Test the lvalue path with the const original instead of a mutable copy
and the rvalue path with a temporary (misc-const-correctness), and mark
the intentional char8_t array with NOLINT (avoid-c-arrays).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
- unit-json_patch.cpp: move multi-line raw strings out of CHECK(), which
GCC 4.8 cannot parse inside a macro argument
- unit-recursion_depth_limit.cpp: value-initialize the const std::hash
(Clang 3.4 rejects default initialization of a const object)
- json_view: silence modernize-use-transparent-functors (std::less<> is
C++14), bugprone-suspicious-stringview-data-usage (the length comes from
the node) and the deliberate use-after-clear() / owning-memory hits in
unit-json_view_builder.cpp; use a raw string literal there
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Read a std::u8string from a JSON string and store it as one in every configuration
In C++20, json(std::u8string) was stored as a JSON string only when
std::filesystem::path support was available (the to_json overload sat
inside the JSON_HAS_FILESYSTEM guard), and there was no matching
from_json, so get<std::u8string>() threw type_error.302 ("type must be
array, but is string"). Without std::filesystem, the same expression
still produced an array of code units (the 3.12.0 behavior).
Move the to_json overload out of the filesystem guard so that a
std::u8string is a string in every configuration, build the value
directly from the code units (this also works for a custom string_t
such as the tests' alt_string), and add a from_json overload that reads
a JSON string. The array of numbers written by 3.12.0 is still accepted;
other types throw type_error.302 ("type must be string or array").
std::u8string_view and char8_t arrays are unchanged.
The tests now run in C++20/23 (the file mentions JSON_HAS_CPP_20/23),
also without std::filesystem (test-conversions2_no_filesystem), and with
ordered_json and a custom string type. The new behavior is documented.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fill the std::u8string with resize and indexing instead of push_back
The push_back loop is not vectorized: reading a 1 kB string took about
2.2 us against 0.39 us with resize and direct element access (clang -O2).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Write the std::u8string from_json template header in the compact form
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Ignore libstdc++ char to char8_t sign change in the clang sanitizer job
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Two bugs of 3.12.0 are fixed on develop without a note on the pages.
With JSON_DIAGNOSTIC_POSITIONS, start_pos() of a string that contains
escape sequences was too large; the position is now that of the opening
quote. A parse error for an unexpected number that is followed by a line
feed reported column 0 (for "1 2" and a line feed, line 1, column 0); for
"1", line feed, "2", line feed it now reports line 2, column 1.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: state that NaN ordering inside containers depends on the standard
When the element-wise comparison of arrays or objects reaches a NaN and
a number (or another NaN) before any other difference, the result
depends on the language standard. Before C++20 the pair counts as
equivalent and the following elements (or the sizes) decide, so
[1] <= [NaN] is true. Since C++20 the comparison is unordered and
<, <=, >, >= all yield false. Document this on operator<, <=, >, >=
and <=>.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: fix the FILE* notes of parse() and the locking promise
The performance note of parse() said a FILE* is read one character at a
time. With glibc and the Apple C library the characters in the FILE's
buffer are scanned in bulk; only elsewhere is it one character at a
time. The file is locked once only where the C library has unlocked
stdio functions (not on musl, MinGW, newlib, with
JSON_DISABLE_UNLOCKED_FILE_IO, or under MSan). Qualify the promise on
parse.md, sax_parse.md, the parsing page and the performance page.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: fix integer ranges in the MessagePack and BJData tables
number_integer_t is std::int64_t, so number_integer cannot hold values
above 9223372036854775807; those are number_unsigned. The MessagePack
row for uint 64 listed the range up to 18446744073709551615, and the
BJData table had a uint64 row for number_integer that can never be
selected. The CBOR table was already corrected.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: name the macros that turn off FILE* locking and bulk scans
parse() and sax_parse() now say that the FILE* is locked unless
JSON_DISABLE_UNLOCKED_FILE_IO is defined to 1, and the input-source
table and the performance page name JSON_DISABLE_STREAM_BULK_SCAN and
JSON_DISABLE_UNLOCKED_FILE_IO with what each turns off.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The test for json_view documents over an alternative string type called alt_editable_document::load() and save(). Both exist only on little-endian targets, so the test suite did not compile on big-endian targets such as s390x. Guard the two image lines with the condition the other image tests use (unit-json_view_image.cpp, unit-json_view_positions.cpp).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Two views compared equal when the tokens of two floats were equal, and
the same node was equal to itself. An edit writes a NaN as the token
"nan", so a view of it (or of an array holding it) was equal to itself
and to another NaN, while json(NaN) == json(NaN) and view == json are
false. The token shortcut now excludes the edited "nan" token (found by
the missing digit layout), dispatched on the document mode by a tag: a
read-only document cannot hold a NaN, and its walk is unchanged
(instruction count and cycles on canada, citm and twitter within
noise). For editable documents the check costs about 2 % instructions
on canada (cycles within noise). The same-node shortcut is kept for
read-only documents and for editable ones that were never edited; a
document with edits is walked, so comparing it with itself is linear
instead of constant.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
image_check::full accepted a float node whose token is an integer literal
that fits 64 bits (e.g. 10446744073709551616 changed from 18446744073709551616).
The parser stores an integer node for such a token, so the loaded
document differed from what parsing the same text gives. check_float_ranges
now requires an integer token of a float node not to fit uint64_t (or
int64_t when negative).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
dump() said a view never throws type_error.316 because the text is always
validated. A document loaded with image_check::bounds or none can hold
invalid UTF-8: dump() writes it unchanged, and dump(ensure_ascii) throws
type_error.316. (The matching correction of number_token() is part of the
read() documentation change below which this commit is stacked.)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Document that read() must not be given a view of the document itself
basic_json_document::read() releases the previous text, the decoded
strings and the edits before it parses its input. An input that points
into them (source(), get_string(), number_token(), or a string of an
edited document) is read after its memory was cleared or freed.
A guard that copies such input costs about 1 ns per read() (5 % of a
read of a 7-byte input), which this API exists to avoid, so state the
precondition in read.md, lifetime.md and the pages of the views that
hand out such strings instead, and show how to copy the string first.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Assert in debug builds that read() is not given its own text
read() releases the document's text, decoded strings, owned image and
edits before it parses, so an input that points into them is read after
release. Without NDEBUG, read() now asserts that a borrowed input, a
copied contiguous input and (before C++17) a string_ref input are not
held by the document: its owned text, its decoded strings, an owned
image, and the current buffer of edited strings. Release builds keep
the documented precondition without a check, which would cost 2-4.5 %
per read() of a small message.
JSON_ASSERT is undefined at the end of json.hpp, so the view uses
assert() through a new internal NLOHMANN_VIEW_ASSERT.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The Dependabot bump to 10.1.0 (#6059) conflicts with the pinned
opentelemetry-api 1.37.0 (importlib-metadata<8.8.0), so the Semgrep job
failed with ResolutionImpossible. Ignore importlib-metadata in Dependabot
since semgrep pins it indirectly.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Read iterator pairs of std::string and std::vector as pointer ranges
Before C++20, a pair of iterators of a contiguous container cannot be told
from any other random-access iterator, so json::parse(s.begin(), s.end())
on a std::string or std::vector<char> was read one character at a time,
without the bulk scans of strings, numbers and indentation that the
container itself gets (the container overload of input_adapter() already
maps it to a pointer range). The iterators of std::string and of a
std::vector of 1-byte integral elements are now matched exactly and mapped
to the pointer range they cover; an empty range is not dereferenced. The
character type stays the same, so the results and error positions do not
change.
parse(first, last) of a std::string gets 1.7-2.0x as fast in C++17 on an
Apple M1 Max, accept(first, last) 2.7-3.1x, and from_cbor(first, last) of a
std::vector 8-23% faster.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI: clang-tidy, unused result, Infer false positive in tests
- unit-deserialization.cpp: raw string literals, and assign the result
of parse() in CHECK_THROWS_AS (-Wunused-result)
- unit-bson.cpp: mark Infer's NULLPTR_DEREFERENCE on from_bson() with an
iterator pair as a false positive
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix implicit char conversion in iterator-pair test
The test built std::vector<unsigned char> and <signed char> from a char
range, which -fsanitize=integer reports as an implicit conversion.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: sweep_allocator::construct() accepts pointers to const
Recent libc++ (emsdk latest) probes construct(const T*, const T&) in an
unevaluated context while checking for trivial copies; the static_cast to
void* in the noexcept specification then fails to compile.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: guard sweep_allocator::construct() against const types instead of const_cast
The const_cast added in the previous commit is rejected by
cppcoreguidelines-pro-type-const-cast (clang-tidy). Make construct() not
viable for const U instead, which is what libc++ probes for.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI: astyle and clang-tidy for sweep_allocator::construct()
astyle 3.4.13 reformats the enable_if<!...> default template argument
(Check amalgamation). Delete the const overload instead, which makes the
libc++ probe for const objects fail in the SFINAE context just the same
and needs no <type_traits>.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Iterator ranges: astyle-safe trait members; reserve in the test helper
The byte check and the container match are static constexpr members
instead of integral_constant arguments and a default template argument
with comparisons, which astyle spaced out.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>
* SWAR: test for special bytes in the reduced form
The usual test for a zero byte, (x - ones) & ~x & high, needs `& ~x` only
to keep bytes from 0x80 out. The tests for quotes, backslashes and control
characters in string_scan.hpp and the serializer also flag every byte from
0x80 with `v & high`, so the `& ~x` terms can be dropped. Clang finds this
reduction itself; GCC does not and emits 24 instead of 16 instructions.
The masks are the same for 1.3 billion random words and for every pair of
adjacent byte values. With GCC 15 on x86-64: accept() -2 to -4 %,
sax_parse() -2 %, dump() -3 %. Clang is unchanged.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Vector scans: one compare for the quote and the control characters
The SSE2/NEON tests for the bytes a string run stops at compared with the
quote, with the backslash and with 0x20 separately. Flipping bit 1 maps
0x00-0x1F onto itself and the quote onto 0x20, and every other ASCII byte
to 33 or more, so (c ^ 2) < 33 finds the quote and the control characters
with one compare: signed where the bytes from 0x80 stop the run too,
unsigned (or with a saturating subtraction / minimum on SSE2) where they
do not. This saves one vector operation per 16 bytes in all twelve vector
tests: the lexer's vector_plain_run() and vector_utf8_run(), dump()'s
copy_plain_halves() and copy_plain_vectors(), and json_view's scanner and
serializer. The DEL tests of the ensure_ascii paths stay.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: sweep_allocator::construct() accepts pointers to const
Recent libc++ (emsdk latest) probes construct(const T*, const T&) in an
unevaluated context while checking for trivial copies; the static_cast to
void* in the noexcept specification then fails to compile.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
(cherry picked from commit 794bf70823c12a2a1cb2a8a95f34dfb6357746a8)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: guard sweep_allocator::construct() against const types instead of const_cast
The const_cast added in the previous commit is rejected by
cppcoreguidelines-pro-type-const-cast (clang-tidy). Make construct() not
viable for const U instead, which is what libc++ probes for.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
(cherry picked from commit de099fa607001b710862fd1bbecef3609c54cbc4)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI: astyle and clang-tidy for sweep_allocator::construct()
astyle 3.4.13 reformats the enable_if<!...> default template argument
(Check amalgamation). Delete the const overload instead, which makes the
libc++ probe for const objects fail in the SFINAE context just the same
and needs no <type_traits>.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>
semgrep requires exact or compatible-release versions of mcp, boltons and
the opentelemetry packages. Bumping them alone makes the Semgrep job fail
at pip install (see #6054, #6055, #6057, #6058, #6060, #6061), so leave
them to move with the semgrep bump.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Regenerate the hash-pinned requirements file. This raises the transitive
pins pyjwt 2.13.0 -> 2.15.1 and mcp 1.23.3 -> 1.29.0 (also click 8.1.8 ->
8.4.2, new structlog 26.1.0), closing 18 of the 23 open Dependabot alerts.
