Commit Graph
84 Commits
Author SHA1 Message Date
Niels Lohmann 02d2fa8605 Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-11-02 13:47:30 +01:00
Niels Lohmann a47170346a docs: new design for the documentation site (#5934)
* docs: new design for the documentation site

Apply the brand to the Material for MkDocs site: Inter and JetBrains Mono
served by the site (upright and real italic), brand colours, blue header band
with the syntax pattern, wordmark in the header, new home page (hero, cards,
animated feature tour), 404 page, polish for tabs, search, footer, focus
rings, tables and code blocks, and theme features (code copy, previous/next
footer, TOC follow, search suggestions).

Draw the number railroad diagram, the parser callback events and the iterator
illustrations as inline SVGs that follow the light and dark scheme. The
generator scripts are in docs/mkdocs/scripts/figures; the feature slideshow
(json-light.svg, json-dark.svg, replacing json.gif on the home page) is built
by docs/mkdocs/scripts/slideshow. Decision nodes in five flowcharts become
hexagons, which need far less room.

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

* docs: add figures, table captions and a macro chooser

- Figures with numbered captions: SAX stepper, json_view layout and edit
  stepper, exception map, JSON pointer and patch walkers, QA pipeline,
  scaling and binary size charts, roadmap lanes, release timeline,
  integration decision tree and namespace builder
- Table captions (nj-table-caption) on 9 pages
- Compile times: modules and PCH charts, filesystem section, re-measured
  Figure 1, links between features/modules.md and compile_times.md
- Interactive macro chooser for features/arbitrary_types.md
- Link check: exclude URLs that answer the plugin with 400/401/419 or are
  dead (customers.md)

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

* docs: macro chooser generates adl_serializer for non-default-constructible types

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

* docs: cross-link concept pages and API pages in See also sections

Add See also links in both directions between the concept pages (features,
home, integration) and the API pages, write API links in code font, give every
entry a comment after a dash, and show the callback event figure on the parser
callbacks page.

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

* docs: address review comments on the new design

- Home: add a "Latest release" button
- Sponsors: update the list and group it by tier
- Features: list all feature pages on the index page
- Releases: add highlights per release, link the 4.0 roadmap, add the first commit to the timeline
- Exceptions: prefix all example messages with the exception name
- API: no code font for format names in the See also links of the to_/from_ pages
- Merge Patch: show the document before, the patch, and the result
- Replace "--" with typographic dashes, mark external links with an icon, center Mermaid diagrams

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-27 07:41:42 +01:00
Niels Lohmann e5fe4ebdd2 json_view: from_json() of the macros reads views directly (#5922)
get<T>() and get_to() of a view call T's from_json() with the view itself
when that from_json() accepts views but not an unrelated probe type, and
fall back to materialize() otherwise. The from_json() functions of the
NLOHMANN_DEFINE_TYPE_*, NLOHMANN_DEFINE_DERIVED_TYPE_* and
NLOHMANN_JSON_SERIALIZE_ENUM(_STRICT) macros accept basic_json values and
views; a derived type whose base reads only json reads the base part
through materialize(). The library's own from_json() overloads are not
called with views: from_json() of a view (and of the probe) only looks up
functions by ADL.

New public trait nlohmann::is_json_view<T>, and the member type
basic_json_type of basic_json_view. With duplicate keys, the members of
such a T are those the view's lookups find (the first ones).

bench_decode.cpp measures decoding into structs (4-6x faster than
materialize().get<T>() on twitter, citm_catalog, and synthetic records).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-26 20:13:31 +01:00
Niels Lohmann 5a2819c940 json_view: one SIMD macro set with the library (#5921)
The view's vector code follows JSON_NO_SIMD, like the lexer and the float
writer, and skips the CPU check of SSSE3 when the code is compiled for
SSSE3 anyway (__SSSE3__), like the lexer. JSON_VIEW_NO_SIMD and
JSON_VIEW_USE_SSSE3 and their ABI tags _vns and _vssse3 are removed; they
were never released. JSON_NO_SIMD keeps its tag _ns.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-26 20:13:31 +01:00
Niels Lohmann 731f1b5bfb json_view: view_mode enum instead of bool Editable, node_kind for node::kind (#5919)
* json_view: view_mode enum instead of bool Editable, node_kind for node::kind

basic_json_document and basic_json_view take a view_mode (read_only, the
default, or editable) instead of a bool: basic_json_document<json, true>
did not say what true means. The shortcut aliases are unchanged.

The kind of a node is a node_kind (the value_t values plus link, 10 as
before), which removes the static_cast<std::uint8_t>(value_t::...) of
every comparison. The node and image layouts are unchanged.

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

* json_view: node_kind in the node writers, spell out read_only, comment fixes

The builder and the edit functions take and store a node_kind instead of
casting a value_t; the numbering assertions and the comments now speak of
node_kind, and the link kind notes that it follows value_t::discarded.
The read-only aliases name view_mode::read_only like the editable ones.
view_mode.md says the mode is a compile-time property of the type.

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

* json_view: views of read-only documents convert to editable views

A read-only document has no edits, so a view of it reads correctly as a
view of an editable document before its first edit. The implicit
conversion lets a function taking a json_editable_view accept the views
of both modes. There is no conversion the other way: a read-only view of
an editable document would read wrong values after the next edit.

The mode comparisons in the cross-mode operator==/!= use an
is_other_mode trait, which astyle keeps compact.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-26 20:13:30 +01:00
Niels Lohmann 60107eda3f Read BJData ND-arrays of float16, restrict ND-array char to 0..127, correct BJData docs (#5931)
* Read ND-arrays of half floats and enforce the char limit in ND-arrays

BJData N-dimensional arrays with element type 'h' (float16) failed to
read with a misleading parse_error.112, because the reader's dtype name
table lacked 'h'. It now maps to "half", the JData name. The writer still
does not pack "half"; such an object is written as a plain object and
reads back equal.

BJData limits 'C' (char) to 0..127 in Draft 2 and Draft 3, and the 1-D
reader enforces this, but ND-arrays with _ArrayType_ "char" wrote values
up to 255 as 'C' elements and read them back without a check. The writer
now only packs values in 0..127 (others fall back to a plain object that
round-trips), and the reader rejects 'C' elements above 127 with
parse_error.113 like the 1-D reader.

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

* docs: correct and complete the BJData documentation

Verify the BJData chapter against the library and the Draft 2/3/4
specifications and fix what did not match:

- bjdata.md: correct the list of unused markers (N, not Z), the ND-array
  example (3x2, not 2x3), the conditions under which an object is packed
  as an ND-array (exactly three keys, row vectors, float-only elements for
  single/double, char 0..127, byte only in Draft 3), the binary table row
  and notes (which flag/draft combinations write [$B), the "$" type
  restriction (Draft 3, Z is excluded too), the H marker in the
  deserialization table, and the claim of a complete deserialization
  mapping. Document the supported drafts, that Draft 4 (SoA containers,
  extension type E) and column-major ND-arrays are rejected, ND-arrays of
  half floats, duplicate object keys, and link the Draft 3 specifications
  instead of master.
- Add an API page for basic_json::bjdata_version_t with an example, and
  link it from the nav, the API index and to_bjdata.
- Update binary_formats/index.md and binary_values.md, which still claimed
  that BJData has no binary type, and fix a wrong byte comment there.
- Document parse_error.115 and the out_of_range.408 cases for from_bjdata,
  the precise other_error.502 condition for to_bjdata, and reword the note
  on truncated unsigned integers in exceptions.md (only ND-array elements
  were truncated before 3.13.0).

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

* Regenerate single_include and apply astyle

Result of make amalgamate (including make pretty) for the preceding changes.

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

* Address review of the BJData documentation

The $ type restriction exists since Draft 2 (Draft 3 added B), $ requires a count, ND char above 127 is rejected on read, and the new API page is listed in alphabetical order in the nav.

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

* docs: format tables, use the Oxford comma

Reformat the tables changed by this PR (BJData serialization and
deserialization mappings, completeness and binary-value tables) so all
rows are aligned, and add the Oxford comma to lists of three or more
items in the added text.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-26 18:25:46 +01:00
Niels Lohmann 52e9f098eb Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-25 18:01:19 +01:00
Niels Lohmann ffd4242dc2 Docs: fill documentation gaps found in user questions (#5907)
* Docs: fill documentation gaps found in user questions

Add pages on class-hierarchy/smart-pointer/variant/chrono recipes, working
without exceptions, and large, streamed and partial input. Extend the FAQ
(23 entries, Known bugs first), parse error documentation (empty-input
checklist, line/column, diagnostic positions), element access, conversions,
creating values, ADL troubleshooting, memory, and build/distribution notes.
Add 14 examples with generated output. Correct the statement that parse errors
cannot be recovered from with -fno-exceptions.

The topics come from recurring questions on Stack Overflow, Reddit, Hacker
News, YouTube, and the project's GitHub discussions and issues.

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

* docs: declare range-for lists in variables to keep astyle quiet

astyle reformats a braced init list placed directly in a range-for
header; declare the list first so check_amalgamation passes.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-25 12:07:13 +01:00
Niels Lohmann a6c5d970f3 Merge branch 'develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-25 06:24:39 +01:00
Niels Lohmann 52b72b5684 Improve documentation: byte layouts, release pages, See also, dark-mode images (#5906)
- Make the iterator range illustrations legible in dark mode (prefers-color-scheme
  rules inside the SVGs).
- Add a "Byte layout" section with a color-coded byte table to each binary format
  page (BJData, BON8, BSON, CBOR, MessagePack, UBJSON), and highlight the smallest
  size per file in the comparison table.
- Add "See also" sections to the overview pages that lacked one.
- Split the release notes into one page per release, grouped by minor version on
  the overview page, with an "API changes" section per release generated from the
  API pages' version histories (hooks/api_changes.py).
- Fact-check the release notes and version histories against the release tags and
  correct wrong or misleading entries (e.g., json_serializer 2.1.0, merge_patch
  3.1.0, items, count, operator[], to_bjdata, std::string_view key support).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-24 17:57:44 +02:00
Niels Lohmann 5c2aba70f9 Merge branch 'develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-23 06:35:52 +02:00
Niels Lohmann e9970066c5 Scan strings with SSE2, SSSE3, or NEON (#5853)
* Scan strings with SSE2, SSSE3, or NEON

The string fast path found the end of a run of plain characters 8 bytes at
a time (SWAR) and validated non-ASCII text one sequence at a time, calling
validate_one_utf8() out of line for each.

