G <118352827+Krishnanand-G@users.noreply.github.com>

* Re-amalgamate single_include/json.hpp

The previous commit updated the split headers but the amalgamated
file didn't go back through astyle before I committed it, so CI's
amalgamation check caught formatting drift in json_fwd.hpp and a
few noexcept clauses in basic_json, plus one doc example. None of
it touches the UBJSON logic. Applied the patch CI generated to
bring single_include back in sync.

Signed-off-by: Krishnanand G <118352827+Krishnanand-G@users.noreply.github.com>

---------

Signed-off-by: Krishnanand G <118352827+Krishnanand-G@users.noreply.github.com>
2026-08-25 07:16:10 +01:00
Niels Lohmann 734fd305a1 Format-check the documentation examples in CI (#5386)
* Reformat parser_callback_t example with astyle

The file uses "json & /*parsed*/" in three lambda parameter lists, which
astyle rewrites to "json& /*parsed*/" per --align-reference=type. The
drift went unnoticed because CI never format-checked the documentation
examples; "make pretty" does cover them.

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

* Format-check the documentation examples in CI

The examples live in docs/mkdocs/docs/examples, but both format checks
still referenced the long-gone docs/examples path:

- check_amalgamation.yml passed it to find, which printed an error for
  the missing path and carried on, so astyle only ever saw include and
  tests. The step still exited 0.
- ci.cmake globbed it into INDENT_FILES, and a GLOB_RECURSE over a
  missing directory silently yields nothing, so the ci_test_amalgamation
  target skipped the examples too.

Either way the 231 example files have never been format-checked. Point
both at the real path, and guard the workflow with an explicit directory
check so a future rename fails the job instead of quietly shrinking the
file list again.

Also drop the dead docs/examples/** path filter from
publish_documentation.yml; docs/mkdocs/** already covers the examples.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-20 12:32:50 +02:00
dependabot[bot] 36187cacfb ⬆️ Bump wheel from 0.47.0 to 0.48.0 in /docs/mkdocs (#5385)
Bumps [wheel](https://github.com/pypa/wheel) from 0.47.0 to 0.48.0.
- [Release notes](https://github.com/pypa/wheel/releases)
- [Changelog](https://github.com/pypa/wheel/blob/main/docs/news.rst)
- [Commits](https://github.com/pypa/wheel/compare/0.47.0...0.48.0)

---
updated-dependencies:
- dependency-name: wheel
  dependency-version: 0.48.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
2026-08-20 12:32:34 +02:00
Sahil_Kamate b5378e8deb Fix CBOR tag handlers not recognizing tags 0-5 and 21-23 (#5331)
* Fix CBOR tag handlers not recognizing tags 0-5 and 21-23

The tagged-item switch in binary_reader::parse_cbor_internal() only handled
head bytes 0xC6-0xD4 and 0xD8-0xDB. Bytes 0xC0-0xC5 (tags 0-5: date/time,
epoch, bignum, decimal, bigfloat) and 0xD5-0xD7 (tags 21-23: base64url,
base64, base16 conversion hints) fell through to the default case and were
reported as invalid bytes, even under cbor_tag_handler_t::ignore and ::store,
despite being valid CBOR major-type-6 tags per RFC 8949.

Add the missing case labels so the full 0xC0-0xDB range is handled
uniformly. Extend the "Tagged values" test in unit-cbor.cpp to cover
0xC0-0xD7, and update the CBOR docs to state the corrected tag range.

Fixes #5315

Signed-off-by: sahilkamate03 <45514385+sahilkamate03@users.noreply.github.com>

* Fix stale CBOR tag docs and add store-mode binary-payload test

The "Incomplete mapping" warning still listed tags 0-5 (date/time,
bignum, decimal fraction, bigfloat) and 21-23 (expected conversions)
as unsupported, even though they now parse correctly under
cbor_tag_handler_t::ignore/store, same as 0xC6..0xD4/0xD8..0xDB.
Remove those five bullets and cross-reference the "Tagged items"
warning below, matching the equivalent docs fix landed independently
in PR #5367.

