Commit Graph
1160 Commits
Author SHA1 Message Date
Niels Lohmann 1457bfb948 Merge branch 'develop' into claude/parser-stream-performance-8cebe9
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:22:53 +02:00
Niels Lohmann b41228c227 Fix AppVeyor failures from the Zmij double writer (#5843)
MSVC 2015 warns C4554 on the shifts with casts in the fractional part
of zmij::to_shortest despite the parentheses; with /WX every target
fails to build. Name the shift amounts as constants instead.

The shortest-digits test built the candidates with one digit fewer via
a stream with std::setprecision(digits.size() - 2); the standard library
of MSVC 2017 ignores a precision of 0, so for two-digit values the
"shorter" candidates were the value itself. Truncate the digits
instead: the value lies within half a unit of the last digit, so the
truncated digits and their successor are the closest candidates.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:08:12 +02:00
Niels Lohmann dcb96e82fb Escape characters below 0x60 from a table straight into the write buffer (#5822)
* Escape characters below 0x60 from a table straight into the write buffer

When the bulk scanner in dump_escaped_impl() stops at a control
character, a quote or a backslash, that byte used to go through the
UTF-8 decoder and a switch that wrote the escape byte by byte into
string_buffer, which was then copied into write_buffer at the next run.

A byte below 0x60 at a character boundary is a complete code point, so
it now skips the decoder: its escape sequence comes from a 96-entry
table of 8-byte rows (sequence padded with zeros, length in the last
byte), and all 8 bytes are copied straight into write_buffer with one
room check. The check sits inside the existing character-boundary
block, so it runs once per scanner stop and not once per byte; testing
every byte cost about 6% on twitter.json with ensure_ascii.

The switch in the decoder's accept branch lost its cases for
characters below 0x60, which can no longer reach it.

Output is byte-identical. The string-buffer boundary tests now use
\u-escaped non-ASCII characters, since simple escapes no longer reach
string_buffer, and a new test case checks every ASCII character at
every position against a reference escaper.

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

* Avoid raw string literals with backslashes in CHECK macros

MSVC's traditional preprocessor mis-lexes raw string literals inside
macro arguments and reports illegal escape sequences (C2017, C3850).

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

* Sweep invalid UTF-8 at every position through dump()

Compare dump() of strings with ill-formed UTF-8 (stray continuation
bytes, invalid lead bytes, overlong encodings, surrogates, code points
above U+10FFFF, and sequences cut short by ASCII, a quote, a backslash,
a lead byte, or the end of the string) with an independent reference
serializer, for every error handler and with ensure_ascii on and off.
The pattern is put at every position of short strings to cross the
strides of the bulk scanners, and of longer ones to cross the end of the
512-byte string buffer.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:08:10 +02:00
Niels Lohmann 91b9ee2602 Update cppcheck to 1.5.2 (Cppcheck 2.20) and fix its new findings (#5829)
Cppcheck 2.20 rejects invocations of unknown function-like macros in #if
conditions instead of evaluating them as 0. default_defines.hpp expands
the Hedley macros to the compiler's feature-test operators (__has_attribute
etc.), so define them as 0 in a generated include file.

It also reports a false bufferAccessOutOfBounds in the float overload of
float_from_bits, sizing the parameter as the double overload's; use the
size of the source instead (equal by the static_assert).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:04:46 +02:00
Niels Lohmann ce28c722bc Allow the same type for number_integer_t and number_unsigned_t (#5815)
* Allow the same type for number_integer_t and number_unsigned_t

basic_json did not compile with NumberUnsignedType == NumberIntegerType
because overloads on both types collided. Such a basic_json now stores
every integer as number_integer: the colliding overloads take a
placeholder type, unsigned C++ integers are converted to number_integer_t,
and value_t::number_unsigned maps to number_integer.

Also fixes two problems this configuration would hit: the unsigned
integer parser accepted values that wrap around to negative numbers, and
dump() overflowed when computing the absolute value of the minimum.

A repeated NumberFloatType gets a static_assert.

Refs #2573

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

* Use json::with_integers_t in the test and the docs

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

* ✅ skip patch test on GCC 5 to avoid internal compiler error

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

* Fix CI: name the unsigned overload type through template parameters

basic_json used number_unsigned_overload_t<basic_json> while the class was
still incomplete. MSVC rejected it as a recursive alias declaration and GCC
4.9, 5 and 7 crashed with an internal compiler error. basic_json now uses
number_unsigned_overload_type<NumberIntegerType, NumberUnsignedType>, which
also makes the GCC 5 workaround in the patch test unnecessary.

Infer reported a null dereference for the number_unsigned case in
from_json, which cannot happen for a basic_json whose number_unsigned_t is
number_integer_t; assert it.

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

* Address review: conjunction/negation trait, astyle-friendly alias, docs table order

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:04:42 +02:00
Niels Lohmann 6261d1e432 Construct the JSON Patch exceptions out of line (#5842)
patch_inplace() built its error messages inline. In particular get_value()
concatenated the context-sensitive "operation 'x'" string on every call, even
when nothing was wrong. The patch exceptions now come from NEVER_INLINE
helpers: the index and key errors reuse basic_json's existing
throw_array_index_out_of_range/throw_key_not_found, and the seven
patch-specific messages get one helper each in detail/exceptions.hpp. Ids
and messages are unchanged, and unit-throw_messages pins them (with and
without JSON_DIAGNOSTICS).

citm_catalog patch: -6.6 % (Apple clang), -9.5 % (GCC 16).
The other remaining throw sites (parser::syntax_error, binary_writer,
serializer, input_adapters, enum_key_duplicate, format_error) were prototyped
and measured: no gain beyond noise, so they stay as they are.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:01:23 +02:00
Niels Lohmann ed86019a21 Move binary reader error construction out of line (#5839)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:01:23 +02:00
Niels Lohmann 4f11512641 Speed up container destruction, iterator access and diff() (#5835)
* Speed up container destruction, iterator access and diff()

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

* Destroy the first levels of a value by recursion

The pointer-reversing walk in destroy_container() avoids the call stack but
moves a value around for every container it visits. Recurse for the first
recursion_depth_limit() levels instead - no allocation, no thread-local, a
bounded frame - and hand anything deeper to the walk. Destroy twitter
0.49 -> 0.36 ms, citm 0.80 -> 0.74 ms (3.12.0: 0.47 / 1.00).

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:01:22 +02:00
Niels Lohmann 6a27b9acb2 Construct remaining hot-path exceptions out of line so core functions inline (#5838)
* Construct remaining hot-path exceptions out of line so core functions inline

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

* Move throw_key_not_found() before at_impl()'s comment block

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:01:22 +02:00
Niels Lohmann 91869983a0 Make the value lifecycle inline-friendly (#5840)
* Make the value lifecycle inline-friendly

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

* Compare standard containers without a thread-local depth count

operator== on objects and arrays recursed through the containers' own
operator== and counted the depth in a thread-local variable. Where reading a
thread-local costs a call (macOS), that added about 10% to comparing documents
with many small containers. For the standard containers, walk objects and
arrays directly, compare scalars and strings inline, and pass the depth as an
argument, falling back to compare_iteratively beyond the depth limit. Other
container types keep the previous path.

