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@@ -42,6 +42,8 @@ Some aspects of the library can be configured by defining preprocessor macros **
- [**JSON_SKIP_UNSUPPORTED_COMPILER_CHECK**](https://json.nlohmann.me/api/macros/json_skip_unsupported_compiler_check/index.md) - do not warn about unsupported compilers
- [**JSON_USE_GLOBAL_UDLS**](https://json.nlohmann.me/api/macros/json_use_global_udls/index.md) - place user-defined string literals (UDLs) into the global namespace
- [**JSON_USE_SIMDUTF**](https://json.nlohmann.me/api/macros/json_use_simdutf/index.md) - use the simdutf library to accelerate UTF-8 validation
- [**JSON_VIEW_NO_SIMD**](https://json.nlohmann.me/api/macros/json_view_no_simd/index.md) - use only portable code in the parser of `json_view.hpp`
- [**JSON_VIEW_USE_SSSE3**](https://json.nlohmann.me/api/macros/json_view_use_ssse3/index.md) - validate non-ASCII strings with SSSE3 in the parser of `json_view.hpp`
## Library version
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/json_assert/" rel="canonical"><link href=../ rel=prev><link href=../json_brace_init_copy_semantics/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>JSON_ASSERT - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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</code></pre></div> <p>This macro controls which code is executed for <a href=../../../features/assertions/ >runtime assertions</a> of the library.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>x</code> (in)</dt> <dd>expression of a scalar type</dd> </dl> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <a href="https://en.cppreference.com/w/cpp/error/assert"><code class=highlight><span class=n>assert</span><span class=p>(</span><span class=n>x</span><span class=p>)</span></code></a>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_ASSERT(x) assert(x)</span>
</code></pre></div> <p>Therefore, assertions can be switched off by defining <code>NDEBUG</code>.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <ul> <li>The library uses numerous assertions to guarantee invariants and to abort in case of otherwise undefined behavior (e.g., when calling <a href=../../basic_json/operator%5B%5D/ >operator[]</a> with a missing object key on a <code>const</code> object). See page <a href=../../../features/assertions/ >runtime assertions</a> for more information.</li> <li>Defining the macro to code that does not call <code>std::abort</code> may leave the library in an undefined state.</li> <li>The macro is undefined outside the library.</li> </ul> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: default behavior</summary> <p>The following code will trigger an assertion at runtime:</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -1,4 +1,4 @@
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</code></pre></div> <p>When defined to <code>1</code>, single-element brace initialization of a <code>basic_json</code> value is treated as a copy/move of the element rather than wrapping it in a single-element array.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code> (disabled — existing behavior is preserved).</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_BRACE_INIT_COPY_SEMANTICS 0</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>Background</p> <p>C++ always prefers the <code>initializer_list</code> constructor over the copy/move constructor for brace initialization. This means that code like</p> <div class=highlight><pre><span></span><code><span class=n>json</span><span class=w> </span><span class=n>obj</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=p>{{</span><span class=s>"key"</span><span class=p>,</span><span class=w> </span><span class=s>"value"</span><span class=p>}};</span>
<span class=n>json</span><span class=w> </span><span class=n>j</span><span class=p>{</span><span class=n>obj</span><span class=p>};</span>
@@ -1,4 +1,4 @@
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</code></pre></div> <p>When defined to <code>1</code>, all <a href=../../../community/roadmap/#removal-of-deprecated-functions>deprecated functions</a> of the library are declared as deleted (<code>= delete</code>) instead of only being marked as deprecated. Code that still calls one of them no longer compiles. This way, you can find all calls that need to be replaced before version 4.0.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span> removes these functions; the <a href=../../../integration/migration_guide/#replace-deprecated-functions>migration guide</a> describes how.</p> <p>A deleted function, unlike a removed one, still takes part in overload resolution. A call that would select it therefore fails to compile instead of silently selecting another overload. This matters for the deprecated <code>from_*(ptr, len)</code> overloads of <a href=../../basic_json/from_cbor/ ><code>from_cbor</code></a>, <a href=../../basic_json/from_msgpack/ ><code>from_msgpack</code></a>, <a href=../../basic_json/from_ubjson/ ><code>from_ubjson</code></a>, <a href=../../basic_json/from_bjdata/ ><code>from_bjdata</code></a>, <a href=../../basic_json/from_bon8/ ><code>from_bon8</code></a>, and <a href=../../basic_json/from_bson/ ><code>from_bson</code></a>: without them, a call like <code>from_cbor(ptr, len)</code> would compile, read <code>ptr</code> as a NUL-terminated string, and convert <code>len</code> to the <code>strict</code> parameter.</p> <p>The macro does not affect the deprecated legacy comparison of discarded values, which is controlled by <a href=../json_use_legacy_discarded_value_comparison/ ><code>JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON</code></a>.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code> (disabled, the deprecated functions can still be called, and the compiler warns about it).</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DELETE_DEPRECATED_FUNCTIONS 0</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition info"> <p class=admonition-title>CMake option</p> <p>The macro can also be set with the CMake option <a href=../../../integration/cmake/#json_deletedeprecatedfunctions><code>JSON_DeleteDeprecatedFunctions</code></a> (<code>OFF</code> by default).</p> </div> <div class="admonition warning"> <p class=admonition-title>Opt-in only</p> <p>This macro must be defined <strong>before</strong> including <code>&lt;nlohmann/json.hpp&gt;</code>. Defining it after the include has no effect. Define it for the whole project to avoid different declarations of the same class in different translation units.</p> </div> <div class="admonition note"> <p class=admonition-title>ABI compatibility</p> <p>The macro only turns calls that compile into calls that do not; it does not change the layout or the behavior of any type. Its value is therefore not encoded in the <a href=../../../features/namespace/ >namespace</a>.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: default behavior (macro not defined)</summary> <p>Without the macro, the deprecated overload is called, and the compiler warns about it:</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -1,4 +1,4 @@
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6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 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</code></pre></div> <p>This macro enables position diagnostics for generated <abbr title="JavaScript Object Notation">JSON</abbr> objects.</p> <p>When enabled, two new member functions <a href=../../basic_json/start_pos/ ><code>start_pos()</code></a> and <a href=../../basic_json/end_pos/ ><code>end_pos()</code></a> are added to <a href=../../basic_json/ ><code>basic_json</code></a> values. If the value was created by calling the<a href=../../basic_json/parse/ ><code>parse</code></a> function, then these functions allow querying the byte positions of the value in the input it was parsed from. In case the value was constructed by other means, <code>std::string::npos</code> is returned.</p> <p><a href=../../basic_json/start_pos/ ><code>start_pos()</code></a> returns the position of the first character of a given value in the original <abbr title="JavaScript Object Notation">JSON</abbr> string, while <a href=../../basic_json/end_pos/ ><code>end_pos()</code></a> returns the position of the character <em>following</em> the last character. For objects and arrays, the first and last characters correspond to the opening or closing braces/brackets, respectively. For primitive values, the first and last character represents the opening and closing quotes (strings) or the first and last character of the field's numerical or predefined value (<code>true</code>, <code>false</code>, <code>null</code>), respectively.</p> <table> <thead> <tr> <th><abbr title="JavaScript Object Notation">JSON</abbr> type</th> <th>return value <a href=../../basic_json/start_pos/ ><code>start_pos()</code></a></th> <th>return value <a href=../../basic_json/end_pos/ ><code>end_pos()</code></a></th> </tr> </thead> <tbody> <tr> <td>object</td> <td>position of the opening <code>{</code></td> <td>position after the closing <code>}</code></td> </tr> <tr> <td>array</td> <td>position of the opening <code>[</code></td> <td>position after the closing <code>]</code></td> </tr> <tr> <td>string</td> <td>position of the opening <code>"</code></td> <td>position after the closing <code>"</code></td> </tr> <tr> <td>number</td> <td>position of the first character</td> <td>position after the last character</td> </tr> <tr> <td>boolean</td> <td>position of <code>t</code> for <code>true</code> and <code>f</code> for <code>false</code></td> <td>position after <code>e</code></td> </tr> <tr> <td>null</td> <td>position of <code>n</code></td> <td>position after <code>l</code></td> </tr> </tbody> </table> <p>Given the above, <a href=../../basic_json/end_pos/ ><code>end_pos()</code></a><code>-</code><a href=../../basic_json/start_pos/ ><code>start_pos()</code></a> for a <abbr title="JavaScript Object Notation">JSON</abbr> value provides the length of the parsed <abbr title="JavaScript Object Notation">JSON</abbr> string for that value, including the opening or closing braces, brackets, or quotes.</p> <p>Note that enabling this macro increases the size of every <abbr title="JavaScript Object Notation">JSON</abbr> value by two <code>std::size_t</code> fields and adds slight runtime overhead to parsing, copying <abbr title="JavaScript Object Notation">JSON</abbr> value objects, and the generation of error messages for exceptions. It also causes these values to be reported in those error messages.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code> (position diagnostics are switched off).</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DIAGNOSTIC_POSITIONS 0</span>
</code></pre></div> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>CMake option</p> <p>Diagnostic positions can also be controlled with the CMake option <a href=../../../integration/cmake/#json_diagnostic_positions><code>JSON_Diagnostic_Positions</code></a> (<code>OFF</code> by default) which defines <code>JSON_DIAGNOSTIC_POSITIONS</code> accordingly.</p> </div> <div class="admonition note"> <p class=admonition-title>Availability</p> <p>Diagnostic positions are only available if the value was created by the <a href=../../basic_json/parse/ ><code>parse</code></a> function. The <a href=../../basic_json/sax_parse/ ><code>sax_parse</code></a> function or all other means to create a <abbr title="JavaScript Object Notation">JSON</abbr> value <strong>do not</strong> set the diagnostic positions and <a href=../../basic_json/start_pos/ ><code>start_pos()</code></a> and <a href=../../basic_json/end_pos/ ><code>end_pos()</code></a> will only return <code>std::string::npos</code> for these values.</p> </div> <div class="admonition warning"> <p class=admonition-title>Invalidation</p> <p>The returned positions are only valid as long as the <abbr title="JavaScript Object Notation">JSON</abbr> value is not changed. The positions are <em>not</em> updated when the <abbr title="JavaScript Object Notation">JSON</abbr> value is changed.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: retrieving positions</summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
