Commit Graph
479 Commits
Author SHA1 Message Date
Niels Lohmann c25aad3ca5 Merge branch 'develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-21 11:59:40 +02:00
Niels Lohmann 43e97b629b Add element access, iteration, values, and JSON pointers to json_view (#5622)
* Add element access, iteration, values, and JSON pointers to json_view

Give basic_json_view the read-only access functions of basic_json:
operator[] and at() with keys and indices, front()/back(), find(),
contains(), count(), begin()/end() and cbegin()/cend(), items()
with structured bindings from C++17 on, and type_name().

Exceptions have the ids and messages of the const functions of
basic_json. Where basic_json has undefined behavior the view
answers safely: operator[] with a missing key or an out-of-range
index returns a discarded view, and front()/back() of an empty
container throw invalid_iterator.214. Objects are iterated in
document order, and all members are visited; duplicate-key lookups
find the first member (as yyjson and simdjson do), while parse(),
materialize(), and the map conversions keep the last value, as
parse() does. Keys of up to 16 bytes are compared with two
overlapping loads.

Add value conversions: get<T>()/get_to() for arithmetic types,
bool, nullptr_t, strings (std::basic_string copied,
string_view_t without a copy), BasicJsonType, views, std::vector,
and maps with string keys; get_string() for the string without a
copy; number_token() for the number exactly as written in the
source; value() with keys and JSON pointers; and operator[]/at()/
contains() with JSON pointers. Everything else, including types
with from_json(), goes through materialize() of that subtree.
get<T>() of arithmetic types is inlined down to the conversion, so
reading an integer needs no call.

detail::json_pointer_access exposes a pointer's reference tokens
to code outside basic_json.

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

* Make view lookups last-wins and chained access safe

* Lookups (operator[], at, find, contains, count, value, JSON pointers)
  return the last member of a duplicate key, as materialize() and
  parse() keep it.
* operator[] on a discarded view returns a discarded view instead of
  throwing, so v["a"]["b"] is safe for a missing "a".
* operator[] and at() take any integer type (not only int and size_t),
  fixing ambiguous calls with unsigned, long, std::int64_t, ...
* Fix the operator[] documentation, which claimed a discarded view for
  a type mismatch where type_error.305 is thrown.

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

* Replace the removed operator bool of basic_json_view in the header and its tests

A view is tested with is_discarded(); the lookups in at(), value() and
contains(json_pointer) and the unit tests no longer rely on the explicit
conversion to bool.

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

* Use named documents in the json_view tests that called root() on a temporary

root() of an rvalue document is deleted, because the views would dangle.

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

* Test discarded views with is_discarded() in the operator[] docs and examples

The explicit conversion to bool of basic_json_view is gone.

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

* Return the first member of duplicate keys from lookups again

Looking up the last member of a duplicate key cannot stop at a match, so
every lookup scanned the whole object (1.6 to 3.4 times slower for small
objects). operator[](key), at, find, value, contains, count, and JSON
pointer resolution return the first member again, as yyjson and simdjson
do; materialize() and get<map>() keep the last value, as parse().

The documentation says so in the feature page and on each lookup page,
and explains how to get the value parse() would give. The integer index
templates and the discarded chaining of operator[] stay.

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

* Do not force-inline the view's functions on MSVC

__forceinline makes MSVC report C4714 for function templates it cannot
inline (get<std::string>), an error under /WX. The forced inlining is
only a performance hint, so use plain inline there.

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

* Make json_view.hpp pass include-what-you-use

Mark the includes that are needed by design (json.hpp, the macro
unscope, <tuple> for the tuple_size specialization), take size_t from
<cstring>, and drop the forward declaration of basic_json_document that
the friend declaration makes redundant.

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

* Avoid GCC useless-cast warnings in the integer index tests

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

* Make json_view.hpp pass include-what-you-use

ci_single_binaries runs IWYU with --error on every header. For json_view.hpp
it suggested adding <array> (std::array is used), the headers that json.hpp
already provides (abi_config, abi_macros, input_adapters, json_pointer,
cpp_future, string_concat, value_t, json_fwd), and <version> for
std::nullptr_t, and removing <cstddef>.

- include <array>
- keep <cstddef> (nullptr_t, size_t; IWYU attributes them to <version> and <cstring>)
- tell IWYU not to suggest the headers that json.hpp provides: the amalgamated
  json_view.hpp only includes json.hpp, so including them here would duplicate
  their definitions

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

* Fix the clang-tidy 22 findings in json_view and its tests

The same changes as on the dump branch, where they were first made, so
that this branch passes clang-tidy on its own.

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

* Regenerate the amalgamated headers

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

* Report one-character non-numeric array indices like basic_json in the view

Develop's #5800 made basic_json report a JSON pointer array index such as
"/a" as parse_error.109 instead of out_of_range.404, as longer ones were;
the view's array_index() follows, with "-" and the empty token still
unresolved.

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

* Address the review of json_view element access

From gregmarr's review of #5622:

- count() counts every member with the key, so count(key) > 1 detects
  duplicate keys; it was contains() as 0/1 before.
- get_to() passes types that get<T>() does not convert directly to
  from_json with the existing value, as basic_json::get_to() does, so that
  a from_json which sets only the fields present keeps the others.
- array_index() checks the empty token and "-" first; the results are
  unchanged.
- Docs: no "if an exception is thrown" where a view never changes
  anything; the borrowed source must also stay unmodified; items() on a
  temporary view is safe; back()/front() notes shortened; the basic_json
  see-also entries say how the view's results can differ.

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

* Regenerate the amalgamated headers

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

* Count matching keys as unsigned in the json_view access test

The conditional added 1 or 0 as int to a std::size_t, which GCC rejects
with -Werror=sign-conversion (ci_test_standards_gcc).

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

* Address the second review round of json_view element access

From gregmarr's review of #5622:

- begin()/end(): "a null value or a discarded view iterates as an empty
  range", singular like the primitive case before it.
- The class page's list of function groups has no trailing commas.
- document_data::key_equals() compares a key node with a string, for the
  key comparisons that were spelled out in each lookup.

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

* Regenerate the amalgamated headers

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

* Write the negated enable_if conditions of json_view with negation<>

With a ! or && in the condition, astyle spaces the whole template
header (template < ... >); detail::negation and a named trait keep it
compact, as the library writes such conditions elsewhere. From gregmarr's
review of #5630.

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

* Regenerate the amalgamated headers

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

* Keep detail::negation out of json_view.hpp's enable_ifs

include-what-you-use asks json_view.hpp to include
detail/meta/type_traits.hpp for it, which the single header must not do
(the amalgamation would duplicate json's internals). The two conditions of
value() go through a trait in value.hpp, like the others.

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>
2026-10-21 10:21:27 +02:00
Niels Lohmann 122d718330 Add json_document and json_view: node index, parser, and document (#5620)
* Add json_document and json_view: node index, parser, and document

Add json_document and json_view, a read-only, zero-copy index of a
JSON text, as the first public slice of the zero-copy view (#5295).

A parse produces a flat array of 16-byte nodes in document order,
one per value and one per object key. Strings stay in the source
text; escaped strings are decoded into an arena. Integers are
converted while their digits are in the cache; floats keep only
their digit layout and are converted on read. Containers store the
size of their subtree, so a reader can step over one in constant
time. A document makes a handful of allocations, however many
values it has.