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

* Address review: owns_memory() helper, leaf compare naming, astyle

- Add detail::owns_memory(value_t), a switch listing every enumerator so
  -Wswitch-enum flags it when a type is added; destroy() and the copy
  constructor use it instead of hand-written comparisons. Clang emits the
  same bitmask test as before.
- Drop the parentheses around the scalar operands in
  JSON_IMPLEMENT_SCALAR_CASES; they are only needed for the container
  operands (#1530), which the comment now says.
- Build equal_bounded_containers from detail::conjunction so astyle no
  longer pads the template brackets.
- Rename equal_scalar() to equal_leaf() and document why it also compares
  strings, unlike JSON_IMPLEMENT_SCALAR_FAST.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:01:21 +02:00
Niels Lohmann 4530d9681c Fix quadratic parent updates for ordered_json with JSON_DIAGNOSTICS (#5832)
* Fix quadratic parent updates for ordered_json with JSON_DIAGNOSTICS

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

* Only trust containers known to keep their elements in place

Address review: decide whether an insertion may have moved the other
members by naming the containers that are known not to, instead of the
ones that are known to.

- detail::has_stable_elements: std::map, std::multimap,
  std::unordered_map and std::unordered_multimap; object_capacity()
  reports 0 for them.
- detail::is_nlohmann_ordered_map: only the real nlohmann::ordered_map
  (which only appends) reports its capacity().
- Any other object type reports unknown_size(), so it gets a full
  set_parents() on every insertion. Before, an object type without
  capacity() was treated as never moving, and one with capacity() (a
  sorted flat map, say) was trusted to move only on reallocation.
- set_parents_after_object_erase() re-parents unless the object type is
  stable; the unused set_parent() is removed.
- Comments say "the object type" instead of "ordered_json".
- New test with an object type that moves its members without changing
  its capacity; it fails without this change.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:01:21 +02:00
Niels Lohmann ca7740fef2 Move elements when converting rvalue containers to JSON (#5837)
* Move elements when converting rvalue containers to JSON

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

* Simplify the rvalue to_json traits

Use negation<disjunction<...>> instead of a conjunction of negations and
keep the template argument lists compact (astyle only keeps the spaced
'< ... >' form when it is written that way).

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:01:20 +02:00
Niels Lohmann 6ba53e63dd Speed up array-to-container from_json (#5833)
* Speed up array-to-container from_json

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

* Hint the end when converting an object to a standard container

from_json for map-like containers called emplace() without a hint, which
searches the tree for every key. The keys of the source object are sorted, so
inserting with the end as the hint is constant time, as it was in 3.12.0 via
std::inserter. get<std::map<...>>() of a 25,000 entry object: 4.2 ms -> 3.25 ms
(3.12.0: 3.7 ms).

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

* Fall back to emplace() in object from_json for containers without emplace_hint()

ordered_map has no hinted insert, so the insert(end(), ...) call broke
from_json into types holding an ordered_map (regression test #5122).
Use emplace_hint() where available and plain emplace() otherwise.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:01:20 +02:00
Niels Lohmann 0a4b3a84ee Speed up JSON pointer parsing, formatting, comparison and lookup (#5836)
* Speed up JSON pointer parsing, formatting, comparison and lookup

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

* Restore unflatten() speed after the linear-time rewrite

The prefix tree introduced for linear unflatten() kept a std::map per prefix,
copied each token into it and looked every token up a second time while
creating the values. Replace the per-prefix maps by one open-addressing table
keyed by (parent, token) that refers to the parsed tokens, skip the lookups for
the prefix shared with the previous key (flattened objects are mostly sorted),
and derive the prefix numbers of the second pass from parent links instead of
lookups.

Time and memory stay linear in the pointer depth, and the result is still
independent of the iteration order of the flattened object.

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

* Put [[noreturn]] before __attribute__ on the JSON pointer throw helpers

Clang 18 on Linux rejects a C++11 attribute list after a GNU
__attribute__ ("an attribute list cannot appear here").

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:01:20 +02:00
Niels Lohmann 0c4e7c103c Make flatten() linear for ordered_json (#5834)
* Make flatten() linear for ordered_json

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

* Use priority_tag instead of a C-style variadic overload in add_flattened

clang-tidy flags the ellipsis fallback (cert-dcl50-cpp,
modernize-avoid-variadic-functions).

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:01:19 +02:00
Niels Lohmann a6e9785ab6 Look up the key only once in the callback parser's key() (#5831)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:01:19 +02:00
Niels Lohmann 898084b386 Merge branch 'develop' into claude/parser-stream-performance-8cebe9
Resolve the macro_unscope.hpp conflict by keeping both sets of #undefs
and regenerate the amalgamation.

The \u fast path from #5738 (get_codepoint_bulk) assumed that bulk
scanning implies lazy position tracking and advanced the adapter with a
bare bulk_skip(4). Stream adapters now scan in bulk but track position
and token eagerly, so a lone-surrogate error was reported 4 columns too
early. Advance through bulk_consume() instead.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-14 21:30:06 +02:00
Niels Lohmann 91a7a94cc6 Write doubles with the shortest digits (Żmij), digits in registers (#5634)
* Write doubles with the shortest digits (Żmij), digits in registers

Write doubles with the conversion of Zmij by Victor Zverovich (MIT),
ported to C++11 (detail/conversions/zmij.hpp). It finds the
shortest decimal that reads back as the same double, and the
closest one if there are several. Grisu2, used until now, is fast
but not always shortest: it sometimes writes a 17th digit where 16
suffice, or a last digit that is not the closest. The layout is
unchanged (1.5, 100.0, 1e+100, -0.0); float keeps Grisu2.

Digits are converted eight at a time with the BCD conversion of
Xiang JunBo, as in Zmij, and written with one byte swap per eight
digits and fixed-size moves instead of per-digit loops. Leading and
trailing zeros are counted from those bytes. to_chars() uses a
local buffer when the caller's is shorter than the 41 bytes this
may write. The powers of ten come from the number-parsing table,
adjusted where it holds values rounded up, and extended with Zmij's
compressed tables beyond 10^308.

write_shortest() converts its 16 digits in one vector register
(SSE2 on x86-64, NEON on 64-bit Arm, both baseline) and inserts the
decimal point inside the register, avoiding a store-forwarding
stall that cost about 25% of the time to write a double. dump()
writes floats and integers straight into the serializer's write
buffer instead of copying them from a member buffer, and small
integers eight digits at a time. read_eight_bytes() and
parse_eight_digits() are marked always-inline, which GCC had been
calling out of line in the number-parsing loops.

Of one million random doubles, about 0.14% are now written with
different digits, always to a value that still reads back as the
same double.

