Two further serialization speedups on top of the ensure_ascii=false bulk
copy, both reusing the SWAR primitives in detail/input/string_scan.hpp.
1. Internal write buffer (devirtualization). Every structural character
('{', '"', ',', ...) previously went straight to the output adapter
through a virtual call. Route all writes through put_char/put_chars
into a 1 KiB buffer that flushes in bulk; the public dump() flushes
once the top-level value is done (the recursive worker is split out as
dump_internal). Runs larger than the buffer are written straight
through, so large payloads are not copied twice. This is the dominant
cost for object/array-heavy values.
2. ensure_ascii fast path. dump_escaped previously ran the UTF-8 DFA over
every byte when escaping non-ASCII. Add find_ascii_copyable_run() (a
SWAR scan stopping at '"', '\\', < 0x20, 0x7F, and >= 0x80) so runs of
printable ASCII are bulk-copied, with the byte path handling each
escape/non-ASCII byte exactly as before.
Behavior is unchanged: dump output is byte-for-byte identical to the
previous implementation across ~20k randomized byte strings plus curated
edge cases (all escapes, control chars, 0x7F, valid multibyte,
surrogates, overlong, truncated), for object/array/pretty output, both
ensure_ascii settings, and all three error handlers, in C++11/17/20 at
-O2/-O3. New unit tests cover the buffer flush boundaries, the escape and
0x7F handling, multibyte under both settings, and invalid-UTF-8 handling.
Throughput (g++ -O3, vs the ensure_ascii=false-only baseline):
long ASCII, ensure_ascii=0 4.2x
long ASCII, ensure_ascii=1 4.1x
twitter-like objects 2.7x
dense CJK 1.8x
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XAYM1qhSA2FDaDcGfPW3fG
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
GCC 7 sets __cplusplus to the C++17 value under -std=gnu++1z, so
JSON_HAS_CPP_17 is defined, but its libstdc++ ships no <charconv> header
(added in GCC 8; floating-point from_chars in GCC 11). The unconditional
"#if defined(JSON_HAS_CPP_17) #include <charconv>" therefore failed to
compile there: "fatal error: charconv: No such file or directory" in the
ci_test_compilers_gcc (7) job.
Wrap the include in __has_include(<charconv>), mirroring the library's
existing handling of <version> and <filesystem> in macro_scope.hpp. When
the header is absent, __cpp_lib_to_chars stays undefined and
parse_float_from_chars() takes its scalar fallback, so the from_chars use
site (already gated on __cpp_lib_to_chars) is never reached. GCC 8-10,
which have <charconv> but no floating-point from_chars, are unaffected:
they include the header but still take the fallback. GCC 11+ is unchanged.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The contiguous number fast path uses a Clinger-style exact algorithm
(significand * 10^scale in double arithmetic), which is only correctly
rounded when double operations are evaluated in true 53-bit precision.
On the x87 FPU used by 32-bit x86 (FLT_EVAL_METHOD == 2) the single
multiply/divide is computed in 80-bit and then double-rounded to double,
so a small fraction of values land 1 ULP off.
This surfaced as test-cbor_cpp11 and test-msgpack_cpp11 failing on the
mingw (x86) job for regression/floats.json: the C++17 builds pass because
they take the correctly-rounded std::from_chars path, while C++11 falls
back to parse_float_fast(). A 5M-sample check over shortest round-trip
decimals reproduces it: 0 divergences with 53-bit doubles, ~1 in 25 000
with 80-bit intermediates; declining to std::strtod fixes all of them.
Guard parse_float_fast() on FLT_EVAL_METHOD so it declines whenever the
platform evaluates doubles in extended precision, letting the caller use
the correctly-rounded std::from_chars / std::strtod path instead. On
mainstream x86-64/ARM64 (FLT_EVAL_METHOD == 0) the fast path is unchanged.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
libstdc++ 15 defines __cpp_lib_to_chars even in C++14 mode (via
bits/version.h pulled in by other headers), but <charconv> is only included
under JSON_HAS_CPP_17. That made parse_float_from_chars() reference
std::from_chars without the header in C++14 builds, breaking gcc-latest,
icpx, and the offline-testdata jobs.