The remaining alerts cannot be fixed until Semgrep relaxes its pins:
mcp needs 1.30.0 (Semgrep pins mcp==1.29.0) and opentelemetry-api needs
1.45.1 (Semgrep pins ~=1.37.0).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: update the README for the release
- Show the animated SVG feature slideshow (light and dark variant) instead
of json.gif.
- Thank 20 further contributors and extend two existing entries.
- Fix the bad_serializer example (invalid template header, second function
named to_json instead of from_json, missing template keyword).
- Add "Zero-copy views" to the table of contents, link ordered_json to its
API page, and point the speed design goal to the performance page.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* chore: remove the stale ChangeLog.md and docs/json.gif
ChangeLog.md was last generated in January 2025 and still ends at
"unreleased (2024-12-22)"; 3.12.0 shipped without an entry. The release
notes live on the GitHub releases page and in docs/mkdocs/docs/home/releases/.
Remove the file, the Makefile target that called github_changelog_generator,
and the README credit for that tool.
docs/json.gif is an old copy of the feature slideshow that nothing
references; the home page uses the SVGs built by docs/mkdocs/scripts/slideshow/.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* chore: remove the unreferenced docs/mkdocs/docs/images/json.gif
The README header and the home page use the SVG slideshow built by
docs/mkdocs/scripts/slideshow/.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
dump() batches float tokens of 16 or 17 digits with at least 8 fraction
digits. A damaged image loaded with image_check::bounds can record a
token with no digit before the point and 17 after it, which no JSON
number has. Its q = -17 is outside the range of locate_token(), which
then read fives[17] past its 17 entries; on x86-64 the resulting digits
had 18 digits and failed the assertion of write_decimal() (OSS-Fuzz
issue 583898810, json_view_image_fuzzer).
The batch now takes 8 to 16 fraction digits, which every valid token of
16 or 17 digits has, so it batches the same tokens of valid documents.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Install Semgrep from a new hash-pinned requirements file in
cmake/requirements (covered by Dependabot) instead of a version-only
"pip install semgrep==1.168.0", and pass --require-hashes to the astyle
and natvis installs in check_amalgamation.yml, whose requirements files
got their hashes in #6046. Addresses the Scorecard Pinned-Dependencies
code-scanning alerts for semgrep.yml and check_amalgamation.yml.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: blog post: describe the performance work of #6020, #6028-#6031 and #6033
Theme 1 gets the iterator pairs of std::string and std::vector, a new
subsection on the fused contiguous parser after yyjson's reader, and the
FILE buffer window after gnulib's freadptr(). Theme 2 shows the reduced
SWAR test and the (c ^ 2) < 33 vector compare. Themes 4 and 6 get the
binary strings without a zero fill and the 64 KiB window of the vector
sink. Appendices H and J list the new pull requests and their checks.
The numbers of the suite, the timeline, the comparison and the compile
times are not remeasured yet.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: blog post: remeasure on develop with #6029, #6031, #6033 and #6039
Rerun on develop 7fc8312c64 with the open pull requests #6029, #6031,
#6033 and #6039 merged, measured on November 7: the suite (median of 12
runs, now 3.3x), the timeline (358 commits, #6031 shown as a pending
step on the candidate, #6028 labeled, a tick for November), the compile
times, the stream gap, the allocator check and the comparison on the
Mac and on x86-64, including the held-out files.
The comparison now leaves out the "copy untimed" variants, as the post
describes, and the held-out chart no longer counts json::accept() as
another library. Appendix D, the Intel column of Appendix B and the
GCC 16/Clang 23 check on the Mac are still from November 3.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Parse JSON in one block of memory with a fused pointer-based parser
The parser and the lexer exchange one token at a time, and the lexer keeps
its state (the current character, a pending unget, where the token starts)
in members, which every character pays for: json::accept() of twitter.json
took 2.8x as long as json_document::accept(). detail::contiguous_parser
reads text in one block of memory through a local pointer, with the
grammar, the whitespace and the tokens in one loop (after yyjson's reader),
and drives a SAX handler: parse()'s DOM handler, accept()'s handler, or the
user's handler of sax_parse(). It is used with the default options (no
callback, no comments, no trailing commas; sax_parse() with strict = true).
Errors are reported by the library parser, so the exception, its message and
its position stay the same. contiguous_parser stops at the token that the
library parser would reject, before reporting it, so the events up to the
error are the same; then:
- parse() runs the library parser with a handler that only reports the
error (json_sax_error_reporter), with the lexer of parse(), which is
instantiated anyway;
- sax_parse() runs it with a handler that forwards only parse_error() to
the user's handler (json_sax_error_forwarder), so no event arrives twice;
- accept() returns the verdict.
A handler that returns false stops the parse as before. An error at the end
of a large input costs parse() about 1.2x of what it cost before.
On an Apple M1 Max: accept() 1.6-2.0x as fast, parse() 10-16% faster,
ordered_json 11-16%, sax_parse() with a user's handler 1.36-1.46x, small
messages 12-22% (parse()) and 2.1-2.4x (accept()). On x86-64 (GCC 15,
Clang 21): accept() 1.6-1.9x, parse() 5-17%, ordered_json 12-19%,
sax_parse() 1.32-1.57x. A translation unit that parses a string compiles 3%
(-O0) and 9% (-O2) slower.
unit-contiguous_parser.cpp compares the contiguous path with the byte path
(std::list iterators) on corner cases, generated documents, their
truncations and mutations, deep nesting, and narrow number types: the same
values with the same number types and float bits, exception messages,
accept() verdicts and sax_parse() events.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI: unused parameter without exceptions, cpplint, BUILD.bazel
- json_sax_error_reporter::parse_error: mark the exception unused, as
JSON_THROW does not use it with JSON_NOEXCEPTION
- unit-contiguous_parser.cpp: compare the exceptions of both paths only
when exceptions are enabled (invalid input aborted the test otherwise)
- silence cpplint's readability/braces false positives on the if
statements inside the parser's macros
- add contiguous_parser.hpp to BUILD.bazel
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* accept(): skip digits without computing their value
accept() needs the value of a number only for a float whose exponent may
reach the largest value. skip_digits() finds the end of the digits without
the multiply-adds of accumulate_digits(), and once an 8-byte word fails the
digit test, the remaining loop needs no bounds check: a non-digit is in
that word. The value is computed afterwards for the rare floats that need
it.
accept() of canada.json: -16 % on Apple M1, -22 % with GCC 15 and -21 %
with Clang 21 on x86-64; files with many numbers -9 to -15 %.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: mark parser callback in unit-contiguous_parser noexcept
Fixes the -Werror=noexcept failure with GCC 26 (ci_test_standards_gcc (26)).
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: sweep_allocator::construct() accepts pointers to const
Recent libc++ (emsdk latest) probes construct(const T*, const T&) in an
unevaluated context while checking for trivial copies; the static_cast to
void* in the noexcept specification then fails to compile.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
(cherry picked from commit 794bf70823c12a2a1cb2a8a95f34dfb6357746a8)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: guard sweep_allocator::construct() against const types instead of const_cast
The const_cast added in the previous commit is rejected by
cppcoreguidelines-pro-type-const-cast (clang-tidy). Make construct() not
viable for const U instead, which is what libc++ probes for.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
(cherry picked from commit de099fa607001b710862fd1bbecef3609c54cbc4)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI: astyle and clang-tidy for sweep_allocator::construct()
astyle 3.4.13 reformats the enable_if<!...> default template argument
(Check amalgamation). Delete the const overload instead, which makes the
libc++ probe for const objects fail in the SFINAE context just the same
and needs no <type_traits>.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Contiguous parser: review fixes (wording, macros, diagnostic positions)
- "default parser" instead of "library parser" in comments and tests
- the three comments in json.hpp say the same thing
- current() replaces the repeated `p != end ? *p : 0`
- the backslashes of each macro are aligned
- the docs say that JSON_DIAGNOSTIC_POSITIONS turns the fast path off
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>
Add sha256 hashes for every release file to the requirements of the
astyle and natvis tools, and install Meson in the ubuntu workflow from a
new hashed requirements file with --require-hashes instead of an
unpinned "pip install meson". pip verifies all installs from these files
once they contain hashes, including the ones of the Makefile and
cmake/ci.cmake. Addresses the Scorecard Pinned-Dependencies alerts for
ubuntu.yml; the check_amalgamation.yml flags follow once develop has the
hashes.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Autobuild compiled the whole test suite. The resulting database was so
large that the hosted runner repeatedly lost communication with the
server while importing the TRAP files (about 80 minutes in), which left
failed CodeQL analyses on develop and on pull requests. Analyze the
sources without building them instead.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
#6018 split features/json_view.md into features/json_view/ sub-pages while
#6022 added a blog post linking to the old page, so `mkdocs build --strict`
failed on develop (Publish documentation run 42577793091). Point the links
to json_view/index.md and json_view/editing.md.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Split the json_view feature page into sub-pages
The single features/json_view.md page grew to ~600 lines covering eight
topics. Split it into features/json_view/ with an overview page and
pages for ownership and lifetime, differences from basic_json, reading
values, generic code, editing, and images.
The new differences page collects what was spread over several sections
("What is the same", "What is different", "Duplicate keys", and notes in
the conversion and serialization sections) under one summary table, and
adds the parts of the basic_json interface a view does not have. The
other pages now link to it instead of restating the rules.
Internal links across the documentation point to the new pages.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Docs: fix stale comments and trim repeated text in json_view pages
- fig-jsonview.js/.css: point the header comments at the new pages
- reading.md: views' strings are valid as long as the document (and a
borrowed source text), as lifetime.md says
- reading.md, generic_code.md: link to differences.md instead of
restating the member-order and repeated-key rules
- differences.md: drop the third mention of ordering comparisons, name
rbegin()/rend() in the iterator row
- exceptions.md: link editable documents to editing.md
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
#5835 replaced the switch on the value type in operator*, operator->,
operator++, operator-- and operator== of iter_impl with an if chain that
tests for an array first. Every step over an object then pays for a
failed test and a taken branch: with the iterator inlined, walking
twitter.json took 14% more cycles than with 3.12.0, and citm_catalog.json
3.5% more.