The parser accepts exactly what json::parse accepts, with every
combination of ignore_comments and ignore_trailing_commas, with and
without a trailing NUL, and under JSON_STRICT_NUL_HANDLING. It is
portable C++11 and does not depend on byte order.

basic_json_document adds parse, parse_copy, accept, read (reuses a
document's memory), root, is_discarded, source, owns_source,
node_count, memory_usage, and shrink_to_fit. basic_json_view adds
type, the is_* queries, operator bool, size, empty, materialize,
and source_offset. A parse error throws the same exception
basic_json::parse would throw for the same input, message and
position included.

detail::abi_config keeps JSON_STRICT_NUL_HANDLING and
JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON readable after json.hpp
undefines them, in the ABI namespace so they always match the
basic_json in use.

A NUL byte that ends a // comment is the end of the input, as in
parse() since #5696.

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

* Fix document_data for old Clang (3.4-3.6)

Drop the empty braced NSDMIs of the std::string members: old Clang
rejects the defaulted constructor when it is used by a member
initializer before the end of the class definition.

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

* Exclude libstdc++'s string_view comparison from the sign-change check

basic_string_view::_S_compare stores the difference of two lengths in a
signed difference_type on purpose, which -fsanitize=integer reports for
every comparison with a shorter view (test-json_view_cpp17).

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

* Reject integer lengths in json_document::parse

parse(ptr, len) compiled: len converted to allow_exceptions, and ptr was
read as a C string, past the end of a buffer without a terminating NUL.
Delete the overloads of parse, parse_copy, accept, and read that take an
integer other than bool where the flags are expected.

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

* Copy const rvalue strings and document the accepted inputs

json_document::parse(std::move(const_string)) failed to compile with
"no matching read_kind": only a non-const rvalue std::string can be moved
from. Treat a const rvalue as a copied byte container.

parse() does not accept everything BasicJsonType::parse() does: a FILE*
and pointers to or arrays of wide characters are rejected at compile time.
List the supported inputs instead.

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

* Remove the conversion to bool from json_view

explicit operator bool meant "refers to a value", which silently differs
from what a basic_json converts to. Use !v.is_discarded() instead.

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

* Delete json_document::root() on temporary documents

auto v = json_document::parse(text).root() compiled and left the view
dangling. Delete the overload for rvalue documents, take a named document
in the tests, and document the lifetime rule.

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

* Store node integers by halves on big-endian targets

The non-little-endian path of the node writer wrote the integer's native
word over len and next, so len got the high half there. Compose and split
the value explicitly (len is the low half, next the high half); the
little-endian path stays a plain memcpy.

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

* Check the node array size for overflow

reserve(n) and the growth of the index computed n * sizeof(node) without a
check, which wraps around on 32-bit targets for inputs of about 1 GiB and
allocates a too small array. Throw std::bad_alloc for a count beyond the
address space and clamp the growth step to it.

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

* State the exact input size limit of json_document

The check rejects inputs of 0xFFFFFFF0 bytes or more, but the exception
message and the documentation said 4 GiB. Name the limit once
(max_input_size), and state 4 GiB minus 16 bytes in the message and the
documentation. Test the limit with a container that only claims the size.

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

* Remove the unused legacy_discarded_value_comparison from abi_config

Nothing reads it: the view does not compare values.

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

* Align the banner comment of json_view.hpp

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

* Fuzz json_document with exact-size buffers and parse options

The fuzzer only parsed a std::string with default options. Also parse an
exact-size byte vector, which has no NUL after its last byte and takes the
bounds-checked path, and derive ignore_comments and ignore_trailing_commas
from the first input byte, comparing against json::parse and json::accept
with the same options.

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

* Give document_data a user-provided constructor

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

* Fix clang-tidy findings in unit-json_view_builder.cpp

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

* Annotate intentional patterns in unit-json_view.cpp for clang-tidy

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

* Suppress Flawfinder's read() finding on the deleted overload

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

* Check the steps of the deep-nesting test separately

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

* Make max_input_size a function (GCC -Wunused-const-variable)

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

* Make json_view.hpp pass include-what-you-use

ci_single_binaries runs IWYU with --error on every header. For json_view.hpp
it suggested adding <array> (std::array is used), the headers that json.hpp
already provides (abi_config, abi_macros, input_adapters, json_pointer,
cpp_future, string_concat, value_t, json_fwd), and <version> for
std::nullptr_t, and removing <cstddef>.

- include <array>
- keep <cstddef> (nullptr_t, size_t; IWYU attributes them to <version> and <cstring>)
- tell IWYU not to suggest the headers that json.hpp provides: the amalgamated
  json_view.hpp only includes json.hpp, so including them here would duplicate
  their definitions
- export json.hpp, keep macro_unscope.hpp, and drop the unused forward declaration of the document class

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

* Read the node array base after emit() in the view builder's open()

emit() moves the node array when it grows, and the subtraction read base
in the same expression, so the order was unspecified. MSVC Release builds
without forced inlining read the old base; the container index then
pointed outside the array and close() wrote out of bounds.

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

* Silence a clang-tidy use-after-move finding in the json_view test

const_text is const, so std::move does not move from it; the second call
is part of the const rvalue test.

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

* Regenerate the amalgamated headers

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

* Address the review of the view builder and document

Changes promised in the replies to the review of #5620:

- read() reuses the owned copy: a copied input (an rvalue byte container,
  a stream, FILE*, wide characters, an iterator range) is appended to the
  cleared owned buffer instead of a fresh std::string being move-assigned
  over it. A moved-in std::string still replaces it.
- The error replay runs the library parser with a SAX handler that stores
  nothing and throws the reported exception, instead of
  BasicJsonType::parse(), which built a DOM up to the error.
- Pointers to and arrays of wide characters, and FILE*, take the input
  adapter path (converted to UTF-8 into an owned buffer) instead of
  failing a static_assert. Wide pointers are NUL-terminated.
- Streams are read in blocks through rdbuf() into the buffer, instead of
  character by character through the input adapter; eofbit is set at the
  end, as by the library's stream adapter.
- tape/tape_size/tape_cap are now nodes/node_count/node_capacity.
- The builder's members get descriptive, m_-prefixed names.
- The shallow frame stack is a std::array (in a wrapper with a
  user-provided constructor: -Weffc++ wants the member initialized, and
  value-initializing the 64 frames costs up to 30 % on small documents).
- The value dispatch macro has no NEXT parameter; the switch is left with
  break, and the macro is undefined after its last use.
- literal() and digits_exceed() deduce the length from the string literal;
  each literal has one helper; the two `if (!is_float)` blocks are merged.
- arena_ensure() sits right before the writes; the decode arena is a
  std::vector<char>.
- The builder records the deepest nesting, and materialize() sizes its
  stack from it once (growing it only if a subtree is deeper).
- Comment fixes (hex4, slow_string, the NUL rule, put_utf8, 0 - m, the
  arena resize, grow()) and formatting (macro backslashes, digit cases,
  one power of ten per line, value_t assertion next to is_container()).
- build_with's template parameters follow the builder's order.

Greg's idea of keeping the source offset in `off` and the arena offset in
`next` for escaped strings was measured and not adopted: string access got
7-18 % slower with a select, and 3.5-18 % slower with a branch-free field
pick (Apple M-series, clang -O3), parsing was unchanged.

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

* Apply the review's wording fixes to the json_view documentation

- Copying is disabled because of its cost, not because of two documents
  borrowing the same buffer; the unique_ptr follows from move-only.
- Inputs: streams, FILE*, and wide characters (strings, arrays, pointers)
  are all supported and owned; point to parse_copy() for owned copies.
- The error replay only runs for failing input, builds no values, and is
  skipped with allow_exceptions = false.
- read() writes copied inputs into the previous owned copy.
- Views can dangle like std::string_view, and why there is no
  shared/weak pointer design.
- The 4 GiB limit (16-byte nodes, 16-byte scanner steps), streams being
  read to the end first, which macros apply, why materialize() has no
  source positions, and wording nits (accept() vs basic_json::accept(),
  is_binary, is_discarded, see-also lists, size table, "back into").