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</code></pre></div> <p>This macro enables <a href=../../../home/exceptions/#extended-diagnostic-messages>extended diagnostics for exception messages</a>. Possible values are <code>1</code> to enable or <code>0</code> to disable (default).</p> <p>When enabled, exception messages contain a <a href=../../json_pointer/json_pointer/ ><abbr title="JavaScript Object Notation">JSON</abbr> Pointer</a> to the <abbr title="JavaScript Object Notation">JSON</abbr> value that triggered the exception. Note that enabling this macro increases the size of every <abbr title="JavaScript Object Notation">JSON</abbr> value by one pointer and adds some runtime overhead.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code> (extended diagnostics are switched off).</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DIAGNOSTICS 0</span>
</code></pre></div> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>ABI compatibility</p> <p>As of version 3.11.0, this macro is no longer required to be defined consistently throughout a codebase to avoid One Definition Rule (ODR) violations, as the value of this macro is encoded in the namespace, resulting in distinct symbol names. </p> <p>This allows different parts of a codebase to use different versions or configurations of this library without causing improper behavior.</p> <p>Where possible, it is still recommended that all code define this the same way for maximum interoperability.</p> </div> <div class="admonition hint"> <p class=admonition-title>CMake option</p> <p>Diagnostic messages can also be controlled with the CMake option <a href=../../../integration/cmake/#json_diagnostics><code>JSON_Diagnostics</code></a> (<code>OFF</code> by default) which defines <code>JSON_DIAGNOSTICS</code> accordingly. Note this only applies when building the library from source — see the pre-installed-package caveat on that page.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: default behavior</summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
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</code></pre></div> <p>When defined to <code>1</code>, default serialization and deserialization functions for enums are excluded and have to be provided by the user, for example, using <a href=../nlohmann_json_serialize_enum/ ><code>NLOHMANN_JSON_SERIALIZE_ENUM</code></a> (see <a href=../../../features/arbitrary_types/ >arbitrary type conversions</a> for more details).</p> <p>Parsing or serializing an enum will result in a compiler error.</p> <p>This works for both unscoped and scoped enums.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DISABLE_ENUM_SERIALIZATION 0</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition hint"> <p class=admonition-title>CMake option</p> <p>Enum serialization can also be controlled with the CMake option <a href=../../../integration/cmake/#json_disableenumserialization><code>JSON_DisableEnumSerialization</code></a> (<code>OFF</code> by default) which defines <code>JSON_DISABLE_ENUM_SERIALIZATION</code> accordingly.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: Disabled behavior</summary> <p>The code below forces the library <strong>not</strong> to create default serialization/deserialization functions <code>from_json</code> and <code>to_json</code>, meaning the code below <strong>does not</strong> compile.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DISABLE_ENUM_SERIALIZATION 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
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</code></pre></div> <p>When defined to <code>1</code>, parsing from a <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>istream</span></code> reads the input one character at a time through the stream buffer, as in version 3.12.0 and earlier, instead of scanning the characters that the stream buffer already holds in bulk.</p> <p>The macro is an escape hatch for stream buffers that do not follow the usual contract of <code>std::basic_streambuf</code> (see the requirements on the stream buffer in the notes below). It does not change any result: values, exceptions, and the position of the stream after parsing are the same either way. Only the speed differs.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code>: streams are scanned in bulk.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DISABLE_STREAM_BULK_SCAN 0</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>How streams are scanned</p> <p>A <code>std::streambuf</code> keeps the part of the input it has read but not yet handed out in its <em>get area</em>, the range from <code>gptr()</code> to <code>egptr()</code>. A <code>std::filebuf</code>, for instance, reads the file in blocks of a few kilobytes into its get area, and a <code>std::stringbuf</code> exposes its whole string as one get area.</p> <p>When parsing from a <code>std::istream</code>, the parser scans this get area directly, with the same fast paths that it uses for a <code>std::string</code>: runs of ordinary string characters, numbers, and indentation are recognized several bytes at a time instead of being requested from the stream buffer one character at a time. When the parser reaches the end of the get area, it asks the stream buffer for the next character as before, which makes the stream buffer refill its get area.</p> <p>The parser only reads characters that it would also have read one at a time, and it advances the stream buffer exactly over the characters it consumes. Nothing is read ahead, buffered elsewhere, or put back. Therefore, the stream is left exactly where it was left before:</p> <ul> <li><a href=../../operator_gtgt/ ><code>operator&gt;&gt;</code></a> and <a href=../../basic_json/sax_parse/ ><code>sax_parse</code></a> with <code>strict = false</code> can still read several values from one stream, and the stream can still be used with other <code>std::istream</code> functions after a value has been read.</li> <li>With <a href=../json_precise_stream_position/ ><code>JSON_PRECISE_STREAM_POSITION</code></a>, the stream is still positioned right after a parsed number.</li> <li>Exception messages, including the line, the column, and the last read token, are unchanged.</li> </ul> </div> <div class="admonition note"> <p class=admonition-title>Performance</p> <p>Parsing from a <code>std::ifstream</code> or <code>std::istringstream</code> is typically 1.5 to 2 times as fast as before, and reading many small values from one stream with <code>operator&gt;&gt;</code> 1.4 to 4 times as fast. Parsing from a stream is then within about 10 to 20 % of first reading the whole file into a <code>std::string</code> and parsing that.</p> <p>A stream buffer without a get area (one that only overrides <code>underflow()</code> and <code>uflow()</code> and hands out every character from there) offers nothing to scan in bulk, so it is read one character at a time as before.</p> </div> <div class="admonition note"> <p class=admonition-title>Requirements on the stream buffer</p> <p>The bulk scan relies on the following behavior, which every stream buffer of the standard library and every stream buffer that keeps its input in its get area has:</p> <ul> <li>When <code>sgetc()</code> returns a character while <code>gptr() &lt; egptr()</code>, that character is <code>*gptr()</code>; when <code>sbumpc()</code> returns one, it was at <code>gptr()</code> before the call.</li> <li>Characters in the get area are not changed while they are in the get area.</li> <li><code>underflow()</code> or <code>uflow()</code> either sets up a get area that holds the returned character at <code>gptr()</code> (or at <code>gptr() - 1</code> after <code>uflow()</code>), or leaves the get area empty.</li> </ul> <p>A stream buffer that returns characters from <code>uflow()</code> while leaving unrelated characters in its get area, or that changes the characters in its get area in place, does not meet these requirements. Define the macro to <code>1</code> for such stream buffers.</p> </div> <div class="admonition note"> <p class=admonition-title>ABI compatibility</p> <p>The value of this macro is encoded in the <a href=../../../features/namespace/ >namespace</a> (tag <code>_dsbs</code>), 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.</p> </div> <div class="admonition note"> <p class=admonition-title>Other inputs</p> <p>Strings, string views, vectors, arrays, and pointer or iterator ranges over contiguous memory are scanned in bulk anyway. Reading from a <code class=highlight><span class=kt>FILE</span><span class=o>*</span></code> is not affected by this macro; see <a href=../json_disable_unlocked_file_io/ ><code>JSON_DISABLE_UNLOCKED_FILE_IO</code></a> for that input.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: reading values from a stream (default)</summary> <p>The stream is scanned in bulk, and the values are read one after the other:</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span clLine truncated
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;sstream&gt;</span>
@@ -1,4 +1,4 @@
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</code></pre></div> <p>When defined to <code>1</code>, a <code>basic_json</code> value can no longer be constructed from a one-element <code>std::tuple</code> whose element is a reference to that <code>basic_json</code> type, such as <code>std::tuple&lt;json&amp;&gt;</code>, <code>std::tuple&lt;const json&amp;&gt;</code>, or <code>std::tuple&lt;json&amp;&amp;&gt;</code>. These are the tuples created by <code>std::forward_as_tuple(j)</code>.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code> (disabled — existing behavior is preserved).</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION 0</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>Background</p> <p>By default, <code>basic_json</code> can be constructed from any <code>std::tuple</code> whose elements can be converted to <abbr title="JavaScript Object Notation">JSON</abbr>; the result is an array. This includes <code>std::tuple&lt;json&amp;&gt;</code>, which becomes a one-element array.</p> <p><code>std::tuple</code> only converts another tuple element by element if its element type cannot be constructed from the whole source tuple. Because <code>json</code> <em>can</em> be constructed from <code>std::tuple&lt;json&amp;&gt;</code>, <code>std::tuple</code> instead converts the whole tuple into a single <code>json</code> value. This has two surprising effects:</p> <div class=highlight><pre><span></span><code><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=nb>true</span><span class=p>;</span>