Test for objects first. Walking every value of the three files now
takes fewer cycles than with 3.12.0 (Apple M1 Max, Apple clang 21):
citm_catalog.json 1.21x, twitter.json 1.04x, canada.json 1.17x as fast.
canada.json, which holds only arrays, gives back part of the gain of
#5835 (develop: 1.62x); the other orders tried (arrays first without
hints, objects first without hints, a switch) each left one of the
files slower than 3.12.0.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: add the blog post "How 3.13.0 got faster"
A post for the documentation (Home > Blog) on how 3.13.0 became faster:
eight themes with the pull requests behind them, the ideas taken from other
libraries, what did not work, how the fast paths are tested, and the
compile-time cost. Every number comes from a run on 2026-10-27 (3.12.0 against
develop plus the open non-draft PRs, Apple M1 Max) or from the linked PR.
- docs/mkdocs/docs/home/blog/how_3_13_0_got_faster.md: the post.
- docs/mkdocs/scripts/figures/perf_blog.py: draws its 12 figures (overview,
eight timeline panels, the SWAR test, the cliffs, json_view throughput) as
inline SVGs in the nj-charts style; data/perf_timeline.csv holds the
timeline.
- tests/benchmarks/history: history.cpp and history.py time one fixed program
against the header of every commit that changed it, interleaved, and write
one CSV row per commit with its PR. The timeline of the post comes from it.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: compare json_document with Glaze, sonic, RapidJSON and Rust parsers
Extends the comparison in "How 3.13.0 got faster" from yyjson, simdjson and
Boost.JSON to eleven engines: sonic-cpp, RapidJSON and Glaze (generic DOM,
lazy_json, reading into structs) in C++, sonic-rs, simd-json and serde_json in
Rust. Measured on an Apple M1 Max (Apple clang 21, Rust 1.99) and an x86-64
Haswell server (GCC 13, Clang 18). Every engine must return the same values,
string bytes and bit-identical number sums before it is timed.
The post now answers whether json_document is the fastest parser: it is the
fastest document parser at parse+dump everywhere and at parsing on Apple
silicon, ties with simdjson's DOM on x86-64, and loses to simdjson On-Demand
and Glaze structs when only a few fields are read.
tests/benchmarks/json_view/others holds the programs (bench_all.cpp, the Rust
crate with its Cargo.lock), summarize.py and the pinned versions and checksums.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: captions, test-file table and figure fixes for the 3.13.0 post
- caption every table and figure
- describe what makes twitter.json, citm_catalog.json, canada.json and
jeopardy.json hard, and what each timeline panel exercises
- split the json_view layout figure into the tree and the index, with
the example text above; fix the arrows into the string boxes
- arrows and a "less is better" axis label in the cliffs figure
- name nlohmann/json in the comparison tables and chart
- licenses of the adapted code in the thanks section
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: byline and licenses for the 3.13.0 post
- author and date below the title, styled as .nj-byline; its link gets
no external-link icon
- the license of every library in the thanks section, checked against
each project's license files; credit sonic-rs for QUOTE_TAB, which
orjson adapted from it
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: dump comparison and split acknowledgments in the 3.13.0 post
- a dump workload in bench_all and bench_rs: each engine writes a
document parsed beforehand, and every output must read back with
bit-identical numbers; an optional argument selects one workload
- the post's comparison gains a write table, a throughput chart, a dump
row for all three configurations, and the x86-64 cases it loses
- the thanks section is split into adapted code and borrowed ideas
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: x86-64 dump numbers with #5908's branch-free token digits
The dump of canada.json with GCC on x86-64 lost to yyjson by 0.78 because
GCC compiled #5908's token-digit selections as branches; 9fad526888 fixed
that. The post's x86-64 dump and parse+dump rows of canada.json are now
measured with it (GCC 0.95, Clang 0.91 against yyjson), theme 5 tells the
story, and "How we measured" says which rows include the commit.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Compare JSON libraries by use case in the json_view harness
bench_all and bench_rs now time use cases (validate, sum, select, edit,
minify, write) instead of library functions. Every library may solve a
use case in every way it offers; each variant's result is checked, and
three malformed inputs give its validation level (full, no UTF-8,
partial). summarize.py reports each library's fastest fully validating
variant and a faster one at a lower level, as text and as JSON.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: restructure the 3.13.0 post around themes and use cases
- deeper technical detail and code in the eight themes; pull request
numbers move to the appendix, timeline steps are labelled by theme
- comparison with other libraries by use case, as heatmaps per
platform, with validation levels and the caveats next to the results
- appendix: test files, all 182 suite rows with a histogram, timeline
steps, algorithmic fixes, per-file tables, behaviour changes, setup,
pull requests by theme
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Measure each library's fastest modes in the json_view harness
Address the points of a review from the other libraries' side:
- simdjson 5.0.8 (On-Demand structs, key selectors) and Glaze 9.1.0
- number-skipping modes: yyjson and RapidJSON raw numbers, Boost.JSON
number_precision::none
- reused parsers and allocators for yyjson, RapidJSON and Boost.JSON
- Boost.JSON parse_into, Glaze generic with double numbers, and the
same struct types for nlohmann, Glaze, simdjson and serde
- minified copies of twitter.json and citm_catalog.json
- a fourth probe (trailing garbage) and Glaze "(strict)" variants
- a new random variant order in every round, as a variant's time could
depend on the one before it by up to 15 % on the Mac
- --files for other test files and --conformance for JSONTestSuite,
with conformance-rs.sh for the Rust program
summarize.py also reports each library's best reused variant.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: rerun the library comparison of the 3.13.0 post with fairer rules
The figures and Appendix E use the reruns with each library's fastest
modes. Skipping number conversion while reading is now allowed for
every library; copying number text is still not chosen when writing.
The text now says who set the rules, where libraries that check less
win select, how minified files change the picture, and that the
reused jeopardy.json claim holds with every library reused. A new
section covers 19 held-out files and JSONTestSuite, including where
json_document loses, and lists what was not measured. Every
comparison number was recomputed; Glaze is credited in the intro.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: measure the 3.13.0 post against develop with #5964 and #5908
The suite (Appendix B, the short-version table, the overview and distribution
figures) and the timeline endpoint now measure develop d20c4dcd89 with #5964
and #5908 merged. The geometric mean stays 2.9x (2.95); Dump/signed_ints and
Dump/unsigned_ints gain 1.5x and 2.1x from #5964; GetVectorDouble/floats drops
from 10.3x to 7.0x because the old candidate's suite binary happened to compile
that loop faster (a standalone build takes 0.97 ms with both headers).
The timeline endpoint is the 10-27 value scaled by the ratio of the new to the
old candidate, both measured on 10-30, so that it stays comparable with the
other points of the timeline.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: add three figures to the 3.13.0 post
- short strings: two overlapping 16-byte loads and stores
- eight digits at a time: the three multiplications, lane by lane
- validate on the 19 held-out files, per file, Mac and x86-64
The prose the figures replace is trimmed.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: measure the 3.13.0 post against develop with all open pull requests
The baseline is now develop 9c349b1d7c with every open non-draft pull
request merged, including #5968, #5970, #5971, #5975, #5976, #5978,
#5979, #5980, #5981 and #5982. The suite was rerun on 11-01 with every
step repeated when the load rose above 5 while it ran; the comparison
with other libraries and the held-out files were rerun on 10-31.
- suite: 3.0x geometric mean (median 2.9x); Appendix B, the overview
and the distribution regenerated
- timeline endpoint, Appendix D and the cliffs figure updated
- the held-out figure compares json_document with the fastest other
library
- new paragraphs for the pull requests listed above
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: measure the 3.13.0 post against develop with the open pull requests of 11-02
Suite, timeline endpoint, Appendix D and the scalar-run numbers now come from
develop b2674a4a2f with #5990, #5991, #5992, #5996, #5997, #5998, #5999 and
#6000 merged. The scalar runs are measured against a build without them on
develop's code, which no longer checks for a scalar before entering the loop.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: measure the 3.13.0 post against develop with all open pull requests of 11-02
Suite, timeline endpoint, Appendix D and the scalar-run numbers now come from
develop b2674a4a2f with #5990-#5992, #5996-#6006 and #6008 merged. With #6008,
arrays of one element skip the scalar run, so nested arrays no longer pay for
it. The suite ran three rounds per version; the round of 3.12.0 and of 3.13.0
that differed from the other two was dropped, as the setup table says.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: fix the facts the review of the 3.13.0 post found wrong or imprecise
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: re-measure the 3.13.0 post and apply the review
Measure everything again against develop with the open pull requests of
11-03 (suite, timeline, comparison on the Mac and on x86-64, compile
times, stream gap), add the suite on an Intel MacBook Pro as a check,
mark the ways that keep number text as "N" in the use-case charts, move
the loop-shape box to theme 5, and apply the style and wording fixes of
the review.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: make the comparison of the 3.13.0 post fairer
Three reviews of "How it compares" (a maintainer audit of the harness, a
methodology review, a reader's red team) led to a full rerun on the Mac and
x86-64 with simdjson 5.1.1 and new ways in the harness:
- in-place parses with the copy made before the timer ("(copy untimed)",
never chosen as a library's best) and json_document::parse_copy();
- RapidJSON through StringStream, and with default precision in validate,
which reads no number;
- BENCH_ONLY takes several prefixes.
The post now gives the copy's real cost (11-14 us for twitter.json on the
Mac, not 30), what yyjson gains without it, the run-to-run noise, the LTO
check, the single-file losses that were missing, and qualifies the headline
claim. Every number in the section and Appendix E is recomputed; the
NUL-byte remark moved out of the body.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Format bench_all.cpp with astyle
The amalgamation check runs astyle over tests/ and failed on bench_all.cpp. The variant tables keep one variant per
line between *INDENT-OFF* and *INDENT-ON*; astyle formats the rest, and the list of use cases becomes a named array so
the loop header stays on one line.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Print the history benchmark's results with a stream
Flawfinder flagged the printf in history.cpp (CWE-134), although its format string is a constant. The stream prints the
same text, so history.py reads it as before.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: address review comments on the performance blog post
- fix wording: "are new", "for each input source", "the strings", "the last zero to seven bytes", "by" Danila
Kutenin, "the result of that query"
- introduce `json_document` where it first gets a detail, say that the `-mbranches` flag is not used, explain
why the position and token bookkeeping overloads are empty, and say that a step's percentage is relative to
the time before the step and that a median of 4 is the mean of the two middle values
- write percentages without a space before `%` in the post and in the price figure (regenerated)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: wrap the prose of the performance blog post at 120 columns
Only line breaks change: the rendered page is identical after whitespace normalization.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: blog post: address the second round of review comments
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: blog post: note that Boost.JSON's tree lead comes from its arena
The comparison builds Boost.JSON's tree in a monotonic_resource. With its
default allocator and precise numbers, boost::json::parse() takes as long
as json::parse() on twitter.json, 5% longer on citm_catalog.json and 17%
less time on canada.json (M1, C++23 -O3, best of 3 x 30 runs; the arena
saves Boost.JSON 28-41%).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: blog post: comparing already passes the depth; copying measured slower without the counter
operator== walks the standard containers itself and passes the depth as an
argument (#5840). A copy that does the same, inserting element by element,
measured 4-16% slower on an M1 Max with Apple clang, so copying keeps the
thread_local counter.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* docs: blog post: name every user of the depth counter and every input the document copies
The "Bounded recursion" paragraph said only copying and equality for custom
containers use the thread_local counter. Converting from another basic_json
specialization and the ordering comparisons use it too; equality for the
standard containers passes the depth instead.