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

* Fix CI findings in the Zmij writer and its tests

- bit_ops.hpp: include macro_scope.hpp (JSON_HEDLEY_ALWAYS_INLINE); fixes IWYU
- to_chars.hpp: C4100 for the unused parameter in release builds, clang-tidy
  sign comparison, cpplint runtime/int, GCC -Wstrict-overflow (unsigned abs)
- unit-to_chars.cpp: parse with the library instead of strtod (MinGW's strtod
  rounds some 16/17 digit inputs wrongly); no floating-point std::to_chars
  with icpc

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

* Select the Zmij conversion by a trait, not by the double overload

The non-template overloads for double asserted binary64 doubles wherever json.hpp was included, so the library no longer compiled where double is not IEEE 754 binary64 (AVR, -fshort-double). A trait now picks Zmij for any binary64 type, including a long double of that format (MSVC, Apple Arm), and Grisu2 for the others. Remove the unused write_short_decimal, powers_of_ten_16, zmij::decimal, zmij::to_decimal, and shortest_digits(double).

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

* Credit Zmij's authors in to_chars.hpp, the README, and the license page

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

* Silence MSVC C4127 for a platform-constant check in the to_chars test

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

* Regenerate the amalgamated headers

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-14 17:38:37 +02:00
Niels Lohmann 5b4c8f9b00 Speed up the lexer: own float parser, string scan, and \u table (#5738)
* Speed up the lexer: own float parser, string scan, and \u table

Give the library its own correctly rounded float converter for
binary32 and binary64 (IEEE 754), and speed up the lexer's string
and escape scanning.

The converter splits a number token into sign, significand, and
decimal exponent, then tries Clinger's fast path, then a templated
Eisel-Lemire step, and falls back to an exact big-integer digit
comparison for tokens with more than 19 significant digits whose two
candidate values round differently. This replaces std::from_chars
and strtod/strtof for both formats, so parsed values no longer
depend on the C/C++ library or the current locale. The strtold
fallback kept for other long double formats (x87, binary128) now
also copies a multi-byte decimal point correctly, fixing #5660.
eisel_lemire() and decimal_to_float() are always inlined so callers
keep the whole conversion in their hot loop.

The string-scanning kernels in string_scan.hpp find a stop byte with
the trailing-zero count of the SWAR mask instead of a byte loop, and
scalar_string_bulk_run() validates a run of multi-byte UTF-8
sequences one after another instead of re-searching after each one.

get_codepoint() decodes a contiguous \uXXXX escape with one table
lookup per byte instead of four range-checked get() calls; the
streaming path and all error positions are unchanged.

Adds 508 generated hard float-parsing cases with expected binary32
and binary64 bits, and kernel-comparison tests for the string scans
and the escape table against byte-by-byte references.

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

* Fix CI warnings in own float parser

- pow5_table.hpp: pow5_128_largest_power was unused in this branch's
  own code (GCC -Werror=unused-const-variable); tie it to the table
  size with a static_assert instead of removing it, since a later
  branch in the stack (json-view/23-zmij) uses it.
- number_parse.hpp: rename the local variable `copy` to `buffer` to
  satisfy cpplint's build/include_what_you_use check.
- unit-class_lexer.cpp: extend the NOLINT list on the seeded mt19937
  with bugprone-random-generator-seed, and parenthesize
  `8 * sizeof(Bits) - 1` for clang-tidy.

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

* Load string scan words with memcpy and use MSVC bit-scan intrinsics

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

* Reword float conversion notes for the string type and number_float_t docs

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

* Fix clang-tidy 22 findings in unit-class_lexer.cpp

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

* Mark the unsigned long of the MSVC bit scans for cpplint

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

* Regenerate the amalgamated headers

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

* Drop the position updates in the bulk \u path, which #5809 made unused

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

* Address review: std::any_of in has_nonzero_digit, comment punctuation

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

* Use data() instead of c_str() in the multi-byte decimal point path

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-14 17:38:36 +02:00
Niels Lohmann c391abccb1 Lock a FILE once per parse instead of once per character
Parsing from a FILE* reads one character at a time with std::fgetc, which
locks and unlocks the FILE object for every character. file_input_adapter
now locks the file once when it is created and unlocks it when it is
destroyed - also when parsing throws - and reads with the unlocked stdio
functions in between: flockfile/getc_unlocked/funlockfile with glibc,
Apple, Android, and the BSDs, and _lock_file/_fgetc_nolock/_unlock_file
with the Microsoft C runtime. Other C libraries keep std::fgetc. The lock
is recursive, so fread() in the binary readers and stdio calls of a SAX
handler or parser callback on the same thread keep working.

On an Apple M1 Max, parsing from a FILE* is 2.9 to 4.0 times as fast
(twitter.json 14.3 -> 4.1 ms, citm_catalog.json 35.4 -> 8.8 ms); with
glibc, whose locking is cheaper, 1.1 to 1.3 times. The values and the
position of the file after parsing are unchanged.

Other threads that use the same FILE object now wait until parsing is
done instead of interleaving their reads with the parser's.
JSON_DISABLE_UNLOCKED_FILE_IO restores std::fgetc, for programs in which a
SAX handler waits for another thread that uses the same FILE. The new
tests check from a second thread that the lock is released after success
and after a parse error, and run again with the macro.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-14 17:34:00 +02:00
Niels Lohmann d5631dccbd Scan the get area of an input stream in bulk
Parsing from a std::istream read one character at a time through the
streambuf, so none of the parser's fast paths applied: it was 1.8 to 2.5
times slower than reading the file into a string and parsing that.

input_stream_adapter now exposes the streambuf's get area (gptr() to
egptr()) to the lexer as a window. The protected get-area members are
reached through member pointers formed in a class derived from
std::streambuf, which is ordinary, standard-conforming member access. The
lexer scans the window with the same bulk paths as a string, and asks
the streambuf for the next character as before when the window is used
up. Nothing is read ahead, copied, or put back, so the stream is left
exactly where it was left before, with and without
JSON_PRECISE_STREAM_POSITION, and a streambuf without a get area is still
read one character at a time.

The adapter also keeps the current token for error messages as a pointer
into the get area, and copies it out only before the get area is
refilled, instead of the lexer copying every character.

On an Apple M1 Max (Apple Clang, -O3), parsing from an std::ifstream is
1.6 to 2.1 times as fast (twitter.json 4.08 -> 2.30 ms, citm_catalog.json
8.75 -> 4.08 ms), and reading 100,000 small values with operator>> 1.4
(objects) to 4.0 (integers) times as fast. With GCC 13 and libstdc++ on
x86-64 Linux, std::ifstream is 1.5 to 2.2 times as fast. Parsing from a
stream is now within 11 to 18 % of reading the file into a string first.