The vector code of json_view's scanner, in the new shared header
detail/input/simd_scan.hpp, now does both 16 bytes at a time: SSE2 finds
the end of a run on x86-64, and the UTF-8 check of Keiser and Lemire runs
with NEON on AArch64 and with SSSE3 on x86-64. SSSE3 is not part of x86-64,
so the check is compiled for it with a function attribute and used when the
CPU has it (cached in a constant-initialized atomic), else the scalar check;
code compiled with -mssse3 skips the CPU check. The first word of a run is
still checked with SWAR (the first four with NEON, where a vector mask
costs more), as most keys and short values end there, and the scalar
helpers are always inlined. On anything else, the scalar code is unchanged.

The new macro JSON_NO_SIMD selects the portable code everywhere, including
the SSE2/NEON digit formatting of the floating-point writer. The lexer tests
now also run with JSON_NO_SIMD and, on x86-64, with -mssse3, and a new test
places every byte that ends a run at each offset across several 16-byte
blocks, after ASCII and after CJK text.

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

* Keep the string scan from slowing down short strings and dump() on Arm

Three benchmarks were 7-9% slower than develop on Apple M1 (Apple Clang,
-O3 -flto): Accept/jeopardy, Dump/citm_catalog, and Dump/jeopardy.

- dump(): the serializer passes a string without its closing quote, so
  plain_run_end() ran out of input and called the out-of-line NEON loop
  for every string, with fewer than 16 bytes left. The loop is now only
  called for 16 bytes or more.
- accept(): no string of jeopardy.json reaches the vector UTF-8 check,
  yet compiling it into the lexer's scan function made it 5% slower: the
  function runs once per token and now saved more registers and kept a
  stack slot. lexer_string_bulk_run() checks the first four words inline
  and continues out of line, and the serializer keeps string_bulk_run()
  inline, which is faster there.
- The byte that ends a run is read from the scanned buffer instead of
  through get(), which Apple Clang merged with the other get() calls that
  load the read position again right after it was stored (3%).

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

* Define string_bulk_run_from() only where lexer_string_bulk_run() calls it

With NEON and simdutf in C++17, lexer_string_bulk_run() takes the
string_bulk_run() path, so the out-of-line helper was unused.

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

* Do not dispatch the SSSE3 string scan with GCC's C++20 modules

GCC does not keep the target("ssse3") attribute on functions it reads
back from a module interface, so the module build (ci_module_cpp20,
gcc:latest) rejected the intrinsics in vector_utf8_run() with "needs isa
option -mssse3". With __cpp_modules, GCC now uses the portable UTF-8 check
like other compilers without the target attribute; the SSE2 scan stays,
and -mssse3 or more still compiles the SSSE3 check directly. Clang is not
affected.

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

* Include <cpuid.h> only once when json.hpp and json_view.hpp are both used

The SSSE3 dispatch of the string scan and the one of json_view each
include <cpuid.h>. Before GCC 11 the header has no include guard, so a
translation unit that includes both headers fails with GCC 10:
"redefinition of 'unsigned int __get_cpuid_max(unsigned int, unsigned int*)'".
Guard both includes with NLOHMANN_JSON_CPUID_INCLUDED.

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

* Add an ABI tag for JSON_NO_SIMD

JSON_NO_SIMD selects between two definitions of the internal scanning and
formatting functions. Like JSON_VIEW_NO_SIMD (_vns), it now appends _ns to
the inline namespace, so translation units built with and without it can
be linked into one program without ODR violations.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-21 20:00:50 +02:00
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 4971200b54 Add images of json_documents: save() and load() (#5632)
* Add images of json_documents: save() and load()

An image is a document stored so that loading it needs no
parsing: save() writes the node index, the text and the decoded
strings; the static load() reads an image written by save().

load() takes a pointer and size, a borrowed vector, or an owned
rvalue vector; the nodes are copied so they are aligned and can
be edited, while the text and decoded strings stay in the image.

image_check controls how much load() trusts the input: full
checks structure, bounds, strings and numbers, the parser's own
guarantees; bounds checks structure and bounds only; none skips
all checks, for images from a trusted source.

Layout is little-endian only ("NJVI" header, nodes, text, decoded
strings), following the idea of zero-copy formats such as
FlatBuffers and YaFF; the check follows FlatBuffers' Verifier.

New errors: parse_error.116 for a malformed image or a failed
check, type_error.320 for a discarded document or a big-endian
target.

A dedicated fuzzer and 6,000 seeded corruptions, checked under
ASan/UBSan, found and fixed two gaps: unchecked reserved header
fields, and unbounded null/boolean offsets that could make
dump() throw std::length_error.

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

* Fix MSVC errors in image test and add image_check doc anchor

Move the raw string literal out of the CHECK macro (MSVC preprocessor),
cast 64-bit header fields to std::size_t (C4244 on 32-bit), and give the
image_check section in load.md a real anchor for the mkdocs strict build.

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

* Check each distinct string and float range once in the full image check

The full check scanned the contents of every string node and every float token over its own range, so many nodes pointing to one large range made load() quadratic. The structural walk now only collects the ranges; after it, each kind is sorted and checked once per distinct range. Ranges of one kind that overlap without being identical are rejected, as save() never writes them (nodes that share a value share the whole range). The cost is linear in the size of the image plus sorting the ranges.

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

* Adapt the image tests to named documents and last-wins lookups

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

* Test that the targets of links never reach an image

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

* Test lookups in loaded images with duplicate and colliding keys

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

* Release the list of large objects once load() has built the indexes

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

* Test that invalid UTF-8 of a loaded image is not copied into an editable document

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

* Document that editable documents refuse invalid UTF-8 copied from a loaded image

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

* Expect first-wins lookups in the image tests

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

* Avoid useless casts of header fields in the image tests

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

* Fix clang-tidy 22 findings in unit-json_view_image.cpp and image.hpp

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

* Fix MSVC C4244 and C2017 in the image test

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

* Fix the indentation of a loop in the image test

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
- drop edit_storage.hpp, which edit.hpp includes

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

* Silence a clang-tidy C++17 finding in the image test

bugprone-suspicious-stringview-data-usage flags data() of the source view
under C++17, although the length is passed and checked by the REQUIRE
before it.

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

* Build the image link test without exceptions

load_result() exists only with exceptions; with JSON_NOEXCEPTION the test
loads the image with the check directly (a failed check aborts).

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

* Regenerate the amalgamated headers

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

* Follow the renames from the review of the view builder

The review of #5620 renamed document_data's tape/tape_size/tape_cap to
nodes/node_count/node_capacity and made the decode arena a
std::vector<char>; adapt the code of this change to it.

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

* Rename the emit lambda in the image writer for Qt compatibility

Qt defines emit as an empty macro, so a Qt header included before
json_view.hpp broke the lambda's declaration (see #5865). The slots
variables in the image tests are renamed as well.

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

* Address the review of json_document images

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 10:21:29 +02:00
Niels Lohmann 823eee3b59 Add editable json_documents: set, push_back, insert, and erase (#5630)
* Add editable json_documents: set, push_back, insert, and erase

basic_json_document gets a second template parameter, Editable
(false by default), plus the aliases json_editable_document,
json_editable_view, ordered_json_editable_document and
ordered_json_editable_view.

Editable documents can change values and structure without
rewriting the source text: set()/push_back() on values, keys,
array indices and JSON pointers; insert() before an array
element; erase() of an object key, array index or JSON pointer.

New values and element sequences go into edit storage that the
document owns and never moves, so views keep referring to their
value across edits and a parsed node never moves. Read-only
documents walk the plain node array and are unaffected.

Strings are checked for UTF-8 on entry, so dump() of an editable
document never throws type_error.316. Binary values cannot be
stored (type_error.319).

A seeded differential test applies random edits to an editable
document and to the equivalent ordered_json and compares both
after every step.

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

* Fix old clang and MSVC C4127 in editable json documents

Value-initialize the const std::less in find_parent (clang 3.4/3.6 do not
implement DR 253), and test the Editable template argument through a
function to avoid MSVC C4127.

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

* Copy nested values into a document without recursion

Counting and copying the nodes of a view or a basic_json value into an
editable document recursed once per nesting level, so that a deeply
nested value overflowed the stack. The four functions now walk the value
with an explicit stack, as materialize() does.

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

* Do not leave a half-assigned container when set_moved() throws

assign() rewrote the kind, length and extent of a slot before set_moved()
registered its new element sequence. set_moved() can throw
(std::bad_alloc from reserving the bookkeeping vectors) for a slot that
is not moved yet, which left a container without the moved flag that
showed its old children. The bookkeeping is now reserved first
(reserve_moved()), so that nothing after the first write to the slot can
throw. block_of() reserves before it marks anything for the same reason.

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

* Check strings copied from another document for valid UTF-8

An editable document only holds valid UTF-8, but copy_scalar() copied the
strings and keys of a view of another document unchecked. A document of
a weaker check (or a borrowed text that changed after parsing) could
therefore bring ill-formed UTF-8 into it. The copy is checked now, with
the error that dump() reports for the string; copies within the same
document stay unchecked.

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

* Allow the edit arena to grow up to 4 GiB - 1 bytes

append_text() doubled the capacity of the arena and rejected the result
if it exceeded 4 GiB, so that an arena of more than 2 GiB could not grow
even though the 32-bit offsets of nodes address 4 GiB - 1 bytes. The
capacity is now clamped to that limit (text_capacity()), and an append
is rejected only if the bytes themselves do not fit.

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

* Set a null value below a pointer as basic_json does

set(json_pointer, value) turned a null parent into an object for every
last reference token, so "/a/0" and "/a/-" below {"a":null} made
{"a":{"0":1}}, where basic_json's operator[](json_pointer) makes an
array. A null parent now becomes an array for "-" and for digit tokens
(filled with nulls up to the index) and an object otherwise. An invalid
index is reported before the parent changes.

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

* Replace a container by a scalar in constant time once it is linked

Replacing an array or object that spans several nodes by a scalar looks
up its parent from the root (find_parent), which is linear in the size
of the document: setting every element of a 20,000 element array took
more than half a second. The parent only has to switch to links once;
afterward the extent of the replaced value no longer matters. Nodes that
an entry of a moved sequence links to are now marked (node_flags::linked),
and assign() skips the lookup for them.

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

* Update the json_view banner and type_error.319 for editable documents

The banner still described a read-only view, and the documentation of
type_error.319 listed set and push_back only, although insert rejects
binary values as well.