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</code></pre></div> <p>When defined to <code>1</code>, parsing from a <code class=highlight><span class=kt>FILE</span><span class=o>*</span></code> reads every character with <code>std::fgetc</code>, as in version 3.12.0 and earlier, instead of locking the file once and reading it with the unlocked stdio functions.</p> <p>It does not change any result: values, exceptions, and the position of the file after parsing are the same either way. Only the speed and the locking of the file differ (see the notes on locking below).</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code>: the file is locked once and read with the unlocked stdio functions where they are available.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DISABLE_UNLOCKED_FILE_IO 0</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>Background</p> <p>The C standard library makes every <code>std::fgetc</code> call thread-safe by locking and unlocking the <code>FILE</code> object. When parsing from a <code>FILE*</code>, the parser reads one character at a time, so this happens for every character of the input.</p> <p>Instead, the parser locks the file once when parsing starts and unlocks it when parsing ends - also when an exception is thrown - and reads the characters in between without locking:</p> <table> <thead> <tr> <th>C library</th> <th>functions</th> </tr> </thead> <tbody> <tr> <td>glibc (Linux), Apple (macOS, iOS), Android, FreeBSD, NetBSD, OpenBSD, DragonFly BSD</td> <td><code>flockfile</code>, <code>getc_unlocked</code>, <code>funlockfile</code> (POSIX)</td> </tr> <tr> <td>Microsoft (<abbr title="Microsoft Visual C++">MSVC</abbr>, clang-cl)</td> <td><code>_lock_file</code>, <code>_fgetc_nolock</code>, <code>_unlock_file</code></td> </tr> <tr> <td>others (e.g., musl, MinGW, newlib)</td> <td><code>std::fgetc</code>, as before</td> </tr> </tbody> </table> <p>This makes parsing from a <code>FILE*</code> 3 to 4 times as fast with the Apple C library and 1.1 to 1.3 times as fast with glibc, whose locking is cheaper. The binary formats (<a href=../../basic_json/from_cbor/ ><code>from_cbor</code></a>, <a href=../../basic_json/from_msgpack/ ><code>from_msgpack</code></a>, ...) read from a <code>FILE*</code> the same way.</p> </div> <div class="admonition note"> <p class=admonition-title>Locking</p> <p>While a value is parsed from a <code>FILE*</code>, the parsing thread holds the file's lock. The lock is recursive, so the parsing thread itself - for instance, a <a href=../../json_sax/ ><abbr title="Simple API for XML">SAX</abbr></a> handler or a <a href=../../basic_json/parser_callback_t/ >parser callback</a> - can keep using the file with stdio functions such as <code>std::ftell</code>. Other threads that use the same <code>FILE</code> object wait until the parser is done. Before, they could interleave their reads with the parser's, which made the parsed input unpredictable anyway.</p> <p>A program in which a <abbr title="Simple API for XML">SAX</abbr> handler or parser callback waits for <strong>another</strong> thread that uses the <strong>same</strong> <code>FILE</code> object would deadlock. Define the macro to <code>1</code> for such programs.</p> </div> <div class="admonition note"> <p class=admonition-title>ABI compatibility</p> <p>The value of this macro is encoded in the <a href=../../../features/namespace/ >namespace</a> (tag <code>_dufio</code>), 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.</p> </div> <div class="admonition note"> <p class=admonition-title>Other inputs</p> <p>Reading from a <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>istream</span></code> is not affected by this macro; see <a href=../json_disable_stream_bulk_scan/ ><code>JSON_DISABLE_STREAM_BULK_SCAN</code></a> for that input.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: parsing from a <code>FILE*</code> (default)</summary> <p>The file is locked once while it is parsed:</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;cstdio&gt;</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
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<span class=cp>#define JSON_HAS_CPP_14</span>
<span class=cp>#define JSON_HAS_CPP_17</span>
<span class=cp>#define JSON_HAS_CPP_20</span>
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<span class=cp>#define JSON_HAS_EXPERIMENTAL_FILESYSTEM </span><span class=cm>/* value */</span>
</code></pre></div> <p>When compiling with C++17, the library provides conversions from and to <a href="https://en.cppreference.com/w/cpp/filesystem/path"><code>std::filesystem::path</code></a>. As compiler support for filesystem is limited, the library tries to detect whether <a href="https://en.cppreference.com/w/cpp/header/filesystem"><code>&lt;filesystem&gt;</code>/<code>std::filesystem</code></a> (<code>JSON_HAS_FILESYSTEM</code>) or <a href="https://en.cppreference.com/w/cpp/header/experimental/filesystem"><code>&lt;experimental/filesystem&gt;</code>/<code>std::experimental::filesystem</code></a> (<code>JSON_HAS_EXPERIMENTAL_FILESYSTEM</code>) should be used. To override the built-in check, define <code>JSON_HAS_FILESYSTEM</code> or <code>JSON_HAS_EXPERIMENTAL_FILESYSTEM</code> to <code>1</code>.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is detected based on the preprocessor macros <code class=highlight><span class=n>__cpp_lib_filesystem</span></code>, <code class=highlight><span class=n>__cpp_lib_experimental_filesystem</span></code>, <code class=highlight><span class=n>__has_include</span><span class=p>(</span><span class=o>&lt;</span><span class=n>filesystem</span><span class=o>&gt;</span><span class=p>)</span></code>, or <code class=highlight><span class=n>__has_include</span><span class=p>(</span><span class=o>&lt;</span><span class=n>experimental</span><span class=o>/</span><span class=n>filesystem</span><span class=o>&gt;</span><span class=p>)</span></code>.</p> <div class="admonition info"> <p class=admonition-title>Known compiler/stdlib exclusions</p> <p>Even when the feature-test macro indicates filesystem support is available, the library disables it on the following broken toolchains:</p> <ul> <li><strong>MinGW + <abbr title="GNU Compiler Collection">GCC</abbr> 8</strong> — disabled entirely (broken <code>std::filesystem</code> implementation; <a href="https://sourceforge.net/p/mingw-w64/bugs/737/">MinGW-w64 bug 737</a>)</li> <li><strong><abbr title="GNU Compiler Collection">GCC</abbr> (non-Clang) &lt; 8</strong> — disabled (no filesystem support)</li> <li><strong>Clang &lt; 7</strong> — disabled (no filesystem support)</li> <li><strong><abbr title="Microsoft Visual C++">MSVC</abbr> &lt; 19.14</strong> — disabled (no filesystem support)</li> <li><strong>iOS &lt; 13</strong> — disabled (no filesystem support)</li> <li><strong>macOS &lt; Catalina (10.15)</strong> — disabled (no filesystem support)</li> </ul> <p>If <code>JSON_HAS_FILESYSTEM</code> or <code>JSON_HAS_EXPERIMENTAL_FILESYSTEM</code> is <code>0</code> despite <code>__cpp_lib_filesystem</code> being defined, one of the exclusions above likely applies to your toolchain.</p> </div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <ul> <li>Note that older compilers or older versions of libstdc++ also require the library <code>stdc++fs</code> to be linked to for filesystem support.</li> <li>Both macros are undefined outside the library.</li> </ul> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library to use the header <code>&lt;experimental/filesystem&gt;</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
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</code></pre></div> <p>This macro indicates whether a <abbr title="JavaScript Object Notation">JSON</abbr> array can be constructed directly from a C++20 range view (<code>std::ranges::view</code>), such as the result of <code>std::views::filter</code> or <code>std::views::transform</code>. Possible values are <code>1</code> when supported or <code>0</code> when unsupported.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>1</code> if <a href=../json_has_ranges/ ><code>JSON_HAS_RANGES</code></a> is <code>1</code> and the compiler is not MinGW (that is, <code class=highlight><span class=n>__MINGW32__</span></code> is not defined), and <code>0</code> otherwise.</p> <p>When the macro is not defined, the library will define it to its default value.</p> <div class="admonition info"> <p class=admonition-title>Known compiler/stdlib exclusions</p> <ul> <li><strong>MinGW</strong> -- disabled, because its <code>std::ranges</code> support is incomplete (<a href="https://github.com/nlohmann/json/issues/4916">issue #4916</a>).</li> <li>All toolchains for which <a href=../json_has_ranges/#default-definition><code>JSON_HAS_RANGES</code></a> is disabled.</li> </ul> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library to disable the conversion from range views:</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_HAS_RANGE_VIEW_CONVERSION 0</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
+1 -1
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@@ -1,4 +1,4 @@
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<svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> JSON_HAS_RANGES </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio 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15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 1Line truncated
</code></pre></div> <p>This macro indicates whether the standard library has any support for ranges. Implies support for concepts. Possible values are <code>1</code> when supported or <code>0</code> when unsupported.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is detected based on the preprocessor macro <code class=highlight><span class=n>__cpp_lib_ranges</span></code>.</p> <p>When the macro is not defined, the library will define it to its default value.</p> <div class="admonition info"> <p class=admonition-title>Known compiler/stdlib exclusions</p> <p>Even when the feature-test macro <code>__cpp_lib_ranges</code> indicates ranges support is available, the library disables it on the following incomplete or broken toolchains:</p> <ul> <li><strong><abbr title="GNU Compiler Collection">GCC</abbr> 11.1.0</strong> — disabled (the shipped <code>&lt;ranges&gt;</code> header has a syntax error; <a href="https://github.com/nlohmann/json/issues/4440">issue #4440</a>)</li> <li><strong>libstdc++ &lt; 11</strong> — disabled (incomplete C++20 ranges support; <a href="https://github.com/nlohmann/json/issues/4440">issue #4440</a>)</li> <li><strong>Clang &lt; 16 with libstdc++</strong> — disabled (incomplete ranges support; <a href="https://github.com/nlohmann/json/issues/5161">issue #5161</a>)</li> <li><strong>libc++ &lt; 160000</strong> — disabled (incomplete C++20 ranges support; <a href="https://github.com/nlohmann/json/issues/4440">issue #4440</a>)</li> <li><strong>nvcc (CUDA) 12.0.x and 12.1.x</strong> — disabled (the <code>enable_borrowed_range</code> variable-template syntax triggers a parse error under these two toolkit versions; fixed in CUDA 12.2; <a href="https://github.com/nlohmann/json/issues/3907">issue #3907</a>)</li> </ul> <p>If <code>JSON_HAS_RANGES</code> is <code>0</code> despite <code>__cpp_lib_ranges</code> being defined, one of the exclusions above likely applies to your toolchain.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library to enable support for ranges:</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_HAS_RANGES 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
