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>
* 📝 Fix documentation gaps found in a full GitHub Discussions review
Reviewed all 1008 GitHub Discussions (2020-2026) for recurring questions
that better or more visible documentation would have avoided. Adds/expands
documentation for ~26 distinct gaps, including:
- New "Debugging" page collecting natvis, GDB pretty printer, LLDB status,
and JSON_DIAGNOSTICS pointers (previously scattered/undiscoverable)
- Thread-safety and schema-validation FAQ entries
- StringType's char-based requirement (no wstring/u16string/u32string)
- Brace-initialization-yields-arrays warning directly on the constructor
reference page (previously only in the FAQ, missed by users reading
the constructor docs)
- std::any exclusion from get<T>(), with a manual-dispatch example
- Non-string-keyed std::map serializing as an array of pairs
- ordered_json compatibility with NLOHMANN_DEFINE_TYPE_* macros
(already worked, was undocumented)
- std::array truncation on size-mismatched conversion (no exception)
- static_cast vs. get<std::optional<T>>() divergence
- Recipe for omitting a std::optional field instead of emitting null
- No built-in nesting-depth limit during parsing + a callback-based
workaround recipe
- Recipe for streaming a large homogeneous array via parser callbacks
- operator>> stream-position semantics for concatenated JSON values
- JSON Pointer array-vs-object creation rule for non-existing paths
- CMake target name (nlohmann_json_modules) needed to link C++20 modules
- ESP-IDF/PlatformIO: no official package, link to a community fork
- get(key, default) as the Python dict.get() equivalent
- reserve() recipe for pre-allocating array capacity
- JSONC as an alias for the existing ignore_comments/ignore_trailing_commas
combination (distinct from the unsupported JSON5)
- items() dereferenced-element type: decltype() idiom + detail-namespace
stability caveat
- Various macro/type-conversion limitations (MSGPACK_DEFINE_ARRAY
equivalent, char-array round-tripping, ADL serializer macro gap)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* 🎨 fix format
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Implement the scoped agent-readiness subset for json.nlohmann.me:
- Add the mkdocs-llmstxt plugin to generate llms.txt from the nav
(full_output/llms-full.txt deliberately omitted to avoid dumping
500+ API reference pages into one giant file).
- Add a permissive robots.txt with a Sitemap reference.
- Add a build hook (hooks/copy_markdown_source.py) that copies each
page's Markdown source into the built site as a `<path>.md` sibling
of its HTML output, so agents/tools can fetch raw Markdown directly.
sitemap.xml was already emitted by default and needed no change.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Added NLOHNMANN_JSON_SERIALIZE_ENUM_STRICT
- duplicate of NLOHMANN_JSON_SERIALIZE_ENUM
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* Added failing tests for NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* modified NLOHMANN_JSON_SERIALIZE_STRICT to throw
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* added documentation and changed readme to include NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* ran amalgamate
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* docs(macros): add page for JSON_SERIALIZE_ENUM_STRICT
- added page to nav
- added links to new page where appropriate
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* refactor(macros): make JSON_SERIALIZE_ENUM_STRICT use JSON_THROW
- added templated wrapper function to fix scope error in calling JSON_THROW
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* refactor(macros): make NLOHMANN_SERIALIZE_ENUM_STRICT use error code 410
- added error code 410 to docs
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* tests(macros): add test for to_json with enum value not mentioned
in mapping for NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* Apply suggestions from code review
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
Signed-off-by: Caillin Nugent <nugentcaillin@gmail.com>
* fix(macro): prevent compilation error with -Werror and -Wunused-parameter
with NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
- casted exception to void to avoid warning
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* fix(docs): add link to NLOHMANN_SERIALIZE_ENUM_STRICT docs to exception page
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* docs(macros): add example of exception throwing for NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* refactor(macros): add more in-depth error message to NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
- changed error message to follow style of nlohmann/json#4989
- made description of throw wrapper more general
- updated tests and example of exceptions
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
---------
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
Signed-off-by: Caillin Nugent <nugentcaillin@gmail.com>
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
* Add new macros for named conversions
* Unit tests for the named conversion macros
* Update the docs to include the new macros
* Fix the documentation for the macros
the correct maximum number of member variables is 63
* Fix CI tests
* update the named macros
* move the example files
* update the explicit macros expansion
* update documentation
* fix documentation hiccups
* astyle changes
* add static analysis exceptions
* change md header to explicit html to fit the length
* Small corrections to docs
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
Signed-off-by: George Sedov <radist.morse@gmail.com>
---------
Signed-off-by: George Sedov <radist.morse@gmail.com>
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
* Move UDLs into nlohmann::literals::json_literals namespace
* Add 'using namespace' to unit tests
* Add 'using namespace' to examples
* Add 'using namespace' to README
* Move UDL mkdocs pages out of basic_json/
* Update documentation
* Update docset index
* Add JSON_GlobalUDLs CMake option
* Add unit test
* Build examples without global UDLs
* Add CI target
* Add versioned inline namespace
Add a versioned inline namespace to prevent ABI issues when linking code
using multiple library versions.
* Add namespace macros
* Encode ABI information in inline namespace
Add _diag suffix to inline namespace if JSON_DIAGNOSTICS is enabled, and
_ldvcmp suffix if JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON is enabled.
* Move ABI-affecting macros into abi_macros.hpp
* Move std_fs namespace definition into std_fs.hpp
* Remove std_fs namespace from unit test
* Format more files in tests directory
* Add unit tests
* Update documentation
* Fix GDB pretty printer
* fixup! Add namespace macros
* Derive ABI prefix from NLOHMANN_JSON_VERSION_*
* Add operator<< for json_pointer
* Deprecate json_pointer::operator string_t()
* Update documentation
* Move operator<<(basic_json) example
* Add example
* Add mkdocs-redirects
* Move operator<< and operator>> doc pages out of basic_json/
* Rename JSON pointer operator_string to operator_string_t
* Add unit test
* Add C++20 3-way comparison operator and fix broken comparisons
Fixes#3207.
Fixes#3409.
* Fix iterators to meet (more) std::ranges requirements
Fixes#3130.
Related discussion: #3408
* Add note about CMake standard version selection to unit tests
Document how CMake chooses which C++ standard version to use when
building tests.
* Update documentation
* CI: add legacy discarded value comparison
* Fix internal linkage errors when building a module
Niels Lohmann
trdesilvaandGitHub
DmitriBogdanovandGitHub
MikoandGitHub
NikhilandGitHub
Einars Netlis-GalejsandGitHub
Florian AlbrechtskirchingerandGitHub
Richard HozákandGitHub