The "Strings stay in the input" bullet named only parse_copy() and an rvalue
std::string as owning inputs. Streams, FILE* and other input that is not one
contiguous block of bytes are read into an owned buffer as well.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Scan the buffer of a FILE in bulk with glibc and the Apple C library
Parsing from a FILE* still read one character at a time through
getc_unlocked(), while a std::istream has its get area scanned in bulk.
file_input_adapter now offers the lexer the same kind of window into the
buffer of the FILE: it reads the fields that the C library's own
getc_unlocked() macro reads (glibc: _IO_read_ptr and _IO_read_end; Apple:
_p and _r) and consumes exactly the characters getc_unlocked() would
return, so the file is left where it was left before. The part of the
current token in a buffer that is about to be refilled is kept for error
messages, as for streams. The window needs the file locked for the whole
parse, so JSON_DISABLE_UNLOCKED_FILE_IO and MemorySanitizer builds turn it
off; uClibc, which defines __GLIBC__ but has other fields, does not get it.
parse() from a FILE* gets 2.0-2.6x as fast on an Apple M1 Max and 1.7-2.2x
on x86-64 (glibc, GCC 15 and Clang 21), accept() 2.9-4.4x; that is about as
fast as parsing from a std::ifstream. The new tests read with FILE buffers
of 1 to 70 bytes and unbuffered files, after ungetc(), with SAX positions
and with binary strings across the buffer's edges.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: no setvbuf() buffer below 2 bytes on Windows
The Microsoft C runtime rejects a _IOFBF buffer size below 2 as an
invalid parameter and ends the process (0xc0000409), which made
test-file_input fail on all MSVC and clang-cl jobs.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI: astyle formatting in unit-file_input.cpp
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: limit the multi-character ungetc() test to glibc and Apple
The Windows C runtime only supports one pushed-back character, which
broke the Windows CI jobs.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: sweep_allocator::construct() accepts pointers to const
Recent libc++ (emsdk latest) probes construct(const T*, const T&) in an
unevaluated context while checking for trivial copies; the static_cast to
void* in the noexcept specification then fails to compile.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
(cherry picked from commit 794bf70823c12a2a1cb2a8a95f34dfb6357746a8)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: guard sweep_allocator::construct() against const types instead of const_cast
The const_cast added in the previous commit is rejected by
cppcoreguidelines-pro-type-const-cast (clang-tidy). Make construct() not
viable for const U instead, which is what libc++ probes for.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
(cherry picked from commit de099fa607001b710862fd1bbecef3609c54cbc4)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI: astyle and clang-tidy for sweep_allocator::construct()
astyle 3.4.13 reformats the enable_if<!...> default template argument
(Check amalgamation). Delete the const overload instead, which makes the
libc++ probe for const objects fail in the SFINAE context just the same
and needs no <type_traits>.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>
* Binary readers: append strings straight from contiguous input
get_bytes() read every string into a zero-filled resize() and copied the
bytes over it, so each byte was written twice. A string that the input holds
in one block (bulk_remaining() at least its length) is now appended from it
directly. The claimed length is checked against the input first, so a huge
claimed length still allocates nothing it cannot fill; other inputs and
binary values keep the chunked loop.
from_cbor() and from_msgpack() of twitter.json and citm_catalog.json get
5.5-9.1% faster on an Apple M1 Max and 2.7-8.6% on x86-64 (GCC 15, Clang 21);
canada.json, which has few strings, is unchanged.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Binary readers: keep the tag argument of append_from_block() astyle-proof
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI: bugprone-signed-char-misuse in append_from_block
Convert the (positive) length to its unsigned type before widening it
to std::size_t, as clang-tidy flags the int8_t to std::size_t cast.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: sweep_allocator::construct() accepts pointers to const
Recent libc++ (emsdk latest) probes construct(const T*, const T&) in an
unevaluated context while checking for trivial copies; the static_cast to
void* in the noexcept specification then fails to compile.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
(cherry picked from commit 794bf70823c12a2a1cb2a8a95f34dfb6357746a8)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: guard sweep_allocator::construct() against const types instead of const_cast
The const_cast added in the previous commit is rejected by
cppcoreguidelines-pro-type-const-cast (clang-tidy). Make construct() not
viable for const U instead, which is what libc++ probes for.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
(cherry picked from commit de099fa607001b710862fd1bbecef3609c54cbc4)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI: astyle and clang-tidy for sweep_allocator::construct()
astyle 3.4.13 reformats the enable_if<!...> default template argument
(Check amalgamation). Delete the const overload instead, which makes the
libc++ probe for const objects fail in the SFINAE context just the same
and needs no <type_traits>.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>
* Tests: make sweep_allocator::construct() not viable for const types
The newest libc++ (emsdk latest, used by ci_emscripten) probes
construct(const T*, const T&) in an unevaluated context while checking
whether copies are trivial. For the test allocator, instantiating the
noexcept specification then fails to compile, because static_cast<void*>
cannot drop the const qualifier. Constrain construct() to non-const types,
which makes the probe fail in the SFINAE context instead of with a hard
error.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI: astyle and clang-tidy for sweep_allocator::construct()
astyle 3.4.13 reformats the enable_if<!...> default template argument
(Check amalgamation). Delete the const overload instead, which makes the
libc++ probe for const objects fail in the SFINAE context just the same
and needs no <type_traits>.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasEsrzHhSNouxSoEwqz
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>
Add sections on switching off std::format and ranges support to the
compile-times page, with measurements (Apple clang, GCC 16, -std=c++20),
the functionality that is lost, and chart rows (issue #5294).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Binary reader and writer: remove checks that invariants make dead
Branch coverage of the test suite and of 24k mutated inputs showed
these conditions as never taken; each is implied by a check made
earlier on the same path:
- check_bson_document_size: `document_size < 0` (the size was rejected
below 5 before it was stored)
- get_ubjson_ndarray_size: `second != 'N'` ('N' is rejected as a type
marker before `second` can be set)
- bjd_type_name() == nullptr for an ndarray dtype: every marker
is_valid_optimized_type() accepts for BJData has a name (now an assert)
- the early is_bjd_excluded_optimized_type() check in
get_ubjson_size_type(): is_valid_optimized_type() rejects the same
eight markers with the same error
- `input_format == bjdata` next to `is_ndarray`, bit 8 of the type, or a
'B'/'u'/'m'/'M' marker: these only arise for BJData
- `first != npos` next to bit 8: the bit is only set after a count
- MessagePack writer: the `<= max` halves of the negative int8/16/32
ladder (the ladder is in the `else` of `n >= 0`)
No change in behaviour: a build that aborts on each removed side passes
the test suite and the fuzz corpora, and a 1.6M-input differential run
of the reader against the original headers found no difference.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Remove is_bjd_excluded_optimized_type(), which has no caller left; fix two comments
is_valid_optimized_type() rejects the markers BJData excludes, so the reader
no longer needs its own list; the test now checks is_valid_optimized_type()
of a BJData reader against the writer's list. The BSON size comment now says
that open_bson_document() rejects a size below 5.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Make the BJData reader in the lookup test const (misc-const-correctness)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
json_sax_dom_parser::insert_key_with_index: own the new object_key_index
in a unique_ptr before key_indexes may reallocate; a throwing reallocation
leaked it.
Signed-off-by: Christoph Grüninger <foss@grueninger.de>
output_vector_sink grew the vector by resizing it to its whole new
capacity. resize() zeroes the characters it adds, so every doubling
zeroed megabytes of a fresh allocation at once: that faults in all its
pages and evicts them from the cache before the writer reaches them,
and the writer's stores then miss again. The sink now reserves the same
capacity as before but resizes the vector only to 64 KiB
(vector_sink_window) ahead of the position, which is still cached when
the writer's stores come.
to_cbor(), to_msgpack(), to_ubjson(), to_bjdata() and to_bon8() of an
array of one million numbers into a fresh vector: 4-26 % faster on x86
(Skylake laptop with Apple clang 13, Haswell VPS with GCC 16 and
Clang 23), 1-2.5 % on Apple M1 Max; other documents unchanged (within
0.4 % in reruns). The capacity and growth of the vector are as before.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* UBJSON/BJData reader: reject a container count equal to SIZE_MAX
The reader marks a container whose count is not known by npos, which
is SIZE_MAX. A count of exactly that value was stored unchanged and
then read as "no count", so the BJData input
[ # M ff ff ff ff ff ff ff ff i 01 ]
parsed as [1] instead of throwing out_of_range.408 as a count of
2^64-2 does. Where size_t is 32 bits, the same holds for 'm' and 'L'
counts of 2^32-1, in UBJSON too.