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

* Say that json_view converts integers while parsing

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

* Address the review: null inline nodes, trait spelling, and max() in json_view

- inline_nodes is null when the document has no inline nodes, instead of
  pointing past the end of the allocation; shrink_to_fit() no longer
  passes it to memcpy() for an empty node array
- is_byte_char and is_wide_char use conjunction/disjunction, which
  astyle leaves unspaced
- append_stream() uses (std::max) for the count read

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

* Include materialize.hpp in the view builder test

The test calls detail::view::materialize(), which only the single header
pulled in; the multiple-header build (JSON_TEST_USING_MULTIPLE_HEADERS)
failed with "'materialize' is not a member of detail::view".

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

* Rename emit() in the view builder for Qt compatibility

Qt defines emit as an empty macro, so a Qt header included before
json_view.hpp broke the declaration of the builder's emit(), see
issue #5865. It is now called push_node().

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

* Do not copy an empty run into an unallocated arena

memcpy() must not be passed a null pointer even for zero bytes, which
arena_run() did for an empty run while the arena was still empty
(ci_test_clang_sanitizer: "null pointer passed as argument 1" in
builder.hpp). Only the slow path can see such a run.

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

* Exclude the view builder test from Infer's reports

Infer's std::unique_ptr model confuses the values that the test's build()
helper returns by value and reports USE_AFTER_DELETE for one of them after
the destructor of an unrelated temporary (ci_infer, 12 reports, all in
tests/src/unit-json_view_builder.cpp). AddressSanitizer is clean on the
same tests.

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

* Skip the deleted-overload checks of json_view on MSVC 2015

MSVC 2015 does not treat selecting a deleted function in decltype as a
substitution failure, so is_detected reports the deleted
parse/parse_copy/accept/read(ptr, len) overloads as callable and the
static_asserts in "integer arguments do not compile" fail (AppVeyor
VS2015 jobs). Calling them still fails to compile there. Guard the
negative checks as unit-delete_deprecated_functions.cpp does.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-21 10:21:27 +02:00
Niels Lohmann fb729028ba Merge branch 'develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-17 08:35:02 +02:00
Niels Lohmann cd6b428ef0 Fix CI failures on develop from the API performance stack (#5860)
Fixes every CI failure develop has had since the API performance stack (#5831-#5842) was merged: compiler warnings and errors (Clang, GCC 4.9/11, MSVC 2015/2017/2022), clang-tidy, cpplint, Cppcheck, IWYU, the examples check, the no-exceptions, diagnostic-positions, implicit-conversions and strict-NUL test configurations, and the MinGW link (now with LLD).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-16 19:16:21 +02:00
Niels Lohmann c9fdfc39db Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 22:46:35 +02:00
Niels Lohmann 5683f5e024 Define less_general() only without three-way comparison (#5859)
less_general() (#5840) calls operator<(value_t, value_t), which exists in
C++20 only for GCC. Explicit instantiation of basic_json compiles every
member, so clang-cl and MSVC failed on unit-explicit_instantiation and
unit-regression2 in C++20 mode. Its only caller, operator<, is defined
only without three-way comparison, as it was before #5840.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 22:45:56 +02:00
Niels Lohmann 4da73dc5ff Fix compiler warnings on develop from the API performance stack (#5858)
These PRs were merged while their CI runs were cancelled, so the warnings
went unnoticed. All of them fail the -Werror builds:

- json_pointer.hpp (#5836): size_t += int under GCC -Wsign-conversion
- binary_reader.hpp (#5839): char_int_type passed as char under GCC
  -Wconversion
- json.hpp (#5838): @throw without a description under clang
  -Wdocumentation
- string_escape.hpp (#5836): escape_into() was inserted between escape()
  and its documentation, so the @return was attached to a void function
- unit-diagnostics.cpp (#5832): clang -Wnrvo in a lambda without an
  explicit return type
- unit-to_json-rvalue.cpp (#5837): GCC -Wnoexcept (C++20) and clang
  -Wunneeded-member-function on the test type

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 22:42:46 +02:00
Niels Lohmann c314cf8bd4 Fix the indentation of the destroy comment in json.hpp (#5857)
The comment block about destroying the tree without recursion was indented
one level too deep since #5835. make amalgamate reformatted it with astyle,
leaving an unrelated diff in every branch. single_include is unchanged.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 22:25:47 +02:00
Niels Lohmann 870bdec01f Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-15 20:56:37 +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 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 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 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
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 Lohmann 545477ffa8 Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-11 08:33:14 +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 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
Niels Lohmann a2766df787 Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-07 07:42:58 +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
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 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
Niels Lohmann 632f5369fe Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-06 07:43:24 +02:00
0a365865f9 Make basic_json destruction allocation-free and non-recursive (#5762)
* Use the provided allocator in destroy() (#4842)

Uses the provided allocator to allocate the stack used to avoid
recursion in the destroy() implementation used by ~basic_json.

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

* Test that the destructor uses the provided allocator

Adds a regression test for #4842: destroying a nested array or object must allocate its temporary stack through the basic_json allocator, not std::allocator.

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

* Fix allocation failure during JSON destruction

Signed-off-by: Michael Sam <michaelsam94@users.noreply.github.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Make json_value::destroy() non-recursive and allocation-free

destroy() used to flatten a nested array/object into a heap-allocated
std::vector to avoid recursing per nesting level. That vector could
itself throw bad_alloc under memory pressure, and since it now used the
basic_json's own allocator (#4842), a failing allocator supplied by the
caller made this more likely, not less. An exception thrown from inside
~basic_json(), which is noexcept, terminates the program (#5135).

Replace the vector-based stack with a pointer-reversal walk that visits
the tree without recursing per level and without allocating anything:
cur is the array/object currently being emptied, prev is its parent
(or null at the top). A parent's last child slot doubles as storage for
that parent's own parent link while we are below it, so no extra memory
is needed. A child is only ever removed once it is a scalar or an empty
array/object, which neither allocates nor recurses more than one level
deep. take() moves m_data between these locals directly, bypassing
set_parents()/assert_invariant() (the former is O(#children) per call
under JSON_DIAGNOSTICS, which would make the walk quadratic otherwise).

This also removes the std::vector<basic_json, allocator_type> stack
added by #4842, so the extra allocations it introduced disappear along
with it.

Co-authored-by: Michael Sam <9461037+michaelsam94@users.noreply.github.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Test that destroy() performs no allocation, even under memory pressure

Update the #4842 regression test: it used to check that destroying a
nested array/object made at least one allocation through the provided
allocator (the old flattening stack). Now that destroy() does not
allocate at all, assert the opposite: zero allocations, deallocations
only.

Rework the #5135 regression test to use a dedicated failing/counting
allocator instead of overriding the process-wide ::operator new and
::operator delete, which affected every allocation in the whole
unit-regression2 binary rather than just the values under test. Keep
the original small repro as one case, and add deep (100000 levels) and
wide-and-deep nested array/object/ordered_json cases, all destroyed
while every further allocation is made to fail: the destructor must
complete without allocating, without throwing, and without leaking.