Gate the use on JSON_HAS_CPP_17 && __cpp_lib_to_chars so it matches the
include condition exactly; C++11/14 always take the scalar fallback.
Verified by forcing __cpp_lib_to_chars in a C++14 build: the guard
suppresses std::from_chars and it compiles. C++17 behavior is unchanged.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The Clinger fast path is exact only for the "easy" subset (<=19 significant
digits, |exp10| <= 22); high-precision and scientific floats fall through to
strtod, where the failed Clinger attempt actually makes parsing a net loss.
std::from_chars implements the Eisel-Lemire algorithm in modern standard
libraries: locale-independent, correctly rounded, and fast over the whole
value range.
convert_number() now tries parse_float_from_chars() first (guarded by
__cpp_lib_to_chars, so C++11 and libc++-without-float-support keep the
Clinger + strtod path unchanged), then Clinger, then strtof. from_chars is
used only when it consumes the entire token; a partial parse means a non-'.'
locale decimal point, and an under-/overflow (result_out_of_range) also
declines - in both cases the existing strtod fallback supplies the exact
value and the well-defined +/-inf/0 the parser expects, side-stepping the
P4168 divergence between implementations. float and long double now get the
fast path too (Clinger was double-only).
Measured, C++17, g++ 13 -O3, json::parse/accept:
- canada-style floats: ~unchanged (Clinger already covered them)
- high-precision (17 digits): parse 2.1x, accept 2.5x
- scientific (17 digits + exp): parse 3.6x, accept 4.1x
Verified: C++11 (Clinger/strtod) and C++17 (from_chars) parse every value -
including subnormals, boundary values, and 1e9999/1e-9999 over-/underflow -
to bit-identical results; 2M number-fuzz clean; conversions/deserialization/
locale/number-fast-path suites pass in both C++11 and C++17; clang-tidy
clean; warning-clean on g++ and clang in C++11/17/20.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The CI clang-tidy (newer than the locally available version) reported two
additional checks on the new code:
- readability-math-missing-parentheses: parenthesize the (a * b) + c digit
accumulations in number_parse.hpp.
- cppcoreguidelines-missing-std-forward: the contiguous-byte-container
input_adapter overload took a forwarding reference but only reads
data()/size() and never forwards it. It is already disjoint from the
generic container overload via SFINAE, so a plain const& is correct and
clearer (and keeps the container alive for the whole parse just as before).
No behavior change; char_type and routing are unchanged (std::string and
std::vector<std::uint8_t> still take the pointer adapter with char/uint8_t
char_type), CBOR/MsgPack round-trips and the 2M number fuzz still pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The contiguous number fast path materialized token_buffer with
token_buffer.assign(data, len), but string_t is only required to provide
the minimal interface the rest of the lexer uses (push_back, append,
clear, operator[], ...). Custom string types such as the test's alt_string
do not implement assign(), so scan_number_bulk_contiguous() failed to
compile for them (unit-alt-string), breaking the gcc/clang standards and
old-compiler CI jobs.
reset() already clears token_buffer, so fill it with append() - which
alt_string and std::string both provide and which the string fast path
already relies on - instead of assign().
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
- number_parse.hpp: use std::array for the powers-of-ten table
(avoid-c-arrays) and `auto` for the cast-initialized result
(modernize-use-auto), matching the codebase style (cf. the serializer's
utf8d table). Indexing casts keep the -Wsign-conversion build clean.
- add JSON_USE_SIMDUTF to the mkdocs navigation so the macro page is
reachable.
No behavior change; clang-tidy is clean on the new headers and the
amalgamation is regenerated.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
lexer.hpp had grown by ~600 lines of byte-level helpers that have no
dependency on the lexer's template parameters and clutter the state
machine. Move them, unchanged, into two focused headers as free functions
in namespace detail:
- number_parse.hpp: parse_integer_unsigned/parse_integer_signed (now
templated on the number type) and parse_float_fast (Clinger's exact
double fast path, with the decimal point passed as an argument instead of
read from a lexer member).