JSON_DISABLE_STREAM_BULK_SCAN restores reading one character at a time,
for streambufs that do not follow the usual get-area contract. The new
tests compare every observable result (values, exception messages, stream
state, remaining characters) for get areas of 1 to 4096 bytes against a
streambuf without a get area, and run again with the macro and with
JSON_PRECISE_STREAM_POSITION.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-14 17:26:38 +02:00
Niels Lohmann 80d00eda50 Let the lexer's bulk fast paths run on a window of the input
The SWAR string scan, the bulk number scan, and the indentation skip were
only enabled for adapters that support seeking (contiguous random-access
input), because they rely on the lazy token and position tracking that
reconstructs both from the consumed input on demand.

This decouples the bulk paths from seeking, so that an adapter can expose
a contiguous block that is only a window into its input (bulk_window):

- bulk_consume() does the bookkeeping that get() would have done for the
  skipped characters when token and position are tracked eagerly.
- A number that reaches the end of a window is finished character by
  character, because it may continue after the window.
- After a bulk-scanned number, a window adapter reads the terminating
  character and ungets it, as scan_number() does, so that the input
  handed back to the user is consumed exactly as before.
- An adapter can keep the current token itself (supports_token_tracking,
  begin_token(), mark_token_start(), copy_token()) so the lexer need not
  copy every character for its error messages.

No adapter declares any of this yet, so the behavior is unchanged.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-14 17:13:58 +02:00
Niels Lohmann e839bbd1c0 Export client-facing headers from json.hpp for IWYU / include-cleaner, and check clients in CI (#5813)
* Mark json_fwd.hpp as exported by json.hpp for IWYU / include-cleaner

json_fwd.hpp is the only header declaring the nlohmann::json alias, so
include-what-you-use and clang-tidy's misc-include-cleaner attributed
the name to it and told users of <nlohmann/json.hpp> to include
json_fwd.hpp as well (or instead, which breaks compilation).

Fixes #5812

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

* Export the remaining client-facing headers from json.hpp and check clients with IWYU

Besides json_fwd.hpp, include analyzers also told clients of
<nlohmann/json.hpp> to include detail/json_ref.hpp (brace
initialization), json_literals.hpp (_json, _json_pointer),
adl_serializer.hpp, detail/macro_scope.hpp (NLOHMANN_DEFINE_*) and
detail/abi_macros.hpp. Mark those includes as exported, too.

ci_single_binaries only checked each header on its own, so it could not
notice this. It now also runs IWYU and clang-tidy's misc-include-cleaner
on small client programs in tests/iwyu_consumer, which fail on develop.
With the exports, json_literals.hpp no longer gets the json_fwd.hpp
suggestion that kept it out of the IWYU gate, so it is gated again.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-13 17:17:15 +02:00
Niels Lohmann aa9620fb15 Skip the indentation after a newline 8 bytes at a time (#5810)
Pretty-printed JSON indents every line with a run of spaces, which
skip_whitespace() read one character at a time. For contiguous input
(bulk_scan) the lexer now skips the spaces after a newline 8 bytes at a
time directly in the input buffer, including the leading spaces of the
last, partial word. This bypasses get(), which is safe because
bulk_scan implies the lazy position from the previous commit: nothing
is counted per character.

Compared to lazy positions alone, pretty-printed input (twitter,
citm_catalog with indent 2 and 4) parses up to 13% faster and accept()
gets up to 30% faster (GCC 13 and clang 18 on x86-64, Apple clang 21 on
arm64). Minified input is unchanged within noise.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-13 17:16:52 +02:00
Niels Lohmann f23830b65e Derive the lexer position lazily for seekable input (#5809)
* Derive the lexer position lazily for seekable input

The lexer counted the read position on every character: two increments
and a newline check per get(), all on members kept in memory. For
seekable input (pointers, strings, other random-access byte ranges) the
position can be derived instead: chars_read_total is the adapter's read
count (including reads at EOF) minus a pending unget, and line and
column are recomputed from the consumed input only when get_position()
is called, i.e. on parse errors. JSON_DIAGNOSTIC_POSITIONS uses the new
O(1) get_chars_read_total(). Stream, file, wide-string and user-defined
adapters keep the eager counters.

Parsing pretty-printed input gets 8-12% faster and accept() 12-27%
(canada, citm_catalog, twitter; clang 21 arm64 and GCC 13 x86-64).
Error messages, byte offsets, SAX positions and diagnostic positions are
unchanged (differential comparison against develop on 548k inputs).

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

* Move the std::vector<std::byte> binary type tests out of unit-regression3

The #4804/#4209 tests instantiated a second basic_json specialization
(with_binary_t<std::vector<std::byte>>), including its parser and CBOR
reader. With clang 18, the C++20 object of unit-regression3.cpp had
32656 COFF sections on develop; the lazy position helpers pushed it to
32975, past what the MinGW linker of the Windows clang jobs handles
("relocation truncated to fit: IMAGE_REL_AMD64_REL32 against .rdata").
unit-custom-binary-type.cpp already instantiates the same type, so the
tests move there; unit-regression3.cpp drops to 27616 sections.

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

* Report the parse errors of the position test via SAX

The test caught json::parse_error, so it aborted in the
ci_test_noexceptions build, where JSON_NOEXCEPTION turns the throw into
std::abort(). sax_parse() hands the error position and the exception
object to parse_error() without throwing, so the test now records them
there and runs in every configuration.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-13 17:16:52 +02:00
satelliteprogrammer 40a62947d3 support JSON Merge Patch (RFC 7396) diff creation (#4965)
* support JSON Merge Patch (RFC 7396) diff creation

The JSON merge patch document format describes the set of modifications
to a resource's content, that more closely mimics the syntax of the
resource being modified.

However, and in contrast to JSON Patch (RFC 6902), a JSON Merge Patch
cannot express certain modifications, e.g., changing an array element
at a specific index, or setting a specific object value to null.
The null value in a JSON Merge Patch is used to remove the key from the
object.

The diff algorithm is not part of the RFC 7396, but it was tested
against all examples provided, plus additional cases on how null values
are handled.

Signed-off-by: Luís Murta <luis@murta.dev>

* improve algorithm efficiency

Signed-off-by: Luís Murta <luis@murta.dev>

* fix inconsistent nulls and empty arrays

Also add CHECKs for the patch, documentation and run `make amalgamate`.

Signed-off-by: Luís Murta <luis@murta.dev>

* documentation cleanups

Signed-off-by: Luís Murta <luis@murta.dev>

* add an iterative fallback to merge_diff

Bound the recursion depth like diff() and merge_patch(), and test values
nested past the bound.

Signed-off-by: Luís Murta <luis@murta.dev>

* address the remaining review comments

Signed-off-by: Luís Murta <luis@murta.dev>

* move multi-line raw strings out of CHECK macros

GCC 4.8/5, ICPC and NVHPC mis-tokenize multi-line raw string literals
inside macro arguments, breaking the build or the parsed JSON.

