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* 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>
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JSON_USE_GLOBAL_UDLS
#define JSON_USE_GLOBAL_UDLS /* value */
When defined to 1, the user-defined string literals (UDLs) are placed into the global namespace instead of
nlohmann::literals::json_literals.
Default definition
The default value is 1.
#define JSON_USE_GLOBAL_UDLS 1
When the macro is not defined, the library behaves as if it were defined to its default value.
Notes
!!! info "Future behavior change"
The user-defined string literals will be removed from the global namespace in the next major release of the library.
To prepare existing code, define `JSON_USE_GLOBAL_UDLS` to `0` and bring the string literals into scope where
needed. Refer to any of the [string literals](#see-also) for details.
See the [migration guide](../../integration/migration_guide.md#import-namespace-literals-for-udls) for how to update existing code.
!!! hint "CMake option"
The placement of user-defined string literals can also be controlled with the CMake option
[`JSON_GlobalUDLs`](../../integration/cmake.md#json_globaludls) (`ON` by default) which defines
`JSON_USE_GLOBAL_UDLS` accordingly.
!!! info "Leaving out the literals"
If [`JSON_NO_AUTOMATIC_UDLS`](json_no_automatic_udls.md) is defined, the literals are only declared where
`<nlohmann/json_literals.hpp>` is included; this macro then applies to that header.
Examples
??? example "Example: Default behavior"
The code below shows the default behavior using the `_json` UDL.
```cpp
#include <nlohmann/json.hpp>
#include <iostream>
int main()
{
auto j = "42"_json;
std::cout << j << std::endl;
}
```
Output:
```json
42
```
??? example "Example: Namespaced UDLs"
The code below shows how UDLs need to be brought into scope before using `_json` when `JSON_USE_GLOBAL_UDLS` is
defined to `0`.
```cpp
#define JSON_USE_GLOBAL_UDLS 0
#include <nlohmann/json.hpp>
#include <iostream>
int main()
{
// auto j = "42"_json; // This line would fail to compile,
// because the UDLs are not in the global namespace
// Bring the UDLs into scope
using namespace nlohmann::json_literals;
auto j = "42"_json;
std::cout << j << std::endl;
}
```
Output:
```json
42
```
See also
operator""_jsonoperator""_json_pointerJSON_NO_AUTOMATIC_UDLS- do not include the user-defined string literals automatically- :simple-cmake: JSON_GlobalUDLs - CMake option to control the macro
Version history
- Added in version 3.11.0.