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json_view: one SIMD macro set with the library

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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>
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Niels Lohmann committed 2026-10-25 12:17:42 +01:00
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docs/mkdocs/docs/api/macros/index.md
-2
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@@ -43,8 +43,6 @@ header. See also the [macro overview page](../../features/macros.md).
- [**JSON_SKIP_UNSUPPORTED_COMPILER_CHECK**](json_skip_unsupported_compiler_check.md) - do not warn about unsupported compilers
- [**JSON_USE_GLOBAL_UDLS**](json_use_global_udls.md) - place user-defined string literals (UDLs) into the global namespace
- [**JSON_USE_SIMDUTF**](json_use_simdutf.md) - use the simdutf library to accelerate UTF-8 validation
- [**JSON_VIEW_NO_SIMD**](json_view_no_simd.md) - use only portable code in the parser of `json_view.hpp`
- [**JSON_VIEW_USE_SSSE3**](json_view_use_ssse3.md) - validate non-ASCII strings with SSSE3 in the parser of `json_view.hpp`
## Library version
docs/mkdocs/docs/api/macros/json_no_simd.md
+3 -1
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@@ -5,7 +5,8 @@
```
When defined, the library uses only portable C++ code where it would otherwise use vector instructions: when scanning
strings during parsing, and when writing floating-point numbers during serialization.
strings during parsing, and when writing floating-point numbers during serialization. This includes the parser of
[`basic_json_document`](../basic_json_document/index.md) (`<nlohmann/json_view.hpp>`).
The macro is an escape hatch, for example for toolchains that cannot compile the vector code, for sanitizers or
analyzers that do not understand it, or to compare the speed of both variants. It does not change any result: values,
@@ -77,6 +78,7 @@ By default, `#!cpp JSON_NO_SIMD` is not defined, and vector instructions are use
- [**JSON_USE_SIMDUTF**](json_use_simdutf.md) - use the simdutf library to accelerate UTF-8 validation
- [**JSON_DISABLE_STREAM_BULK_SCAN**](json_disable_stream_bulk_scan.md) - read a `std::istream` one character at a time
- [Parsing: input sources and performance](../../features/parsing/index.md#input-sources-and-performance)
- [json_view](../../features/json_view.md) - the zero-copy view, whose parser the macro also affects
## Version history
docs/mkdocs/docs/api/macros/json_view_no_simd.md
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@@ -1,52 +0,0 @@
# JSON_VIEW_NO_SIMD
```cpp
#define JSON_VIEW_NO_SIMD
```
When defined, the parser of [`basic_json_document`](../basic_json_document/index.md) (`<nlohmann/json_view.hpp>`)
uses only portable C++ to scan strings. By default, it scans long runs of string bytes 16 at a time with NEON on
AArch64 (with GCC and Clang) and SSE2 on x86-64, which are part of the baseline instruction sets of these
architectures, and validates non-ASCII text with NEON (or SSSE3, see
[`JSON_VIEW_USE_SSSE3`](json_view_use_ssse3.md)).
The same input is accepted or rejected either way, with the same values, and errors are reported the same way; only
the speed differs. The macro exists for platforms whose compilers lack the intrinsics headers, and to test the portable
code.
!!! note "ABI compatibility"
The macro selects between two definitions of the same inline functions. Whether it is defined is encoded in the
[namespace](../../features/namespace.md) (tag `_vns`), resulting in distinct symbol names. Translation units
compiled with and without it can therefore be linked into the same program without One Definition Rule (ODR)
violations, but they cannot exchange instances of library types.
## Default definition
By default, `#!cpp JSON_VIEW_NO_SIMD` is not defined, and the vector code is used where available.
```cpp
#undef JSON_VIEW_NO_SIMD
```
## Examples
??? example
The code below uses the portable string scanning of the view.
```cpp
#define JSON_VIEW_NO_SIMD
#include <nlohmann/json_view.hpp>
...