Signed-off-by: Luís Murta <luis@murta.dev>

---------

Signed-off-by: Luís Murta <luis@murta.dev>
2026-10-12 09:33:43 +02:00
Niels LohmannandClaude Opus 5.5 b38a2c9177 Stop the BON8 writer overflowing the stack on deep values (#5806)
* Stop the BON8 writer overflowing the stack on deep values

to_bon8() recursed once per nesting level, so a value the iterative
BON8 reader accepts (e.g. ~24k nested one-element arrays) crashed on
the way back out. #5781 bounded the CBOR, MessagePack, and UBJSON/BJData
writers, but BON8 was merged before it and was not covered.

Apply the same scheme: recurse for the first recursion_depth_limit()
levels, then finish the value with write_bon8_iterative, which keeps
the open containers on a heap stack (reusing binary_container_frame)
and writes the 0xFE closer when it leaves a container with more than
four elements. The output is byte-for-byte unchanged.

Fixes https://issues.oss-fuzz.com/issues/572238015

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

* Merge the array and object branches of the BON8 iterative writer

write_bon8_iterative and write_bon8_value_or_push handled arrays and
objects in separate branches that repeated the end-of-container check,
the 0xFE closer and the marker computation. Share those parts and branch
only where arrays and objects really differ. The output is unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Hz7VJi1FTKr6gpseLErbbS
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-11 08:24:35 +02:00
Niels Lohmann eb8899a29c Restore v3.12.0 support for custom object key types (#5795)
* Restore v3.12.0 support for custom object key types

Custom object_t types whose key_type is not string_t compiled with
v3.12.0 for several APIs that unreleased changes broke:

- to_bson failed for every custom key type (#5553 kept a const string_t*
  to the key); the nested entry's header is now written where the entry
  is found.
- Copying deep values (and parse, merge_patch, update, insert) required
  operator== on keys (#5389); keys without one are now paired via find().
- to_cbor/to_msgpack required an implicit conversion to string_t (#5746,
  #5328); keys without one go through a temporary basic_json again.
- at() required a conversion to string_t for its error message (#5727);
  other keys are passed to concat() unchanged again.

The new unit-custom-object-key-type.cpp covers five key types with
different capabilities.

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

* Use the with_object_t alias for the custom object key test types

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

* Avoid floating-point equality in custom key type test

GCC with -Werror=float-equal rejects comparing the double value with ==.

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

* Write the head of nested BSON elements in one helper

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

* Suppress bugprone-return-const-ref-from-parameter in key_for_message

The reference is only passed to concat() within the full-expression that
holds the key, like the similar helpers in binary_writer.hpp.

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

* Make the value of the custom test key types private

clang-tidy (cppcoreguidelines-non-private-member-variables-in-classes)
rejects the protected member; the derived key types use a protected
accessor instead.

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

* Pass keys with data() and size() unchanged into the at() miss message

key_for_message() converted every key that string_t can be constructed
from, so a miss on a string_t or string_view key copied it before
concat() copied it again. Keys that concat() can append through data()
and size() are now passed through; only other keys (string literals,
key types that just convert to string_t) are converted.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-11 08:24:31 +02:00
Niels Lohmann 74a03dec84 Throw type_error.321 for discarded values in to_bon8 (#5802)
write_bon8_value silently skipped discarded values, but the array/object
count marker still counted them, so [1, discarded] produced 82 91: a marker
announcing two elements followed by one. Throw type_error.321 like the other
binary writers do, at any nesting level.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-11 08:22:00 +02:00
Niels Lohmann 2cca04ae6f Report one-character non-numeric array indices like longer ones (#5800)
* Report one-character non-numeric array indices like longer ones

A JSON pointer reference token that is not a number but has only one
character (e.g. "/a/x") was reported as out_of_range.404 ("unresolved
reference token"), because the "is not a number" check only ran for
tokens longer than one character; "/a/xy" got parse_error.109. Both now
throw parse_error.109. "-" and the empty token are still reported as
out_of_range.404. As a consequence, value(json_pointer, default) on an
array now throws for "/x" as it already did for "/xy".

Also document why ordered_map::erase's destroy/placement-new loop on
pair<const Key, T> is kept despite [basic.life]/8 before C++20.

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

* Document the one-character array index change

Add 3.13.0 version-history entries to at, operator[], value, patch,
patch_inplace, and unflatten, and describe in exceptions.md which array
indices throw parse_error.109 and which out_of_range.404.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-11 08:21:41 +02:00
Niels Lohmann 1649d9eda4 Use and extend the detail helpers to remove duplicated code (#5783)
* Use and extend the detail helpers to remove duplicated code

Library:
- binary_reader: format bytes with hex_byte() instead of snprintf
- add throw_type_must_be() for the 20 copies of type_error.302
- binary_reader: add last_byte_error()/unexpected_byte() for the 32
  "parse error at the last read byte" sites (replaces bon8_error)
- json_sax: add check_container_size() for out_of_range.408 and
  diagnostic_positions::set_container_start/_end()
- json_pointer: add throw_no_parent() (405) and throw_unresolved() (404)

Tests:
- unit-class_parser uses the shared utils::SaxCountdown
- move SaxEventLogger (and its ExitAfter* variants) from unit-class_parser
  and unit-deserialization into the new tests/src/test_sax.hpp

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

* Factor out more repeated error paths and test boilerplate

Library:
- add throw_cannot_use_with() for the 34 copies of type_error.304-312
  "cannot use X with Y"
- iter_impl: add throw_cannot_get_value() (invalid_iterator.214)
- parser: add syntax_error() for the 12 parse_error.101 sites
- ordered_map: share the four at() bodies via at_impl()
- json_sax_dom_callback_parser: add pop_container() for end_object()
  and end_array()
- binary_reader: build the two UBJSON/BJData length-type messages with
  concat() and last_byte_error()

Tests:
- move same_value(), the NDEBUG guard, and step 0 (parse without
  exceptions) of the seven fuzzer drivers into tests/src/fuzzer_common.hpp

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

* Name the exception ids and address review comments

Add detail::exception_id, a scoped enum with one named enumerator per
documented exception id, and use it for every id in the library. The
create() functions get an overload for it; the int overloads stay for
user code.

Following the review of #5783: add binary_reader::invalid_byte() and
length_type_error(), basic_json::throw_subscript_wrong_type(), move the
fuzzer includes and the using-declaration into fuzzer_common.hpp, and
rename test_sax.hpp to sax_event_loggers.hpp.

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

* Silence -Wweak-vtables for the SAX event loggers

The loggers moved from anonymous namespaces in the test files into
sax_event_loggers.hpp, so clang now warns that their vtables are
emitted in every translation unit.