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</code></pre></div> <p>This macro indicates whether the standard library has any support for <abbr title="Runtime Type Information">RTTI</abbr> (run time type information). Possible values are <code>1</code> when supported or <code>0</code> when unsupported.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is detected based on the preprocessor macro <code class=highlight><span class=n>_HAS_STATIC_RTTI</span></code>.</p> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library to enable support for libraries with <abbr title="Runtime Type Information">RTTI</abbr> dependence:</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_HAS_STATIC_RTTI 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 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</code></pre></div> <p>This macro indicates whether the standard library has support for <code>std::format</code>/<code>std::formatter</code> (that is, the <code>&lt;format&gt;</code> header). Possible values are <code>1</code> when supported or <code>0</code> when unsupported.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is detected based on the preprocessor macros <code class=highlight><span class=n>JSON_HAS_CPP_20</span></code> and <code class=highlight><span class=n>__cpp_lib_format</span></code>.</p> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition info"> <p class=admonition-title>Enabled functionality</p> <p>When this macro evaluates to <code>1</code>, the library provides a <a href=../../basic_json/std_formatter/ ><code>std::formatter&lt;basic_json&gt;</code></a> specialization so <abbr title="JavaScript Object Notation">JSON</abbr> values can be used directly with <code>std::format</code>.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library to disable support for <code>std::format</code>, even if the standard library would otherwise support it:</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_HAS_STD_FORMAT 0</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
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</code></pre></div> <p>This macro indicates whether the compiler and standard library support 3-way comparison. Possible values are <code>1</code> when supported or <code>0</code> when unsupported.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is detected based on the preprocessor macros <code class=highlight><span class=n>__cpp_impl_three_way_comparison</span></code> and <code class=highlight><span class=n>__cpp_lib_three_way_comparison</span></code>.</p> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library to use 3-way comparison:</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_HAS_THREE_WAY_COMPARISON 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
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</code></pre></div> <p>When defined, <code>&lt;nlohmann/json.hpp&gt;</code> does not include <code>&lt;nlohmann/json_literals.hpp&gt;</code>, so the user-defined string literals <a href=../../operator_literal_json/ ><code>operator""_json</code></a> and <a href=../../operator_literal_json_pointer/ ><code>operator""_json_pointer</code></a> are not declared. Include <code>&lt;nlohmann/json_literals.hpp&gt;</code> in the files that use them.</p> <p>The literals are ordinary inline functions whose bodies call the parser, so every translation unit that includes them instantiates the parser — even if it never parses anything itself. Defining <code>JSON_NO_AUTOMATIC_UDLS</code> for a whole project avoids this cost in translation units that do not parse (e.g., ones that only define types and conversions or pass <code>json</code> values around) and reduces their compile time.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, <code class=highlight><span class=n>JSON_NO_AUTOMATIC_UDLS</span></code> is not defined, and <code>&lt;nlohmann/json.hpp&gt;</code> includes <code>&lt;nlohmann/json_literals.hpp&gt;</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_NO_AUTOMATIC_UDLS</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition info"> <p class=admonition-title>Header <code>&lt;nlohmann/json_literals.hpp&gt;</code></p> <p>The header includes <code>&lt;nlohmann/json.hpp&gt;</code> itself and places the literals according to <a href=../json_use_global_udls/ ><code>JSON_USE_GLOBAL_UDLS</code></a>. It is part of the multi-header sources (<code>include/nlohmann</code>) and of the single-header sources (<code>single_include/nlohmann</code>), next to <code>json.hpp</code>.</p> </div> <div class="admonition info"> <p class=admonition-title>C++ modules</p> <p>The <code>nlohmann.json</code> <a href=../../../features/modules/ >module</a> always exports the literals, regardless of this macro.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below includes the library without the literals and adds them in a single translation unit.</p> <div class=highlight><pre><span></span><code><span class=c1>// compiled with -DJSON_NO_AUTOMATIC_UDLS for the whole project</span>
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15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/Line truncated
</code></pre></div> <p>When defined, headers <code>&lt;cstdio&gt;</code>, <code>&lt;ios&gt;</code>, <code>&lt;iosfwd&gt;</code>, <code>&lt;istream&gt;</code>, and <code>&lt;ostream&gt;</code> are not included and parse functions relying on these headers are excluded. This is relevant for environments where these I/O functions are disallowed for security reasons (e.g., Intel Software Guard Extensions (SGX)).</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, <code class=highlight><span class=n>JSON_NO_IO</span></code> is not defined.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_NO_IO</span>
</code></pre></div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library not to use the headers <code>&lt;cstdio&gt;</code>, <code>&lt;ios&gt;</code>, <code>&lt;iosfwd&gt;</code>, <code>&lt;istream&gt;</code>, and <code>&lt;ostream&gt;</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_NO_IO 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/json_no_thread_local/" rel="canonical"><link href=../json_no_io/ rel=prev><link href=../json_precise_stream_position/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>JSON_NO_THREAD_LOCAL - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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</code></pre></div> <p>When defined, the library does not use <code class=highlight><span class=k>thread_local</span></code> storage. This is relevant for the few environments whose toolchain does not support it.</p> <p>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 <code class=highlight><span class=k>thread_local</span></code> variable, as a counter shared between threads would be raced.</p> <p>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% (<code>canada.json</code>) to 34% (<code>twitter.json</code>) longer, and comparing two equal ones 10% (<code>citm_catalog.json</code>) to 90% (<code>canada.json</code>) longer.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, <code class=highlight><span class=n>JSON_NO_THREAD_LOCAL</span></code> is not defined.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_NO_THREAD_LOCAL</span>
</code></pre></div> <p>The library defines it by itself for Clang targeting MinGW, which does not survive the <code class=highlight><span class=k>thread_local</span></code> storage: copying a value segfaults there, with both old and current Clang versions, while <abbr title="GNU Compiler Collection">GCC</abbr> targeting MinGW is unaffected. Copying and comparing fall back to working without the call stack there, as they do whenever the macro is defined.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library not to use <code class=highlight><span class=k>thread_local</span></code> storage.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_NO_THREAD_LOCAL 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
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</code></pre></div> <p>Exceptions can be switched off by defining the symbol <code>JSON_NOEXCEPTION</code>. When defining <code>JSON_NOEXCEPTION</code>, <code class=highlight><span class=k>try</span></code> is replaced by <code class=highlight><span class=k>if</span><span class=w> </span><span class=p>(</span><span class=nb>true</span><span class=p>)</span></code>, <code class=highlight><span class=k>catch</span></code> is replaced by <code class=highlight><span class=k>if</span><span class=w> </span><span class=p>(</span><span class=nb>false</span><span class=p>)</span></code>, and <code class=highlight><span class=k>throw</span></code> is replaced by <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>abort</span><span class=p>()</span></code>.</p> <p>The same effect is achieved by setting the compiler flag <code>-fno-exceptions</code>.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, the macro is not defined.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_NOEXCEPTION</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <p>The explanatory <a href="https://en.cppreference.com/w/cpp/error/exception/what"><code>what()</code></a> string of exceptions is not available for <abbr title="Microsoft Visual C++">MSVC</abbr> if exceptions are disabled, see <a href="https://github.com/nlohmann/json/discussions/2824">#2824</a>.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below switches off exceptions in the library.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_NOEXCEPTION 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -1,4 +1,4 @@
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</code></pre></div> <p>When defined to <code>1</code>, <a href=../../operator_gtgt/ ><code>operator&gt;&gt;</code></a> and <a href=../../basic_json/sax_parse/ ><code>sax_parse</code></a> with <code>strict = false</code> leave a <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>istream</span></code> positioned right after the parsed value for every value type. By default, the character that terminates a number is consumed as well.</p> <p>The macro only affects reading from a <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>istream</span></code> when the rest of the stream is not required to be consumed. <a href=../../basic_json/parse/ ><code>parse</code></a>, <a href=../../basic_json/accept/ ><code>accept</code></a>, and all other inputs (strings, iterators, containers, <code class=highlight><span class=kt>FILE</span><span class=o>*</span></code>) are never affected.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code> (disabled — existing behavior is preserved).</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_PRECISE_STREAM_POSITION 0</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>Background</p> <p>A number is the only <abbr title="JavaScript Object Notation">JSON</abbr> value whose end can be detected solely by reading the character that follows it. By default, that character is consumed and not put back, so the stream is left one byte too far after a number, and only after a number:</p> <div class=highlight><pre><span></span><code><span class=n>std</span><span class=o>::</span><span class=n>istringstream</span><span class=w> </span><span class=n>input</span><span class=p>(</span><span class=s>"1true"</span><span class=p>);</span>
<span class=n>json</span><span class=w> </span><span class=n>j</span><span class=p>;</span>
@@ -1,4 +1,4 @@
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</code></pre></div> <p>When defined, the library will not create a compiler warning when a different version of the library was already included.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, the macro is not defined.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_SKIP_LIBRARY_VERSION_CHECK</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition danger"> <p class=admonition-title>ABI compatibility</p> <p>Mixing different library versions in the same code can be a problem as the different versions may not be ABI compatible.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: switch off the version check</summary> <p>The code below switches off the warning about including a different version of the library.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_SKIP_LIBRARY_VERSION_CHECK 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -1,4 +1,4 @@