Co-authored-by: Michael Sam <9461037+michaelsam94@users.noreply.github.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Refactor destroy() for readability and add edge-case tests

Apply review feedback from Greg Marr on the json_value::destroy()
non-recursive, allocation-free destruction walk (#5135):

- last_child() now uses object->rbegin()->second instead of
  std::prev(object->end())->second; pop_last_child() keeps
  std::prev(end()) since erase() needs a forward iterator.
- is_empty_container() becomes has_no_children(), a switch that
  returns true for every non-container type as well as empty
  array/object, simplifying the "scalar or already-empty child"
  check at the call site. The local variable `last` is renamed to
  `cur_last_ref` for clarity.
- free_container() asserts the array/object is already empty before
  freeing it, and the object branches assert the expected type.
- destroy(value_t t) is now a thin dispatcher to destroy_string(),
  destroy_binary(), and destroy_container(t), each handling its own
  "not initialized" check and sharing the simple cases first in the
  switch.
- destroy_container() moves the top-level container into the local
  stand-in via a plain swap of the json_value union, instead of a
  manual copy plus clearing array/object by hand.
- The "cur has no children and there is no parent" case now frees
  cur and returns immediately, so the main loop is a plain
  while (true) with no trailing code after it.

Also adds edge-case tests for both json and ordered_json (mixes of
empty/non-empty arrays and objects, container children in first/last
position, single-element chains, top-level empty containers, and
destruction via erase()/assignment), plus a mixed-tree case in the
"destructor performs no allocation" test.

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

* Make the destroy() walk helpers private

They modify basic_json internals without maintaining its invariants and
are only meant for destroy_container(), so they no longer need to be
reachable from the rest of basic_json.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Signed-off-by: Michael Sam <michaelsam94@users.noreply.github.com>
Co-authored-by: Vesko Karaganev <vesko.karaganev@gmail.com>
Co-authored-by: Michael Sam <michaelsam94@users.noreply.github.com>
Co-authored-by: Michael Sam <9461037+michaelsam94@users.noreply.github.com>
2026-10-06 07:40:39 +02:00
Niels Lohmann 8a142bc436 Fix CI on develop after #5600, #5607, and #5755 (#5764)
* Fix CI on develop after #5600, #5607, and #5755

- binary_reader: cast the result of -1 - number back to number_integer_t,
  because a number_integer_t narrower than int is promoted to int, which
  GCC's -Warith-conversion rejects (ci_test_gcc, ci_test_standards_gcc)
- JSON_DELETE_DEPRECATED_FUNCTIONS: declare the deleted stream operators
  as function templates at namespace scope, because GCC < 5 rejects deleted
  friend functions ("can't initialize friend function") and Clang 7-9 report
  a redefinition when a class template has a deleted friend function
- docs: give the examples of JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS "Example:"
  titles and add the page to the docset (style_check)

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

* Ignore libstdc++'s <format> sign change in the sanitizer job

libstdc++ 14's <format> initializes a size_t parameter with -1 (GCC bug
119429), so every std::format call fails ci_test_clang_sanitizer under
-fsanitize=integer (test-std-format_cpp20). Exclude only the
implicit-integer-sign-change check and only that header via
-fsanitize-ignorelist.

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

* Fix the AppVeyor (MSVC 2015-2019) build

- binary_reader: emit_signed/emit_unsigned pass integers that do not fit
  the number types to emit_float as long double, because MSVC's <cmath>
  has no integer overloads of std::isfinite (C2668 'fpclassify'), from #5607
- scalar comparisons: the friend operators take the JSON type for their
  noexcept from their parameter, because MSVC 2015/2017 take basic_json as
  the class template there (C3203) and MSVC 2019 16.0 does not see member
  types or template parameters, from #5751
- unit-conversions2: skip the !is_nothrow_constructible static_assert for
  std::optional on MSVC 2017, which evaluates the conditional noexcept as
  true (C2607), from #5754

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

* Re-amalgamate

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

* Avoid MSVC 2015's C4800 for enums with underlying type bool

MSVC 2015 warns about any conversion to bool (C4800), even with an
explicit cast, so the enum conversions from #5754 (#5671) failed the
AppVeyor build with /WX. Convert to bool by comparing with zero via the
new detail::bool_aware_static_cast, and keep doctest from printing the
enum in the test.

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

* Skip the #5650 allocator test on MSVC 2015 debug builds

MSVC 2015's debug STL constructs the containers' debug proxies through
the allocator in noexcept constructors, so countdown_allocator's failing
construction crashes test-allocator (SIGSEGV) instead of throwing
std::bad_alloc. Use the guard #5585 uses for the same reason.

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

* Skip deleted-function detection checks on MSVC 2015

MSVC 2015 does not treat selecting a deleted function in decltype as a
substitution failure, so the detection traits in
unit-delete_deprecated_functions (#5755) and the integral-key checks in
unit-element_access2 (#5657) report deleted overloads as callable there.
Calling them still fails to compile. Skip those checks for
_MSC_VER < 1910, and use the stream operators for real in the runtime
section, so MSVC 2015 still compiles them with the macro set.

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

* Split the Visual Studio 2017 AppVeyor jobs in two

The VS 2017 jobs hit AppVeyor's 60-minute limit per job while still
compiling the tests (77 of about 108 test targets after 58 minutes).
They pass /std:c++17 for everything anyway, so build only the C++17
variant of each test (JSON_TestStandards=17), and split the unit test
files across two jobs each with the new JSON_TestShard=<index>/<count>
option, which keeps every <count>-th test file starting at <index>.
The extra variants of single test files are built in shard 0 only.

CMAKE_OPTIONS is no longer quoted in appveyor.yml, so that it can hold
more than one option.

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

* Fix std::terminate when converting std::optional with MSVC 2017

MSVC 2017 evaluates std::is_nothrow_assignable<json&, const T&> as true
even if T's to_json throws, so to_json(json&, const std::optional<T>&)
was noexcept there and the exception from #5642's test called
std::terminate instead of propagating. Make that conversion never
noexcept on MSVC 2017; all other compilers keep the exact condition.
The static_asserts on the condition are skipped for MSVC 2017; the
runtime check that the exception propagates still runs there.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-06 07:22:55 +02:00
Niels Lohmann 23d3b373e1 Add JSON_DELETE_DEPRECATED_FUNCTIONS to delete the deprecated functions (#5755)
* Add JSON_DELETE_DEPRECATED_FUNCTIONS to delete the deprecated functions

Defining JSON_DELETE_DEPRECATED_FUNCTIONS to 1 (or the CMake option
JSON_DeleteDeprecatedFunctions) declares every deprecated function as
deleted instead of deprecated, so that code that is not ready for 4.0.0
no longer compiles. A deleted function still takes part in overload
resolution, so from_*(ptr, len) cannot silently bind len to the strict
parameter of from_*(InputType&&, bool); the roadmap now plans to keep
these overloads deleted in 4.0.0 instead of removing them.

The legacy discarded-value comparison is left to its own macro.

Also update the 4.0 roadmap: add JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
and JSON_DELETE_DEPRECATED_FUNCTIONS to the macro table, add the
from_bjdata/from_bon8 (ptr, len) overloads to the deprecated functions,
document the macro in the migration guide, and fix the docs style check
findings (example titles, missing docset entry for JSON_STRICT_BINARY_UTF8).

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

* Declare each deprecated function once and guard only its body

Instead of repeating every deprecated declaration in an
#if JSON_DELETE_DEPRECATED_FUNCTIONS branch, keep one declaration
(with its deprecation attribute) and switch only between "= delete;"
and the function body. Suggested by @gregmarr in the review.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 22:11:34 +02:00
Niels Lohmann c5a7a4b46d Add deprecated from_bon8/from_bjdata(ptr, len) overloads (#5688)
from_bon8(ptr, len) and from_bjdata(ptr, len) had no overload for a
pointer and a length, unlike from_cbor/from_msgpack/from_ubjson/
from_bson. The call instead bound to from_*(InputType&&, bool strict),
which read ptr as a NUL-terminated C string via strlen and silently
converted len to the strict flag. Data containing a 0x00 byte was cut
off there; data without one was read past the end of the buffer.