Also add a cbor_tag_handler_t::store test that wraps a binary
payload (not just a string) for every byte in 0xC0..0xD7, confirming
these tags are unwrapped the same way as 0xC6..0xD4 rather than
mistaken for the 0xD8..0xDB binary-subtype marker syntax, per review
feedback on #5331.

Signed-off-by: sahilkamate03 <45514385+sahilkamate03@users.noreply.github.com>

---------

Signed-off-by: sahilkamate03 <45514385+sahilkamate03@users.noreply.github.com>
2026-08-19 20:19:47 +02:00
Niels Lohmann 23518f54fe Add an Ecosystem page for third-party projects built on nlohmann::json (#5369) 2026-08-07 19:29:58 +02:00
Niels Lohmann 9a091d2b82 Do not write BJData ndarrays whose size overflows std::size_t (#5362)
* Do not write BJData ndarrays whose size overflows std::size_t

write_bjdata_ndarray() multiplied the _ArraySize_ dimensions into a
std::size_t without checking for overflow. A product that wraps around
to a value that happens to match the size of _ArrayData_ passed the
length check, and the writer emitted an ndarray header announcing an
element count that cannot be represented:

    {"_ArrayType_":"uint8","_ArraySize_":[9223372036854775808,2],"_ArrayData_":[]}

was encoded as 5b 24 55 23 5b 4d 00 00 00 00 00 00 00 80 69 02 5d, an
ndarray of 2^64 elements followed by no data. Reading that back throws
out_of_range.408 ("excessive ndarray size caused overflow"), so to_bjdata
produced output that from_bjdata rejects. This is reachable by parsing
untrusted JSON and re-encoding it as BJData.

Mirror the overflow check the binary reader already performs, and also
reject a single dimension that does not fit into std::size_t, which the
previous cast silently truncated where std::size_t is narrower than 64
bits. Such objects now fall back to a plain object encoding, which is
what the surrounding type and length validation already does for
annotations it cannot represent, and they round-trip unchanged.

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

* Document when to_bjdata converts a JData annotation to an ND-array

The BJData page described the 1-D vector case as the only situation in
which an object carrying _ArrayType_/_ArraySize_/_ArrayData_ is not
written as a compact ND-array. The writer has always had several other
fallbacks -- an unknown _ArrayType_, a dimension that is not a
non-negative integer, an _ArrayData_ whose length does not match the
product of the dimensions, and elements that are not numbers of the
annotated kind -- all of which cause the value to be serialized as a
regular JSON object instead.

Spell out the conditions, including the size-overflow check added in the
preceding commit, so the documented behavior matches the implementation.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-05 13:44:15 +02:00
Petr Bělohlávek acd87e2336 CI: Add clang 21&22 to Ubuntu CLang build matrix (#5347)
* Add clang 21 to ubuntu build matrix (CI)

Signed-off-by: Petr Belohlavek <me@petrbel.cz>

* Add clang 22 to ubuntu build matrix (CI)

Signed-off-by: Petr Belohlavek <me@petrbel.cz>

* Register Clang 22.1.8 to quality_assurance.md

Signed-off-by: Petr Belohlavek <me@petrbel.cz>

---------

Signed-off-by: Petr Belohlavek <me@petrbel.cz>
2026-08-04 16:14:35 +02:00
Niels Lohmann ad94fb01cc docs: document size-mismatch behavior of fixed-size conversions (#5352)
Conversions whose element count is fixed by the destination C++ type --
`std::pair`, `std::tuple`, `std::array<T, N>`, C arrays, and
`std::map`/`std::unordered_map` with a non-string key -- read exactly the
elements they need via `at` and never compare the JSON array's size to
that number. Excess elements are silently discarded, while a shortfall
throws `out_of_range.401` rather than a `type_error`. Neither direction
was documented in `conversions.md`, `get.md`, or `from_json.md`.