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</code></pre></div> <p>When defined, the library will not create a compile error when a known unsupported compiler is detected. This allows using the library with compilers that do not fully support C++11 and may only work if unsupported features are not used.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, the macro is not defined.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_SKIP_UNSUPPORTED_COMPILER_CHECK</span>
</code></pre></div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below switches off the check whether the compiler is supported.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_SKIP_UNSUPPORTED_COMPILER_CHECK 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -1,4 +1,4 @@
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</code></pre></div> <p>When defined to <code>1</code>, the <code>error_handler</code> parameter of the binary writers <a href=../../basic_json/to_cbor/ ><code>to_cbor</code></a>, <a href=../../basic_json/to_ubjson/ ><code>to_ubjson</code></a>, <a href=../../basic_json/to_bjdata/ ><code>to_bjdata</code></a>, and <a href=../../basic_json/to_bson/ ><code>to_bson</code></a> defaults to <a href=../../basic_json/error_handler_t/ ><code>error_handler_t::strict</code></a> instead of <code>error_handler_t::keep</code>. These writers then check every string value and object key for valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and throw <a href=../../../home/exceptions/#jsonexceptiontype_error316><code>type_error.316</code></a> for ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8, like <a href=../../basic_json/dump/ ><code>dump</code></a> does. Without it, they write the bytes unchanged. An <code>error_handler</code> passed explicitly always takes precedence.</p> <p>The macro does not affect:</p> <ul> <li><a href=../../basic_json/to_msgpack/ ><code>to_msgpack</code></a>: the MessagePack specification allows a <code>str</code> value to contain bytes that are not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8, so its <code>error_handler</code> always defaults to <code>keep</code>.</li> <li><a href=../../basic_json/to_bon8/ ><code>to_bon8</code></a>: <abbr title="Binary Object Notation 8">BON8</abbr> always checks, because the <abbr title="Unicode Transformation Format">UTF</abbr>-8 lead bytes mark where a string ends.</li> <li>The binary readers (<a href=../../basic_json/from_cbor/ ><code>from_cbor</code></a>, <a href=../../basic_json/from_msgpack/ ><code>from_msgpack</code></a>, <a href=../../basic_json/from_ubjson/ ><code>from_ubjson</code></a>, <a href=../../basic_json/from_bjdata/ ><code>from_bjdata</code></a>, <a href=../../basic_json/from_bson/ ><code>from_bson</code></a>): none of these formats requires a decoder to reject ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8, so by default they return the bytes unchanged (<code>error_handler_t::keep</code>), independent of this macro. Pass an <code>error_handler</code> argument explicitly to validate or sanitize the strings they read.</li> <li><a href=../../basic_json/from_bon8/ ><code>from_bon8</code></a>: <abbr title="Binary Object Notation 8">BON8</abbr> always validates, because the <abbr title="Unicode Transformation Format">UTF</abbr>-8 lead bytes mark where a string ends.</li> </ul> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code> (disabled, the behavior of version 3.12.0 and earlier is preserved).</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_STRICT_BINARY_UTF8 0</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>Background</p> <p><abbr title="Concise Binary Object Representation">CBOR</abbr>, <abbr title="Universal Binary JSON">UBJSON</abbr>, <abbr title="Binary JData">BJData</abbr>, and <abbr title="Binary JSON">BSON</abbr> all require strings to be <abbr title="Unicode Transformation Format">UTF</abbr>-8. Up to version 3.12.0, the writers did not check this, so they could produce output that other decoders reject. Checking by default would break code that stores other encodings (for instance <abbr title="International Organization for Standardization">ISO</abbr> 8859-1) in a string and only ever writes it to a binary format. You can pass <code>error_handler_t::strict</code> to each call, or use this macro to check by default ahead of version 4.0.0, where <code>strict</code> is planned to become the default (see <a href="https://github.com/nlohmann/json/issues/5529">#5529</a> and <a href="https://github.com/nlohmann/json/issues/5651">#5651</a>).</p> </div> <div class="admonition warning"> <p class=admonition-title>Opt-in only</p> <p>This macro must be defined <strong>before</strong> including <code>&lt;nlohmann/json.hpp&gt;</code>. Defining it after the include has no effect.</p> </div> <div class="admonition note"> <p class=admonition-title>ABI compatibility</p> <p>The value of this macro is encoded in the <a href=../../../features/namespace/ >namespace</a> (tag <code>_sbu8</code>), 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.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: default behavior (macro not defined)</summary> <p>Without the macro, the bytes are written unchanged:</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -1,4 +1,4 @@
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</code></pre></div> <p>When defined to <code>1</code>, a <code>'\0'</code> (NUL) byte in <abbr title="JavaScript Object Notation">JSON</abbr> text input is rejected with <code>parse_error.101</code>, like any other unexpected byte, instead of being silently treated as end of input.</p> <p>The macro only affects the <abbr title="JavaScript Object Notation">JSON</abbr> text parser (<a href=../../basic_json/parse/ ><code>parse</code></a>, <a href=../../basic_json/accept/ ><code>accept</code></a>, <a href=../../basic_json/sax_parse/ ><code>sax_parse</code></a>, and <a href=../../operator_gtgt/ ><code>operator&gt;&gt;</code></a>). There are three cases where a NUL byte is still not rejected:</p> <ul> <li>The binary formats (<a href=../../basic_json/from_bjdata/ ><code>from_bjdata</code></a>, <a href=../../basic_json/from_bon8/ ><code>from_bon8</code></a>, <a href=../../basic_json/from_bson/ ><code>from_bson</code></a>, <a href=../../basic_json/from_cbor/ ><code>from_cbor</code></a>, <a href=../../basic_json/from_msgpack/ ><code>from_msgpack</code></a>, <a href=../../basic_json/from_ubjson/ ><code>from_ubjson</code></a>) are never affected: there, <code>0x00</code> is ordinary data.</li> <li>A bare <code>const char*</code> pointer has no length of its own, so its length is still determined with <code>strlen()</code>. The first NUL byte therefore still marks the end of the input, and nothing after it is read.</li> <li>One trailing <code>'\0'</code> at the end of a <code>char</code>, <code>wchar_t</code>, <code>char16_t</code>, <code>char32_t</code>, or (C++20) <code>char8_t</code> array (e.g., a string literal) is trimmed; see the warning below.</li> </ul> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code> (disabled — existing behavior is preserved).</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_STRICT_NUL_HANDLING 0</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>Background</p> <p>By default, a <code>'\0'</code> byte anywhere in the input is treated the same as the real end of the input, rather than as an ordinary (and, outside of a string, invalid) byte. Everything from that byte onward is silently ignored, without a parse error - including further, otherwise well-formed <abbr title="JavaScript Object Notation">JSON</abbr>:</p> <div class=highlight><pre><span></span><code><span class=n>json</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=p>(</span><span class=s>"123"</span><span class=p>)</span><span class=w> </span><span class=o>+</span><span class=w> </span><span class=sc>'\0'</span><span class=p>);</span><span class=w> </span><span class=c1>// == 123, no error</span>
<span class=n>json</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=p>(</span><span class=s>"123"</span><span class=p>)</span><span class=w> </span><span class=o>+</span><span class=w> </span><span class=sc>'\0'</span><span class=w> </span><span class=o>+</span><span class=w> </span><span class=s>"true"</span><span class=p>);</span><span class=w> </span><span class=c1>// == 123, the "true" is silently ignored too</span>
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/json_throw_user/" rel="canonical"><link href=../json_brace_init_copy_semantics/ rel=prev><link href=../json_diagnostics/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>JSON_CATCH_USER, JSON_THROW_USER, JSON_TRY_USER - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 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<span class=cp>#define JSON_CATCH_USER(exception) </span><span class=cm>/* value */</span>
<span class=c1>// (2)</span>
<span class=cp>#define JSON_THROW_USER(exception) </span><span class=cm>/* value */</span>
+1 -1
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/json_use_global_udls/" rel="canonical"><link href=../json_strict_nul_handling/ rel=prev><link href=../json_use_implicit_conversions/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>JSON_USE_GLOBAL_UDLS - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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</code></pre></div> <p>When defined to <code>1</code>, the user-defined string literals (UDLs) are placed into the global namespace instead of <code>nlohmann::literals::json_literals</code>.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>1</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_USE_GLOBAL_UDLS 1</span>
</code></pre></div> <p>When the macro is not defined, the library behaves as if it were defined to its default value.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition info"> <p class=admonition-title>Future behavior change</p> <p>The user-defined string literals will be removed from the global namespace in the next major release of the library.</p> <p>To prepare existing code, define <code>JSON_USE_GLOBAL_UDLS</code> to <code>0</code> and bring the string literals into scope where needed. Refer to any of the <a href=#see-also>string literals</a> for details.</p> <p>See the <a href=../../../integration/migration_guide/#import-namespace-literals-for-udls>migration guide</a> for how to update existing code.</p> </div> <div class="admonition hint"> <p class=admonition-title>CMake option</p> <p>The placement of user-defined string literals can also be controlled with the CMake option <a href=../../../integration/cmake/#json_globaludls><code>JSON_GlobalUDLs</code></a> (<code>ON</code> by default) which defines <code>JSON_USE_GLOBAL_UDLS</code> accordingly.</p> </div> <div class="admonition info"> <p class=admonition-title>Leaving out the literals</p> <p>If <a href=../json_no_automatic_udls/ ><code>JSON_NO_AUTOMATIC_UDLS</code></a> is defined, the literals are only declared where <code>&lt;nlohmann/json_literals.hpp&gt;</code> is included; this macro then applies to that header.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: Default behavior</summary> <p>The code below shows the default behavior using the <code>_json</code> UDL.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -1,4 +1,4 @@