- string_scan.hpp: the SWAR string helpers (is_string_special,
swar_string_special, find_string_special, validate_one_utf8,
scalar_string_bulk_run) and the backend-dispatched string_bulk_run,
including the optional simdutf include and find_string_delimiter.
lexer.hpp now includes these and calls the free functions; the methods that
touch lexer state (scan_string, scan_number, scan_string_bulk,
scan_number_bulk_contiguous, convert_number) stay put. This is a pure code
move with no behavior change: lexer.hpp drops from 2357 to 1934 lines, the
now-unused <cstdint>/<cstring>/<limits> includes are removed, and the
free-function form makes the SWAR helpers reusable elsewhere (e.g. the
serializer's string escaping).
Verified: default and JSON_USE_SIMDUTF builds compile; 2,000,000 number and
2,000,000 arbitrary-byte-string differential-fuzz documents parse
identically to before; lexer/parser/conversions/deserialization/locale/
diagnostic-position suites pass (20,576 assertions); warning-clean on g++
and clang in C++11/17/20; the amalgamation regenerates and passes
check-amalgamation.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
scan_number() reads a number one character at a time through the input
adapter (get()) and appends each byte to token_buffer (add()) before
converting. For contiguous input, the per-character get()/add() overhead
dominates: it is roughly two thirds of the time spent on number-heavy
parsing, far more than the value conversion itself.
Add scan_number_bulk_contiguous(), which parses the whole number token
straight from the input buffer: it validates and classifies the extent
with the same grammar as scan_number()'s state machine, materializes
token_buffer in one copy (substituting the locale decimal point exactly as
scan_number() does), advances the adapter, and reuses the shared
convert_number() tail. On anything it does not recognize as a well-formed
number it makes no state change and returns token_type::uninitialized, so
the caller falls back to scan_number(), which then produces the exact
diagnostic. Errors and their positions are therefore unchanged.
The conversion tail is factored out of scan_number() into convert_number()
so both scanners share it; the fast path is selected by tag dispatch on the
existing bulk_scan capability, so streaming/wide/user adapters are
unaffected.
Measured on pointer input, g++ 13 -O3:
- integers: parse +65%, accept +98%
- floats: parse +39%, accept +70%
Verified: 2,000,000 randomized number documents (including overflow-range
integers, long digit strings and %.17g doubles) parse identically via the
contiguous path and the streaming byte path, matching value, type and
round-trip text; the locale suite and existing parser/lexer/conversions/
deserialization tests pass; a new "lexer number fast path" test checks
contiguous-vs-streaming parity, token classification, and that malformed
numbers are rejected identically. Pure C++11, no intrinsics.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The bulk string scanner validates UTF-8 straight from a contiguous buffer.
The scalar validator caps at ~0.3-0.7 GB/s on non-ASCII text; a SIMD
validator reaches several GB/s. Rather than hand-rolling SIMD UTF-8
validation (easy to get subtly wrong - a from-scratch SSE attempt rejected
valid CJK), wire in the vetted simdutf library behind an opt-in switch.
simdutf is not header-only (it ships simdutf.cpp and uses runtime CPU
dispatch), so it is not vendored: defining JSON_USE_SIMDUTF includes
<simdutf.h> and routes the bulk validator through simdutf::validate_utf8;
the project supplies and links simdutf. Undefined (the default), nothing
external is included and the portable C++11 scalar path is used, so the
library stays header-only and its baseline behavior is unchanged.
Design keeps behavior identical either way:
- scan_string_bulk() now finds the run up to the next quote/escape/control
byte (non-ASCII allowed) and validates it in one shot; on the rare
validation failure it recomputes the exact valid prefix with the scalar
helper, so ill-formed input still falls through to the byte path and is
reported at the same position with the same message.
- the per-sequence scalar path is factored into scalar_string_bulk_run()
and is the default backend; the refactor is behavior-preserving and does
not change scalar throughput.
Verified: default and JSON_USE_SIMDUTF builds accept/reject/parse
identically across 2,000,000 arbitrary-byte documents and 1,000,000
mixed-escape/UTF-8 documents (differential fuzz vs the streaming byte
path); lexer/parser/diagnostic-position/deserialization suites pass under
both configurations (20,188 assertions with the backend enabled);
warning-clean on g++ and clang, C++11 and C++20, both configurations.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
json::parse(std::string) - the most common entry point - did not benefit
from the contiguous fast paths (bulk string scanning, UTF-8 bulk
validation, memcpy for binary formats) in C++11..17: std::string::iterator
is a library wrapper, not a raw pointer, and pre-C++20 there is no portable
way to prove it contiguous, so supports_bulk_scan was false. Only raw
pointers, string literals, and C-arrays (and, in C++20, anything modelling
std::contiguous_iterator) took the fast path.