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

* Assign the member that lookups find when set() meets duplicate keys

An editable document reads the last member of a repeated key (as the
read-only document does), but set(object, key, value) assigned the first
one: a view taken from object[key] before the call did not show the new
value. It now assigns the last member's value, keeps the key at the
position of its first occurrence (where materialize() puts it), and drops
the other members.

The seeded differential test now also edits documents whose objects
repeat keys and compares every lookup (operator[], at, find, value,
contains, count, and JSON pointers) with the parsed basic_json value.
A targeted test covers duplicates before and after edits that move the
object, in large objects with an index, in moved arrays, and in values
copied from other documents.

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

* Assign the first member when set() meets duplicate keys again

Lookups find the first member of a repeated key again, so set(object, key,
value) assigns that member (keeping the key where it is) and drops the
others, as documented before, and a view taken from object[key] shows the
new value. This undoes the code and documentation changes of 5cbb8e6d6.
Lookups in edited objects (navigation of editable documents) stop at the
first match, like those of parsed objects.

The tests that commit added expect the first member from lookups now. In the
seeded differential test, the documents with repeated keys repeat them after
the real members; the reference holds the first members, which the edits
address and the lookups are compared with, while materialize() is compared
with what parse() makes of the document's dump.

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

* Fix MSVC C4127 in the lookups of editable json documents

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

* Fix clang-tidy 22 findings in the json_view headers

Silence bugprone-casting-through-void for the SSE loads (a reinterpret_cast
would trip -Wcast-align=strict), use auto for a cast initialiser, add
parentheses to a mixed expression, and name bugprone-std-namespace-modification
in the NOLINTs of the tuple_size/tuple_element specialisations.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
(cherry picked from commit 0effbaa7a2)

* Fix clang-tidy 22 findings in unit-json_view_edit.cpp and edit.hpp

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

* Keep a raw string with a backslash out of a CHECK (MSVC C2017)

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), and the headers that json.hpp
already provides (abi_config, abi_macros, input_adapters, json_pointer,
cpp_future, string_concat, value_t, json_fwd), plus <version> for
std::nullptr_t, and removing <cstddef> and edit_storage.hpp.

- 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
- drop edit_storage.hpp, which edit.hpp includes

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

* Keep the view's edit headers clean for clang-tidy in C++17 mode

clang-tidy 22 checks the headers with -std=gnu++17 as well, where it asks
for a transparent comparator and std::make_unique. The regions map uses its
default comparator, and the allocation of the edit state keeps new (the
library is C++11) with a NOLINT.

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

* Regenerate the amalgamated headers

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

* Follow the renames from the review of the view builder

The review of #5620 renamed document_data's tape/tape_size/tape_cap to
nodes/node_count/node_capacity and made the decode arena a
std::vector<char>; adapt the code of this change to it.

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

* Expect count() to count every member in the edit tests

Since #5622, count() counts every member with the key, so documents
with duplicate keys no longer give 1.

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

* Count matching keys as unsigned in the json_view edit tests

Like in the access test, adding the int result of the conditional to a
std::size_t fails -Werror=sign-conversion with GCC.

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

* Address the review of erase() in editable json documents

From gregmarr's review of #5630:

- invalid_iterator.202 is thrown by overloads 1 and 2 only; the page said
  "every overload" and then excluded 3 in parentheses.
- The note on links says what moves (the links after the removed element,
  as insert() moves them the other way) and that every iterator over the
  container is invalidated, not only those after the removed element.
- edit.hpp compares keys with document_data::key_equals().

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

* Regenerate the amalgamated headers

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

* Address the review of editable json documents

From gregmarr's review of #5630:

- set() with a JSON pointer below a null value checks for "-" before
  scanning the token for digits.
- node_flags::storage is defined as escaped | edited, and the comment on
  document_data::base says that the fourth slot is unused.
- source_extent() names its root check.
- The integer-index overloads of set(), insert(), and erase() use a named
  trait instead of a negated condition, which astyle formats like the
  library's other enable_ifs.

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

* Regenerate the amalgamated headers

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

* Address the rest of the review of editable json documents

From gregmarr's review of #5630:

- alloc_nodes() gives a request of half of the next chunk or more a chunk
  of its own, so that the rest of the current chunk stays available for
  smaller requests instead of being abandoned.
- The comments on edit_state, append_text(), and reserve_moved() say that
  views stay valid across every edit (not just the first), that n is 0 for
  empty strings, and why both capacities are checked.
- The architecture page names flag bits 3, 4, and 5 (linked) separately
  and says that a discarded view has no node; erase.md rewords overload 3
  and says why it never throws invalid_iterator.202.

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

* Call alloc_nodes() before reading chunks.back() in the json_view chunk test

The operands of == are unsequenced, and MSVC evaluated
d->edits->chunks.back() before alloc_nodes() added the new chunk, so the
check compared the result with the previous chunk and failed on
msvc-arm64 (Debug and Release).

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-21 10:21:29 +02:00
Niels Lohmann 3ff37ead75 Scan json_view strings with SIMD and index large objects (#5628)
* Scan json_view strings with SIMD and index large objects

Speed up json_view's parser with SIMD scanning and a hash table
for large objects.

Long runs of string bytes are scanned 16 bytes at a time with NEON
(AArch64, GCC and Clang) and SSE2 (x86-64), both baseline
instruction sets. Keys keep 16 table checks before the vector
loop, because their lengths repeat from record to record; string
values get 8, because their lengths vary more. Non-ASCII text is
validated 16 bytes at a time with simdjson's "lookup4" check
(Keiser and Lemire, 2021), with NEON on AArch64 and, on x86-64,
with SSSE3. SSSE3 is not part of baseline x86-64, so the check is
compiled for SSSE3 with a function attribute and used only where
CPUID reports it, which all x86-64 CPUs since about 2011 do; the
answer is cached in a statically initialized atomic, so there is
no guard of a local static and no global constructor. The same
input is accepted either way. JSON_VIEW_NO_SIMD selects the
portable code.

On x86-64, string runs are now checked vector-first: one SSE2
compare from the first byte finds the end of most keys and short
values, instead of a branch per byte for the first 8-16 bytes.
AArch64 keeps the byte-wise steps, where a NEON mask costs more and
the branches predict well. Entering an object or array no longer
stalls: open() stores the parent's frame field by field instead of
building it on the stack and reading it back with wider loads,
which waited for the narrower stores to retire.

Objects with 128 members or more get an open-addressing hash table
built when the object closes, so operator[], at(), find(),
contains(), count(), value(), and JSON pointers take constant time
on average in such objects; of duplicate keys, the first is kept,
as for the linear search. The idea comes from Boost.JSON.

simdjson is credited in simd.hpp's SPDX block, the README, and
license.md.

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

* Fix GCC module build and MSVC C4127 in the json_view SIMD code

GCC ignores the target attribute in modules, so the SSSE3 dispatch is
disabled for the module interface (the check stays portable, SSE2 is kept).
Make the 8-vs-16 byte unrolling condition in scan_string_run a
preprocessor/template split to avoid a constant condition (C4127).

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

* Remove an accidentally committed GCC module cache

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

* Bound the probe length of the large-object hash index

The key hash is not seeded, so keys chosen to collide made building the table quadratic (20,000 colliding keys took 470 ms to parse). A key may now sit at most 64 slots from its home slot; if a key would sit further away, the table is dropped and the object is searched linearly. Lookups stop after the same distance.

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

* Release the spare capacity of the hash index in shrink_to_fit

shrink_to_fit() now trims the tables of large objects like the node array and the decoded strings, and the list of large objects is released as soon as the tables are built.

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

* Use the portable string scan on non-x86 targets that define __SSE2__

WebAssembly with -msse2 defines __SSE2__, but has no <cpuid.h> or x86 intrinsics headers.

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

* Document the hash index number in node::extra

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

* Keep the last of duplicate keys in the object hash index

Lookups in objects with 128 members or more now return the last member of
a repeated key, like the linear search of smaller objects and like
materialize() and basic_json::parse(). build_object_index let the first
occurrence win, so the same text gave different results depending on the
size of the object.

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

* Keep the first of duplicate keys in the object hash index again

Lookups in objects with 128 members or more return the first member of a
repeated key again, like the linear search of smaller objects. This undoes
the code change of a69542046; its test now expects the first member from
lookups (with and without a table) and the last value from materialize()
and basic_json::parse().

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

* Fix clang-tidy 22 findings in the json_view headers

Silence bugprone-casting-through-void for the SSE loads (a reinterpret_cast
would trip -Wcast-align=strict), use auto for a cast initialiser, add
parentheses to a mixed expression, and name bugprone-std-namespace-modification
in the NOLINTs of the tuple_size/tuple_element specialisations.

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

* Fix clang-tidy 22 findings in unit-json_view.cpp and unit-json_view_builder.cpp

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

* Avoid GCC useless-cast and strict-overflow warnings in unit-json_view.cpp

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

* Index strings with size_t in the colliding-keys test (MSVC C4244 on Win32)

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>

* Move the dump, comparison, and large-object tests to unit-json_view_dump.cpp

The dump and comparison tests moved to their own file in the dump pull
request; the hash index tests of this branch join them there.

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

* Regenerate the amalgamated headers

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

* Follow the renames from the review of the view builder

The review of #5620 renamed document_data's tape/tape_size/tape_cap to
nodes/node_count/node_capacity and made the decode arena a
std::vector<char>; adapt the code of this change to it.

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

* Rename slots in the object index for Qt compatibility

Qt defines slots as a macro, so a Qt header included before
json_view.hpp broke the declarations of the local variable (see #5865).
The test variable is renamed as well.

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

* Address the review of the json_view object index and SIMD scan

From gregmarr's review of #5628:

- Docs and comments say that the hash index is one of the object's keys.
- object_index.hpp: conditional_static_cast for the hash, "slot" for the
  table position, no flag for a degenerate table, and a static_assert
  that the smallest indexed object is larger than the probe window.
- scan.hpp unrolls with NLOHMANN_VIEW_REPEAT_FIRST_8/SECOND_8.

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

* Regenerate the amalgamated headers

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

* Encode JSON_VIEW_NO_SIMD and JSON_VIEW_USE_SSSE3 in the ABI namespace

Both macros select between definitions of the same inline functions, so
translation units that disagree on them violated the ODR. Like the other
ABI-affecting macros, they now add a tag to the inline namespace (_vns and
_vssse3), and the docs replace the "Define consistently" warning with the
usual ABI compatibility note. From gregmarr's review of #5628.

nlohmann_json.natvis covers twice as many tags now, so it lists four times
as many namespaces (14.7 MB instead of 3.4 MB).