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</code></pre></div> <p>When defined to <code>0</code>, implicit conversions are switched off. By default, implicit conversions are switched on. The value directly affects <a href=../../basic_json/operator_ValueType/ ><code>operator ValueType</code></a> and the <a href=../../basic_json/basic_json/ >converting constructor</a> from a <code>basic_json</code> specialization with a different string type (overload 4).</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, implicit conversions are enabled.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_USE_IMPLICIT_CONVERSIONS 1</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition info"> <p class=admonition-title>Future behavior change</p> <p>Implicit conversions will be switched off by default in the next major release of the library.</p> <p>You can prepare existing code by already defining <code>JSON_USE_IMPLICIT_CONVERSIONS</code> to <code>0</code> and replace any implicit conversions with calls to <a href=../../basic_json/get/ ><code>get</code></a>.</p> <p>See the <a href=../../../integration/migration_guide/#replace-implicit-conversions>migration guide</a> for how to update existing code.</p> </div> <div class="admonition tip"> <p class=admonition-title>Automatic migration</p> <p>The community-maintained clang-tidy check <code>modernize-nlohmann-json-explicit-conversions</code> rewrites implicit conversions into explicit calls to <a href=../../basic_json/get/ ><code>get</code></a>; for example, <code class=highlight><span class=kt>int</span><span class=w> </span><span class=n>i</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j</span><span class=p>;</span></code> becomes <code class=highlight><span class=kt>int</span><span class=w> </span><span class=n>i</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j</span><span class=p>.</span><span class=n>get</span><span class=o>&lt;</span><span class=kt>int</span><span class=o>&gt;</span><span class=p>();</span></code>. The check is not part of clang-tidy itself, and it does not catch every case (for example, constructing a <code>std::optional</code> from a <abbr title="JavaScript Object Notation">JSON</abbr> value), so review the result. See <a href="https://github.com/nlohmann/json/discussions/4610">discussion #4610</a> for how to build and use it.</p> </div> <div class="admonition hint"> <p class=admonition-title>CMake option</p> <p>Implicit conversions can also be controlled with the CMake option <a href=../../../integration/cmake/#json_implicitconversions><code>JSON_ImplicitConversions</code></a> (<code>ON</code> by default) which defines <code>JSON_USE_IMPLICIT_CONVERSIONS</code> accordingly.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: implicit and explicit conversions</summary> <p>This is an example for an implicit conversion:</p> <div class=highlight><pre><span></span><code><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>"Hello, world!"</span><span class=p>;</span>
<span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=w> </span><span class=n>s</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j</span><span class=p>;</span>
@@ -1,4 +1,4 @@
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</code></pre></div> <p>This macro enables the (incorrect) legacy comparison behavior of discarded <abbr title="JavaScript Object Notation">JSON</abbr> values. Possible values are <code>1</code> to enable or <code>0</code> to disable (default).</p> <p>When enabled, comparisons involving at least one discarded <abbr title="JavaScript Object Notation">JSON</abbr> value yield results as follows:</p> <table> <thead> <tr> <th><strong>Operator</strong></th> <th><strong>Result</strong></th> </tr> </thead> <tbody> <tr> <td><code>==</code></td> <td><code class=highlight><span class=nb>false</span></code></td> </tr> <tr> <td><code>!=</code></td> <td><code class=highlight><span class=nb>true</span></code></td> </tr> <tr> <td><code>&lt;</code></td> <td><code class=highlight><span class=nb>false</span></code></td> </tr> <tr> <td><code>&lt;=</code></td> <td><code class=highlight><span class=nb>true</span></code></td> </tr> <tr> <td><code>&gt;=</code></td> <td><code class=highlight><span class=nb>true</span></code></td> </tr> <tr> <td><code>&gt;</code></td> <td><code class=highlight><span class=nb>false</span></code></td> </tr> </tbody> </table> <p>Otherwise, comparisons involving at least one discarded <abbr title="JavaScript Object Notation">JSON</abbr> value yield <code class=highlight><span class=nb>false</span></code>, except for <code>!=</code>, which is the negation of <code>==</code> and yields <code class=highlight><span class=nb>true</span></code>.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 0</span>
</code></pre></div> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition warning"> <p class=admonition-title>Inconsistent behavior in C++20 and beyond</p> <p>When targeting C++20 or above, enabling the legacy comparison behavior is <em>strongly</em> discouraged.</p> <ul> <li>The 3-way comparison operator (<code>&lt;=&gt;</code>) will always give the correct result (<code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>partial_ordering</span><span class=o>::</span><span class=n>unordered</span></code>) regardless of the value of <code>JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON</code>.</li> <li>Overloads for the equality and relational operators emulate the legacy behavior.</li> </ul> <p>Code outside your control may use either 3-way comparison or the equality and relational operators, resulting in inconsistent and unpredictable behavior.</p> <p>See <a href=../../basic_json/operator_spaceship/ ><code>operator&lt;=&gt;</code></a> for more information on 3-way comparison.</p> </div> <div class="admonition warning"> <p class=admonition-title>Deprecation</p> <p>The legacy comparison behavior is deprecated and may be removed in a future major version release.</p> <p>New code should not depend on it and existing code should try to remove or rewrite expressions relying on it.</p> <p>See the <a href=../../../integration/migration_guide/#miscellaneous-functions>migration guide</a> for how to update existing code.</p> </div> <div class="admonition hint"> <p class=admonition-title>CMake option</p> <p>Legacy comparison can also be controlled with the CMake option <a href=../../../integration/cmake/#json_legacydiscardedvaluecomparison><code>JSON_LegacyDiscardedValueComparison</code></a> (<code>OFF</code> by default) which defines <code>JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON</code> accordingly.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below switches on the legacy discarded value comparison behavior in the library.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -1,4 +1,4 @@
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6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-Line truncated
</code></pre></div> <p>When defined to <code>1</code>, maps whose keys are enums (such as <code>std::map&lt;E, T&gt;</code> or <code>std::unordered_map&lt;E, T&gt;</code>) are stored as <abbr title="JavaScript Object Notation">JSON</abbr> objects, using the enum's own conversion for the keys. By default, they are stored as arrays of <code>[key, value]</code> pairs.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code> (disabled — existing behavior is preserved).</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS 0</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>Background</p> <p><abbr title="JavaScript Object Notation">JSON</abbr> object keys are strings, so a map is only stored as an object if its keys can be converted to a string type. Enums are not, even if <a href=../nlohmann_json_serialize_enum/ ><code>NLOHMANN_JSON_SERIALIZE_ENUM</code></a> maps them to strings, so a map with enum keys becomes an array of <code>[key, value]</code> pairs:</p> <div class=highlight><pre><span></span><code><span class=p>[[</span><span class=s2>"stopped"</span><span class=p>,</span><span class=w> </span><span class=s2>"aa"</span><span class=p>],</span><span class=w> </span><span class=p>[</span><span class=s2>"completed"</span><span class=p>,</span><span class=w> </span><span class=s2>"bb"</span><span class=p>]]</span>
</code></pre></div> <p>With this macro, the same map becomes an object (see <a href="https://github.com/nlohmann/json/issues/4378">#4378</a>):</p> <div class=highlight><pre><span></span><code><span class=p>{</span><span class=nt>"completed"</span><span class=p>:</span><span class=w> </span><span class=s2>"bb"</span><span class=p>,</span><span class=w> </span><span class=nt>"stopped"</span><span class=p>:</span><span class=w> </span><span class=s2>"aa"</span><span class=p>}</span>
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6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 Line truncated
</code></pre></div> <p>When defined, the parser validates the <abbr title="Unicode Transformation Format">UTF</abbr>-8 content of <abbr title="JavaScript Object Notation">JSON</abbr> strings that come from a <strong>contiguous byte input</strong> (<code>std::string</code>, <code>std::vector&lt;char&gt;</code>/<code>&lt;std::uint8_t&gt;</code>, string literals, <code>const char*</code> ranges, …) using the <a href="https://github.com/simdutf/simdutf">simdutf</a> library instead of the built-in scalar validator. On text with many non-<abbr title="American Standard Code for Information Interchange">ASCII</abbr> characters (e.g. CJK or emoji) this can validate several times faster.</p> <p>This is an <strong>opt-in external dependency</strong>. The library itself remains header-only and its behavior is unchanged: the same input is accepted or rejected either way, and every parse error is reported at the same position with the same message (simdutf is only used to fast-path <em>valid</em> runs; anything it flags falls back to the scalar path so the exact diagnostic is preserved). A <code>std::istream</code> uses simdutf for the characters its stream buffer holds (see <a href=../json_disable_stream_bulk_scan/ ><code>JSON_DISABLE_STREAM_BULK_SCAN</code></a>); other streaming inputs (<code>FILE*</code>, wide strings, user-defined adapters) always use the scalar path.</p> <p>When <code>JSON_USE_SIMDUTF</code> is defined you must make the <code>simdutf.h</code> header available on the include path and link the simdutf library. When it is not defined, no simdutf header is included and there is no dependency.</p> <div class="admonition note"> <p class=admonition-title>Requires C++17</p> <p>simdutf requires C++17 and its header rejects older standards with an <code class=highlight><span class=cp>#error</span></code>. The backend is therefore only compiled in from C++17 on. In C++11 and C++14 the macro has no effect and the scalar validator is used, which accepts and rejects exactly the same input -- only throughput differs. Setting the macro project-wide is therefore safe even when some translation units are built with an older standard.</p> </div> <div class="admonition warning"> <p class=admonition-title>Define consistently</p> <p>The macro selects between two definitions of the same inline validation function. It must therefore be defined identically for <strong>every</strong> translation unit that includes the library; mixing translation units that define it with ones that do not is an ODR violation. Prefer setting it as a compile definition on the target rather than with <code class=highlight><span class=cp>#define</span></code> in individual source files.</p> </div> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, <code class=highlight><span class=n>JSON_USE_SIMDUTF</span></code> is not defined and the portable C++11 scalar validator is used.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_USE_SIMDUTF</span>
</code></pre></div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below enables the simdutf backend for <abbr title="Unicode Transformation Format">UTF</abbr>-8 validation.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_USE_SIMDUTF 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
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# 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.