Detect contiguous single-byte containers (std::string, std::vector<char>,
std::vector<std::uint8_t>, std::string_view, ...) via is_contiguous_byte_
container and route them through an iterator_input_adapter built from
data()/data()+size(). The generic iterator-based container overload is
constrained to exclude these, so the two overloads are disjoint and there
is no ambiguity (a plain competing overload loses to the greedy
forwarding-reference container overload on reference binding, and a factory
partial-specialization is ambiguous - both were tried and rejected).
The pointer keeps the container's own element type, so char_type - and
therefore all parsing behavior - is byte-for-byte identical to the iterator
path (const char* for std::string, const std::uint8_t* for
std::vector<std::uint8_t>); only the raw pointer additionally turns on the
fast paths. Lifetimes are unchanged: the container outlives the adapter for
the full parse expression, exactly as the iterators it replaces did.
Measured, C++11, json::parse/accept(std::string), g++ 13:
long ASCII strings: accept 201 -> 3200 MB/s (~16x), parse 174 -> 1444
dense CJK: accept 263 -> 697 MB/s (~2.6x)
short strings: accept 163 -> 243 MB/s (~1.5x)
Verified: char_type preserved for std::string (char) and
std::vector<std::uint8_t> (uint8_t); CBOR/MsgPack round-trips from
std::vector<std::uint8_t> unchanged; 1,000,000 randomized documents accept
and parse identically via std::string and via std::istream;
deserialization/user-defined-input/parser/lexer/conversions/diagnostic-
position suites pass (20,480 assertions); warning-clean on g++ and clang in
C++11/17/20.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The SWAR bulk string path stopped at the first non-ASCII byte and handed
every multibyte character to the byte-at-a-time scanner, whose per-byte
get()/next_byte_in_range()/add() machinery runs at roughly half the speed
of validating straight from the buffer. As a result, dense non-ASCII text
(CJK, emoji, accented Latin) parsed ~10-15x slower than ASCII.
Fold well-formed UTF-8 into the bulk run: scan_string_bulk() now, on a
non-ASCII lead byte, validates one sequence with validate_one_utf8() -
which mirrors scan_string()'s per-byte switch ranges exactly (rejecting
overlong forms, surrogates, and out-of-range code points) - and appends it
in place, continuing until the closing quote, an escape, a control byte,
or an ill-formed sequence. All error handling still defers to the byte
path, so error messages and positions are byte-for-byte unchanged.
Because only well-formed content is fast-pathed and every rejection falls
through to the existing scanner, behavior is identical; the win is purely
throughput. Measured on pointer input (accept, string values discarded):
content g++ 13 clang 18
dense CJK 277 -> 648 ~605 MB/s (~2.3x)
dense emoji 299 -> 857 ~702 MB/s (~2.6-2.9x)
mixed 90% ASCII 246 -> 331 ~334 MB/s (~1.35x)
pure ASCII unchanged (~3.2 / 4.1 GB/s)
Verified: 2,000,000 randomized documents built from arbitrary bytes
(overlong, surrogate, truncated, out-of-range sequences) accept/reject and
parse identically via the contiguous path and the streaming byte path;
lexer/parser/diagnostic-position/deserialization/conversions suites pass
unchanged. Pure C++11, no intrinsics.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
scan_string() read the input one character at a time through the input
adapter and classified every byte with a large switch. For contiguous
byte buffers we can instead scan 8 bytes at a time with a SWAR word test
that finds the first byte needing individual handling (the closing quote,
an escape, a control character, or a non-ASCII UTF-8 byte) and bulk-append
the ordinary run in one go.
- input adapters expose supports_bulk_scan / bulk_data / bulk_remaining /
bulk_skip for provably-contiguous, same-type, 1-byte iterator ranges
(raw pointers in every standard; std::string/std::vector/std::array and
friends additionally in C++20 via std::contiguous_iterator).