Add a deprecated (ptr, len, strict, allow_exceptions) overload for
each function that forwards to (ptr, ptr + len, ...), matching the
existing deprecated overloads of the other four binary readers. Since
neither function ever had this overload, the deprecation is declared
as of version 3.13.0, the next unreleased version, rather than the
version each function was originally added in.

Fixes #5648.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 22:11:34 +02:00
Niels Lohmann 351aeb7440 Merge remote-tracking branch 'origin/develop' into HEAD
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 17:19:32 +02:00
Niels Lohmann d8d47be4a5 Fix CI on develop after merging the ready-to-merge PRs (#5754)
* Keep the serializer conversion for objects whose keys cannot be converted

#5591 added a test converting nlohmann::json into a basic_json whose
string type cannot be constructed from std::string. That instantiates
convert_iteratively(), whose members.emplace_back(next.key(), ...) needs
exactly that key conversion, and broke the build of unit-alt-string.
Dispatch on the key's constructibility and leave such conversions to the
serializers, as the levels above the nesting bound already do (#3425).

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

* Fix the remaining CI failures on develop

- unit-wstring: with a 16-bit wchar_t (Windows), a lone surrogate is
  reported as the ill-formed byte 0xFF since #5704; the std::wstring
  expectations still had the previous <U+0000>.
- ci_single_binaries: json_literals.hpp (#5610) and json.hpp include each
  other on purpose, and IWYU, not following the cycle, asks to replace
  json.hpp with json_fwd.hpp. Report its findings without failing the
  build, as already done for json.hpp.

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

* Fix the library warnings and noexcept specifications from the merged PRs

- binary_reader: rename the error_handler constructor parameter, which
  shadowed the member (-Wshadow, -Wshadow-field-in-constructor; #5746)
- basic_json(copy_construct_tag, ...): declare it noexcept when copying
  the base class is (GCC 16 -Wnoexcept; #5690)
- the scalar-on-left legacy comparison operators: noexcept only when
  converting the scalar is, like their member counterparts (#5682, #5751)
- compare_leaves: use std::is_eq/is_lt/is_gt instead of comparing a
  std::partial_ordering with 0 (-Wzero-as-null-pointer-constant; #5686)
- serializer: silence MSVC C4127 for the EnsureAscii template parameter
  (#5741, #5746)
- clang-tidy: return the sanitized reference in binary_writer, take the
  key of ordered_map::find_impl by const reference (#5727), and mark the
  switches over parse_array_index (#5728)
- ordered_map: keep <memory> for std::allocator (IWYU)

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

* Split unit-conversions.cpp so MinGW can link it

clang 18 with the MinGW linker failed to link test-conversions_cpp17
("relocation truncated to fit: IMAGE_REL_AMD64_REL32"). As windows.yml
recommends, keep the objects small by splitting the test file.

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

* Fix the tests added by the merged PRs for all CI configurations

- discard the results of dump() and from_*() in CHECK_THROWS with
  utils::ignore_return_value (GCC -Werror=unused-result)
- give unit-bson's huge_string_t a default constructor (MSVC C2512,
  GCC 5, clang 3.5)
- unit-disabled_exceptions: use the literals namespace when the global
  UDLs are off (ci_test_noglobaludls; #5700)
- unit-binary_utf8_strict: expect the JSON pointer prefix with
  JSON_DIAGNOSTICS (#5741)
- skip the tests that rely on exceptions under JSON_NOEXCEPTION
  (#5678, #5732)
- clang-tidy and clang -Werror: static test data, CAPTURE(...);,
  const-correctness, use-after-move alias, unused conversion operator,
  a missing <iterator> include

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

* Title the macro examples and add JSON_STRICT_BINARY_UTF8 to the docset

The documentation style check requires "Example: ..." titles on pages with several examples (#5741, #5591) and a docset entry for every macro page.

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

* Regenerate BUILD.bazel and nlohmann_json.natvis

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

#5746 added detail/output/error_handler.hpp and #5741 the json_abi_sbu8 ABI tag.

* Install libidn11 for the CMake 3.5.0 binary in ci_cmake_flags

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

#5733 moved ci_cmake_options from ubuntu:focal to ubuntu:24.04, which no longer ships libidn.so.11; the CMake 3.5.0 release binary links against it, so every ci_cmake_flags run has failed since. Install focal's libidn11 package for that matrix entry only.

* Suppress Infer's false STACK_VARIABLE_ADDRESS_ESCAPE in get_impl

get_impl() returns its local by value. A test added by the merged PRs instantiates it with a type Infer misreads, so ci_infer reported the 2021 code for the first time.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 17:18:19 +02:00
Niels Lohmann 7b0af0072e Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

# Conflicts:
#	include/nlohmann/detail/input/binary_reader.hpp
#	include/nlohmann/detail/string_utils.hpp
#	single_include/nlohmann/json.hpp
2026-10-04 12:22:05 +02:00
Niels Lohmann 73e9eae3c1 Add an error_handler parameter for UTF-8 to the binary readers and writers (#5746)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 12:13:49 +02:00
Niels LohmannandRaphael Grimm 40021f38fb Add basic_json::as_base_class and document name conflicts with custom base classes (#5589)
* Add basic_json::as_base_class and document name conflicts with custom base classes

Members of basic_json hide members of a custom base class with the same
name, and future releases may add members that hide ones accessible
today. Document this in json_base_class_t and add as_base_class() to
reach hidden members without spelling out the cast.

Also make json_base_class_t a public member type. It was documented
since 3.12.0, but declared private, so users could not name it.

Supersedes #3899.

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

* Add as_base_class to the docset search index

New public members get an entry in docs/docset/docSet.sql (as done for
to_bon8/from_bon8 in #2998). Without it, the Dash/Zeal docset built from
the documentation cannot find basic_json::as_base_class.

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

* Silence clang-tidy for the hidden type_name() in the base class test

ci_clang_tidy failed with readability-convert-member-functions-to-static
on base_class_with_hidden_members::type_name(). It must stay a
non-static member: the test shows that it is hidden by the non-static
basic_json::type_name() and reachable through as_base_class().

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Raphael Grimm <1005058+barcode@users.noreply.github.com>
2026-10-04 12:00:31 +02:00
Niels Lohmann a0b71e2720 Deduplicate basic_json internals; make insert(pos, json&&) move (#5727)
* Remove unused private aliases from basic_json

The private aliases primitive_iterator_t, internal_iterator and
output_adapter_t are not used anywhere: iter_impl, binary_writer and
the tests refer to the detail:: names directly. As the aliases are
private, no user or derived class can depend on them. The
internal_iterator.hpp include stays because iter_impl needs it.

Part of #5724

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

* Fix meta()'s dead, syntactically invalid HP aCC branch

The HP aCC branch of basic_json::meta() was missing a semicolon and
has therefore never compiled; adding only a semicolon would also make
it throw type_error.305, since it assigned a plain string to
result["compiler"] and then indexed into it like the other branches
do into an object. Make the branch consistent with the others by
assigning an object with "family" and "version" keys, narrow the
condition to __HP_aCC (a C compiler cannot build this header-only
library), and fix meta.md, which documented the old (impossible)
plain-string behavior.

Part of #5724

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

* Stop the noexcept null constructor delegating to a throwing one

basic_json(std::nullptr_t) delegated to basic_json(value_t), whose
underlying json_value(value_t) constructor allocates for other types
and can therefore throw, which is why the noexcept had a
NOLINT(bugprone-exception-escape). The delegated-to constructor also
called assert_invariant() a second time. The default member
initializers of data already produce the same null state (a
value-initialized, i.e. zeroed, union with object == nullptr), so the
delegation and its NOLINT can simply be dropped.