The counts of 'm', 'M' and the signed types now go through
store_ubjson_count(), which rejects npos with "integer value overflow"
(the message a count beyond size_t already gets), as the CBOR reader
does in get_cbor_container_size(). An ND-array dimension of 2^64-1 gets
the same message now, where it was "excessive ndarray size caused
overflow" (the product check) on 64-bit platforms.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* MessagePack reader: reject an array/map 32 length equal to SIZE_MAX
On a platform with a 32-bit std::size_t, an array 32 or map 32 length of
0xFFFFFFFF equals unknown_size(), so start_array()/start_object() were
told the size was unknown and skipped the max_size() check. Route both
through the CBOR length check, renamed get_container_size(), which
already rejects that value.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix the build of develop: tests from #5997 and #5991
- unit-msgpack-cpp17: assign the result of json::parse in
CHECK_THROWS_WITH_AS (GCC -Werror=unused-result)
- unit-json_view: failing_allocator::allocate is [[noreturn]]
(clang -Wmissing-noreturn)
- unit-class_lexer: build the quoted string once
(clang-tidy performance-inefficient-string-concatenation)
- unit-allocator: sweep_allocator provides pointer, reference and size
typedefs, which GCC 4.8's std::map takes from the allocator
- unit-allocator: skip the "sax_parse into an existing value" sweep with
iterator debugging, like the parser callback sweep: MSVC's std::vector
default constructor is noexcept but allocates its debug proxy through
the allocator, so a failing allocation in create<array_t>() terminates
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix the remaining CI failures of the tests from #5997 and #5991
- unit-custom-object-key-type: drop the redundant member initializer and
return a braced init list (clang-tidy); direct-initialize the converted
value, as copy-initialization makes GCC 4.8 instantiate the copy
constructor, which needs a range constructor strict_object lacks
- unit-stream-bulk-scan: pick the claimed get area size by tag dispatch
instead of a constant condition (MSVC C4127)
- unit-allocator: skip the parser callback and sax_parse sweeps with
Clang 3.4 and 3.5, which leak memory when an element constructor throws
inside a libstdc++ std::map copy or std::vector reallocation
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix the CI failures that the first failing TU of each job hid
- unit-stream-bulk-scan: compute the claimed size without a condition;
the tag-dispatched template was unused with a 64-bit std::size_t
(-Wunused-template)
- unit-json_view: give failing_allocator the typedefs, rebind and
members that GCC 4.8's std::map takes from the allocator directly
- clang-tidy hits in the tests from #5997: raw string literals
(unit-json_view), redundant c_str() and a NOLINT for &text[0]
(unit-locale-cpp), reserve() before a loop (unit-ordered_json), and a
NOLINT for a return that a braced list would turn into an array
(unit-regression1)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Skip the 3 GiB get-area test with a 32-bit std::size_t in the preprocessor
The claimed size was a constant 0 on Win32, so `claimed == 0 || ...` was a
constant condition and MSVC reported C4127. Guard the section with
`#if SIZE_MAX > UINT32_MAX` instead, as unit-msgpack-custom-types.cpp does.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Silence modernize-use-transparent-functors for failing_map in unit-json_view
std::less<> needs C++14, and the test is also built as C++11.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
json_view number(): #6006 folded the check of the digit after a minus
sign into `else if (!negative || ...)`, which MSVC 19.44 reports as
C4127 (conditional expression is constant) and /WX turns into an
error in every MSVC and clang-cl job. The check now sits in the
`if (negative)` block, right after the sign is skipped; the error and
its position are unchanged.
unit-locale-cpp.cpp: the locale_switching_token added in #5997 held a
`const char*`, so GCC's -Weffc++ asked for a copy constructor and copy
assignment. The locale name is now a std::string.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Since #6004 made the "while parsing" part unconditional, the three appends
at the start of exception_message() are one fixed string around the
context. Review follow-up to #6004.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
enter_cbor_array and enter_msgpack_array called the out-of-line scalar
run for every non-empty array. When the array's element is an object or
an array, as on every level of [[...]] or the single ring of a GeoJSON
polygon, the call reads nothing; it made 1,000 arrays nested in each
other cost 4 % more instructions (GCC 13) and up to 8 % more time (Apple
clang) than without the run. #5975 had fixed that with an inline
pre-check, which was later dropped after measuring canada only.
The run is now entered only for arrays of two or more elements: the same
comparison as before, so no other row changes. Arrays of one scalar,
which the run read faster, now take the general path; they are rare in
documents (one in citm_catalog, none in twitter or canada). The new
benchmark FromBinaryShape/singles measures them, next to
FromBinaryShape/nested.
Instructions per repetition, new/old, GCC 13 callgrind: nested arrays
0.973 (CBOR) and 0.971 (MessagePack), arrays of one scalar 1.037 and
1.021, every other row within 0.15 %.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Create the DOM parser's member value before placing it (#5985)
json_sax_dom_parser::set_member() constructed the new value in place over
the null member. basic_json(value_t) sets the type before the json_value
allocates, so a std::bad_alloc left a member typed object/array with a
null pointer, and the destructor crashed instead of propagating the
exception. Construct the value first and move it over the member (the
move constructor is noexcept).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI for the parse() bad_alloc sweep test (#5985)
- sweep_allocator: provide max_size(), construct() and destroy(), which
GCC 4.8's std::map calls on the allocator directly.
- Declare the non-throwing test lambdas noexcept (-Werror=noexcept on
recent GCC).
- Give the sax_parse lambda an explicit return type; Clang 3.4 crashes on
the deduced one in C++11 mode.
- Skip the parser callback sweep with iterator debugging (MSVC debug
builds, clang-cl), where containers allocate debug proxies inside
noexcept move constructors and terminate instead of throwing, as in the
other allocator tests.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasAgbDGG28MqXjQvLqp
Signed-off-by: Claude <noreply@anthropic.com>
* Construct a scalar member in place; only a throwing value goes through a temporary
Creating the value first and moving it over the member is needed only when
creating it can throw (a string, a binary value or a container). A scalar
or null is again constructed in place, without the extra move and destroy
per member (and, with JSON_DIAGNOSTICS, without the extra set_parents()).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Spell the nothrow trait without && and fix the construct_member comments
The dispatch in set_member tests std::is_nothrow_constructible, not
whether the value is a scalar. Say so in the comments, and drop the &&
from the trait argument (equivalent for a forwarding reference) so that
astyle no longer inserts spaces around the template brackets.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Say "for example" in the construct_member comments
The overloads are selected by std::is_nothrow_constructible, not by the
kind of value: a custom type that cannot throw takes the first one.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Signed-off-by: Claude <noreply@anthropic.com>
Co-authored-by: Claude <noreply@anthropic.com>
* basic_json, iterators, serializer: remove checks that invariants make dead
Branch coverage of the test suite and of 24k mutated inputs showed
these conditions as never taken; each is implied by the code around it:
- copy_object_level(): `src_it != src_object.cend()`; dst was built from
exactly src_object.size() unique keys and src_it advances at most once
per member
- the general comparison operators (equal_general, less_general,
three_way_general): the five same-type scalar cases, which the inline
fast path of every operator handles before calling them (now an
assert); and the NaN half of compares_unordered() in the mixed-type
branch, reached only after all six number pairs returned, where only
a discarded operand is unordered
- serializer, ensure_ascii: the reset of `bytes` under error_handler_t::keep
and the surrogate-pair escape in the UTF8_ACCEPT case; every
well-formed multi-byte character is escaped by write_u_escapes() before
decode() sees it, so decode() only ever accepts DEL here, a single byte
of which nothing was buffered (now asserts)
- iter_impl(pointer): the if/else chain assigned value-initialized
iterators to the value-initialized m_it
No change in behaviour: a build that aborts on each removed side passes
the test suite, the fuzz corpora and 23.2M dumps of all 1-, 2- and
boundary 4-byte strings in both ensure_ascii modes.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* iter_impl: keep the type-dependent initialization in the constructor
The check is not needed for correctness (m_it is value-initialized), but
without it GCC 13 generates slower iteration loops: a recursive walk over
a parsed document takes 0.5-2.7 % longer (callgrind: +1.9 % instructions
on twitter.json, +0.95 % on canada.json). Clang generates identical code
either way. See the measurements in #6005.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Branch coverage of the test suite and of 24k mutated inputs showed
these conditions as never taken; each is implied by the code around it:
- view_serializer::write_codepoint<EnsureAscii>(): the only caller
passes the byte a run of plain output stopped at (a quote, a
backslash or a control character), so the function is now
write_escaped(), which writes that byte's escape sequence
- load_image(): `owned_image.empty() || image != owned_image.data()`;
both callers hand in a fresh document_data, and for load(vector&&)
the image is owned_image itself
- set_moved(): reserve_moved(); all three callers reserved first or
have the moved flag set (the documented precondition)
- view_side::string() and json_side::string() in equal(): only used
after both sides were found to be strings, so they read the string
directly (and are noexcept)
- number<false>(): the '1'..'9' test after a sign-less dispatch, which
only happens for a digit
- value_range(): the pre-loop `is_new || off >= size` test, which the
loop's first pass repeats on the same node
No change in behaviour: a build that aborts on each removed side passes
the test suite and the fuzz corpora.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Without the same-type scalar cases, the macro body has no use for it, and
JSON_IMPLEMENT_SCALAR_CASES is now used only by JSON_IMPLEMENT_SCALAR_FAST.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Branch coverage of the test suite and of 24k mutated inputs showed
these conditions as never taken; each is implied by the code around it:
- lexer: `next_unget` in get_codepoint_bulk() and scan_literal_bulk().
unget() is only called at the end of scan_number(), in scan_comment()
and in skip_bom(); every token scan starts with a plain get() in
skip_whitespace() that consumes a pending unget, and nothing between
that get() and the bulk helpers ungets (now asserts, as in
get_after_string_run())
- lexer: `number_type == value_integer` in convert_integer(): both
callers exclude value_float and the type has three values
- parser: `!context.empty()` in exception_message(): all callers pass a
literal
- input_stream_adapter: `refill` in get_character_slow(): the function
is only called after get_character() found the get area exhausted,
and the variable recomputed that comparison
- json_sax_dom_callback_parser: `ref_stack.back()` in key() (the null
case returned a few lines earlier, and the callback in between cannot
reach ref_stack), `is_structured()` in end_object() (non-null entries
are only pushed for objects and arrays), `!key_stack.empty()` in
current_key() (a kept object pushed its key before any value)
No change in behaviour: a build that aborts on each removed side passes
the test suite, the fuzz corpora and 40k random documents through every
input adapter in four macro configurations.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* CI: measure line coverage without lcov's unexecuted-block adjustment
Drop geninfo_unexecuted_blocks=1 from the lcov capture of ci_test_coverage:
it reset every line of an inlined or templated function to 0 as soon as one
copy had an unexecuted block, which understated the line coverage by about
three points.
Add -fvar-tracking-assignments to both coverage builds. At -O0, GCC inlines
always_inline functions before it places the coverage counters, so the call
sites of such helpers (put_literal() and others) got no line record and
showed as 0 in an -O3 translation unit that never reaches them. With the
flag, the call sites carry counts in every translation unit. The generated
code is identical.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Remove unreachable code found by the coverage analysis
Remove code that no input can reach, and mark the lines that cannot be
covered with LCOV_EXCL_LINE:
- BJData writer: the dry_run parameter of the ND-array element writers was
always true; replace them by range checks.
- BON8 writer: call throw_integer_out_of_range() directly instead of
write_bon8_value() for values that always throw.
- binary_writer: integer_bits() is only called for integers of up to 64 bits.
- serializer, view serializer, lexer: replace guards that the callers make
unreachable by assertions or by the simpler code (surrogate pairs under
ensure_ascii, next_unget, '-' at the end of the buffer).
- json_view: drop unreachable branches in scalar(), set(), check_utf8_scan(),
append_input_impl() and unescape().
- Mark exception-cleanup braces, 2 GiB limits, big-endian and 32-bit code, and
fall-through case labels with LCOV_EXCL_LINE.
No behavior changes for any input that reaches these functions.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tests: cover the remaining lines of the library headers
Add tests for the lines of include/nlohmann that were not covered: the
binary readers and writers, the lexer and locale paths, the json_view
modules, the custom number, key and array types, json_pointer, json_patch,
diff and the iterators.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix test failures in the coverage tests
- unit-custom-object-key-type: remove the unused make_strict_key(strict_key)
overload, the unused range constructor and default constructor, and guard
data() with JSON_DIAGNOSTICS (unused-function/-member-function errors with
GCC and clang -Weverything).