```
## See also
- [JSON_VIEW_USE_SSSE3](json_view_use_ssse3.md) - validate non-ASCII strings with SSSE3 on x86-64
- [json_view](../../features/json_view.md) - the zero-copy view
## Version history
- Added in version 3.13.0.
docs/mkdocs/docs/api/macros/json_view_use_ssse3.md
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@@ -1,53 +0,0 @@
# JSON_VIEW_USE_SSSE3
```cpp
#define JSON_VIEW_USE_SSSE3
```
When defined on x86-64, the parser of [`basic_json_document`](../basic_json_document/index.md)
(`<nlohmann/json_view.hpp>`) validates non-ASCII text in strings with SSSE3 without asking the CPU first.
By default, the parser checks once at run time whether the CPU has SSSE3 (all x86-64 CPUs since about 2011 have it)
and then validates non-ASCII text 16 bytes at a time, using the "lookup4" algorithm of
[simdjson](https://github.com/simdjson/simdjson); on CPUs without SSSE3, it validates one UTF-8 sequence at a time.
The vector check is compiled for SSSE3 with a function attribute (GCC 4.9 and later, Clang), so this needs no compiler
option. With MSVC, the check uses `__cpuid`. On AArch64, the vector check uses NEON and is always on.
Define the macro only together with a compiler option that enables SSSE3 (e.g. `-mssse3`, or `-march=` with a CPU that
has it), and only for programs that run on such CPUs. It saves the check of the CPU, which costs little. The same
input is accepted or rejected either way; only the speed of non-ASCII text differs.
!!! note "ABI compatibility"
The macro selects between two definitions of the same inline functions. Whether it is defined is encoded in the
[namespace](../../features/namespace.md) (tag `_vssse3`, on every architecture), resulting in distinct symbol
names. Translation units compiled with and without it can therefore be linked into the same program without One
Definition Rule (ODR) violations, but they cannot exchange instances of library types.
## Default definition
By default, `#!cpp JSON_VIEW_USE_SSSE3` is not defined.
```cpp
#undef JSON_VIEW_USE_SSSE3
```
## Examples
??? example
With CMake, for a program that only runs on CPUs with SSSE3:
```cmake
target_compile_definitions(your_target PRIVATE JSON_VIEW_USE_SSSE3)
target_compile_options(your_target PRIVATE -mssse3)
```
## See also
- [JSON_VIEW_NO_SIMD](json_view_no_simd.md) - use only portable code in the view's parser
- [JSON_USE_SIMDUTF](json_use_simdutf.md) - validate UTF-8 with simdutf in `basic_json`'s parser
## Version history
- Added in version 3.13.0.
docs/mkdocs/docs/api/macros/nlohmann_json_namespace.md
+2 -2
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@@ -39,6 +39,6 @@ the library.
## Version history
- Added in version 3.11.0. Changed inline namespace name in version 3.11.2. Added the ABI tag `_dp` in
version 3.12.0, and the ABI tags `_bics`, `_psp`, `_snul`, `_sbu8`, `_ekmo`, `_dsbs`, `_dufio`, `_ns`, `_vns`,
and `_vssse3` in version 3.13.0; see
version 3.12.0, and the ABI tags `_bics`, `_psp`, `_snul`, `_sbu8`, `_ekmo`, `_dsbs`, `_dufio`, and `_ns` in
version 3.13.0; see
[`nlohmann` Namespace](../../features/namespace.md#structure).
docs/mkdocs/docs/features/macros.md
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@@ -287,23 +287,6 @@ external dependency and is not defined by default.
See [full documentation of `JSON_USE_SIMDUTF`](../api/macros/json_use_simdutf.md).
## `JSON_VIEW_NO_SIMD`
When defined, the parser of [`basic_json_document`](../api/basic_json_document/index.md)
(`<nlohmann/json_view.hpp>`) uses only portable C++ to scan strings, instead of vector instructions (SSE2 on x86-64,
NEON on AArch64). The same input is accepted or rejected either way; only the speed differs. It is not defined by
default.
See [full documentation of `JSON_VIEW_NO_SIMD`](../api/macros/json_view_no_simd.md).
## `JSON_VIEW_USE_SSSE3`
When defined on x86-64, the parser of [`basic_json_document`](../api/basic_json_document/index.md)
(`<nlohmann/json_view.hpp>`) validates non-ASCII text in strings with SSSE3 without asking the CPU first. It is not
defined by default.
