Niels Lohmann
a47170346a
* 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>
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JSON_NO_THREAD_LOCAL
#define JSON_NO_THREAD_LOCAL
When defined, the library does not use #!cpp thread_local storage. This is relevant for the few environments whose
toolchain does not support it.
Copying a value and comparing two values both descend into the first levels by letting the containers copy or compare
themselves, and finish whatever is nested deeper than that without the call stack, so that neither can exhaust the stack
however deeply the values are nested. Each counts the levels it has descended into in a #!cpp thread_local variable, as
a counter shared between threads would be raced.
Without those counters, no descent can be bounded safely, so objects and arrays are copied and compared without the call
stack right away. Both keep working exactly as they do otherwise - the same values come out, the same comparisons hold,
and deeply nested values are handled just as safely - but both are slower, because the containers no longer copy or
compare themselves. Copying the benchmark documents takes 9% (canada.json) to 34% (twitter.json) longer, and
comparing two equal ones 10% (citm_catalog.json) to 90% (canada.json) longer.
Default definition
By default, #!cpp JSON_NO_THREAD_LOCAL is not defined.
#undef JSON_NO_THREAD_LOCAL
The library defines it by itself for Clang targeting MinGW, which does not survive the #!cpp thread_local storage:
copying a value segfaults there, with both old and current Clang versions, while GCC targeting MinGW is unaffected.
Copying and comparing fall back to working without the call stack there, as they do whenever the macro is defined.
Examples
??? example
The code below forces the library not to use `#!cpp thread_local` storage.
```cpp
#define JSON_NO_THREAD_LOCAL 1
#include <nlohmann/json.hpp>
...
```
See also
- FAQ: Thread safety - thread-safety guarantees of the library
- Supported Macros - guide to all supported macros
Version history
- Added in version 3.13.0.