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</code></pre></div> <p>When defined, the parser of <a href=../../basic_json_document/ ><code>basic_json_document</code></a> (<code>&lt;nlohmann/json_view.hpp&gt;</code>) 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 <abbr title="GNU Compiler Collection">GCC</abbr> and Clang) and SSE2 on x86-64, which are part of the baseline instruction sets of these architectures, and validates non-<abbr title="American Standard Code for Information Interchange">ASCII</abbr> text with NEON (or SSSE3, see <a href=../json_view_use_ssse3/ ><code>JSON_VIEW_USE_SSSE3</code></a>).</p> <p>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.</p> <div class="admonition note"> <p class=admonition-title>ABI compatibility</p> <p>The macro selects between two definitions of the same inline functions. Whether it is defined is encoded in the <a href=../../../features/namespace/ >namespace</a> (tag <code>_vns</code>), 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.</p> </div> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, <code class=highlight><span class=n>JSON_VIEW_NO_SIMD</span></code> is not defined, and the vector code is used where available.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_VIEW_NO_SIMD</span>
</code></pre></div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below uses the portable string scanning of the view.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_VIEW_NO_SIMD</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json_view.hpp&gt;</span>
<span class=p>...</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../json_view_use_ssse3/ >JSON_VIEW_USE_SSSE3</a> - validate non-<abbr title="American Standard Code for Information Interchange">ASCII</abbr> strings with SSSE3 on x86-64</li> <li><a href=../../../features/json_view/ >json_view</a> - the zero-copy view</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 21, 2026 08:21:28 UTC">October 21, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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# JSON_VIEW_NO_SIMD
```
#define JSON_VIEW_NO_SIMD
```
When defined, the parser of [`basic_json_document`](https://json.nlohmann.me/api/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`](https://json.nlohmann.me/api/macros/json_view_use_ssse3/index.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.
ABI compatibility
The macro selects between two definitions of the same inline functions. Whether it is defined is encoded in the [namespace](https://json.nlohmann.me/features/namespace/index.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, `JSON_VIEW_NO_SIMD` is not defined, and the vector code is used where available.
```
#undef JSON_VIEW_NO_SIMD
```
## Examples
Example
The code below uses the portable string scanning of the view.
```
#define JSON_VIEW_NO_SIMD
#include <nlohmann/json_view.hpp>
...
```
## See also
- [JSON_VIEW_USE_SSSE3](https://json.nlohmann.me/api/macros/json_view_use_ssse3/index.md) - validate non-ASCII strings with SSSE3 on x86-64
- [json_view](https://json.nlohmann.me/features/json_view/index.md) - the zero-copy view
## Version history
- Added in version 3.13.0 unreleased.
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# 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.
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</code></pre></div> <p>When defined on x86-64, the parser of <a href=../../basic_json_document/ ><code>basic_json_document</code></a> (<code>&lt;nlohmann/json_view.hpp&gt;</code>) validates non-<abbr title="American Standard Code for Information Interchange">ASCII</abbr> text in strings with SSSE3 without asking the CPU first.</p> <p>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-<abbr title="American Standard Code for Information Interchange">ASCII</abbr> text 16 bytes at a time, using the "lookup4" algorithm of <a href="https://github.com/simdjson/simdjson">simdjson</a>; on CPUs without SSSE3, it validates one <abbr title="Unicode Transformation Format">UTF</abbr>-8 sequence at a time. The vector check is compiled for SSSE3 with a function attribute (<abbr title="GNU Compiler Collection">GCC</abbr> 4.9 and later, Clang), so this needs no compiler option. With <abbr title="Microsoft Visual C++">MSVC</abbr>, the check uses <code>__cpuid</code>. On AArch64, the vector check uses NEON and is always on.</p> <p>Define the macro only together with a compiler option that enables SSSE3 (e.g. <code>-mssse3</code>, or <code>-march=</code> 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-<abbr title="American Standard Code for Information Interchange">ASCII</abbr> text differs.</p> <div class="admonition note"> <p class=admonition-title>ABI compatibility</p> <p>The macro selects between two definitions of the same inline functions. Whether it is defined is encoded in the <a href=../../../features/namespace/ >namespace</a> (tag <code>_vssse3</code>, 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.</p> </div> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, <code class=highlight><span class=n>JSON_VIEW_USE_SSSE3</span></code> is not defined.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_VIEW_USE_SSSE3</span>
</code></pre></div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>With CMake, for a program that only runs on CPUs with SSSE3:</p> <div class=highlight><pre><span></span><code><span class=nb>target_compile_definitions</span><span class=p>(</span><span class=s>your_target</span><span class=w> </span><span class=s>PRIVATE</span><span class=w> </span><span class=s>JSON_VIEW_USE_SSSE3</span><span class=p>)</span>
<span class=nb>target_compile_options</span><span class=p>(</span><span class=s>your_target</span><span class=w> </span><span class=s>PRIVATE</span><span class=w> </span><span class=s>-mssse3</span><span class=p>)</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../json_view_no_simd/ >JSON_VIEW_NO_SIMD</a> - use only portable code in the view's parser</li> <li><a href=../json_use_simdutf/ >JSON_USE_SIMDUTF</a> - validate <abbr title="Unicode Transformation Format">UTF</abbr>-8 with simdutf in <code>basic_json</code>'s parser</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 21, 2026 08:21:28 UTC">October 21, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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# JSON_VIEW_USE_SSSE3
```
#define JSON_VIEW_USE_SSSE3
```
When defined on x86-64, the parser of [`basic_json_document`](https://json.nlohmann.me/api/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.
ABI compatibility
The macro selects between two definitions of the same inline functions. Whether it is defined is encoded in the [namespace](https://json.nlohmann.me/features/namespace/index.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, `JSON_VIEW_USE_SSSE3` is not defined.
```
#undef JSON_VIEW_USE_SSSE3
```
## Examples
Example
With CMake, for a program that only runs on CPUs with SSSE3:
```
target_compile_definitions(your_target PRIVATE JSON_VIEW_USE_SSSE3)
target_compile_options(your_target PRIVATE -mssse3)
```
## See also
- [JSON_VIEW_NO_SIMD](https://json.nlohmann.me/api/macros/json_view_no_simd/index.md) - use only portable code in the view's parser
- [JSON_USE_SIMDUTF](https://json.nlohmann.me/api/macros/json_use_simdutf/index.md) - validate UTF-8 with simdutf in `basic_json`'s parser
## Version history
- Added in version 3.13.0 unreleased.