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

* Regenerate the amalgamated headers

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

* Do not include type_traits.hpp directly in the object index

json.hpp, which object_index.hpp already includes, provides it; included
directly, the json_view amalgamation (which only treats nlohmann/json.hpp
as external) copied the json internals into json_view.hpp a second time,
so the fuzzers, which include both single headers, failed with
redefinitions (make_void, integer_sequence, priority_tag, ...).

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

* Compare keys with key_equals() in the object hash index

As the linear lookups do since the second review round of #5622.

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 10:21:28 +02:00
Niels Lohmann 4c3a3eb5b5 Add dump() and comparisons to json_view (#5624)
* Add dump() and comparisons to json_view

Add basic_json_view::dump() and the comparison operators, and read
floats from the parser's digit layout instead of rescanning the
token.

dump(indent, indent_char, ensure_ascii, number_format) writes a
value the way ordered_json::parse(text).dump() writes it for the
same arguments: members in document order, all of them should a
key occur more than once; strings escaped by the same rules, using
the library's scanning kernels; floats written with the library's
to_chars conversion, so the output equals basic_json's byte for
byte; integers copied from the source, where they are already
canonical, except -0, which parse() reads as 0. There is no
error_handler argument, because the view only holds valid UTF-8.
number_format::source copies numbers exactly as they appear in the
source (e.g. "1.50", "1E2", "-0"), which basic_json cannot provide.
operator<< takes the indentation from the stream width, as for
basic_json. The writer walks iteratively, so nesting depth is
limited by memory only.

operator== and operator!= compare two views, or a view and a
basic_json value in either order, by the rules basic_json's
operator== uses: numbers compare by value across their types,
objects compare by their members with duplicate keys resolved as
parse() resolves them, member order matters only where the object
type keeps one, and discarded views compare as discarded basic_json
values do, including under JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON.
Nothing is materialized except single scalars.

While parsing, the view now records where the integer digits, the
fraction digits, and the exponent of a float token are, so floats
and doubles with at most 19 digits are read from that layout with
the library's decimal_to_float() instead of rescanning the token.
Both round correctly, so the values are those of parse(). get<double>(),
materialize(), dump(), and the comparisons all use it.

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

* Avoid raw string with escapes inside CHECK macro (MSVC C2017)

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

* Size the dump buffer of a small value by its own extent

The source extent of a value was read from the next node, falling back to the rest of the document when that node held a decoded string. dump() of a small value could thus allocate a buffer as large as the document. Skip a few such nodes, cap the fallback estimate, and shrink a buffer that is much larger than its output.

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

* Hold the documents of the dump and comparison tests in names

root() of a temporary document is deleted: its views would dangle.

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

* Do not shrink the output of dump()

finish() copied the whole output when the buffer was more than twice as
large as the result (citm dump +11%). The tighter source_extent()
estimate already keeps the buffer of a small value small.

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

* Document and test first-wins lookups next to dump() and ==

dump() writes every member and == resolves duplicate keys as parse()
does, whereas lookups find the first member of a duplicate key.

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

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

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

* Split the dump and comparison tests off unit-json_view.cpp

The MinGW linker of the Windows clang jobs cannot link object files with more
than 32767 sections ("relocation truncated to fit: IMAGE_REL_AMD64_REL32
against `.rdata'"). unit-json_view.cpp reaches that limit as the stack
grows, so its "json_view dump" and "json_view comparison" test cases move
into unit-json_view_dump.cpp. The test generator and has_duplicate_keys()
that both files use move into json_view_test_helpers.hpp.

The new file mentions JSON_HAS_CPP_17, so it is built for C++17 like the file
it was split from.

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>

* Regenerate the amalgamated headers

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

* Follow the renames from the review of the view builder

The review of #5620 renamed document_data's tape/tape_size/tape_cap to
nodes/node_count/node_capacity and made the decode arena a
std::vector<char>; adapt the code of this change to it.

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

* Keep the stream includes of json_view.hpp for IWYU

json_view.hpp uses std::istream and std::ostream itself, but IWYU sees
them through the exported json.hpp and asked to remove both includes,
which fails ci_single_binaries (single_json_view).

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

* Address the review of json_view dump() and comparisons

From gregmarr's review of #5624:

- The output buffer takes string literals without a length.
- write_float() names the IEEE single/double condition once, as the
  library's serializer does.
- equal() checks the types first and compares with !=; the reference to
  the top frame is noted as dangling after pop_back().
- dump.md: one paragraph per case in the notes.

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

* Regenerate the amalgamated headers

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

* Exclude all json_view test files from Infer's reports

The same std::unique_ptr false positive (USE_AFTER_DELETE) also shows for
two json_documents parsed in one lambda in unit-json_view_dump.cpp
(ci_infer). It affects any test that holds several documents, so the
exclusion now covers tests/src/unit-json_view*.cpp; ASan and Valgrind
cover these tests.

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

* Allow the string literal parameter of the view serializer's put() for clang-tidy

The overload takes the literal by array reference so that its length is a
template parameter, like scan_literal() and the C array overloads of
to_json() and from_json().

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

* Bind the serializer's frame only after the check for its end

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 10:21:28 +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 4da932f518 Make parsing from std::istream and FILE* fast (#5828)
* Make parsing from std::istream and FILE* fast

Squashed onto develop cd6b428ef (CI fixes from #5860). Original commits:

- Let the lexer's bulk fast paths run on a window of the input
- Scan the get area of an input stream in bulk
- Lock a FILE once per parse instead of once per character
- Add benchmarks for parsing from a FILE* and for many values from a stream
- Avoid implicit unsigned char to char conversion in stream tests
- Make file_input_adapter::unlock() safe to call on a moved-from adapter

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

* Add ABI tags for JSON_DISABLE_STREAM_BULK_SCAN and JSON_DISABLE_UNLOCKED_FILE_IO

Both macros select between two definitions of an input adapter, so
translation units compiled with different settings violated the ODR when
linked together. Like the other ABI-affecting macros, they now append a
tag to the inline namespace: _dsbs and _dufio. Their defaults move to
abi_macros.hpp so that json_fwd.hpp sees them, and the natvis file is
regenerated for the new namespaces.

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

* Skip the exception-only checks of the stream input tests without exceptions

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-19 22:00:58 +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 99d4d1097d Do not self-host shields.io badges in the documentation (#5821)
The privacy plugin downloads img.shields.io badges at build time; when
shields.io times out, mkdocs build --strict aborts and the
ci_test_build_documentation job fails until it is restarted. Exclude
the host like repology.org; the version badges stay current this way.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-14 17:39:33 +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 6197341a21 Clean up non-code files (#5801)
* Clean up README, contribution guide, and repository metadata

- REUSE.toml: fix the Hedley path and SPDX id (CC0-1.0), mark the docset
  icons as the public-domain JSON logo
- CITATION.cff: v3.12.0 was released on 2025-04-11
- FILES.md: list all workflows, describe the Meson option defaults
- README: ctest -LE, table of contents, typos, stale Android/MinGW advice,
  moved links, merge duplicate Thanks entries, list the analysis tools
  used in CI
- CONTRIBUTING: iterative parser, json_literals.hpp is generated, links
- .gitignore: backups and release outputs; .gitattributes: mark
  generated files
- labeler: label other build systems and .github documentation
- MODULE.bazel: add the module version

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

* Clean up CI, CMake, Makefile, and Bazel files

- CMakeLists.txt: avoid VERSION_GREATER_EQUAL, which CMake < 3.7 lacks
- ci.cmake: test JSON_DisableTupleReferenceConversion in ci_cmake_flags,
  remove unused variables and unreachable per-compiler targets, look up
  Clang tools consistently, forward CMAKE_CXX_FLAGS to ci_module_cpp20,
  format json_literals.hpp and remove backups in ci_test_amalgamation
- BUILD.bazel: add json_literals.hpp to the single-header target
- workflows: format json_literals.hpp before copying it, drop the obsolete
  natvis --version plumbing, name natvis and macro_builder in failure
  messages, drop the duplicate amalgamation job, install Valgrind only
  where needed, republish docs on version bumps, fix stale names
- Makefile: complete .PHONY and help, check-amalgamation always restores
  the checked-in files, natvis uses its own venv, macro_builder_check
  installs astyle, clean removes the fuzzer binaries
- remove tools/amalgamate/config_json_view.json (json_view.hpp is not on
  develop yet)

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

* Fix inaccuracies in the documentation

- version history: json_base_class_t (3.11.3), JSON_HAS_CPP_11 (3.10.0),
  JSON_HAS_RANGES exclusions, define-type macros, ABI tags
- releases: 3.12.0 raised the minimum CMake version
- from_*: the (ptr, len) overloads are deleted, not removed, in 4.0.0
- contains/count/find: document the deleted integral overloads
- add JSON_HAS_RANGE_VIEW_CONVERSION and list the JSON_HAS_* macros in
  the macro overview
- mention BON8 and error_handler where binary formats are listed
- broken links, outdated URLs, warning count, Hunter v0.26.12
- copy_markdown_source hook: expand snippets in the Markdown copies

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

* Pass /EHsc to the Windows C++20 module build

ci_module_cpp20 now forwards CMAKE_CXX_FLAGS to the module build. The
Windows workflow sets CMAKE_CXX_FLAGS, which replaces CMake's MSVC
defaults including /EHsc, so <chrono> failed with C4530 under /WX.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-11 08:21:51 +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
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
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
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 c2619bf460 Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 18:03:20 +02:00
Niels LohmannandMuhammad Amir bin Mohamad Ghazaly 8c1f60a45e Store maps with enum keys as objects (opt-in) (#5600)
* Store maps with enum keys as objects (opt-in)

Maps with enum keys, such as std::map<E, T>, are stored as arrays of
[key, value] pairs, because enums are not convertible to the string type
of object keys - even if NLOHMANN_JSON_SERIALIZE_ENUM maps them to
strings (#4378).

The new JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS macro stores them as objects
instead, converting each key with the enum's to_json. It applies to any
map-like type with enum keys (std::map with any comparator,
std::unordered_map, ...). A key that does not convert to a string throws
type_error.302, and two keys converting to the same string throw the new
type_error.318, rather than losing an entry. The macro changes the output
of inline functions, so it is part of the ABI tag (_ekmo).