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

* Silence MSVC 2015 C4100 in parser::syntax_error for static SAX::parse_error

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

* Inline invalid_byte() into its call sites

The wrapper only fixed the message string of unexpected_byte(), which is
the same kind of per-argument helper that was declined for
throw_type_must_be(). Call unexpected_byte("invalid byte", ...) directly.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-11 08:21:13 +02:00
Bas van Dijkandbvandijk 84ee12a67c Make UTF8_ACCEPT/UTF8_REJECT inline variables to avoid TU-local exposure in modules (#5797)
Signed-off-by: bvandijk <bas.van.dijk@cern.ch>
Co-authored-by: bvandijk <bas.van.dijk@cern.ch>
2026-10-09 23:38:42 +02:00
Niels Lohmann 2913e96433 Unflatten in time and memory linear in the pointer depth (#5793)
* Unflatten in time and memory linear in the pointer depth

#5443 made unflatten() decide between arrays and objects independently
of the iteration order by collecting the pointer prefixes that have a
reference token 0 below them in a std::set<std::vector<string_t>>.
Every such prefix was stored as a copy of all its reference tokens, and
get_and_create() compared whole prefix vectors at every step, so
unflattening a pointer of depth d took time and memory quadratic in d:
a 10,000-level array pointer took 18 s and 1.3 GB, a 100,000-level one
did not finish.

The prefixes are now numbered nodes of a tree, so each is stored once
and get_and_create() follows the tree token by token. The result is
unchanged, including its independence of the iteration order.

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

* Initialize prefix_tree members to satisfy -Weffc++

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

* Move prefix_tree setup and child insertion into member functions

The constructor now creates the root node, add_child() inserts a
reference token below a prefix and returns the child's number, and
find_child() looks one up for get_and_create().

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-09 17:57:31 +02:00
Niels Lohmann 44e8597701 Flatten deeply nested values without recursing per nesting level (#5792)
* Flatten deeply nested values without recursing per nesting level

json_pointer::flatten() called itself once per nesting level, so
flatten() on a value nested deeply enough exhausted the call stack.
#5547 and #5548 fixed merge_patch() and diff() from #5393, but flatten()
was left out.

flatten() now walks the value with an explicit stack and keeps the path
in one buffer that grows and shrinks with it. It has a single code path
and no depth limit: the old version built a new path string per child,
so the iterative one is no slower on shallow values and much faster on
deep ones. The output, including the order of an ordered_json result,
is unchanged.

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

* Construct flatten frames in place

Give the frame a constructor so both call sites can use emplace_back, as
suggested in the review; index starts at 0 for every frame.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-09 17:06:41 +02:00
Niels Lohmann 374dfe4f0f Keep converted object keys alive while writing UBJSON and BJData (#5791)
* Keep converted object keys alive while writing UBJSON and BJData

Since #5746, write_ubjson and write_ubjson_iterative pass each object key
to sanitize_utf8_for_write and keep the returned reference. When
object_t::key_type is not string_t but converts to it, the argument is a
temporary that is destroyed at the end of the statement, and the
function returns a reference to it in every case but a sanitized copy,
so the key bytes are read from a dead object (AddressSanitizer:
stack-use-after-scope). Default json and ordered_json are unaffected.

Bind the key to a named object_key_string_t first: a reference when
key_type is string_t, so no copy is added there, and a converted copy
otherwise. A deleted overload of sanitize_utf8_for_write for anything
other than string_t turns a recurrence into a compile error.

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

* Suppress -Wunused-member-function for the converting_key test type

converting_key::data() is only called when JSON_DIAGNOSTICS is enabled.

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

* Fix clang-tidy findings in the UBJSON/BJData converted-key fix

Suppress hicpp/modernize-use-equals-delete on the deleted
sanitize_utf8_for_write overload: it guards a private helper and must stay
private. Replace the C-style array in the new test with std::array.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-09 17:05:36 +02:00
Alex Prabhat Bara 69a0c1b82c Avoid allocating temporary basic_json for cbor and msgpack object keys (#5328)
* avoid allocating temporary basic_json for CBOR and MessagePack object keys

Signed-off-by: alexprabhat99 <alexpbara@gmail.com>

* add size() to the custom object key test type

UBJSON and BJData access object keys through size() and c_str()
directly, so the key type now provides both and the comment says why.

Signed-off-by: alexprabhat99 <alexpbara@gmail.com>

* address review: drop key size()/c_str(), test keys below the depth limit

Nothing in the library calls size() or c_str() on an object key, so the
test key type only keeps data(), which JSON_DIAGNOSTICS needs.

The CBOR and MessagePack custom key tests now also nest objects deeper
than detail::recursion_depth_limit(), so keys written by
write_cbor_iterative and write_msgpack_iterative are covered as well.

Signed-off-by: alexprabhat99 <alexpbara@gmail.com>

---------

Signed-off-by: alexprabhat99 <alexpbara@gmail.com>
2026-10-09 13:22:07 +02:00
Suyog Verma a269794db7 Use MSVC intrinsics for full multiplication (#5782)
* Use MSVC intrinsics for full multiplication

Signed-off-by: Suyog Verma <suyogverma0057@gmail.com>

* Fix formatting in unit-class_lexer

Signed-off-by: Suyog Verma <suyogverma0057@gmail.com>

* Address review feedback

Signed-off-by: Suyog Verma <suyogverma0057@gmail.com>

---------

Signed-off-by: Suyog Verma <suyogverma0057@gmail.com>
2026-10-08 08:49:32 +02:00
Niels LohmannandAfonso Januário a5f5d3059b Make std::hash<basic_json> consistent with operator== for numbers (#5772)
* Make std::hash<basic_json> consistent with operator== for numbers

operator== converts between number_integer, number_unsigned, and
number_float before comparing, so json(0), json(0U), and json(0.0)
all compare equal. hash() folded the specific value_t into the
result for each of the three numeric cases, giving each a distinct
hash and breaking the standard Hash requirement that a == b implies
hash(a) == hash(b). A std::unordered_set could therefore hold all
three as separate elements even though they compare equal.

hash() now treats all three numeric variants the same way: it
converts the value to number_float_t and combines it with a single
shared type tag, so any two numbers operator== considers equal hash
identically regardless of which internal type actually holds them.

Updated the accompanying test to check this consistency directly
(including via an actual unordered_set) instead of asserting that 0,
0U, and 0.0 hash differently, since that assumption was the bug.
Also corrected the function's own doc comment and the std::hash API
docs, which described the old behavior as intended.

Fixes #5400

Signed-off-by: Afonso Januário <afonso-januario@hotmail.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Remove now-unused number_integer_t/number_unsigned_t typedefs in hash()

Merging the three numeric branches into one that only reads
number_float_t left these two aliases unused, which several CI
configurations treat as a build error under -Wunused-local-typedefs.

Signed-off-by: Afonso Januário <afonso-januario@hotmail.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Mark the unordered_set in the hash regression test const

clang-tidy's misc-const-correctness check flagged it: the set is
never mutated after construction, only read via size().

Signed-off-by: Afonso Januário <afonso-januario@hotmail.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Normalize -0.0 in number hashes and test range ends

operator== compares numbers exactly since #5459, so equal numbers
share one value and convert to the same number_float_t. Update the
comment accordingly, map -0.0 to 0.0 before hashing (std::hash need
not do that), and test -0.0 and the ends of the integer ranges. Show
hash(0.0) in the docs example and note the change in the version
history.