- the lexer gains a bulk_scan capability (gated on lazy_token_string so
bypassing the per-character capture cannot lose error diagnostics) and a
scan_string_bulk() fast path; streaming/wide/user adapters are unchanged
and keep the byte-at-a-time scanner.
The run contains no newline (all bytes < 0x20 are treated as special), so
position bookkeeping stays exact, and error tokens are still reconstructed
lazily from the consumed byte range. The SWAR special-byte test is pure
uint64_t arithmetic - no intrinsics, no runtime dispatch, C++11-clean.
Measured on representative data, pointer input, g++ 13 -O3
(string values discarded by accept() see the largest gains):
long ASCII strings: DOM +4.5x, SAX +14x, accept +17x (to ~2 GB/s)
short strings: DOM +15%, SAX +62%, accept +85%
escape-heavy: DOM +31%, SAX +26%, accept +28%
Same-input parity verified: 200k randomized documents (escapes, multibyte
UTF-8, surrogate pairs) accept/parse identically via the contiguous SWAR
path and the streaming byte path; unit lexer/parser/diagnostic-position/
deserialization/conversions suites pass unchanged.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The number scanner converted its already-validated digit buffer with
std::strtoull/std::strtoll/std::strtod. Those pull in locale and errno
machinery and dominate number-heavy parsing (strtod runs at ~6 M/s).
Replace them with dedicated parsers over the validated buffer:
- parse_integer_unsigned / parse_integer_signed: accumulate digits with
overflow detection, falling back to the float path on overflow exactly
as the strtoull/strtoll round-trip check did. Overflow behavior is
unchanged for narrower or wider custom number types.
- parse_float_fast: Clinger's exact fast path for `double` (<=19 significant
digits, |exp10| <= 22, significand < 2^53), where significand * 10^exp is
exact under IEEE round-to-nearest. This is the same fast path used by
fast_float/simdjson. It is bit-identical to strtod on this subset and
declines (falling back to strtod) otherwise. Only `double` uses it; float
and long double keep std::strtof/std::strtold via a templated overload.
Measured on representative data (g++ 13, -O3):
- integers: DOM parse +11%, SAX +25-34%
- floats: DOM parse +37%, SAX +70% (clang: float DOM ~1.9x)
No dependencies added; header-only and C++11-clean. Existing parser,
lexer, conversion and deserialization unit tests pass unchanged; a
3M-value random-double fuzz matches strtod bit-for-bit.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Add iterator+sentinel tests and docs for binary deserializers
This commit extends the C++20 ranges support (iterator+sentinel pairs) to the
binary format deserializers from_cbor, from_msgpack, from_ubjson, from_bjdata,
and from_bson, matching what was already done for parse(), accept(), and
sax_parse().
Changes:
- Add istreambuf_sentinel helper to test_utils.hpp for EOF detection in tests
- Add 5 new test cases that read binary files directly via
std::istreambuf_iterator<char> + sentinel, without pre-buffering
- Update documentation for all 5 from_* functions to document overload (3)
with SentinelType parameter
- All tests pass; verified against existing test suite data
- Fix potential buffer over-read warning in heterogeneous iterator test
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Merge iterator+sentinel overloads and fix ambiguity/CI issues
Address PR review feedback and CI failures:
- Merge the separate same-type and sentinel-type iterator overloads of
parse(), accept(), sax_parse(), and the five from_* binary deserializers
into a single overload with SentinelType defaulted to IteratorType,
as suggested in review. Applied the same simplification to the
detail::input_adapter() free functions.
- Fix a latent ambiguity: some compilers (e.g. GCC 4.8) unreliably SFINAE
the operator!= detection for std::nullptr_t against container/string
types, making calls like parse(s, nullptr, ...) ambiguous with the
compatible-input overload. can_compare_ne now explicitly excludes
std::nullptr_t as a SentinelType.
- Use a named enable_if_t template parameter instead of an unnamed
function parameter for the SFINAE guard, fixing a clang-tidy
hicpp-named-parameter/readability-named-parameter failure.
- Update parse.md, accept.md, sax_parse.md, and the five from_*.md pages
to document the merged overload instead of separate (2)/(3) overloads,
also fixing an over-160-char line that broke the documentation
style_check CI job.