The existing warning covered only `std::array` and stated that a too-short
JSON array leaves the remaining elements default-constructed with no
exception thrown; that is not what happens. Generalize it to all
fixed-size destinations and correct the shortfall direction.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-04 08:45:50 +02:00
Niels Lohmann c2e1cc50e0 docs: document the complexity of ordered_map operations (#5353)
* docs: document the complexity of ordered_map operations

ordered_map stores its elements in a std::vector in insertion order and
has no lookup index, so emplace, operator[], at, find, count, erase, and
insert are all linear scans. The documentation stated no complexity for
any operation, neither in ordered_map.md nor in ordered_json.md.

Add a per-operation complexity table and note the consequence: building
or parsing an ordered_json object of n keys is O(n^2). Measured with
-O2 -DNDEBUG for parsing a flat object of n keys, ordered_json is 5x
slower than json at n=2000 and 54x slower at n=16000, with the timings
quadrupling per doubling of n. Cross-reference the table from
ordered_json.md and from the object order page, which recommends
ordered_json without mentioning the cost.

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

* docs: move the Complexity section after Member functions

scripts/check_structure.py enforces a fixed section order for pages under
docs/mkdocs/docs/api, in which Complexity comes after Member functions.
The section had been placed right after Iterator invalidation, which made
ci_test_build_documentation fail with structure/section_order.

No content change beyond the move; the table columns are realigned to the
narrower content.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-04 08:45:35 +02:00
Niels Lohmann 173f2a7407 Documentation review: exceptions from binary-format hardening, and tuple reference types (#5359)
* 📝 Document exceptions newly thrown by the binary-format hardening

A round of binary-format input validation (#5274, #5284, #5287, #5332)
added new failure modes without updating exceptions.md, and left two
descriptions factually narrower than the code:

- parse_error.110 said "CBOR or MessagePack"; BSON and UBJSON also
  throw it. Generalized, and added the BSON EOF example (#5332).
- parse_error.112: added the BSON document-size mismatch example
  (#5287).
- parse_error.113 said "while parsing a map key", but its own existing
  UBJSON char example already contradicted that. Broadened to cover
  invalid length specifications, and added the negative-string-length
  example (#5284).
- out_of_range.408 said "of an UBJSON array or object"; CBOR now throws
  it too (#5274). Generalized and added both CBOR examples.

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

* 📝 Correct which types may be referenced in a tuple extraction

The note added in #5271 said a referenced type must be one the library
stores "or an arithmetic type it can convert to/from". The parenthetical
is wrong: is_compatible_reference_type requires an exact match against
the stored types, so std::tuple<int&> is rejected by static_assert even
though int converts fine as a value. Only the value case is permissive.

Spell out the eight admissible types, give the int& counter-example, and
separate the reference restriction from by-value conversion.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-04 08:45:18 +02:00
Niels Lohmann 1c63a120b6 docs: document how discarded values are removed by the parser callback (#5354)
Follow-up to #5342, which fixed the parser callback leaving a discarded
member behind when an array or a value under an object key was rejected.
The documentation of parser_callback_t only stated that discarded values
in structured types are skipped, without saying that this covers object
parents and that the key is removed along with the value, so there was no
way to tell the fixed behavior from the buggy one.

Spell out the discarding rules, add an example that exercises the cases
the fix repaired, and correct the return value description: a discarded
top-level value is replaced by null, not by "an empty discarded object".

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-04 08:45:02 +02:00
KBSandmanon 78821cd9c2 docs: document standards compliance and parse() vs operator>> strictness (#5326)
* docs: document RFC 8259 / JSONTestSuite compliance and parse() vs operator>> strictness

The compliance story lived only in tests/src/unit-testsuites.cpp, so
drive-by comparisons kept claiming the library "does not fully pass
JSONTestSuite". Make it discoverable:

- README: add a "Standards compliance" note stating that both nst
  JSONTestSuite revisions run in CI, that all mandatory y_/n_ cases pass
  through the strict parse() entry point, and listing the deliberate
  implementation-defined i_ choices (unbounded nesting, silent BOM
  stripping, noncharacters forwarded, strict rejection of invalid UTF-8
  and lone surrogates, out_of_range.406 on numeric overflow).
- features/parsing: add a "Strictness and trailing data" section
  documenting that parse() is strict and rejects trailing data while
  operator>> follows relaxed iostream semantics (parses one value and
  leaves the stream positioned after it) -- the single place a naive
  test yields a "non-compliant" result.