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

* Clarify hash documentation after review

- Say "may hash differently" for null, false, and numbers, since a
  collision across types is possible.
- Name the storage types (signed integer, unsigned integer,
  floating-point number) instead of example literals.
- Explain that the hash survives converting an integer to
  number_float_t but not the lossy conversion back, and that unequal
  numbers may share a hash.
- State that the example hash values are illustrative only and vary by
  platform, compiler, compiler version, and library version.

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

---------

Signed-off-by: Afonso Januário <afonso-januario@hotmail.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Afonso Januário <afonso-januario@hotmail.com>
2026-10-07 19:18:51 +02:00
43fe8928e1 Stop binary writers overflowing the stack on deep values (#5781)
* Stop binary writers overflowing the stack on deep values

to_cbor, to_msgpack, and to_ubjson recurse once per nesting level.
The parser is iterative, so a value the library accepts can crash on
the way back out.

Keep the existing recursive path for the first 128 levels and finish
anything deeper on a heap stack. Output is unchanged. BSON is left
alone because its extra size walk is a separate change.

Rebased onto the value-type output sink. The heap frames now initialize
every member, which is what -Weffc++ was rejecting.

See #5392.

Signed-off-by: ayush-singh-0601 <singhayush062006@gmail.com>
(cherry picked from commit cf65ac438f)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Redesign the iterative binary writers around a shared recursion depth limit

Address the open review on the non-recursive CBOR/MessagePack/UBJSON/BJData
writers (#5518):

- Delete the CBOR array/object prefix helpers; both the recursive and
  iterative paths call write_cbor_head(), which already existed on develop.
- MessagePack: share one write_msgpack_array_prefix()/write_msgpack_object_prefix()
  helper per container kind between the recursive and iterative paths, both
  going through to_msgpack_length() so an over-long container throws
  out_of_range.412 identically either way.
- Reuse detail::recursion_depth_limit() instead of a separate constant, the
  same bound serializer::dump() and write_bson_document() already use.
- Redesign the frames after bson_frame/dump_frame: only a container with
  elements is ever pushed, its header is written at the point it is pushed,
  and the iterator is set in the frame's constructor instead of a
  default-then-assign two-step with a since-removed "started" flag. The
  UBJSON frame keeps only the value pointer, the per-element prefix_required
  flag, and the iterator; write_closer and is_object are no longer stored,
  since the former is always !use_count (use_count is constant for the whole
  document) and the latter follows from value->is_object().
- Factor the BJData ND-array shape check into is_bjdata_ndarray(), used by
  both the recursive object case and the iterative pushing logic.
- Give the frame classes the GCC -Weffc++ treatment already used for
  diff_frame: a noexcept converting constructor plus the five special members
  defaulted with no explicit noexcept.
- Fix two @ref self-references in write_cbor/write_msgpack/write_ubjson's own
  doc comments to point at the public to_cbor/to_msgpack/to_ubjson/to_bjdata
  API instead.
- The iterative object-key write for CBOR/MessagePack now runs the same
  strict-mode check_utf8() against the parent object as diagnostics context
  that the recursive path already ran, so the two paths raise identical
  diagnostics across the switch-over.
- Rewrite the tests: round trips instead of a bare size check, byte-exact
  comparisons against the recursive output at depths around the bound, a
  deep object and a BJData ND-array past the bound, a deep discarded value
  (type_error.321), and the OSS-Fuzz 566583014 CBOR/MessagePack regression.

BSON is unaffected by this change; it already walks its documents
iteratively and is covered separately by #5553.

Co-authored-by: ayush-singh-0601 <179524189+ayush-singh-0601@users.noreply.github.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: ayush-singh-0601 <singhayush062006@gmail.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: ayush-singh-0601 <singhayush062006@gmail.com>
Co-authored-by: ayush-singh-0601 <179524189+ayush-singh-0601@users.noreply.github.com>
2026-10-07 19:18:20 +02:00
Niels Lohmann 069ace74af Round-trip BJData ND-array annotations exactly (single precision, key order) (#5707)
Squashed onto develop from:
- Round-trip BJData ND-array annotations exactly (single precision, key order)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-07 19:17:18 +02:00
Niels Lohmann 367336c83d Fix CI on develop after #5585 (#5779)
* Fix CI on develop after #5585

- test-diagnostics-optimized: -O3 makes GCC's -Winline and
  -Wsuggest-attribute=pure/const warnings fire with the ci_test_gcc flag
  set; turn them off for this test.
- test-diagnostics-optimized: suppress Clang's -Wexit-time-destructors for
  the static table in to_json.
- Infer: raise pulse-max-disjuncts from 20 to 40. With the default,
  Pulse loses the stored type in basic_json::replace_value() and reports
  false null dereferences of get_ptr() results in unit-pointer_access.cpp.

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

* Ignore Infer's false USE_AFTER_DELETE in ordered_map::erase

Infer's std::string model keeps the buffer of a moved-from string, so the
destroy-and-reconstruct loop in erase(first, last) looks like it destroys a
buffer twice.

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

* Mark throw_on_discarded()'s parameters as used without exceptions

With JSON_NOEXCEPTION, JSON_THROW expands to std::abort(), so Clang's
-Wunused-parameter breaks test-disabled_exceptions (since #5761).

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

* Skip the span_input_adapter sax_parse checks with deleted deprecated functions

The #5676 regression test (#5740) calls the deprecated
sax_parse(span_input_adapter&&, ...), which JSON_DELETE_DEPRECATED_FUNCTIONS
deletes, so ci_test_delete_deprecated_functions failed to build.

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

* Fall back to the first entry in test-diagnostics-optimized's to_json

clang-tidy (clang-analyzer-security.ArrayBound) flagged it->second for a
value not in the table. Use the same fallback as
NLOHMANN_JSON_SERIALIZE_ENUM; the test still fails with -Werror=array-bounds
on the headers from before #5585.

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

* Fix clang-tidy findings in tests from #5762 and #5774

- unit-regression2.cpp (#5762): const/auto for the destroy() test values;
  NOLINT the intended copy in check_destroy_edge_case().
- unit-serialization.cpp (#5774): build the expected strings with += instead
  of chained operator+ (performance-inefficient-string-concatenation).