- Rework the BSON iterator+sentinel test to parse a BSON file already
present in the test suite instead of writing/deleting a temp file.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix -Wunneeded-internal-declaration for CustomSentinel in test
CustomSentinel lives in an anonymous namespace (internal linkage), and
the library's parse loop only ever evaluates the iterator-first
direction (it != last), so the reversed-order friend operator!= was
never referenced. Clang's -Weverything flags such unused internal
declarations as an error. Drop the unused overload; the used direction
is enough to satisfy can_compare_ne's either-order detection.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix clang-tidy hicpp-named-parameter and misc-const-correctness
- Drop the unused reversed-order operator!= overload from
utils::istreambuf_sentinel (only iterator != sentinel is ever
evaluated) and name the remaining friend's sentinel parameter, fixing
hicpp-named-parameter/readability-named-parameter.
- Mark the istreambuf_iterator first/last helper variable const in the
five binary-format sentinel tests, fixing misc-const-correctness.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix clang-tidy misc-const-correctness in heterogeneous sentinel test
json_str is only read via .data()/.size() and never reassigned, so
clang-tidy correctly flags it as const-able. Verified against the exact
CI job (silkeh/clang:dev, ci_clang_tidy target) by running clang-tidy
directly on this file plus the five binary-format sentinel tests
touched by prior commits; all are now clean.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix container input_adapter SFINAE for lvalue-only ADL begin/end (#111)
The container overload of json::parse(c) / accept(c) / sax_parse(c, ...)
silently dropped from overload resolution for user types whose ADL
begin(T&) / end(T&) accepted only non-const lvalue references
(a legitimate pattern matching std::begin semantics). This was because
the detection code used std::declval<ContainerType>() which synthesized
an rvalue, and the rvalue failed to bind to lvalue-only ADL functions.
Fix by making both the outer input_adapter(ContainerType&&) and the
factory's create(ContainerType&&) forwarding references, preserving the
caller's value category and constness via reference collapsing. This
ensures detection (std::declval) and actual use (std::forward) always
match without needing decay/remove_reference.
- Rewrite input_adapters.hpp container overload with forwarding refs
- Add regression tests for lvalue-only non-const ADL begin/end
- Add regression test for rvalue containers (no breakage)
- Update API docs (parse, accept, sax_parse, from_*) to clarify
that begin/end must match std::begin/std::end semantics
- Add version history notes for 3.13.0
- Regenerate amalgamation
Second-order effect: binary_reader.hpp's internal call to
input_adapter(number_vector) now deduces iterator vs const_iterator
based on the lvalue; functionally harmless (iterator_input_adapter is
iterator-type-agnostic), verified via unit-ubjson/unit-bjdata tests.
Closes remaining limitation from #4354 / PR #5218 (todo 106).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Avoid strlen() in test container to fix Codacy CWE-126 flag
Suppressing the strlen()-based CWE-126 warning with NOLINT/nosec
comments only silenced clang-tidy and the standalone Flawfinder
Action; Codacy's own analysis (which also flags this pattern and
doesn't honor those suppression comments) still reported it as a new
issue, plus flagged the near-duplicate begin/end pair as cloned code.
Store the buffer's size explicitly in MyContainerNonConstADL instead
of computing it via strlen() in end(), which removes the flagged
pattern outright and also de-duplicates the struct from the existing
MyContainer's char*-based begin/end pair.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Avoid trailing return type to satisfy clang-tidy fuchsia-trailing-return
The forwarding-reference input_adapter(ContainerType&&) entry point was
written with an auto/trailing-decltype return type, but this project's
ci_clang_tidy job enables the fuchsia-trailing-return check as an
error, which rejects it. The return type only depends on the template
parameter ContainerType, not on the runtime parameter, so it can be
written as an ordinary leading return type instead - no functional
change.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Avoid C-style array in test to satisfy clang-tidy avoid-c-arrays
clang-tidy's cppcoreguidelines/hicpp/modernize-avoid-c-arrays checks
flagged the char raw_data[] declaration used to reproduce the
lvalue-only non-const ADL begin/end scenario. Use std::string instead
and take a mutable pointer via &raw_data[0], which is the standard
way to get a non-const char* into a string's buffer under C++11
(std::string::data() only returns non-const in C++17 and later).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix stale Clang -Weverything suppression comments; eliminate -Wno-missing-noreturn
cmake/clang_flags.cmake claimed -Wno-unsafe-buffer-usage was needed only
for Doctest and that -Wno-missing-noreturn had "no way to silence...
otherwise" (PR #4871, which never actually attempted a source fix).