Reading needs no macro: std::map and std::unordered_map with enum keys
are now also read from objects, converting each key with the enum's
from_json. That input was rejected before, and arrays of pairs are still
read, so data written either way can be read.

This supersedes #4531, which first proposed storing these maps as
objects.

Co-authored-by: Muhammad Amir bin Mohamad Ghazaly <amirghaz@umich.edu>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Keep multimaps with enum keys as arrays of pairs

With JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS, is_enum_keyed_map also matched
std::multimap and std::unordered_multimap. Storing them as objects throws
type_error.318 as soon as a key occurs twice, which is the normal case for
a multimap, so such values could no longer be serialized at all once the
macro was enabled, although they are stored losslessly as arrays of
[key, value] pairs without it.

Exclude maps with non-unique keys from is_enum_keyed_map. They are
detected by insert(value_type) returning an iterator rather than a
pair<iterator, bool>. Map-like types without such an insert() are still
treated as before.

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

* Move the default enum-keyed map tests out of unit-conversions.cpp

The Windows clang 20.1.8 job (MinGW, Debug) failed to link
test-conversions_cpp17 with "relocation truncated to fit:
IMAGE_REL_AMD64_REL32 against .rdata": the object file of
unit-conversions.cpp was already close to the limit, and the new
"maps with enum keys" test case pushed it over. windows.yml asks to keep
these objects small by splitting test files.

Move the test case unchanged into unit-enum_keyed_maps_default.cpp,
with the three enums it needs. It still honors a -D flag for
JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS, as before. unit-conversions.cpp
is back to its state on develop.

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

* Build the enum-keyed map test object instead of parsing it

ci_test_diagnostic_positions failed in unit-enum_keyed_maps_default.cpp:
with JSON_DIAGNOSTIC_POSITIONS, a parsed value adds its byte range to
the exception message ("(bytes 0-7) type must be array, but is
object"), so the exact-message checks did not match. Build the object
in memory, like unit-custom-array-type.cpp does.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Muhammad Amir bin Mohamad Ghazaly <amirghaz@umich.edu>
2026-10-04 17:54:05 +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 0c4462676d Document options to reduce compile times (#5611)
* Document options to reduce compile times

Add an integration page that collects the ways to reduce compile times
with measurements: json_fwd.hpp in headers, JSON_NO_AUTOMATIC_UDLS,
explicit instantiation with extern template, modules, and precompiled
headers, and notes that JSON_NO_IO and JSON_USE_GLOBAL_UDLS have no
measurable effect.

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

* Include only json_literals.hpp in the JSON_NO_AUTOMATIC_UDLS examples

json_literals.hpp includes json.hpp itself, so including both is redundant.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 12:23:53 +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 f56b418c56 Follow each binary format's UTF-8 rule: strict writers (CBOR/UBJSON/BJData/BSON), lenient readers (#5741)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 12:13:48 +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 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
Niels Lohmann 63c10a51fc Review and extend the documentation, and check it in CI (#5638)
* Review and extend the documentation, and check it in CI

A review of all documentation pages found factual errors, dead links,
missing cross-references, and gaps in examples. This fixes them and adds
checks so the same problems are caught automatically.

Fixes:
- wrong signatures and version histories (operator!= C++20 member,
  binary() subtype type, get<PointerType>(), JSON_NO_THREAD_LOCAL, ...)
- stale descriptions (number parsing since #5283, UBJSON table, SAX
  example that no longer compiled, tsl::ordered_map advice)
- dead internal and external links; repology.org badges (the domain is
  suspended) replaced by badges that query the registries directly
- deprecation notes link the migration guide; the guide itself fixed

Additions:
- "See also" sections, cross-references, 25 runnable examples, 12
  Mermaid diagrams, new API pages for json_pointer::operator<=> and
  byte_container_with_subtype::operator==/!=
- landing page, guides for untrusted input and performance
- "unreleased" badge after versions newer than the latest release

Checks:
- strict documentation build (broken links/anchors fail it); CI and
  the publish workflow fetch the full history the build needs
- weekly external link check, Mermaid syntax check in CI
- check_structure.py: example titles, heading levels, alt texts,
  header links, docset index coverage; its unused-example check works
  again
- all examples produce the same output on every platform

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

* Keep the customer links that could not be fixed

A dead link on the customers page is still the evidence of where the
use of the library was documented. Keep the original URLs of the entries
without a working replacement (Marne, Cisco Webex Desk Camera, Philips
Hue, CyberArk) and exclude exactly these URLs from the link check.

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

* Correct the duplicate-key recipe's claim about SAX positions

The SAX interface's key() receives no position either; only parse_error()
does. Also note that the recipe does not report the path to the repeated
key (see discussion #5085).

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

* Say the library is available as a single header and mention json_fwd.hpp

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

* Correct documentation errors found while hunting for bugs

- patch/patch_inplace: list the JSON pointer errors parse_error.106-109
  and out_of_range.402/404, and quote the actual parse_error.105 message.
- unflatten: list parse_error.106/107/108 and out_of_range.404.
- to_bson: list out_of_range.415 (binary subtype above 255) and note
  that 412 and 415 are new in 3.13.0.
- to_string: state that string_t must be convertible to std::string, also
  in the StringType requirements table.
- JSON Lines: a `while (input >> j)` loop also throws after the last value
  for concatenated JSON values; show a loop that works for both.
- BON8: a string gets 0xFF only if nothing follows it in the message; a
  string at the end of an array or object is ended by 0xFE.
- custom_string_type.hpp: add operator+=(char), which the "Always
  required" list asks for (json_pointer::to_string, flatten, unflatten,
  and diff did not compile), and an ADL int_to_string for diff and items.

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

* Cache the release headers with functools.lru_cache

Codacy (Pylint) flagged the mutable default argument that header() used
as its cache. functools.lru_cache keeps the same memoization without it.
The script's output is unchanged.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-02 11:32:15 +02:00
Niels Lohmann 7e8e8e219b 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/json.hpp
#	single_include/nlohmann/json.hpp
2026-09-30 22:53:03 +02:00
Niels Lohmann 791cd88dfc Fix raw-TeX formulas and other documentation infrastructure debt (#5736)
* Fix math formulas rendering as raw TeX in the published docs

The privacy plugin self-hosts MathJax 2.7.0 but drops its
?config=TeX-MML-AM_CHTML query string, so the rehosted script loads no
input jax and the 10 formulas across 6 pages render as raw TeX to
readers. Remove pymdownx.arithmatex and the MathJax extra_javascript
entry, and rewrite the formulas in plain HTML (<sup>, <i>) instead.
This also drops a nine-year-old third-party script from every page.

Part of #5718

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

* Fix publish_documentation triggers and persist unneeded git credentials

publish_documentation.yml only triggered on docs/mkdocs/** pushes, but
the site also embeds .github/CODE_OF_CONDUCT.md, CONTRIBUTING.md,
SECURITY.md, cmake/{clang,gcc}_flags.cmake, .clang-tidy,
tools/astyle/.astylerc and tests/fmt_formatter/project/main.cpp via
pymdownx.snippets, so changes to those files never republished the
site. Extend the path filter to cover them, and switch runs-on from
the long-pinned ubuntu-22.04 to ubuntu-latest to match
ci_test_documentation.

Also add persist-credentials: false to the checkouts in ci_icpx and
ci_nvhpc (ubuntu.yml) and msvc-vs2026/msvc-arm64 (windows.yml), none
of which pushes with git, matching every other checkout in these
workflows.

Part of #5718

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

* Fix example build: broken debug echo, deprecations hidden for everything

docs/Makefile's debug echo used a space instead of a comma in
$(call cxx_standard ...), so it always printed an empty standard.
Every example was also compiled with -Wno-deprecated-declarations,
which would silently hide an accidental deprecated-API call in any of
them. Factor the duplicated compile flags into EXAMPLE_CPPFLAGS/
EXAMPLE_WARNFLAGS, build with -Werror=deprecated-declarations by
default, and only allow the three examples that intentionally
document deprecated API (the DEPRECATED_EXAMPLES list) to suppress it.

Part of #5718

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

* Fix check_structure.py NOLINT parsing and an off-by-one report line

`line.strip("<!-- NOLINT")` followed by `.strip(" -->")` strips any of
the characters in those sets from both ends, not a literal prefix; it
only happened to work for "Examples". A NOLINT'd section name
starting with N, O, L, I or T (e.g. "Notes", "Template parameters",
"Iterator invalidation", "Literals") was silently mangled, so the
suppression did not apply and the checker could report a spurious
missing/misordered section. Parse the comment with a regex instead.
The same fragile strip() pattern was used for heading text; replace it
with a plain prefix slice. Also fix the admonition_title report, which
used the 0-based line index while every other report in the file uses
lineno+1.

Part of #5718

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

* Fix docset README's non-existent make target and stale fallback URL

The README told readers to run `make nlohmann_json.docset`, but the
Makefile's targets are `all`, `JSON_for_Modern_C++.docset` and
`install_docset_zeal`; the documented command has failed with "No
rule to make target" since #2967 (2021). Point the README at the real
target and folder name. Info.plist's DashDocSetFallbackURL also still
pointed at the old nlohmann.github.io/json/ URL instead of the
canonical https://json.nlohmann.me/ from mkdocs.yml's site_url.

Leave list_missing_pages/list_removed_paths alone: they may become
redundant once #5638's check_docset() lands, which is a follow-up.

Part of #5718

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

* Remove two leftover Doxygen-era .link files from the examples directory

parse__iterator_pair.link and parse__pointers.link each held only a
Wandbox "online" permalink from the old Doxygen docs. #3071 deleted
every other .link file in 2021; these two came in through a parallel
PR (#3100) and were never referenced by any page, script or config.

Part of #5718

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

* Fix MacPorts CMake example to include its own snippet files

The MacPorts "Example: CMake" block included
integration/homebrew/example.cpp and
integration/homebrew/CMakeLists.txt instead of the MacPorts files
right next to it, a copy-paste slip from the Homebrew section. Nothing
referenced integration/macports/CMakeLists.txt as a result. The page
rendered correctly only because the homebrew, macports and
vcpkg/CMakeLists.txt snippets are byte-identical, so a future edit to
the MacPorts files would not have shown up on the page.

Part of #5718 item 6

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

* Do not persist git credentials in publish_documentation's checkout

The checkout step in publish_documentation.yml left the default
persist-credentials: true, so GITHUB_TOKEN stayed writable in
.git/config for the rest of the job (zizmor's artipacked finding). The
Deploy documentation step authenticates through its own github_token
input to peaceiris/actions-gh-pages and does not push with the
checked-out credentials, so persist-credentials: false is safe here,
matching every other checkout in the workflow set.