- unit-json_view_compare: move the two new sections to the new
unit-json_view_compare_values.cpp, as the object file got too large for the
MinGW assembler again, and use a std::map with std::greater instead of
std::unordered_map, which does not accept the incomplete basic_json
(clang 3.9, icpc).
- unit-json_view_dump: rename the variables that hid outer ones (MSVC C4456).
- unit-stream-bulk-scan: restore the real size of the oversized get area
before the adapter is destroyed (JSON_PRECISE_STREAM_POSITION reads the
character at the read position), and skip the test where the streambuf
cannot hold a get area larger than an int (MSVC).
- unit-regression1: with JSON_NO_THREAD_LOCAL, copies are built member by
member and keep correct timestamps, so check the corresponding outcome.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasAgbDGG28MqXjQvLqp
Signed-off-by: Claude <noreply@anthropic.com>
* Return std::size_t from the hash helper in the ordered_json test
MSVC (Win32) rejected the implicit conversion of the unsigned long long
product to the 32-bit std::size_t (C4244 as an error). Also note when
JSON_NO_THREAD_LOCAL is set in the regression test.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasAgbDGG28MqXjQvLqp
Signed-off-by: Claude <noreply@anthropic.com>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Signed-off-by: Claude <noreply@anthropic.com>
Co-authored-by: Claude <noreply@anthropic.com>
* Keep the byte range in exceptions about the root value (#5987)
With JSON_DIAGNOSTICS and JSON_DIAGNOSTIC_POSITIONS both set, exception::diagnostics()
and the json_view diagnostics() returned early for a value without a path (the
root), dropping "(bytes a-b)". Build the "(path) " prefix only when there are
tokens and always append the byte range.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Guard the null value of a value-initialized iterator; drop the unneeded found flag
With the root's byte range, diagnostics() reaches get_byte_positions() also
with JSON_DIAGNOSTICS when there is no value, as for a value-initialized
iterator (invalid_iterator.212). get_byte_positions() now returns no range
for a null value, the same change as #6003, so either can be merged first.
In the view, a value that value_path() does not find leaves no tokens, so the
found flag added nothing to the tokens.empty() test.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* json_view: get<T>() of a boolean throws for number_integer_t, number_unsigned_t and number_float_t like basic_json (#5988)
basic_json::get<T>() of a boolean throws type_error.302 for exactly
number_integer_t, number_unsigned_t and number_float_t (dedicated from_json()
overloads) and gives 0/1 for every other arithmetic type. The view returned
0/1 for all of them, contradicting its documentation. The view now throws
the same exception (same message, with path/bytes decoration) for these three
types. basic_json is unchanged; its behavior is documented and pinned by a test.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* tests: skip throwing json_view bool get<T>() combinations without exceptions (#5988)
check_boolean_get_parity() called get<T>() for number_integer_t,
number_unsigned_t and number_float_t in its JSON_NOEXCEPTION branch, but a
boolean throws type_error.302 for exactly these types, so JSON_THROW aborted
test-json_view_cpp11/cpp17 in ci_test_noexceptions. Skip these combinations
there; the throwing checks stay in the exceptions-enabled build.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasAgbDGG28MqXjQvLqp
Signed-off-by: Claude <noreply@anthropic.com>
* Expect the byte range of the root in the json_view boolean get<T>() test
With JSON_DIAGNOSTIC_POSITIONS, the type_error.302 message starts with
"(bytes 0-4)"; build the expected text with json_view_test::message(),
as the other tests of the root value do.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasAgbDGG28MqXjQvLqp
Signed-off-by: Claude <noreply@anthropic.com>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Signed-off-by: Claude <noreply@anthropic.com>
Co-authored-by: Claude <noreply@anthropic.com>
* Make basic_json::insert() provide its documented strong exception guarantee (#5986)
A failed allocation while the new elements were copied left the value
changed, and with JSON_DIAGNOSTICS stale parent pointers behind. The
extra work now happens almost only on the failure path:
- Array insert(pos, cnt, val) and insert(pos, first, last) append the
copies at the end and rotate them into place. If a copy throws, the
appended elements are erased again (noexcept) and the parents are set.
Moving a basic_json cannot throw, so reallocation is safe. This is no
slower than vector::insert (faster for numbers), needs no temporary
array, and keeps the elements that libstdc++ lost on reallocation.
- Array insert(pos, val) copies a non-scalar value first and inserts it
by move, except at the end, where vector::insert is strong. Scalars
keep the direct path.
- The object range insert(first, last) into an empty object uses the
container's own range insertion and clears the object on an exception.
Into a non-empty object it inserts member by member and logs one bit
per source member (a new member is detected by the size change; no
allocation for the first 256 members); on an exception the members
added are erased by walking the source range. No assumption that
key_type is string_t.
- The parents are set when a failed insertion is undone.
The regression test fails every allocation of every insert() overload in
turn, for json and ordered_json, and checks the value and its parents.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix clang-tidy and -Wnrvo findings in insert rollback helpers
Declare the rollback helpers non-movable, replace the nested conditional
and C array in object_insert_rollback, silence the intentional copy in the
allocator test, and avoid the missed NRVO in the test factory lambda.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasAgbDGG28MqXjQvLqp
Signed-off-by: Claude <noreply@anthropic.com>
* insert(): strong guarantee for single elements, basic for the rest
Rework of the previous two commits, following the discussion in #5996:
the standard containers give the strong guarantee only for a single
element (std::vector: at the end, or if the exception does not come from
copying T; std::map: single-element insert), and copying a basic_json
allocates. Rebuilding a rollback for the count, range and object-range
overloads on top of array_t/object_t made the code verbose and slower.
- insert(pos, const basic_json&): at end() forward as before (the
standard covers it); elsewhere copy first and insert by move, as
libstdc++ does internally (libc++ shifts the tail before copying).
- insert_iterator() and object insert(first, last) set the parents in a
scope guard, so a failed insertion leaves a valid value with
JSON_DIAGNOSTICS too (the next assert_invariant() aborted before).
- Docs: strong guarantee for (1), basic guarantee for (2)-(5); the
argument checks throw before anything is changed.
- Test: allocation-failure sweep checks the strong guarantee for (1) and
validity, type and parents for the other overloads.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* insert(): document the exception safety of overloads 2 to 5 once
The four basic-guarantee statements were identical up to array/object.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* insert(): simplify the wording of the basic guarantee
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Signed-off-by: Claude <noreply@anthropic.com>
Co-authored-by: Claude <noreply@anthropic.com>
* json_view: dump() without StringType::capacity() (#5994)
output_buffer::grow() compared the output size with m_out.capacity(),
which the StringType requirements do not include, so dump() did not
compile with the tests' alt_string. Keep what was last reserved in the
buffer itself and use it as a lower bound of the capacity instead.
Add json_view tests with alt_string (read-only and editable documents,
dump with several growth steps, save/load), and document reserve(n) and
resize(n) as the StringType requirements of basic_json_view::dump.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Use a raw string literal in the alt-string json_view test
clang-tidy (modernize-raw-string-literal) rejects the escaped literal.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasAgbDGG28MqXjQvLqp
Signed-off-by: Claude <noreply@anthropic.com>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Signed-off-by: Claude <noreply@anthropic.com>
Co-authored-by: Claude <noreply@anthropic.com>
* Do not construct the base class when destroying a container (#5995)
json_value::destroy_container() and destroy_walk() used default-
constructed basic_json values as stand-ins, which construct a
CustomBaseClass that belongs to no value. A base class whose default
constructor allocates made the noexcept destructor allocate again, and
terminate if that allocation failed, which #5762 set out to prevent.
Use data (type and value, no base class) as the stand-in instead, and
pass the children's m_data to the walk helpers.
Add a test with a counting base class: destroying a value constructs no
base object and destroys exactly one per value, also for values nested
deeper than the recursion depth limit.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Release the test value with = nullptr instead of reset()
clang-tidy (readability-ambiguous-smartptr-reset-call) rejects j.reset()
because the pointee inherits a reset() from counting_base.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasAgbDGG28MqXjQvLqp
Signed-off-by: Claude <noreply@anthropic.com>
* Use std::swap for the container stand-in in destroy_container
The unqualified call after `using std::swap` would let a user-provided
swap(json_value&, json_value&) intercept the destruction path. Call
std::swap directly.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Signed-off-by: Claude <noreply@anthropic.com>
Co-authored-by: Claude <noreply@anthropic.com>
* JSON_DIAGNOSTIC_POSITIONS: comparing a value-initialized iterator throws instead of crashing
With JSON_DIAGNOSTIC_POSITIONS, comparing a value-initialized iterator
(which has no container) with another iterator built the
invalid_iterator.212 message from the byte positions of the iterator's
value, which is a null pointer: UBSan reports "member call on null
pointer" in exception::get_byte_positions(), then the process crashes.
Every other configuration throws invalid_iterator.212.
get_byte_positions() now returns no positions for a null value, as the
JSON_DIAGNOSTICS path already does.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Declare the value-initialized iterator in the test const
clang-tidy (misc-const-correctness) flags it, as it is only compared.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasAgbDGG28MqXjQvLqp
Signed-off-by: Claude <noreply@anthropic.com>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Signed-off-by: Claude <noreply@anthropic.com>
Co-authored-by: Claude <noreply@anthropic.com>
* CI: give the Valgrind tests a timeout of one hour
Under Valgrind, test-json_view_builder_cpp11 and test-ordered_json_cpp11
took 1435 s and 1390 s on develop (ddc34f5), close to ctest's default
timeout of 1500 s. On the next run (b2674a4) the whole job was about 10 %
slower and both timed out, failing ci_test_valgrind on develop and on
every PR based on it.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasAgbDGG28MqXjQvLqp
Signed-off-by: Claude <noreply@anthropic.com>
* BSON writer: drop the SFINAE guard that Visual Studio 2017 cannot deduce
write_bson_document_single_pass() was a member template enabled by
is_detected<sink_written_t, SinkType>. MSVC 19.16 (Visual Studio 2017)
fails to deduce it through the class-scope alias template (C2672, C2783)
when it compiles to_bson() and to_bon8(), so every Visual Studio 2017
job on AppVeyor fails since #5979.
The guard is not needed: as a non-template member of the class template,
the function is only instantiated when called, and its only caller is
the write_bson_document() overload for sinks that have written(), which
already calls oa.written() and oa.rewind() itself.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasAgbDGG28MqXjQvLqp
Signed-off-by: Claude <noreply@anthropic.com>
---------
Signed-off-by: Claude <noreply@anthropic.com>
Co-authored-by: Claude <noreply@anthropic.com>
GitHub is moving the ubuntu-latest label from Ubuntu 24.04 to 26.04
between October 19 and November 19, 2026 (actions/runner-images#14748).
Pin every ubuntu-latest job to ubuntu-26.04 so the switch does not
change the toolchain under our jobs, and so the behaviour does not
depend on when GitHub reaches our runs.