See [full documentation of `JSON_VIEW_USE_SSSE3`](../api/macros/json_view_use_ssse3.md).
## `NLOHMANN_DEFINE_TYPE_*(...)`, `NLOHMANN_DEFINE_DERIVED_TYPE_*(...)`
The library defines 12 macros to simplify the serialization/deserialization of types. See the page on
docs/mkdocs/docs/features/namespace.md
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@@ -28,8 +28,6 @@ The complete default namespace name is derived as follows:
- [`JSON_DISABLE_UNLOCKED_FILE_IO`](../api/macros/json_disable_unlocked_file_io.md) defined non-zero appends
`_dufio`.
- [`JSON_NO_SIMD`](../api/macros/json_no_simd.md) defined appends `_ns`.
- [`JSON_VIEW_NO_SIMD`](../api/macros/json_view_no_simd.md) defined appends `_vns`.
- [`JSON_VIEW_USE_SSSE3`](../api/macros/json_view_use_ssse3.md) defined appends `_vssse3`.
- The inline namespace ends with the suffix `_v` followed by the 3 components of the version number separated by
underscores. To omit the version component, see [Disabling the version component](#disabling-the-version-component)
below.
@@ -115,7 +113,5 @@ follows:
([`JSON_STRICT_BINARY_UTF8`](../api/macros/json_strict_binary_utf8.md)), `_ekmo`
([`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](../api/macros/json_use_objects_for_enum_keyed_maps.md)), `_dsbs`
([`JSON_DISABLE_STREAM_BULK_SCAN`](../api/macros/json_disable_stream_bulk_scan.md)), `_dufio`
([`JSON_DISABLE_UNLOCKED_FILE_IO`](../api/macros/json_disable_unlocked_file_io.md)), `_ns`
([`JSON_NO_SIMD`](../api/macros/json_no_simd.md)), `_vns`
([`JSON_VIEW_NO_SIMD`](../api/macros/json_view_no_simd.md)), and `_vssse3`
([`JSON_VIEW_USE_SSSE3`](../api/macros/json_view_use_ssse3.md)) in version 3.13.0.
([`JSON_DISABLE_UNLOCKED_FILE_IO`](../api/macros/json_disable_unlocked_file_io.md)), and `_ns`
([`JSON_NO_SIMD`](../api/macros/json_no_simd.md)) in version 3.13.0.
docs/mkdocs/docs/home/debugging.md
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@@ -21,10 +21,10 @@ ABI tags are not covered and may show raw internal fields instead. To generate a
```
3. Generate a Natvis file with the tags of your configuration, for example for `JSON_DIAGNOSTICS`,
`JSON_DIAGNOSTIC_POSITIONS`, and `JSON_VIEW_NO_SIMD`:
`JSON_DIAGNOSTIC_POSITIONS`, and `JSON_NO_SIMD`:
```shell
make natvis NATVIS_ARGS="--abi-tags _diag,_dp,_vns --output my_nlohmann_json.natvis"
make natvis NATVIS_ARGS="--abi-tags _diag,_dp,_ns --output my_nlohmann_json.natvis"
```
4. Use the generated file instead of `nlohmann_json.natvis`.
docs/mkdocs/mkdocs.yml
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@@ -442,8 +442,6 @@ nav:
- 'JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON': api/macros/json_use_legacy_discarded_value_comparison.md
- 'JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS': api/macros/json_use_objects_for_enum_keyed_maps.md
- 'JSON_USE_SIMDUTF': api/macros/json_use_simdutf.md
- 'JSON_VIEW_NO_SIMD': api/macros/json_view_no_simd.md
- 'JSON_VIEW_USE_SSSE3': api/macros/json_view_use_ssse3.md
- 'NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE': api/macros/nlohmann_define_derived_type.md
- 'NLOHMANN_DEFINE_TYPE_INTRUSIVE, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE': api/macros/nlohmann_define_type_intrusive.md
- 'NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE': api/macros/nlohmann_define_type_non_intrusive.md