Overlaps #5638, which edits this same checkout step (adds
fetch-depth: 0); expect a rebase conflict there.

Part of #5718 item 2

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

* Replace list_missing_pages/list_removed_paths with a comm(1)-based diff

The docset Makefile's list_missing_pages ran one sqlite3 query per
mkdocs page, and list_removed_paths nested a loop over all mkdocs pages
inside a loop over all docset index paths (O(n*m) shell iteration).
Issue #5718 item 5 suggested removing or reducing these targets once
#5638's check_docset() lands, but that PR is still open and covers only
API pages and macros, not the full page set these targets check.
Replace the loops with two sorted path lists (DOCSET_PAGE_PATHS from
mkdocs' markdown sources, DOCSET_INDEX_PATHS from the built docset
index) compared with a single comm(1) call each, verified to produce
output identical to the old loops against the current docSet.dsidx.

The sed expression used '#' as its delimiter, which GNU Make reads as
a comment character even inside a variable assignment, truncating the
line and orphaning the closing paren of $(shell ...) ("unterminated
call to function 'shell': missing ')'"). Use '@' as the delimiter
instead.

Part of #5718 item 5

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 22:15:20 +02:00
Niels Lohmann 3b6ae43c53 Add JSON_DISABLE_TUPLE_REFERENCE_CONVERSION to fix std::tuple conversions (#5598)
* Add JSON_DISABLE_TUPLE_REFERENCE_CONVERSION to fix std::tuple conversions

basic_json can be constructed from std::tuple<json&>, which it turns into
a one-element array. Because of this, std::tuple picks its converting
constructor that converts the whole source tuple instead of the
element-wise one. As a result, std::tuple<const json&> built from
std::forward_as_tuple(j) binds to a temporary (a compile error with libc++,
a dangling reference with other standard libraries), and std::tuple<json>
built the same way holds [j] instead of a copy of j.

The new opt-in macro JSON_DISABLE_TUPLE_REFERENCE_CONVERSION (CMake option
JSON_DisableTupleReferenceConversion) removes the conversion from a
one-element tuple holding a reference to the same basic_json type, so
std::tuple converts element-wise. It is off by default, so existing
behavior is unchanged. It does not change any function body and therefore
is not part of the ABI tag.

Fixes #2226

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

* Convert one-element tuples to arrays on every compiler

to_json for std::tuple assigns a braced list, j = { std::get<Idx>(t)... }.
With a single element that is itself a basic_json, Apple clang 15 and 16
treat j = {x} as a copy of x, so std::tuple<json>{true} became true
instead of [true]. The macOS jobs (Xcode 15.1, 16.1) failed the new
checks in unit-disable-tuple-reference-conversion and unit-regression2.

The one-element overload that already handles
JSON_BRACE_INIT_COPY_SEMANTICS builds the array (or object, for a
[string, value] element) explicitly, the same way the initializer-list
constructor does. Use it unconditionally. The output is unchanged on
compilers that already wrapped the element.

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

* Skip json reference tuple tests on clang < 4 and GCC < 5

ci_test_compilers_gcc_old (4.8) and ci_test_compilers_clang (3.4) could
not compile the new tuple tests. Creating a std::tuple of basic_json
references, e.g. std::forward_as_tuple(j), makes these compilers
instantiate basic_json's conversion operator for libstdc++'s internal
tuple bases, which fails hard. This happens with and without
JSON_DISABLE_TUPLE_REFERENCE_CONVERSION, so it is a limitation of these
compilers, not of the new option.

Tested with the CI images: clang 3.4 to 3.9 and GCC 4.8 and 4.9 fail,
clang 4, 5, and 6 and GCC 5 and 6 compile all cases. Skip only the
checks that create such tuples; the is_constructible checks still run.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 20:53:56 +02:00
Niels Lohmann 5f1727cef2 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
2026-09-30 20:11:28 +02:00
Niels Lohmann 6fc0d501f3 Move the user-defined string literals to <nlohmann/json_literals.hpp> and add JSON_NO_AUTOMATIC_UDLS (#5610)
* Add JSON_NO_UDLS to leave out the user-defined string literals

The bodies of operator""_json and operator""_json_pointer call the
parser, so every translation unit including the library instantiates it,
even if it never parses anything. Defining JSON_NO_UDLS leaves the
literals out entirely, which saves 15-35% compile time for such
translation units (#5294). Nothing changes if the macro is not defined.

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

* Mention JSON_NO_UDLS in the list of exported module symbols

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

* Move the user-defined string literals to <nlohmann/json_literals.hpp>

Following the review in #5294, the literals now live in their own header
instead of being removed entirely: <nlohmann/json.hpp> includes it at the
end unless JSON_NO_AUTOMATIC_UDLS (renamed from JSON_NO_UDLS) is defined,
so a project can opt out globally and include the header only where the
literals are used.

The header only uses public and standard macros, because the library's
internal macros are undefined at the end of json.hpp and the amalgamation
inlines macro_scope.hpp only once. For the same reason, the library no
longer defines and undefines JSON_USE_GLOBAL_UDLS, so a user's definition
is still visible to the header. The single-header copy is identical to
the multi-header one, as it only includes <nlohmann/json.hpp>. The module
always exports the literals.

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

* Fix CI: include cycle, GCC 4.8 literal operator spacing, and global UDLs off in the JSON_NO_AUTOMATIC_UDLS test

- Suppress clang-tidy misc-header-include-cycle on the intentional mutual
  include of json.hpp and json_literals.hpp.
- Use operator"" _json with a space for GCC 4.8 in the test's detection
  aliases, as the header does.
- Only test the global literal operators when JSON_USE_GLOBAL_UDLS is on.

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

* Declare the literal operators through a local macro

The GCC 4.8 spacing condition was repeated for both operator definitions
and the global using-declarations. NLOHMANN_JSON_LITERAL_OPERATOR(suffix)
now selects operator""##suffix or operator"" suffix in one place and is
undefined at the end of json_literals.hpp.

Suggested by gregmarr in review.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 20:08:17 +02:00
Niels Lohmann 9adb510a0d Recover from parse errors when parse_error() returns true (#3989)
The return value of json_sax::parse_error() was documented both as "must
return false" and as "whether the parsing should continue", and the code
just passed it on. For JSON text, parsing stopped anyway, but sax_parse()
could report success for invalid input. The binary readers read on after
the error, looping forever on a CBOR indefinite-length array without its
end.

Now false stops parsing, and true recovers from the error:

- JSON text is repaired with the smallest local edit (insert a missing
  ',' or ':', remove a stray token, keep the readable part of a broken
  string or number, null for a value that cannot be read, close the
  innermost container at a wrong closing bracket and all of them at the
  end of the input), and parsing continues. The SAX events stay balanced,
  every key is followed by exactly one value, and each token is reported
  at most once.
- The binary formats cannot resynchronize, so they stop, but complete
  the value read so far.

sax_parse() returns false after any error. parse(), accept(), and the
from_*() functions never recover and compile to the same code as before.

Supersedes #4522.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-27 20:16:42 +02:00
Niels Lohmann 1e101ecac1 Add BON8 support (#2998)
* Add BON8 support

Add to_bon8/from_bon8 and input_format_t::bon8 for BON8, a binary format
that uses the byte values that cannot begin a UTF-8 character as type
markers, so strings need no length prefix. It is the most compact of the
supported binary formats on the benchmark files.

The reader is non-recursive like the other binary readers. A string ends
at the first byte that cannot continue it, so the reader hands the one or
two bytes it reads past a string back to the value that follows. The
writer produces the canonical representation of the specification, except
for NFC normalization; its output is identical to that of the reference
implementation (HikoGUI) on all files of the test data.

The round-trip tests need the .bon8 files of json_test_data 3.2.0.

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

* Address review comments

- Reuse detail::validate_one_utf8 to check strings in to_bon8; the error
  now names the first byte of the invalid sequence.
- Document that to_bon8 leaves bytes in the output adapter on an
  exception, and that string_open is only an output of write_bon8_marker.
- Explain why the pushback buffer of the BON8 reader cannot overflow.

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

* Select the BON8 float prefix by type

get_bon8_float_prefix only depends on the type of its argument, so make
the type a template parameter instead of passing an unused value.

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

* Rename a test variable that Flawfinder mistakes for read()

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

* Fix the BON8 CI failures

- compare the float in write_bon8_float with number_float_t constants,
  so GCC does not warn about a float-to-double conversion
- mark check_bon8_utf8's context as used when exceptions are disabled
- choose the compact float prefix in a helper rather than with nested
  conditional operators (clang-tidy)
- use auto for the cast in the BON8 integer reader (clang-tidy)
- write the int32 minimum test values as long long literals (MSVC C4146)

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

* Amalgamate

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

* Read BON8 strings in bulk from contiguous input

- copy the valid UTF-8 of a string in one step when the input is
  contiguous (twitter.json is read in 1.68 instead of 2.52 ms,
  jeopardy.json in 196 instead of 297 ms, close to CBOR and MessagePack)
- share the new valid_utf8_prefix() with the writer's UTF-8 check, which
  now skips ASCII 8 bytes at a time
- let the fuzzer check that contiguous and stream input give the same
  value or error, and test both paths in the unit tests
- clarify that a second 0xFF after a string is an empty string

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

* Link the BON8 functions from the other binary format pages

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

* Name the bulk scan flag after the input, not BON8

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

* Read BSON keys in bulk from contiguous input

BSON keys (and array indices) are C-style strings, which were read byte
by byte. For contiguous input they are now read up to their \x00-byte in
one step, using the same bulk_scan flag as BON8 strings: twitter.json is
read in 1.46 instead of 2.01 ms, citm_catalog.json in 2.93 instead of
3.33 ms, jeopardy.json in 182 instead of 207 ms. canada.json, whose keys
are almost all one-digit array indices, takes 2 % longer.

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

* Fix the BON8 CI failures of the bulk-read tests

- skip the contiguous-versus-stream tests of BON8 strings and BSON keys
  when exceptions are disabled: they catch the parse errors of invalid
  input, and without exceptions the library aborts instead
- use static_cast for the int64 test value (google-readability-casting)

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

* Move the explicit basic_json instantiation into its own test file

Linking test-regression3_cpp20 with clang and MinGW failed with
"relocation truncated to fit: IMAGE_REL_AMD64_REL32 against `.rdata'",
as test-regression2 did before #5511. The explicit instantiation of
basic_json<> for #4825 compiles every member function, including the
BON8 reader and writer, into that object, and it was already close to
the limit (2,226,104 bytes on develop, 2,234,960 with BON8; clang -O1,
C++20).