Jobs pinned to ubuntu-24.04 and ubuntu-24.04-arm are unchanged.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
readability-math-missing-parentheses in unit-json_view_builder.cpp (#5974)
and performance-inefficient-string-concatenation in
unit-json_view_positions.cpp.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* UBJSON/BJData readers: read optimized arrays of numbers in one loop
An array with a type marker for a fixed-size number ($U, $i, $I, $l, $L,
$d, $D, and BJData's $u, $m, $M), including the data of a BJData ndarray,
gives its elements no markers. When the input is contiguous, read the
elements that are in the input in one loop - load, byte swap for the
format's byte order, emit - instead of one trip through
parse_ubjson_internal and get_ubjson_value per element. Elements the
input ends before, other types, and non-contiguous inputs are read as
before.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* UBJSON/BJData tests: assign the parsed value instead of casting it to void
GCC reports -Werror=unused-result for static_cast<void>(json::from_ubjson(...))
and json::from_bjdata(...): a cast to void does not silence warn_unused_result
on GCC. Assign to a json, as the other tests do.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* MessagePack reader: read runs of scalar array elements in one loop
As for CBOR: when an array opens and the input is contiguous, read the
integers, floats, booleans, and nils that follow in a tight loop instead
of going through parse_msgpack_internal and parse_msgpack_value for every
element. The loop stops at any other kind of value and when fewer than 9
bytes are left; those values are read by the general path as before.
Non-contiguous inputs are not affected.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* MessagePack reader: enter the scalar run only when a scalar follows
As for CBOR: enter_msgpack_array tests the first byte and the remaining length
inline and calls the out-of-line run only for a scalar, so arrays of maps or
strings no longer pay for a call that reads nothing; the run's loop condition
moves to the end (do-while).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* MessagePack reader: mark the initial accepted in the scalar run as a false-positive dead store
ci_infer reports DEAD_STORE for 'bool accepted = true;' in the MessagePack
scalar run, as in the CBOR one, because every case assigns accepted before it
is read.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* MessagePack tests: assign the parsed value instead of casting it to void
GCC (ci_test_gcc) reports -Werror=unused-result for
static_cast<void>(json::from_msgpack(...)): a cast to void does not silence
warn_unused_result on GCC. Assign to a json, as the other tests in the file do.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* MessagePack reader: drop the scalar pre-check before the run
enter_msgpack_array now calls the run directly, and parse_msgpack_scalar_run
tests the remaining count and length at the top of a while loop instead of
relying on msgpack_scalar_follows(); its own switch already leaves on any
value that is not a scalar.
Instructions per repetition, new/old: SAX canada 0.946 (clang) and 0.973
(GCC 13), DOM read canada 0.991 / 0.992; no row more than 0.3 % higher.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* MessagePack reader: say why the initial accepted in the scalar run stays
As for CBOR: Infer's DEAD_STORE report is right, not a false positive. The
initializer is kept for clang-tidy's cppcoreguidelines-init-variables.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* MessagePack reader: give the scalar run the bulk tag instead of a wrapper
As for CBOR: parse_msgpack_scalar_run takes the bulk-scan tag itself and is
the function kept out of line, so parse_msgpack_array_start goes.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* MessagePack reader: start the scalar run's accepted at false
As for CBOR: Infer ignores dead stores of 0, so the suppression goes.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* MessagePack reader: let the scalar run find its array itself
As for CBOR: parse_msgpack_scalar_run reads container_stack.back() in its
bulk version, so the caller no longer evaluates it for input that is not
contiguous.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Binary readers: swap the bytes of floats with a single byteswap
byte_swap reversed float and double values byte by byte. GCC does not
merge that loop into one bswap, and C++23's std::byteswap accepts only
integers. Overloads for float and double now copy the bits into a
uint32_t/uint64_t, call detail::byteswap, and copy them back. This
applies to every binary reader that uses get_number.
In the CBOR reader, the single- and double-precision float cases call a
non-inlined helper. Without it, GCC stopped inlining the stream
adapter's get_character() into parse_cbor_internal, which made reading
from a std::istream about 0.5 % slower.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* CBOR reader: inline get_cbor_float() and always inline get() instead
The never-inlined get_cbor_float() costs a call for every float read
from input without bulk access: reading canada.json from CBOR through a
FILE* became 5.6 % slower on Apple clang in the benchmark suite. The
helper existed only because GCC 13 stopped inlining the stream adapter's
get_character() into parse_cbor_internal. Always inlining
binary_reader::get() fixes that as well.
callgrind, all binary formats on buffer, std::istringstream and FILE*
input (canada and citm_catalog): GCC 13 0.986-1.003, GCC 16 0.994-1.006,
Clang 23 identical. Apple clang suite: FromBinaryFile/cbor/canada 0.939,
geomean of the 53 binary reader rows 0.998.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* CBOR reader: read runs of scalar array elements in one loop
When a definite-length CBOR array opens and the input is contiguous, read
the integers, floats, booleans, and nulls that follow in a tight loop
instead of going through parse_cbor_internal's container logic and
parse_cbor_value's dispatch for every element. The loop stops at any other
kind of value and when fewer than 9 bytes are left; those values are read
by the general path exactly as before. Non-contiguous inputs are not
affected (tag dispatch on the bulk-scan capability).
Also pass a member empty string as the number source to number_float
instead of constructing a std::string for every float.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* CBOR reader: address review of the scalar-run reader
- parse_cbor_scalar_run: set the size explicitly in every case that
reads a value, instead of relying on a default that every other case
overwrites.
- Remove cbor_scalar_follows(): parse_cbor_scalar_run already returns on
the same conditions, and without the pre-check SAX canada needs another
8.5 % fewer instructions with GCC 13 (0.915 against the previous
version), with no row more than 0.5 % worse (Mac and GCC).
- Restore the comment on why parse_cbor_internal copies the container
frame.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* CBOR reader: enter the scalar run only when a scalar follows
An array of containers or strings called the out-of-line run start once per
array only to leave it at once; on nested data (arrays of objects) that call
made reading slower than before the run reader. enter_cbor_array now tests the
first byte and the remaining length inline and calls the run only for a
scalar, so the run's loop condition moves to the end (do-while).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* CBOR reader: mark the initial accepted in the scalar run as a false-positive dead store
ci_infer reports DEAD_STORE for 'bool accepted = true;' in
parse_cbor_scalar_run because every case assigns accepted before it is read.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* CBOR reader: drop the scalar pre-check before the run
enter_cbor_array calls the run directly again, and parse_cbor_scalar_run
tests the remaining count and length at the top of a while loop; its own
switch already leaves on any value that is not a scalar. The MessagePack
reader is built the same way.
Instructions per repetition, new/old: clang SAX canada 0.983, read canada
0.993; GCC 13 read canada 0.997, the other rows at most 1.004.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* CBOR reader: say why the initial accepted in the scalar run stays
Infer's DEAD_STORE report is right, not a false positive: every case that
reaches the read assigns accepted. The initializer is kept for clang-tidy's
cppcoreguidelines-init-variables.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* CBOR reader: give the scalar run the bulk tag instead of a wrapper
parse_cbor_scalar_run takes the bulk-scan tag itself and is the function that
is kept out of line, so the one-line parse_cbor_array_start wrapper goes, as
the UBJSON typed run already does.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* CBOR reader: start the scalar run's accepted at false
Infer ignores dead stores of 0 (--liveness-ignored-constant defaults to "0"),
and false is 0 to it, so the suppression and its comment go.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* CBOR reader: let the scalar run find its array itself
parse_cbor_scalar_run reads container_stack.back() in its bulk version, so
the caller no longer evaluates it for input that is not contiguous.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
#5634 made dump() write integers below 10^16 eight digits at a time; larger
ones still took the two-digits-per-division loop and count_digits(). Random
64-bit integers almost all have 17 to 20 digits (99.9 % of signed_ints.json
and unsigned_ints.json), so Dump/signed_ints and Dump/unsigned_ints gained
only 1.4x over 3.12.0, against 2.3x for small integers.
A 64-bit magnitude is now written as its first one to four digits and two
groups of eight. Wider magnitudes (__int128 and class types, #5805) keep the
loop: number types of at most 64 bits are selected by type, so no comparison
is reported as always true; for others the value is compared. The sign
handling of #1447/#5815 (remove_sign() into number_magnitude_t) is unchanged.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
A json_view or json_document decodes a macro-defined struct directly and looks
the members up by their decoded keys. Only plain keys were covered so far.
The new section decodes structs defined with NLOHMANN_DEFINE_TYPE_INTRUSIVE,
..._WITH_DEFAULT and ..._WITH_NAMES from documents whose keys contain escape
sequences, and compares the result with the conversion of the materialized
value. It also pins the difference for a duplicate key written once plain and
once escaped (the view takes the first member, the materialized value keeps
the last one), and that an escaped backslash is part of the decoded key.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
After the first \uXXXX escape of a string, slow_string() now decodes the
escapes that follow it directly, while the next six bytes are \u and four hex
digits that are not a surrogate, instead of going round its main loop for each
of them (that is how Python's json.dumps writes non-ASCII text by default).
A surrogate, a bad digit, or fewer than six bytes leave the position at the
backslash: the main loop handles them as before and reports the same error at
the same position.
twitterescaped.json (simdjson-data, 549 KB, 33,036 escapes), json_document::parse(),
A/B in one binary, 6 code layouts, time after / before:
- Apple M1 Max, Apple clang 21: 0.897
- x86-64 Haswell, GCC 16.2: 0.907
- x86-64 Haswell, Clang 23: 0.910
The other files of the benchmark set (twitter, citm_catalog, canada, gsoc-2018,
apache_builds, instruments, tree-pretty, github_events, random, update-center,
semanticscholar-corpus, twitter_timeline) stay within the noise of each machine.
New test: chains of every length from 1 to 40 of escapes that give one, two,
and three bytes of UTF-8, followed by the end of the string, text, escapes,
surrogates, bad digits, and cut in every place, in keys and in values, against
json::parse().
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
#5919 replaced the bool template parameter Editable of basic_json_view by
view_mode Mode and defined is_editable from Mode. #5890 was written before
that and added a second is_editable = Editable to the private section, which
no longer compiles ("duplicate member", "undeclared identifier Editable"). It
broke every job that builds the json_view tests (macOS, MSVC, clang-cl,
clang on Windows, the C++20 module job, CodeQL).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-30 16:48:31 +01:00
309 changed files with 105238 additions and 7374 deletions
$(SED) -i '2i All notable changes to this project will be documented in this file. This project adheres to [Semantic Versioning](http://semver.org/).' ChangeLog.md
- [Binary formats (BSON, CBOR, MessagePack, UBJSON, BJData, and BON8)](#binary-formats-bson-cbor-messagepack-ubjson-bjdata-and-bon8)
- [Zero-copy views](#zero-copy-views)
- [Customers](#customers)
- [Ecosystem](#ecosystem)
- [Supported compilers](#supported-compilers)
@@ -68,7 +74,7 @@ Other aspects were not so important to us:
- **Memory efficiency**. Each JSON object has an overhead of one pointer (the maximal size of a union) and one enumeration element (1 byte). The default generalization uses the following C++ data types: `std::string` for strings, `int64_t`, `uint64_t` or `double` for numbers, `std::map` for objects, `std::vector` for arrays, and `bool` for Booleans. However, you can template the generalized class `basic_json` to your needs.