Part of #5724

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

* Remove four cppcheck accessForwarded suppressions in the move constructor

basic_json(basic_json&&) built its base subobject with
std::forward<json_base_class_t>(other), so cppcheck saw the whole of
other as forwarded and flagged every subsequent access to it as
accessForwarded, three of them still marked "TODO check". Only the
base subobject is actually moved from; cast explicitly to the base
type instead, the way ordered_map already does, so cppcheck can tell
the two are unrelated. Behavior is unchanged: for a non-reference T,
std::forward<T>(x) is defined as static_cast<T&&>(x).

Part of #5724

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

* Remove stale cppcheck suppressions and name the local parser in parse()

Running the pinned cppcheck (ci_cppcheck's invocation) without
--inline-suppr across all configurations reports no syntaxError, no
ignoredReturnValue and no assertWithSideEffect, so the corresponding
suppressions in json_fwd.hpp, string_concat.hpp and
assert_invariant() no longer match anything (json_fwd.hpp's is kept,
since downstream users who run an older cppcheck against it could
still hit the warning it once silenced).

The three basic_json::parse() overloads still trigger a false-positive
accessMoved/accessForwarded because they build a temporary parser and
call .parse() on it in the same expression; giving that parser a name
makes the warning go away without changing behavior, and removes the
last of the inline suppressions on these functions.

Part of #5724

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

* Deduplicate the string/binary cleanup in the two erase() overloads

erase(pos) and erase(first, last) each carried a byte-identical
14-line block that destroys and deallocates a string or binary
value before resetting the type to null. That reimplements the
string/binary cases of json_value::destroy(), so any future change to
how those values are freed would have to be made in three places
instead of one. Both overloads now just call destroy() and reset the
union; for the other primitive types (boolean, numbers) destroy() is
a no-op, so behavior is unchanged.

Also fix erase(first, last)'s error-path branch hint, which used
JSON_HEDLEY_LIKELY where erase(pos), the iterator-range constructor,
and every other error path in the class use JSON_HEDLEY_UNLIKELY.
This only affects code layout, not semantics.

Part of #5724

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

* Fix stale and copy-pasted comments in basic_json

Several comments no longer match the code: the class invariant and
assert_invariant()'s doc still named the members m_value/m_type
(now m_data.m_value/m_data.m_type) and did not mention the binary
invariant that assert_invariant() already checks; the json_value note
and the get<PointerType>() @tparam list omitted binary_t even though
binary is a variable-length, pointer-stored type like the others; the
key-based value() overload's brief said "via JSON Pointer", which is
the other overload; and swap(binary_t&)/swap(binary_t::container_type&)
both carried "swap only works for strings", copied from swap(string_t&).

Comment-only change; behavior, the public API and the ABI are
unchanged. The private get_impl() doxygen and the emplace() comments
that border #5585's hunk are intentionally left alone.

Part of #5724

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

* Deduplicate the 16 copied from_cbor/msgpack/ubjson/bjdata/bon8/bson bodies

Each of the 16 binary deserialization overloads (from_cbor,
from_msgpack, from_ubjson, from_bjdata, from_bon8, from_bson, each in
an InputType&& and an iterator/sentinel version, plus the deprecated
span overloads of from_cbor/from_msgpack/from_ubjson/from_bson) had
the same body, differing only in the input_format_t value. Every copy
built a temporary binary_reader from std::move(ia) and called
sax_parse on it in the same expression, which also produced a
false-positive cppcheck accessMoved on all 16 lines and needed a
NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg) on
the four span overloads.

Add a private from_binary_impl() helper that builds the reader as a
named local instead, and make each of the 16 overloads a one-line
forward to it. All public signatures, default arguments,
JSON_HEDLEY_WARN_UNUSED_RESULT and JSON_HEDLEY_DEPRECATED_FOR
attributes are unchanged, tag_handler keeps defaulting to
cbor_tag_handler_t::error for the non-CBOR formats (matching
binary_reader::sax_parse's own default), and the helper is placed in
the existing private section before the binary section banner rather
than between the from_* overloads, so from_binary_impl() itself does
not collide with #5688's insertion point. Collapsing the
from_bjdata/from_bon8 bodies into one-line forwards does rewrite the
"return result; }" context lines that #5688 inserts its two
deprecated overloads after, so that PR will need a small manual
rebase (reinserting its overloads after the new one-line bodies)
rather than applying cleanly.

Part of #5724

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

* Make insert(pos, basic_json&&) move its argument instead of copying it

insert(const_iterator pos, basic_json&& val) delegated to
insert(pos, val), but val is a named rvalue reference, so inside the
function it is an lvalue: the call always resolved to
insert(const_iterator, const basic_json&) and deep-copied the value.
This has been the case since the overload was introduced, in every
release. push_back(basic_json&&), by contrast, already moves.

Give the rvalue overload its own body with the same two checks
(type_error.309, invalid_iterator.202), then move the argument into a
local before inserting it. Moving into a local first, rather than
inserting std::move(val) directly, keeps this safe even when val
aliases an element of the same array (e.g.
arr.insert(arr.begin(), std::move(arr[1]))), since
std::vector::insert(pos, T&&) is not guaranteed to handle an argument
that aliases one of its own elements.

This is a deliberate, small behavior change: the moved-from argument
now ends up null afterwards, the same as after push_back(&&), instead
of keeping its old value unchanged. No signature changes, so the
public API and ABI are unaffected. Add unit-modifiers coverage for
the moved-from state and for self-aliasing insertion, both with and
without reallocation of the underlying array.

Part of #5724

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

* Deduplicate object key lookup and checked at() access

at()/find()/count()/contains()/const operator[]/erase_internal() each
repeated the raw object lookup (m_value.object->find(key)), and the
six at() overloads additionally repeated the type_error.304 check and
out_of_range.401/403 throw. Route them all through two new private
helpers, object_lookup()/object_at() (plus array_at() for the index
overloads of at()), templated on the constness of the receiver so one
body serves both the const and non-const overload. count() is left
untouched, since it already goes through object_t::count() rather
than a second find().

The at(KeyType&&) overloads used to forward the same key twice: once
into object->find() and again, on the not-found path, into the
string_t() conversion for the exception message. object_at() now
forwards it only into the lookup and reuses the (unmoved) key for the
message. clang-tidy 22 (Docker silkeh/clang:22) still flags that reuse
under bugprone-use-after-move/hicpp-invalid-access-moved even with the
single forward, since it cannot see that object_t::find() (a plain
std::map or ordered_map) never actually moves from its argument; add a
NOLINTNEXTLINE with that reasoning rather than avoid the pattern.

No signature, exception id/message, or set_parent() behavior changes.

Overlaps #5689, #5705, #5606, #5687 and #5585, which touch the same
hunks; whichever of this commit and those PRs lands second will need
a small rebase.

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

* Deduplicate the lookup/default/throw body of value()

The six non-deprecated value() overloads each held a full copy of the
same body: the four key-based overloads looked up the key and either
returned the found element converted to the requested type or the
default value (throwing type_error.306 if this is not an object), and
the two json_pointer overloads did the same via
ptr.get_checked_or_null(), throwing type_error.306 unless
is_structured(). Replace the duplicated bodies with two private
helpers, value_member() and value_pointee(), that return a
const basic_json* (null when not found) and do the type check/throw
once each. Every value() overload now just picks between the found
pointer's get<T>() and the default.

Same signatures, template parameters, SFINAE conditions, exception id,
message and this context on every overload.