Neither held up under investigation (todo 130):
- -Wno-unsafe-buffer-usage is pervasive (208 distinct sites across 19
files measured with clang trunk in silkeh/clang:dev), spanning the
library's own low-level numeric/buffer code (to_chars, serializer,
lexer, binary reader/writer, input adapters, json_pointer) as well as
vendored Doctest itself (96 of the 208 sites). A source-level fix is
not feasible at this scale; the comment now says so instead of
blaming Doctest alone.
- -Wno-missing-noreturn had exactly two real trigger sites, both
genuinely and unconditionally non-returning: a test-only throwing
allocator (tests/src/unit-allocator.cpp) and, previously undiscovered,
wide_string_input_adapter::get_elements<T>() in
include/nlohmann/detail/input/input_adapters.hpp. Verified this isn't
a wider pattern by checking all 160 JSON_THROW call sites in the
library for functions whose entire body is an unconditional throw.
Annotated both ([[noreturn]] in the test file, since JSON_HEDLEY_NO_RETURN
is #undef'd by the time test code runs; JSON_HEDLEY_NO_RETURN in the
library file, its first real use anywhere in the codebase) and
dropped the suppression entirely.
single_include/nlohmann/json.hpp regenerated via `make amalgamate`;
`make check-amalgamation` passes.
Verified in Docker (silkeh/clang:dev, matching the ci_static_analysis_clang
CI job): baseline builds clean, and the full 194-target test suite builds
with zero warnings under the corrected CLANG_CXXFLAGS (-Wno-missing-noreturn
no longer in the list). Also sanity-compiled and ran unit-allocator.cpp and
unit-wstring.cpp on host Apple Clang to confirm behavior is unchanged.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix MSVC C4702 warning caused by JSON_HEDLEY_NO_RETURN on get_elements()
PR #5250 annotated wide_string_input_adapter::get_elements<T>() with
JSON_HEDLEY_NO_RETURN (it unconditionally throws). On MSVC this expands to
__declspec(noreturn), and MSVC correctly determined that the code following
its call in binary_reader.hpp is unreachable for that instantiation, firing
C4702 under /W4 /WX in the msvc, msvc-vs2026, and msvc-arm64 Debug jobs.
Clang doesn't flag this case, so the Docker verification for #5250 (which
only checked Clang -Weverything) didn't catch it.
This is the same warning class already tolerated for Release builds since
PR #5216, where MSVC's optimizer independently found the same dead code
after /Od was removed. Extend that existing /wd4702 suppression to Debug
builds too, instead of reverting the noreturn annotation.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
`lexer::get()` copied every scanned character into `token_string` on the
whole successful-parse hot path, yet that buffer is consumed only by
`get_token_string()` when rendering the "last read" fragment of a parse
error. On well-formed input the per-byte copy (plus the `unget()` pop)
is pure overhead that is always discarded.
For seekable input adapters - random-access, single-byte iterators such
as those backing `std::string`, `const char*`, and `std::vector<char>` -
the offending token is now reconstructed on demand from the input when
an error is reported, using a saved start offset, and the eager copy is
skipped. Streaming adapters (file, istream, wide-string, and user-defined
adapters) keep the eager copy; the strategy is chosen at compile time via
`input_adapter_supports_seek`, so adapters without the capability are
unaffected.
Error messages are byte-for-byte identical across all adapters, verified
by a new parity regression test. Microbenchmark (4 MB mixed JSON, parsed
from a std::string): ~149 -> ~160 MB/s, about +8%.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
* fix(cbor): reject negative ints overflowing int64
CBOR encodes negative integers as "-1 - n" where n is uint64_t. When
n > INT64_MAX, casting to int64_t caused undefined behavior and silent
data corruption. Large negative values were incorrectly parsed as
positive integers (e.g., -9223372036854775809 became 9223372036854775807).