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-07 16:37:19 +02:00
Niels Lohmann 30e542e52a Declare the namespace-scope constants in to_chars.hpp inline (#5776)
MSVC warns with C5260 that kAlpha and kGamma have internal linkage when
the header is used as a header unit or through a module. JSON_INLINE_VARIABLE
makes them inline variables from C++17 on.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-07 09:03:18 +02:00
Niels Lohmann 1c754cfe31 Copy a pair-shaped array value under JSON_BRACE_INIT_COPY_SEMANTICS (#5701)
With JSON_BRACE_INIT_COPY_SEMANTICS enabled, single-element brace
initialization from a JSON value decided whether to copy the value or
build an object by inspecting the value's runtime shape: a two-element
array whose first element is a string, such as ["key", 42], was turned
into an object instead of being copied. This made the behavior depend
on the element's content, and it did not distinguish an existing value
of this shape from a nested braced pair written in the source, such as
the inner {"key", "value"} of {{"key", "value"}}.

json_ref now records whether it was constructed from a braced list
(true only for the std::initializer_list<json_ref> constructor used
for nested braced lists) or from a value. The initializer-list
constructor uses this to copy or move a single non-braced-list element
before deciding whether the list describes an object, so a JSON value
is always copied regardless of its shape, while a braced pair written
in the source still creates an object.

Fixes #5662.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-07 07:39:05 +02:00
Niels LohmannandJoseph.Demarest ff6f3d7d4a Reject nested indefinite-length CBOR string chunks (#5766)
* fix(cbor): reject nested indefinite string chunks

Signed-off-by: Joseph.Demarest <joseph@demarest.dev>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Address review comments on nested indefinite-length CBOR strings

Rename is_chunk to inside_indefinite, update the stale test section
names, and use lowercase comments like the surrounding code.

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

---------

Signed-off-by: Joseph.Demarest <joseph@demarest.dev>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Joseph.Demarest <joseph@demarest.dev>
2026-10-07 07:38:52 +02:00
Mohd Quamar TyagiandNiels Lohmann 675e519966 Allow SAX parsing of tagged CBOR (#5740)
* Allow SAX parsing of tagged CBOR

Signed-off-by: Tyagiquamar <mohdquamartyagi@gmail.com>

* Consolidate sax_parse overloads with default tag_handler parameter

Signed-off-by: Tyagiquamar <mohdquamartyagi@gmail.com>

* Add version history entry for tag_handler in sax_parse documentation

---------

Signed-off-by: Tyagiquamar <mohdquamartyagi@gmail.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Niels Lohmann <mail@nlohmann.me>
2026-10-07 07:38:24 +02:00
Niels Lohmann 21a69230bd Create a value before giving it its type (#5585)
* Create a value before giving it its type

Squashed onto develop from:
- Create a value before giving it its type
- Skip the failed-allocation test when exceptions are disabled
- Keep the created pointer rather than an uninitialized json_value
- Skip the vector<bool> failed-allocation check for VS 2015 with iterator debugging
- Test the remaining to_json overloads with a failing allocation
- Skip the to_json allocation-failure section on VS 2015 Debug
- Fix false GCC -Warray-bounds error with JSON_DIAGNOSTICS at -O3 (#5744)

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

* Store the new value with a helper in all to_json constructors

Every external_constructor<>::construct now creates the new value first and
hands it to basic_json::replace_value(), which destroys the old value, stores
the new one before setting its type (as elsewhere in this PR), sets the
parents, and checks the invariant.

The std::vector<bool> and std::valarray overloads use array_t's range
constructor, which the other array overloads already rely on. Range views
keep their loop, as begin() and end() of a view may have different types.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-06 22:59:34 +02:00
162e13b86f Add with_*_t alias templates to create basic_json types with changed template parameters (#5758)
* Add helper types to make it easier to create a basic_json type with modified template parameters

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

* Rename with_changed_*_t aliases to with_*_t and merge integer/unsigned aliases

Per review discussion on #3898 between gregmarr and nlohmann:
- rename with_changed_X_t to with_X_t for brevity
- replace the separate with_changed_integer_t/with_changed_unsigned_t
  aliases with a single with_integers_t<NumberIntegerType2, NumberUnsignedType2>
- add @sa doc comment links for the upcoming documentation page

Co-authored-by: Raphael Grimm <1005058+barcode@users.noreply.github.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Add documentation for the with_*_t member alias templates

Add docs/mkdocs/docs/api/basic_json/with_t.md documenting with_object_t,
with_array_t, with_string_t, with_boolean_t, with_integers_t, with_float_t,
with_allocator_t, with_json_serializer_t, with_binary_t and with_base_class_t,
with an accompanying example, and link the page from the basic_json member
types list and the mkdocs navigation.

Co-authored-by: Raphael Grimm <1005058+barcode@users.noreply.github.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Add tests for the with_*_t member alias templates

Check with std::is_same that each with_*_t alias produces the expected
basic_json type, and that with_string_t keeps nlohmann::ordered_map as
the object type when used on ordered_json.

Co-authored-by: Raphael Grimm <1005058+barcode@users.noreply.github.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix with_t nav entry and document chaining of the with_*_t aliases

Indent the with_t entry in mkdocs.yml so it is listed under basic_json,
explain that the aliases can be chained and work on ordered_json, and
test both, including json::with_object_t<ordered_map> == ordered_json.

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

* Add docset entry for basic_json::with_t

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: barcode <barcode@example.com>
Co-authored-by: Raphael Grimm <1005058+barcode@users.noreply.github.com>
2026-10-06 22:33:29 +02:00
fhgffy 69874e4544 Fix NUL bytes in UBJSON/BJData high-precision numbers (#5760)
* Fix NUL-terminated UBJSON and BJData high-precision payloads

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

* Use English comments for the high-precision NUL fix

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

* Track NUL bytes while reading high-precision payloads

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

* Drop dates from code comments.

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

* Report a NUL in a high-precision number where it is read

Return the parse error from the read loop so the byte offset points at the NUL, and drop the separate check after lexing.

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

* Use fixed text for the high-precision NUL error

2026-10-06: Use the known zero byte directly instead of formatting and concatenating it. Preserve the SAX token, error message, and byte offset.
Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

---------

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>
2026-10-06 22:30:52 +02:00
fhgffy 9b179cee1e Handle all value_t enumerators in has_no_children() (#5770)
2026-10-07: add the scalar enum labels already handled by the default
branch so -Werror=switch-enum builds succeed. Keep the existing behavior
and synchronize the generated single header.

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>
2026-10-06 22:29:22 +02:00
Niels Lohmann 6d4543e743 Fix destroy() for ObjectTypes without reverse iteration (#5767)
The non-recursive destroy walk from #5762 picked an object's last child
via object_t::rbegin() and std::prev(end()). Neither is available for
every ObjectType: no_key_compare_map in unit-custom-object-type.cpp has
no rbegin(), so develop no longer compiles that test, and hash maps such
as std::unordered_map only have forward iterators.

The walk can take an object's children in any order, as long as it
finds the same child again while the object is not modified in between.
So objects with bidirectional iterators keep using their last child
(O(1) to remove from vector-based maps like ordered_map), and objects
with forward-only iterators use begin() instead. No reverse iteration
or rbegin() is needed any more, and the walk stays allocation-free.

Adds a forward-only ObjectType to the tests, destroyed both with mixed
nesting and 100000 levels deep.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-06 22:29:13 +02:00