Overlaps #5689 (routes find() through lookup_key()) and #5705 (adds a
deleted integral-key value() next to these overloads); whichever of
this commit and those PRs lands second will need a small rebase.

#5724 item 4

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

* Deduplicate the null-to-container conversion into convert_null_to()

Nine sites wrote out the same "turn a null value into an empty array
or object" logic with two different idioms: operator[](size_type),
operator[](key_type), operator[](KeyType&&) and update() set m_type
then assigned m_value.array/object directly via create<T>(), while the
three push_back() overloads, emplace_back() and emplace() set m_type
then assigned m_value = value_t::array/object (going through
json_value's converting constructor and a temporary). Both idioms end
up calling create<T>() and produce the same state, just via a
different path; both also share a latent exception-safety bug, since
m_type is written before the (possibly throwing) allocation, so a
throwing allocator leaves m_type == array/object with a null pointer
behind it, violating the class invariant and crashing on the next
access to, or destruction of, the value.

Add a private convert_null_to(value_t) helper and call it from all
nine sites. Unlike the idioms it replaces, it allocates the container
first and only then writes m_type, so a throwing allocation leaves the
value as a valid null instead of a mistyped, half-constructed one;
verified with a throwing allocator (see unit-allocator.cpp's
bad_allocator) that j["x"] = ... on a null j now stays null, and no
longer trips assert_invariant()/crashes, when create<object_t>()
throws. Same allocator usage and assert_invariant() call as before,
otherwise.

Overlaps #5585, which reorders these same nine blocks for exception
safety; whichever of this commit and that PR lands second will need a
small rebase.

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

* Deduplicate the linear key search in ordered_map

emplace, at, erase(key), count and find each repeated the same
"for (auto it = begin(); it != end(); ++it) if (m_compare(it->first,
key)) ..." loop (15 copies across their key_type and transparent
KeyType&& overloads), and both erase(key) overloads additionally
repeated the exception-sensitive in-place reconstruction (destroy,
placement-new, pop_back) used to remove an element while keeping the
const Key non-movable.

Add two private helpers: find_impl(Self&, KeyType&&), a static member
template that runs the search once for either constness of the
receiver, and erase_at(iterator), which keeps the existing
pop_back-based reconstruction instead of switching to erase()/resize()
(which would add a DefaultInsertable requirement). Route find, at,
count, emplace, insert(const value_type&) and both erase(key)
overloads through them.

Same signatures, is_usable_as_key_type constraints and exception
messages/types.

Overlaps #5609 and #5685, which both rewrite emplace (#5609 also
touches insert and adds private members at the end of the class);
whichever of this commit and those PRs lands second will need a
rebase.

#5724 item 6

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

* Re-enable bugprone-use-after-move/hicpp-invalid-access-moved

These two checks (and portability-template-virtual-member-function)
were disabled in #4489 (November 2024) "only removed to get the CI
going". portability-template-virtual-member-function is a separate,
still-open cleanup (#5725 item 3 on its own branch) and stays
disabled here; this commit only re-enables the move/forward checks
and cleans up what they flag on this branch.

The move constructor (json.hpp) already casts to the base type
instead of forwarding the whole object (#5724 item 9), so it no
longer trips either check. The at(KeyType&&) double-forward this
check used to flag was reduced to a single forward with the
now-unforwarded reuse annotated by a NOLINTNEXTLINE in #5724 item 3's
object_at() helper (clang-tidy 22 still flags that reuse even after a
single forward; see that commit's message). What is left here:

- from_json_inplace_array_impl(), from_json_tuple_impl_base() and the
  std::pair overload of from_json_tuple_impl() forwarded j into every
  j.at(...) call in a pack expansion or a pair of calls. at() has no
  ref-qualified overloads, so the forward was a no-op; call j.at(...)
  directly.
- container_input_adapter_factory::create() forwards container twice
  on purpose, into begin() and end(), so both see the same value
  category and produce matching iterator types. Annotate it with
  NOLINTNEXTLINE and a comment instead of changing it.
- unit-class_parser.cpp's "move constructor resets the moved-from
  value to npos" test still pointed at the pre-static_cast move
  constructor by line number and mentioned the cppcheck-suppress
  annotation that #5724 item 9 already removed; update the comment.

No behavior change anywhere in include/. Verified with clang-tidy 22.1.8
(Docker silkeh/clang:22, --platform linux/amd64) against a TU including
json.hpp with the repo's .clang-tidy: bugprone-use-after-move and
hicpp-invalid-access-moved report nothing unsuppressed.

Overlaps #5737 (open PR for the rest of #5725 item 3: the
from_json.hpp/input_adapters.hpp cleanup above, and
portability-template-virtual-member-function), which currently keeps
both checks disabled pending this move-constructor change; whichever
of this commit and that PR lands second will need a small rebase of
.clang-tidy.

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

* Make convert_null_to() take the container type as a template argument

Passing array_t or object_t instead of a value_t makes an invalid target
a compile error instead of a runtime assertion, and removes the branch.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 11:57:41 +02:00
Niels Lohmann 650886d126 Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

# Conflicts:
#	tests/src/unit-alt-string.cpp
2026-10-04 11:50:33 +02:00
Niels Lohmann 1df1e8a845 Make cross-string-type basic_json conversion explicit without implicit conversions (#5591)
* Make cross-string-type basic_json conversion explicit without implicit conversions

The converting constructor from another basic_json specialization was
always implicit, so a value with a different string_t (std::wstring, a
string with a custom allocator, ...) silently converted into a temporary,
e.g. when passed to a function taking const nlohmann::json&. Such
conversions do not produce correct values (#3425), and
JSON_USE_IMPLICIT_CONVERSIONS=0 did not catch them.

When JSON_USE_IMPLICIT_CONVERSIONS is 0, the constructor is now explicit
if the string types differ. Specializations sharing a string type (json
and ordered_json, different serializers or object maps) stay implicitly
convertible, so the NLOHMANN_DEFINE_TYPE_* macros keep working with
nested json members. get<BasicJsonType>() constructs explicitly and
works in both modes.

Fixes #2649.

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

* Construct explicitly in get_to() and to_json(std::optional)

With JSON_USE_IMPLICIT_CONVERSIONS=0 the conversion from a basic_json
with a different string type is now explicit, but two library paths
still assigned such a value implicitly and failed to compile inside the
library:

- get_to() with a basic_json target (the #2175 overload) did
  `v = *this`, so json(42).get_to(alt_json&) broke although
  get<alt_json>() works.
- to_json(BasicJsonType&, const std::optional<T>&) is constrained on
  std::is_constructible (which accepts the explicit constructor) but did
  `j = *opt`, so converting a std::optional<alt_json> into a json broke.

Both now construct the value explicitly, as get_impl() already does.

Also replace static_cast<bool>(JSON_USE_IMPLICIT_CONVERSIONS) with a
comparison: clang-tidy's modernize-use-bool-literals rejected the cast
of the integer literal the macro expands to, failing ci_clang_tidy.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 11:46:52 +02:00
Niels Lohmann a212d3b2e4 Preserve the object comparator's state in a deep copy past the nesting bound (#5722)
* Preserve the object comparator's state in a deep copy past the nesting bound

copy_object_level(), used by the copy constructor and copy assignment once a
value is nested deeper than the iterative deep copy's bound (128 levels, or
every copy under JSON_NO_THREAD_LOCAL), built each object's copy with the
object type's plain range constructor. That default-constructs the object's
comparator instead of copying the original's. For an object type whose
comparator carries state, such as a std::map that compares keys
case-sensitively only when constructed that way, the copy then ordered - and
could even deduplicate - its keys differently from the original.