Add bounds check for to reject values that exceed int64_t
representable range, returning parse_error instead of silently
corrupting data.
Added regression test cases to verify.
Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>
* chore: clarify tests
Add test for "n=0" case (result=-1) to cover the smallest magnitude
boundary. Update comments to explain CBOR 0x3B encoding and why
"result=0" is not possible. Clarify that n is an unsigned integer
in the formula "result = -1 - n" to help understanding the tests.
Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>
* fix(cbor): extend overflow checks for other types
Extend negative integer overflow detection to all CBOR negative
integer cases (0x38, 0x39, 0x3A) for consistency with the existing
0x3B check.
Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>
---------
Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>
Adds pre-multiplication overflow detection to catch cases where dimension
products would exceed size_t max. The previous check only detected when
overflow resulted in exactly 0 or SIZE_MAX, missing other cases.
Retains the original post-multiplication check for backward compatibility.
Adds tests verifying overflow detection with dimensions (2^32+1)×(2^32),
which previously overflowed silently to 2^32.
This prevents custom SAX handlers from receiving incorrect array sizes
that could lead to buffer overflows.
Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>
* Add implementation to retrieve start and end positions of json during parse
* Add more unit tests and add start/stop parsing for arrays
* Add raw value for all types
* Add more tests and fix compiler warning
* Amalgamate
* Fix CLang GCC warnings
* Fix error in build
* Style using astyle 3.1
* Fix whitespace changes
* revert
* more whitespace reverts
* Address PR comments
* Fix failing issues
* More whitespace reverts
* Address remaining PR comments
* Address comments
* Switch to using custom base class instead of default basic_json
* Adding a basic using for a json using the new base class. Also address PR comments and fix CI failures
* Address decltype comments
* Diagnostic positions macro (#4)
Co-authored-by: Sush Shringarputale <sushring@linux.microsoft.com>
* Fix missed include deletion
* Add docs and address other PR comments (#5)
* Add docs and address other PR comments
---------
Co-authored-by: Sush Shringarputale <sushring@linux.microsoft.com>
* Address new PR comments and fix CI tests for documentation
* Update documentation based on feedback (#6)
---------
Co-authored-by: Sush Shringarputale <sushring@linux.microsoft.com>
* Address std::size_t and other comments
* Fix new CI issues
* Fix lcov
* Improve lcov case with update to handle_diagnostic_positions call for discarded values
* Fix indentation of LCOV_EXCL_STOP comments
* fix amalgamation astyle issue
---------
Co-authored-by: Sush Shringarputale <sushring@linux.microsoft.com>
* multibyte binary reader
* wide_string_input_adapter fallback to get_character
Update input_adapters.hpp
* Update json.hpp
* Add from msgpack test
* Test for broken msgpack with stream, address some warnings
* Reading binary number from wchar as an error, address warnings
* Not casting float to int, it violates strict aliasing rule
* fix: integer parsed as float when EINTR set in errno
* chore: make amalgamate
* chore: make pretty
---------
Co-authored-by: Stuart Gorman <Stuart.Gorman@kallipr.com>
* Possible fix for #4485
Throw's an exception when i is nullptr,
also added a testcase for this scenario though most likely in the wrong test file.cpp
* quick cleanup
* Fix compile issues
* moved tests around, changed exceptions, removed a possibly unneeded include
* add back include <memory> for testing something
* Ninja doesn't like not having a \n, at end of file, adding it back
* update input_adapter file to deal with empty/null file ptr.
* ran make pretty
* added test for inputadapter
* ran make amalgamate
* Update tests/src/unit-deserialization.cpp
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
* Update tests/src/unit-deserialization.cpp
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
* Update input adapters.hpp with new includes
* fix unabigious use of _, (there was a double declare)
* did the amalagamate
* rm duplicate includes
* make amalgamate again
* reorder
* amalgamate
* moved it above
* amalgamate
---------
Co-authored-by: Jordan <jordan-hoang@users.noreply.github.com>
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
Niels LohmannandClaude Opus 4.8
Angadi56andGitHub
Ville VesilehtoandGitHub
Michael ValladolidandGitHub
Nebojša CvetkovićandGitHub
Tianyi ChenandGitHub