- **Speed**. There are certainly [faster JSON libraries](https://github.com/miloyip/nativejson-benchmark#parsing-time) out there. However, if your goal is to speed up your development by adding JSON support with a single header, then this library is the way to go. If you know how to use a `std::vector` or `std::map`, you are already set.
- **Speed**. There are certainly [faster JSON libraries](https://github.com/miloyip/nativejson-benchmark#parsing-time) out there. However, if your goal is to speed up your development by adding JSON support with a single header, then this library is the way to go. If you know how to use a `std::vector` or `std::map`, you are already set. The [performance](https://json.nlohmann.me/features/performance/) page shows how to get the most out of the library.
See the [contribution guidelines](https://github.com/nlohmann/json/blob/develop/.github/CONTRIBUTING.md#please-dont) for more information.
// this calls BasicJsonType::json_serializer<T>::from_json(j, value)
// if BasicJsonType::json_serializer == bad_serializer ... oops!
value=j.get<T>();// oops!
value=j.templateget<T>();// oops!
}
};
```
@@ -1769,7 +1775,7 @@ I deeply appreciate the help of the following people.
330. [AniketDhemare](https://github.com/AniketDhemare) fixed a version in the documentation.
331. [Philip Müller](https://github.com/philip-paul-mueller) fixed an example.
332. [Leila Shcheglova](https://github.com/LeilaShcheglova) fixed a warning in a test.
333. [Alex Prabhat Bara](https://github.com/alexprabhat99) fixed a function name in the documentation.
333. [Alex Prabhat Bara](https://github.com/alexprabhat99) fixed a function name in the documentation and avoided temporary `basic_json` values for CBOR and MessagePack object keys.
334. [laterlaugh](https://github.com/laterlaugh) fixed some typos.
335. [Yuanhao Jia](https://github.com/MrJia1997) fixed the GDB pretty printer.
336. [Fallen_Breath](https://github.com/Fallen-Breath) fixed an example for JSON Pointer.
@@ -1847,7 +1853,7 @@ I deeply appreciate the help of the following people.
408. [Luke Banicevic](https://github.com/banaboi) fixed corrupt BSON output for lengths exceeding `INT32_MAX`, cleaned up the BSON writer, and improved the documentation.
409. [Patrick Armstrong](https://github.com/Patrick10199) updated the CBOR references and the half-precision float assertions.
410. [Yash Bavadiya](https://github.com/xevrion) added checks to all BSON reads.
411. [hum4nBeing](https://github.com/hum4nBeing) fixed the overflow handling of high-precision numbers in UBJSON.
411. [hum4nBeing](https://github.com/hum4nBeing) and [AJ369ninja](https://github.com/AJ369ninja) fixed the overflow handling of high-precision numbers in UBJSON.
412. [tomatotomata](https://github.com/tomatotomata) added checks for reading CBOR tagged subtypes.
413. [YingqiDuan](https://github.com/YingqiDuan) documented the BSON interoperability.
414. [KBS](https://github.com/youdie006) documented the standards compliance and the strictness of `parse()` and `operator>>`.
@@ -1861,6 +1867,26 @@ I deeply appreciate the help of the following people.
422. [Avionic Harshit](https://github.com/avionicharshit-byte) made `diff()` linear when an array shrinks.
423. [Qatadaha Bin Matloob](https://github.com/qatcod) fixed comparisons between integers and floats and fixed unparsable BJData output.
424. [Wu Shuwen](https://github.com/dajiaohuang) removed an unused include.
425. [Alexander Lanin](https://github.com/AlexanderLanin) improved the error message of `get_to()` for `const` arguments.
442. [Afonso Januário](https://github.com/afonsojanu) made `std::hash<basic_json>` consistent with `operator==` for numbers.
443. [Kartik Gupta](https://github.com/KartikeyG-world) limited the natvis namespace variants to two ABI tags.
444. [manop55555](https://github.com/manop55555) reported a buffer over-read in `dump()` with large indentation values.
Thanks a lot for helping out! Please [let me know](mailto:mail@nlohmann.me) if I forgot someone.
@@ -1883,7 +1909,6 @@ The library itself consists of a single header file licensed under the MIT licen
- [**cpplint**](https://github.com/cpplint/cpplint) for style checks
- [**doctest**](https://github.com/doctest/doctest) for the unit tests
- [**Flawfinder**](https://dwheeler.com/flawfinder/) for static analysis
- [**GitHub Changelog Generator**](https://github.com/github-changelog-generator/github-changelog-generator) to generate the [ChangeLog](https://github.com/nlohmann/json/blob/develop/ChangeLog.md)
- [**Google Benchmark**](https://github.com/google/benchmark) to implement the benchmarks
- [**Hedley**](https://nemequ.github.io/hedley/) to avoid re-inventing several compiler-agnostic feature macros
- [**include-what-you-use**](https://include-what-you-use.org) to check the included headers
@@ -1950,7 +1975,7 @@ For more information, see [JSON With Commas and Comments (JWCC)](https://nigelta
By default, the library does not preserve the **insertion order of object elements**. This is standards-compliant, as the [JSON standard](https://tools.ietf.org/html/rfc8259.html) defines objects as "an unordered collection of zero or more name/value pairs".
If you do want to preserve the insertion order, you can try the type [`nlohmann::ordered_json`](https://github.com/nlohmann/json/issues/2179). Alternatively, you can use a more sophisticated ordered map like [`tsl::ordered_map`](https://github.com/Tessil/ordered-map) ([integration](https://github.com/nlohmann/json/issues/546#issuecomment-304447518)) or [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map) ([integration](https://github.com/nlohmann/json/issues/485#issuecomment-333652309)).
If you do want to preserve the insertion order, you can try the type [`nlohmann::ordered_json`](https://json.nlohmann.me/api/ordered_json/). Alternatively, you can use a more sophisticated ordered map like [`tsl::ordered_map`](https://github.com/Tessil/ordered-map) ([integration](https://github.com/nlohmann/json/issues/546#issuecomment-304447518)) or [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map) ([integration](https://github.com/nlohmann/json/issues/485#issuecomment-333652309)).
See the [**documentation on object order**](https://json.nlohmann.me/features/object_order/) for more information.
COMMAND${GENHTML_TOOL}--title"JSON for Modern C++"--legend--demangle-cpp--output-directoryhtml--show-details--branch-coverage--ignore-errorsinconsistentjson.info.filtered.noexcept
@@ -13,9 +13,15 @@ function never throws an exception for invalid input, and the returned `#!cpp bo
is returned.
The result is the same as that of `BasicJsonType::accept()` by design; the difference is how the check is made. This
function runs the document's index builder (and discards the index), while `BasicJsonType::accept()` runs the SAX
parser with a handler that ignores every event. Use this one if you go on to parse the same input with
[`parse()`](parse.md) anyway, so that both use the same code; either is fine for a plain yes/no answer.
function runs the document's builder, which checks the text as [`parse()`](parse.md) does, while
`BasicJsonType::accept()` runs the SAX parser with a handler that ignores every event. Use this one if you go on to
parse the same input with [`parse()`](parse.md) anyway, so that both use the same code; either is fine for a plain
yes/no answer.
When both `ignore_comments` and `ignore_trailing_commas` are `#!cpp false` (the default), the builder writes no index.
With either option set, it builds the index as [`parse()`](parse.md) does and discards it: the result is the same, only
the time differs. (Neither option needs the index; the variant that skips it exists only for the default options to
keep the code size down.)
## Template parameters
@@ -71,7 +77,7 @@ compile; see [`parse`](parse.md#notes).
- [`parse`](parse.md) - deserialize from a compatible input
- [`BasicJsonType::accept`](../basic_json/accept.md) - the corresponding function of `basic_json`
- [Zero-copy JSON views](../../features/json_view.md#what-is-the-same-as-parse) - how parsing a document differs from, and matches, basic_json::parse
- [Zero-copy JSON views](../../features/json_view/differences.md#what-is-the-same) - how parsing a document differs from, and matches, basic_json::parse
Every other `T` — user types whose `from_json()` is written for `BasicJsonType` only, types without a default
constructor, `#!cpp std::tuple`s holding references, ... — is converted by `#!cpp materialize().get<T>()`: the subtree is built into a real `BasicJsonType`
@@ -80,14 +81,13 @@ Strong guarantee: there are no changes to the view or the document it refers to.
- For every other `T`: whatever [`materialize().get<T>()`](../basic_json/get.md) throws — typically `type_error.302`,
or whatever a user-provided `from_json()` throws.
None of the exceptions thrown directly by this function or by a `from_json()` that reads the view (the first four
bullets above) carry a
[`JSON_DIAGNOSTICS`](../macros/json_diagnostics.md) path: the view has no `BasicJsonType` value to point at. An
exception thrown while converting through `materialize()` (the last bullet) is different: it is thrown by a real
`BasicJsonType` value, so it **does** carry a `JSON_DIAGNOSTICS` path if `BasicJsonType` was built with it enabled.
That path is relative to the root of the view's subtree, because `materialize()` builds only the subtree (with parent
pointers): it is empty if the failing value is the subtree's root itself, and it never is the path within the whole
document.
The exceptions thrown directly by this function or by a `from_json()` that reads the view (the first four bullets
above) carry the context of those of `BasicJsonType`: with [`JSON_DIAGNOSTICS`](../macros/json_diagnostics.md) the
JSON Pointer path of the value within the document, and with
[`JSON_DIAGNOSTIC_POSITIONS`](../macros/json_diagnostic_positions.md) its bytes in the source text. An exception
thrown while converting through `materialize()` (the last bullet) is thrown by the materialized `BasicJsonType` value
instead: its path is relative to the root of the view's subtree, because `materialize()` builds only the subtree
(with parent pointers), so it is empty if the failing value is the subtree's root itself.
## Complexity
@@ -152,7 +152,7 @@ document.
- [`number_token`](number_token.md) - a number's token text, without a copy
- [`materialize`](materialize.md) - build the `BasicJsonType` value of this subtree
- [`BasicJsonType::get`](../basic_json/get.md) - the corresponding function of `basic_json`
- [Zero-copy JSON views](../../features/json_view.md#getting-values-out-without-copying) - which conversions avoid building a basic_json value
- [Zero-copy JSON views](../../features/json_view/reading.md#getting-values-out-without-copying) - which conversions avoid building a basic_json value
@@ -34,7 +34,7 @@ This type is a [`basic_json_view`](basic_json_view/index.md) of a value of an
- [`ordered_json_editable_document`](ordered_json_editable_document.md) - the document type this view refers into
- [`ordered_json_view`](ordered_json_view.md) - the corresponding read-only view
- [`json_editable_view`](json_editable_view.md) - the corresponding view for `json_editable_document`
- [Zero-copy JSON views](../features/json_view.md#editing-a-document) - editing a document in place and writing it back
- [Zero-copy JSON views](../features/json_view/editing.md) - editing a document in place and writing it back
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