Give the instantiation a file of its own: unit-regression3 is now
1,594,736 bytes and unit-explicit_instantiation 1,095,064. The new file
mentions JSON_HAS_CPP_17 and JSON_HAS_CPP_20 so it keeps being built
for the C++17 standard the regression was about.

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

* Convert the bytes of the BON8 test strings explicitly

The str() helper constructed a std::string from a byte range, which
converts each unsigned char implicitly; -fsanitize=integer reports that
for bytes of 0x80 and above (ci_test_clang_sanitizer).

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-27 16:56:21 +02:00
Niels Lohmann abbe52d6de Add JSON_PRECISE_STREAM_POSITION to leave the character that terminates a number in the stream (#5344)
* docs: qualify the operator>> stream positioning guarantee

operator>>'s notes state that it leaves the stream positioned right
after the parsed value, so that concatenated JSON values can be read
back to back. That does not hold when the value is a number: a number
is only terminated by the character that follows it, and the lexer's
unget() is simulated (it rewinds only the lexer's own bookkeeping),
so that character stays consumed from the stream.

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

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

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

* fix: restore the character that terminates a number (#5340)

operator>> is documented to leave the stream positioned right after the
parsed value, so that concatenated JSON values can be read back to back.
That did not hold for numbers: a number is only terminated by the
character following it, and lexer::scan_number() reads that character
and calls unget() -- which is simulated and rewinds only the lexer's own
bookkeeping. input_stream_adapter consumes via sbumpc() with no matching
sungetc(), so the terminating character stayed consumed and the next
extraction started one byte too late ('1true' left the stream at 'rue').

Propagating unget() to the adapter directly does not work: next_unget
makes the following get() replay the cached character, so the terminator
would be delivered twice. Instead, restore the still-pending character
once at the end of a non-strict parse, where the input is handed back to
the caller:

- input_stream_adapter gains unget_character() (sungetc()) and advertises
  it via supports_unget, detected the same way as supports_seek.
- lexer::restore_pending_unget() turns a pending simulated unget of a
  real (non-EOF) character into a real one and clears next_unget so the
  character is not also replayed. It is a no-op for adapters that cannot
  unget, and reports failure when sungetc() fails, in which case the
  input is left as it was before.
- parser calls it on the three non-strict paths, i.e. for operator>> and
  sax_parse(strict = false).

Strict parse()/accept() are unaffected: they require the input to end
after the value, so the character is consumed by the end-of-input check
anyway. Parse error messages and reported positions are unchanged.

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

* tests: fix CI failures in the #5340 test helpers

Four CI failures, all in the new test code:

- GCC (-Werror=useless-cast): drop the `json(...)` wrapper around
  `json::parse(...)`, which already returns a `json`.
- GCC (-Werror=unused-result): assign the discarded `json::parse()`
  result to a dummy, the idiom used elsewhere in the test suite, and
  catch `json::parse_error&` for consistency.
- clang-tidy (google-default-arguments): remove the default argument
  from the `pbackfail()` override; `sungetc()` supplies the base
  declaration's default.
- MSVC (bad allocation): `no_putback_streambuf::underflow()` set a
  one-character get area without advancing `m_pos`, so an implementation
  whose `istream::get` peeks before it bumps re-read the same character
  forever. Keep no get area at all: `underflow()` peeks, `uflow()`
  consumes, and `sungetc()` still always lands in `pbackfail()`, which
  is what the test needs.

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

* fix: leave the character that terminates a number in the input

Read the character following a number without consuming it, instead of
consuming it and putting it back. input_stream_adapter now peeks with
sgetc() and only steps over the character when the next one is requested
or when the adapter is destroyed, so releasing it cannot fail - no
putback position is required from the streambuf.

Suggested by gregmarr in #5344.

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

* docs: match the version history wording to the peek-based fix

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

* docs: drop the whitespace-separator caveat from the parsing pages

The caveat added in #5343 describes the behavior this branch fixes: a
number no longer consumes the character that terminates it, so
concatenated values need no separator.

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

* refactor: split the strict and non-strict paths in parser

Folding the release_lookahead() call into the existing strict check left
the "in strict mode" comment on an else-if branch, and made the strict
condition in sax_parse() redundant with the branch it followed.

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

* Put the stream position fix behind JSON_PRECISE_STREAM_POSITION

Leaving the character that terminates a number in the stream is observable:
reading "1,2,3" with repeated operator>> works today only because the comma
after each number is swallowed, and std::getline after a number skips the
line break. Both break with the fix, so make it opt-in for 3.x, as suggested
by @gregmarr in the review.

- JSON_PRECISE_STREAM_POSITION (default 0) selects the peek-based
  input_stream_adapter. Without it, the adapter is the consuming one from
  develop and has no supports_lookahead, so lexer::release_lookahead() and
  the parser's calls to it compile to nothing.
- The macro changes input_stream_adapter's layout and member functions, so
  it gets the ABI tag _psp, after _bics. The ABI config tests, the natvis
  generator, and nlohmann_json.natvis (regenerated) know the tag.
- The tests for the fix move to unit-precise-stream-position.cpp, which
  defines the macro itself and runs in every build, and gain the two cases
  above. unit-deserialization.cpp pins the default behavior instead.
- The docs describe the default behavior again and point to the new macro
  page; version history says "added in 3.13.0, planned default in 4.0.0".

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-25 17:56:18 +02:00
Niels Lohmann 80bf54a5a2 Add a security assurance case to the documentation (#5572)
Describe the threat model, the trust boundaries, the secure-design
argument, and how common weaknesses are countered, with links to the
quality assurance page as evidence.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-25 08:28:34 +02:00
Niels Lohmann aada27405d Add a roadmap page to the documentation (#5571)
Describe what the project will and will not do over the next year,
and point to issue #3453 for the open question of a 4.0 release.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-25 08:28:16 +02:00
Niels LohmannandClaude Sonnet 5 56b3ee566c Fix stack overflow when copying a deeply nested value (#5387) (#5389)
* Bound the descent of the copy constructor

basic_json's copy constructor copied objects and arrays by handing the
container to its own copy constructor, which copy-constructs every element
and so reaches this constructor again, once per nesting level. A value
nested deeply enough exhausted the call stack and terminated the process
with a segmentation fault - no exception, nothing the caller could catch.
Parsing such a value works, as the parser is iterative, and so does
destroying one, as #1436 made destruction iterative.

Bound how far the copy descends rather than take the call stack away from
it. The first levels are copied exactly as they were - the containers copy
their own elements, which is by far the fastest way to fill them - and only
once the copy has descended 128 levels is the value below it finished
without the call stack, through an explicit worklist. Copying can therefore
no longer exhaust the stack, however deeply a value is nested, while a value
nested less deeply than the bound - all but a vanishing minority - is copied
by the very same code as before and pays only for one counter.

That counter lives in thread_local storage, as one shared between threads
would be raced. JSON_NO_THREAD_LOCAL switches it off for toolchains without
thread_local; copying then goes through the worklist right away, which
yields the same values but is measurably slower.

The deferred values are completed before the copy they belong to returns, so
a value copied while another copy is going on - by a custom base class, say -
is unaffected by the copy it is nested in.

operator= takes its argument by value, so copy assignment is fixed as well.

Copying is as fast as it was, within measurement noise (medians of 9
interleaved runs, clang -O3): -1.3% for an array of strings, +0.0% for a
flat object, +0.1% for a flat array of numbers, +0.3% for nested arrays,
+0.6% for nested objects and +1.2% for a twitter-like document. Copying a
three-key object costs about ten nanoseconds more, the counter. Deferring
every level instead, rather than only those below the bound, measured
between 3% and 9% slower depending on the shape of the value.

This fixes #5387 for the copy constructor. dump() is still recursive.

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

* Test the copy constructor's iterative path in CI

The copy constructor descends into 128 levels before it finishes a value
without the call stack, so the iterative path is otherwise only reached
by the few tests that nest deeper than that.

JSON_NO_THREAD_LOCAL switches the descent off, which sends every value
down that path. Running the whole test suite that way covers it with
every object type, string type, allocator, and base class the suite
already exercises. The new ci_test_no_thread_local target does that; the
macro had no build coverage at all before.

Copying a nested value also has to carry over what the element-wise copy
constructor would have copied: the parents that JSON_DIAGNOSTICS relies
on, and the positions that JSON_DIAGNOSTIC_POSITIONS reports. Both are
now checked on either side of the descent bound, for objects and arrays.
Neither was tested before, and dropping either one makes the new tests
fail.

Also quantify what JSON_NO_THREAD_LOCAL costs a copy instead of calling
it "measurably slower".

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

* Split the regression tests so that they keep linking

Linking test-regression2 fails with "relocation truncated to fit:
IMAGE_REL_AMD64_REL32 against `.rdata'" once its object grows past what
the MinGW linker copes with, and the copy constructor's helpers push it
over: the object grows by 6.3%, from 4,654,128 to 4,944,920 bytes at -O0,
and develop links at the smaller of the two.

Building the tests optimized shrinks the object enough to link, but the
binaries clang 11.0.1 and clang 18.1.8 then produce crash before doctest
prints its first line - 39 of 102 tests on clang 18 - so the objects have
to become smaller rather than denser.

Moving the test cases that follow "regression tests 2" into a file of
their own brings that object to 4,687,888 bytes, which is 0.7% above the
size that links today rather than 6.3%. Both files still build for C++11,
C++17 and C++20, and run the same 9 test cases and 135 assertions as
before, now spread over two binaries.

New regression tests belong in unit-regression3.cpp from here on, which
is what CONTRIBUTING.md now says.

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

* Do not use thread_local storage with Clang targeting MinGW

Every test that copies a value segfaults there - 42 of 105 on clang
11.0.1, 39 of 102 on clang 18.1.8 - while the same tests pass with GCC
targeting MinGW, with Clang targeting MSVC, and with every other
toolchain the library is tested on. The counter that bounds the copy
constructor's descent is the library's first use of thread_local, so
that job had never exercised it before.

JSON_NO_THREAD_LOCAL already covers toolchains without thread_local
storage, and copying yields the same values with it, only more slowly.
Define it for this one automatically.