Documentation only; no parser behavior change. Closes #5290.

Signed-off-by: manon <youdie006@users.noreply.github.com>

* docs: correct test-data vendoring and parse()/operator>> claims per review

- README: the JSONTestSuite data is downloaded from nlohmann/json_test_data at
  configure time, not vendored/committed; say so.
- README: only the updated suite runs y_ and n_ cases through strict parse();
  the original suite's y_ cases go through operator>>. Narrow the claim.
- parsing/index.md and operator_gtgt.md: note that operator>> consumes a number's
  terminating byte, so concatenated numbers must be whitespace-separated (1 2
  works, 1true does not); structural and literal values are unaffected.

Signed-off-by: manon <youdie006@users.noreply.github.com>

---------

Signed-off-by: manon <youdie006@users.noreply.github.com>
Co-authored-by: manon <youdie006@users.noreply.github.com>
2026-08-03 19:15:53 +02:00
Niels Lohmann 31ba5208c8 docs: qualify the operator>> stream positioning guarantee (#5343)
operator>>'s notes state that it leaves the stream positioned right
after the parsed value, so that concatenated JSON values can be read
back to back. That does not hold when the value is a number: a number
is only terminated by the character that follows it, and the lexer's
unget() is simulated (it rewinds only the lexer's own bookkeeping),
so that character stays consumed from the stream.

Document the actual behaviour: the guarantee holds for all value types
except numbers, which must be followed by whitespace. Also qualify the
cross-reference on the JSON Lines page, which repeated the unqualified
claim.

Documentation only; the behaviour itself is tracked in #5340.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-08-03 08:18:03 +02:00
YingqiDuan de8a099ba5 Document BSON interoperability and subtype-less binary round trips (#5330)
- warn about BSON marker 0x11 interoperability in both directions
- explain subtype-less binary normalization to subtype 0x00
- add a round-trip test for binary values without a subtype

Signed-off-by: YingqiDuan <141370165+YingqiDuan@users.noreply.github.com>
2026-07-31 08:33:07 +02:00
Patrick10199 868506dcc0 Fix CBOR half-float assertion bounds (#5335)
Signed-off-by: Patrick Armstrong <patrick@erpassistant.ai>
2026-07-30 23:38:13 +02:00
Luke Banicevic 2e23687092 to_bson() silently emits corrupt documents when a length exceeds INT32_MAX (#5314) 2026-07-28 09:08:57 +00:00
dependabot[bot] 227c5cdfb1 ⬆️ Bump mkdocs-material from 9.7.6 to 9.7.7 in /docs/mkdocs (#5324) 2026-07-27 17:36:07 +00:00
Niels Lohmann 06ac77f4fd Remove Lion Yang from sponsors list (sponsorship cancelled) (#5306) 2026-07-26 19:42:28 +00:00
Luke Banicevic dfa51af692 Enhance documentation on serializing untrusted input in dump() (#5304) 2026-07-26 08:29:31 +00:00
Luke Banicevic 3296a3ad8c Docs: clarify there is no official npm package (impersonation/typosquat awareness) (#5299) 2026-07-23 16:02:29 +00:00
Niels Lohmann c197feff81 Extend memcpy fast path to sized sentinels (e.g. std::counted_iterator) (#5268) 2026-07-12 09:16:06 +02:00
Niels Lohmann b2b47c69b1 📝 Document std::pair/std::tuple conversion and C++20 range-view construction (#5271)
Both had zero documentation anywhere in docs/mkdocs/. The tuple/pair
gap was first spotted in the very first git-log audit pass but never
turned into an actionable todo, so it persisted uncaught across four
subsequent passes.

- Document basic positional std::pair/std::tuple <-> json array
  conversion, plus #5016's reference-extraction capability
  (get<std::tuple<T&, T&>>() returning references into the stored
  array elements).
- Document #5205's new json-from-C++20-range-view constructor
  (e.g. nums | std::views::filter(...)).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-07-11 23:58:49 +02:00