Add detail::is_comparator_constructible_object_type, a detection trait for
object types that provide a key_comp() and a constructor taking a range and a
comparator, the way std::map does. copy_object_level now dispatches on it: an
object type that qualifies gets its copy built with src_object.key_comp()
passed along; other object types, such as nlohmann::ordered_map (which has a
key_compare for its std::map-like interface, but no key_comp()), keep using
the plain range constructor exactly as before.

merge_patch and update() were checked for the same pattern; neither is
affected, since both only ever add members one at a time to an object that
already has its own comparator (or start a brand new default-constructed one),
rather than rebuilding an object_t from a range copied out of an existing,
possibly custom-comparator object.

Fixes #5649.

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

* Keep astyle from padding the create_object_with_comparator templates

Spell the negated condition as detail::negation<...> instead of a leading
'!', which made astyle spread the template header out.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 11:46:47 +02:00
Niels Lohmann 49cd427196 Copy-construct the base class of a deep copy's elements, not assign it (#5690)
The bounded-descent copy added by #5389 built the elements of a deep copy
(nested past the 128-level bound) by default-constructing them and then
having copy_metadata() assign their base class afterwards. That assignment
is only instantiated for values nested past the bound, but being called
from copy_structured() at all meant it was compiled for every copy, so a
CustomBaseClass that is copy-constructible but not move-assignable (for
example one with a const data member) no longer let its basic_json be
copy-constructed, at any depth.

copy_array_level() and copy_object_level() now build each element with a
private-tag-selected constructor that copy-constructs the base class (and,
under JSON_DIAGNOSTIC_POSITIONS, copies the positions) directly, the same
way the copy constructor already builds elements within the 128-level
bound. Copying a basic_json is therefore back to requiring only a
copy-constructible base class, as documented and as it was before #5389;
copy assignment is unchanged and still requires an assignable one.

Fixes #5674.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 11:46:36 +02:00
Niels Lohmann b730946432 Fix key types convertible to std::string_view breaking lookups (#5689)
Since #4958, a key type implicitly convertible to std::string_view was
accepted by is_usable_as_basic_json_key_type without checking that the
object's comparator can actually compare object_t::key_type with that
key type. The key was then forwarded unchanged to the underlying map,
so const operator[], at, find, count, contains, erase and value failed
to compile (a hard error inside <map>) for a key convertible only to
std::string_view, and value() rejected such keys outright. For keys
convertible to both std::string and std::string_view, the KeyType&&
templates now won overload resolution over the object_t::key_type
overloads and then failed the same way, a regression from 3.12.0. Only
the non-const operator[] worked, because it uses emplace(), which
constructs a std::string from the key explicitly. ordered_json was not
affected, since ordered_map checks comparability itself.

Add a trait, is_string_view_convertible_key_type, that recognizes a key
type that is convertible to std::string_view but not directly
comparable with the object's key type, provided std::string_view itself
is comparable with it. at(), operator[], find(), count(), contains(),
erase() and value() now route such keys through a new lookup_key()
helper that converts them to std::string_view before they reach the
object, matching how the object's transparent comparator already
supports std::string_view lookups.

Fixes #5663.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 11:46:32 +02:00
Niels Lohmann 0d01d6ae90 Classify leaves with operator<=> itself past the nesting bound (#5686)
* Classify leaves with operator<=> itself past the nesting bound

In C++20, an ordered comparison past the nesting bound classified a pair of
leaves by asking == first and then order_leaves(), which calls < and > -
both derived from <=>. For a pair of binary values with the same bytes but a
different subtype, == reports them unequal, while <=> (through
std::vector<std::uint8_t>::operator<=>) reports them equivalent, so the pair
ended the comparison as unordered instead of letting the next element
decide - unlike an array or object within the bound, which compares such a
pair with its own operator<=> and gets equivalent. So operator<=>, and the
<, <=, >, >= derived from it, could give a different result for the same two
values depending on how deeply the values were nested, or unordered at every
depth with JSON_NO_THREAD_LOCAL defined.

compare_leaves() now classifies such a pair in C++20 with operator<=> itself
instead, matching how a value within the bound is compared; the equality-only
and pre-C++20 ordered cases are unchanged. Which of the three runs is chosen
by overloading on std::integral_constant<bool, Ordered>, the same tag
dispatch order_leaves() already uses, rather than a runtime "if (Ordered)" on
a template parameter, which MSVC would flag as a constant condition (C4127).

Added a regression test to unit-comparison.cpp that nests such a pair 0, 127,
128 and 200 levels deep (127 stays within the 128-level bound, 128 and 200
do not) and checks that operator<=> and operator< agree at every depth.

Fixes #5654.

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

* Drop the version history note for a bug that was never released

The regression came from #5390, which is not in any release. Addresses review comment by @gregmarr.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 11:46:29 +02:00
Niels Lohmann df27cc3d4c Add scalar-on-left overloads for legacy discarded comparisons in C++20 (#5682)
With JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON=1 and C++20, a scalar on
the left-hand side of <= or >= (e.g., `1 <= discarded`) yielded false
instead of the documented true. The C++20 legacy block only had member
operators, which are only candidates when the basic_json is the left
operand; for a scalar on the left, overload resolution picked the
candidate rewritten from operator<=>, which does not emulate the legacy
behavior. The C++17 branch already has scalar-on-the-left friend
overloads for <= and >=; add the equivalent pair to the C++20 legacy
block.

Added a regression test to tests/src/unit-comparison.cpp covering all
four operand orders for both operators.

Fixes #5665.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 11:46:21 +02:00
Niels Lohmann d11e89471b Assert on missing array indices in const operator[] and document the JSON pointer case (#5606)
The const operator[] overloads are unchecked by design, and a missing key
or index is undefined behavior. The key overload guards this with a
runtime assertion, but the index overload did not, although the element
access documentation says an assertion fires in both cases. The const
JSON pointer overload inherits both through json_pointer::get_unchecked(),
so a pointer to a missing array index read out of bounds even in debug
builds, and its documentation promised out_of_range.404 for any pointer
that cannot be resolved.

Add JSON_ASSERT(idx < size()) to const operator[](size_type), which also
covers the index leg of the const JSON pointer overload. Document the
undefined behavior for the const JSON pointer overload in operator[].md
and in the runtime assertions page. Release builds are unchanged.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 11:46:18 +02:00
Niels Lohmann 6d0867a85f Make comparisons with scalars noexcept only when the conversion is (#5751)
The comparison operators taking a scalar (==, !=, <, <=, >, >=, and
C++20's <=>) convert the scalar to a basic_json and compare, but were
unconditionally noexcept. When that conversion throws, the program
called std::terminate instead of propagating the exception, e.g. when
comparing a json with a string literal under memory pressure
(std::bad_alloc) or with an enum value not mapped by
NLOHMANN_JSON_SERIALIZE_ENUM_STRICT (out_of_range.410). clang-tidy
22.1 reports the latter as bugprone-exception-escape.

Declare the 16 scalar overloads
noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value):
they stay noexcept for numbers, Booleans, nullptr, and plain enums,
and are noexcept(false) for strings and enums whose to_json may throw.
The comparisons of two basic_json values are unchanged.

Restore the strict-enum comparisons removed from unit-conversions.cpp
in the previous PR, check that comparing an unmapped strict enum now
throws, and pin the new exception specifications in unit-noexcept.cpp.
Document the exception safety of overload (2) on all seven operator
pages. Ran make amalgamate.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-02 17:25:17 +02:00
Niels Lohmann ab52c98f71 Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

# Conflicts:
#	docs/mkdocs/docs/api/json_sax/parse_error.md
#	docs/mkdocs/docs/features/parsing/index.md
2026-10-02 11:38:09 +02:00