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

* Balance the warning suppression the split separated

unit-regression2.cpp opens a DOCTEST_CLANG_SUPPRESS_WARNING_PUSH block at
the top and closed it at the very bottom, which the split moved into
unit-regression3.cpp: one file was left with a push and no pop, the other
with a pop and no push, which clang reports as an error.

Give each file the pair it needs.

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

* Check both shapes without a C-style array

clang-tidy rejects the array the two shapes were iterated over
(cppcoreguidelines-avoid-c-arrays). The array only existed because astyle
reformats a range-for over a braced initializer list into something
unreadable; naming the two cases avoids both.

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

* Split the regression tests far enough to leave room

The first split left unit-regression2.cpp 0.7% below the size develop
links at, which the comparison change in the follow-up immediately used
up: the MinGW linker fails on test-regression2_cpp20 again, naming
copy_shallow and to_partial_ordering among the relocations it cannot fit.

Move the sections from "issue #2067" on, and the helper types they use,
so that the file stops being the one that decides whether the tests can
be linked at all. At -O0 and C++20, unit-regression2.cpp is now 2,964,944
bytes against develop's 4,708,248, and 3,070,568 bytes with the follow-up
applied - roughly a third smaller either way, rather than a fraction of a
percent larger.

The 135 assertions are the same ones as before, now spread over three
test cases in two files.

Also silence the clang-tidy findings the deep-nesting tests draw: the
copies they make are what is being tested, and the reserve() computation
gets its parentheses.

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

* Move the #4804 alias to the file that uses it

The split left the json_4804 alias behind in unit-regression2.cpp while
the test case that uses it went to unit-regression3.cpp, which does not
build for C++17 and C++20 as a result.

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

* Include <span> where the split moved its only use

The #2546 test case guards itself with __has_include(<span>), but the
include itself sat in unit-regression2.cpp's preamble and stayed behind,
so the section compiled without a declaration wherever the guard passed -
which nvhpc reported and libc++ builds do not, as they skip the section
altogether.

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

* Keep the descent bookkeeping in one place

Copying carried a depth count, a depth limit and a guard of its own, and
the comparison in the follow-up added a second set beside them. Neither
operation needs its own: they are never nested inside one another by the
library - copying a value does not compare one, and comparing two values
does not copy them - and where user code nests them anyway, sharing the
count only ends a descent sooner than it had to.

So there is now one nesting_depth(), one nesting_depth_limit() and one
nesting_depth_guard, which the follow-up uses instead of adding its own.
Inverting the test in copy_structured leaves the too-deep case and the
no-thread-local case as the same code.

The guard takes the count rather than looking it up, because the caller
has looked it up already to test it against the limit, and reaching
thread-local storage twice on the path that is taken almost every time is
worth avoiding.

The switch that copies the value of anything that is not an object or an
array was written twice - once in the copy constructor, once in
copy_shallow - so that adding a value_t meant editing both, and missing
one would have been silent. It is copy_leaf_value now, and inlined: both
callers have already sorted the containers out, and folding that test into
the switch is what keeps a value made mostly of numbers copying as fast as
it did.

Copying canada.json, citm_catalog.json and twitter.json is within 0.6% of
what it was before, measured as a paired ratio over 18 interleaved rounds
against a run-to-run spread of 0.3%.

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

* Check that an abandoned copy can still be destroyed

Copying a value without the call stack builds the copy from the top down,
and every value whose own copy has not been made yet stays a null value
until it is. That is what lets a copy be abandoned half-built: the
destructor finds nothing but complete values and null ones.

Nothing tested it. Failing an allocation part-way through a copy of a
deeply nested value does, with the allocator the file already has for
exactly this kind of test.

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

* Name the test's locals so Flawfinder stops matching them

The code scanning job reports CWE-362 - "check when opening files" - for
a test that opens no files: Flawfinder matched a local variable called
open. Rename it and its partner.

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

* Keep the descent guard's bookkeeping self-contained

nesting_depth_limit() and nesting_depth_guard were only used inside
the JSON_NO_THREAD_LOCAL-guarded branch of copy_structured(), but were
defined unconditionally. Move them inside the #ifndef, and have the
guard look up the depth and test it against the limit itself (via
okay()) instead of making the caller do it - the caller no longer
needs to touch nesting_depth() at all. Also shrink the thread-local
counter to std::uint8_t, matching what its own doc comment already
argued.

Addresses gregmarr's review comments on #5389.

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

* Make nesting_depth_guard usable regardless of JSON_NO_THREAD_LOCAL

nesting_depth_limit() and nesting_depth() stay behind #ifndef
JSON_NO_THREAD_LOCAL, since a descent cannot be bounded without a
per-thread count. But the guard itself now always exists, becoming a
no-op that is never okay() under that macro - the same way the bound
is already reached on every call without one. copy_structured() no
longer needs to know which case it is in.

This is what lets #5390 reuse the guard for comparison, which cannot
test JSON_NO_THREAD_LOCAL where the macro-based operators use it: the
guard now carries that distinction itself instead of requiring every
caller to.

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

* Silence VS2015's C4503 for the custom-base-class test

The deep-copy support added for #5387 lengthened the mangled name of
std::allocator_traits<...>::construct for the test's map type past
VS2015's limit, which /WX turns into a build failure even though the
name is only used for (now-truncated) debug info.

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

* Remove dead unused-parameter casts from copy_metadata()

@gregmarr asked whether the static_cast<void> pair in the
JSON_DIAGNOSTIC_POSITIONS-off branch was needed for an empty
json_base_class_t. It isn't: src and dst are already referenced
unconditionally by the base-class copy above, so no -Wunused-parameter
warning fires either way (checked with -Wall -Wextra
-Wunused-parameter, JSON_DIAGNOSTIC_POSITIONS 0 and 1).

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

* Fix CI: build custom array types without a fill constructor, re-amalgamate

copy_array_level() built the destination array with the fill
constructor array_t(count, value), which is not part of the array
container interface the library otherwise assumes (e.g. custom
ArrayTypes that only provide a default and an iterator-pair
constructor, as covered by unit-custom-array-type.cpp). Default-
construct the array and resize() it instead, matching how the rest
of the codebase already grows array_t.

Also re-run the amalgamation, which had fallen out of sync with
include/nlohmann/json.hpp.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
2026-09-24 17:01:15 +02:00
Niels LohmannandClaude Sonnet 5 ed513715a8 Document that a NUL byte in the input is treated as end of input (#5534)
* docs: document that a NUL byte in the input is treated as end of input

A NUL byte anywhere in the input - trailing, or embedded ahead of more
otherwise well-formed JSON - is currently treated the same as genuine
end of input, so parsing silently stops there instead of raising the
parse_error.101 any other unexpected byte triggers. This mirrors the
NUL-terminated-C-string convention already used when no explicit input
length is given (json::parse(const char*) already stops at strlen()),
just applied uniformly rather than only when a length is genuinely
unavailable.

This behavior predates this change and is not being altered here -
changing it would be an observable, backwards-incompatible behavior
change for any caller that (knowingly or not) depends on it, which is
not something to do silently in a patch. Documenting the current,
verified behavior as a new FAQ entry instead, so it's an intentional
and discoverable part of the contract rather than a surprise.

Fixes #5530.

Signed-off-by: Niels Lohmann <niels.lohmann@gmail.com>
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N4RQ1Ahan5YAGbnAQGjZTY

* Add JSON_STRICT_NUL_HANDLING opt-in macro for issue #5530

A NUL byte anywhere in the input is currently treated the same as real
end of input, rather than raising parse_error.101 like any other
unexpected byte (documented in the previous commit's FAQ entry). A full
unconditional fix was tried in PR #5532 but rejected as too risky to
ship by default: any caller could depend on the current behavior, even
unknowingly (e.g. a zero-padded buffer). On PR #5534, gregmarr proposed
a compile-time opt-in flag instead, and the maintainer agreed, wanting
it available now and defaulting to the corrected behavior in 4.0.0.

This mirrors the existing JSON_BRACE_INIT_COPY_SEMANTICS precedent as
closely as sensible:
- JSON_STRICT_NUL_HANDLING defaults to 0 (off); the three lexer sites
  that treat '\0' as EOF/comment-terminator are gated with
  `#if !JSON_STRICT_NUL_HANDLING` so the default-off behavior is
  byte-for-byte identical to today's.
- input_adapters.hpp's `T (&array)[N]` overload additionally trims a
  single trailing '\0' from a `char` array (e.g. a string literal like
  `json::parse("123")`) when the macro is on, so that case keeps
  working; every other element type (unsigned char, std::uint8_t, ...)
  always keeps its full extent. This intentionally does *not* reuse the
  existing strlen()-based pointer overload via SFINAE-excluding `char`
  from the array overload, as originally sketched for this change: that
  approach is ambiguous against the newer generic container overload
  added since PR #5532, and even where it compiles, strlen()-scanning a
  `char` array that is not NUL-terminated within its bounds reads past
  the end of the array (confirmed with AddressSanitizer). Trimming only
  a single trailing byte, without scanning, avoids both problems.
- Documented via docs/mkdocs/docs/api/macros/json_strict_nul_handling.md,
  linked from the macros index/nav/features page, the FAQ entry, and
  the parse/accept/operator>> reference pages.
- Tested in unit-class_parser.cpp and unit-deserialization.cpp, default
  state unguarded and opt-in state guarded. Since the library itself
  #undefs the macro at the end of json.hpp (as JSON_BRACE_INIT_COPY_SEMANTICS
  already does), a plain `#if defined(JSON_STRICT_NUL_HANDLING)` guard
  after the include never actually triggers; the tests instead capture
  the command-line value into a test-local macro before including the
  header. A few pre-existing fixtures elsewhere (std::array<uint8_t, N>
  sized one larger than their literal, relying on value-initialization
  to silently add a trailing zero byte) needed the same one-byte
  adjustment to keep passing under the opt-in behavior.

Unlike the precedent, this adds a proper `JSON_StrictNulHandling` CMake
option (rather than a raw -DCMAKE_CXX_FLAGS injection) and wires its
ci_test_strict_nul_handling target into the ci_cmake_options job matrix
in .github/workflows/ubuntu.yml, so the opt-in build is actually
exercised in CI -- closing the one gap in the precedent's own CI setup
(ci_test_brace_init_copy_semantics is defined but never referenced by
any workflow, so it has never actually run).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Clarify where JSON_STRICT_NUL_HANDLING does not reject NUL bytes

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

---------

Signed-off-by: Niels Lohmann <niels.lohmann@gmail.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
2026-09-24 06:55:21 +02:00