@@ -1,4 +1,4 @@
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<span class=cp>#define NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE(type, base_type, member...)</span>
<span class=c1>// (2)</span>
<span class=cp>#define NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT(type, base_type, member...)</span>
@@ -1,4 +1,4 @@
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<span class=cp>#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(type, member...) </span><span class=c1>// (2)</span>
<span class=cp>#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE(type, member...) </span><span class=c1>// (3)</span>
</code></pre></div> <p>These macros can be used to simplify the serialization/deserialization of types if you want to use a <abbr title="JavaScript Object Notation">JSON</abbr> object as serialization and want to use the member variable names as object keys in that object. The macro is to be defined <strong>inside</strong> the class/struct to create code for. Unlike <a href=../nlohmann_define_type_non_intrusive/ ><code>NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE</code></a>, it can access private members. The first parameter is the name of the class/struct, and all remaining parameters name the members.</p> <ol> <li>Will use <a href=../../basic_json/at/ ><code>at</code></a> during deserialization and will throw <a href=../../../home/exceptions/#jsonexceptionout_of_range403><code>out_of_range.403</code></a> if a key is missing in the <abbr title="JavaScript Object Notation">JSON</abbr> object.</li> <li>Will use <a href=../../basic_json/value/ ><code>value</code></a> during deserialization and fall back to the default value for the respective type of the member variable if a key in the <abbr title="JavaScript Object Notation">JSON</abbr> object is missing. The generated <code>from_json()</code> function default constructs an object and uses its values as the defaults when calling the <code>value</code> function.</li> <li>Only defines the serialization. Useful in cases when the type does not have a default constructor and only serialization is required.</li> </ol> <p>Summary:</p> <table> <thead> <tr> <th>Need access to private members</th> <th>Need only serialization</th> <th>Allow missing values when de-serializing</th> <th>macro</th> </tr> </thead> <tbody> <tr> <td><div style="color: green;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m16.28-2.72a.75.75 0 0 0-.018-1.042.75.75 0 0 0-1.042-.018l-5.97 5.97-2.47-2.47a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042l3 3a.75.75 0 0 0 1.06 0Z"/></svg></span></div></td> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><strong>NLOHMANN_DEFINE_TYPE_INTRUSIVE</strong></td> </tr> <tr> <td><div style="color: green;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m16.28-2.72a.75.75 0 0 0-.018-1.042.75.75 0 0 0-1.042-.018l-5.97 5.97-2.47-2.47a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042l3 3a.75.75 0 0 0 1.06 0Z"/></svg></span></div></td> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><div style="color: green;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m16.28-2.72a.75.75 0 0 0-.018-1.042.75.75 0 0 0-1.042-.018l-5.97 5.97-2.47-2.47a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042l3 3a.75.75 0 0 0 1.06 0Z"/></svg></span></div></td> <td><strong>NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT</strong></td> </tr> <tr> <td><div style="color: green;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m16.28-2.72a.75.75 0 0 0-.018-1.042.75.75 0 0 0-1.042-.018l-5.97 5.97-2.47-2.47a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042l3 3a.75.75 0 0 0 1.06 0Z"/></svg></span></div></td> <td><div style="color: green;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m16.28-2.72a.75.75 0 0 0-.018-1.042.75.75 0 0 0-1.042-.018l-5.97 5.97-2.47-2.47a.75.75 0 0 0-1.042.018.75.75 0 0 0-Line truncated
@@ -1,4 +1,4 @@
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_define_type_non_intrusive/" rel="canonical"><link href=../nlohmann_define_type_intrusive/ rel=prev><link href=../nlohmann_define_type_with_names/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains 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<span class=cp>#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(type, member...) </span><span class=c1>// (2)</span>
<span class=cp>#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE(type, member...) </span><span class=c1>// (3)</span>
</code></pre></div> <p>These macros can be used to simplify the serialization/deserialization of types if you want to use a <abbr title="JavaScript Object Notation">JSON</abbr> object as serialization and want to use the member variable names as object keys in that object. The macro is to be defined <strong>outside</strong> the class/struct to create code for, but <strong>inside</strong> its namespace. Unlike <a href=../nlohmann_define_type_intrusive/ ><code>NLOHMANN_DEFINE_TYPE_INTRUSIVE</code></a>, it <strong>cannot</strong> access private members. The first parameter is the name of the class/struct, and all remaining parameters name the members.</p> <ol> <li>Will use <a href=../../basic_json/at/ ><code>at</code></a> during deserialization and will throw <a href=../../../home/exceptions/#jsonexceptionout_of_range403><code>out_of_range.403</code></a> if a key is missing in the <abbr title="JavaScript Object Notation">JSON</abbr> object.</li> <li>Will use <a href=../../basic_json/value/ ><code>value</code></a> during deserialization and fall back to the default value for the respective type of the member variable if a key in the <abbr title="JavaScript Object Notation">JSON</abbr> object is missing. The generated <code>from_json()</code> function default constructs an object and uses its values as the defaults when calling the <code>value</code> function.</li> <li>Only defines the serialization. Useful in cases when the type does not have a default constructor and only serialization is required.</li> </ol> <p>Summary:</p> <table> <thead> <tr> <th>Need access to private members</th> <th>Need only serialization</th> <th>Allow missing values when de-serializing</th> <th>macro</th> </tr> </thead> <tbody> <tr> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><strong>NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE</strong></td> </tr> <tr> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><div style="color: green;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m16.28-2.72a.75.75 0 0 0-.018-1.042.75.75 0 0 0-1.042-.018l-5.97 5.97-2.47-2.47a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042l3 3a.75.75 0 0 0 1.06 0Z"/></svg></span></div></td> <td><strong>NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT</strong></td> </tr> <tr> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.32Line truncated
@@ -1,4 +1,4 @@
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_define_type_with_names/" rel="canonical"><link href=../nlohmann_define_type_non_intrusive/ rel=prev><link href=../nlohmann_json_namespace/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#parameters class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__buLine truncated
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_define_type_with_names/" rel="canonical"><link href=../nlohmann_define_type_non_intrusive/ rel=prev><link href=../nlohmann_json_namespace/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#parameters class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__buLine truncated
<span class=cp>#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES(type, "json_member_name", member...)</span>
<span class=cp>#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES(type, "json_member_name", member...)</span>
<span class=cp>#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_NAMES(type, "json_member_name", member...)</span>
+2 -2
View File
@@ -54,6 +54,6 @@ 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`, and `_dufio` in version
3.13.0; see
version 3.12.0, and the ABI tags `_bics`, `_psp`, `_snul`, `_sbu8`, `_ekmo`, `_dsbs`, `_dufio`, `_vns`, and
`_vssse3` in version 3.13.0; see
[`nlohmann` Namespace](../../features/namespace.md#structure).
@@ -1,4 +1,4 @@
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_json_namespace/" rel="canonical"><link href=../nlohmann_define_type_with_names/ rel=prev><link href=../nlohmann_json_namespace_begin/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_JSON_NAMESPACE - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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</code></pre></div> <p>This macro evaluates to the full name of the <code>nlohmann</code> namespace.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value consists of the root namespace (<code>nlohmann</code>) and an inline ABI namespace. See <a href=../../../features/namespace/#structure><code>nlohmann</code> Namespace</a> for details.</p> <p>When the macro is not defined, the library will define it to its default value. Overriding this value has no effect on the library.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The example shows how to use <code>NLOHMANN_JSON_NAMESPACE</code> instead of just <code>nlohmann</code>, as well as how to output the value of <code>NLOHMANN_JSON_NAMESPACE</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -14,4 +14,4 @@
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>cout</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>QUOTE</span><span class=p>(</span><span class=n>NLOHMANN_JSON_NAMESPACE</span><span class=p>)</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>endl</span><span class=p>;</span>
<span class=p>}</span>
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=kc>nl</span><span class=err>ohma</span><span class=kc>nn</span><span class=p>::</span><span class=err>jso</span><span class=kc>n</span><span class=err>_abi_v</span><span class=mi>3</span><span class=err>_</span><span class=mi>12</span><span class=err>_</span><span class=mi>0</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../nlohmann_json_namespace_begin/ ><code>NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END</code></a></li> <li><a href=../nlohmann_json_namespace_no_version/ ><code>NLOHMANN_JSON_NAMESPACE_NO_VERSION</code></a></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.0. Changed inline namespace name in version 3.11.2. Added the ABI tag <code>_dp</code> in version 3.12.0, and the ABI tags <code>_bics</code>, <code>_psp</code>, <code>_snul</code>, <code>_sbu8</code>, <code>_ekmo</code>, <code>_dsbs</code>, and <code>_dufio</code> in version 3.13.0; see <a href=../../../features/namespace/#structure><code>nlohmann</code> Namespace</a>.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 19, 2026 20:00:58 UTC">October 19, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-Line truncated
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../nlohmann_json_namespace_begin/ ><code>NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END</code></a></li> <li><a href=../nlohmann_json_namespace_no_version/ ><code>NLOHMANN_JSON_NAMESPACE_NO_VERSION</code></a></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.0. Changed inline namespace name in version 3.11.2. Added the ABI tag <code>_dp</code> in version 3.12.0, and the ABI tags <code>_bics</code>, <code>_psp</code>, <code>_snul</code>, <code>_sbu8</code>, <code>_ekmo</code>, <code>_dsbs</code>, <code>_dufio</code>, <code>_vns</code>, and <code>_vssse3</code> in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>; see <a href=../../../features/namespace/#structure><code>nlohmann</code> Namespace</a>.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 21, 2026 08:21:28 UTC">October 21, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465Line truncated
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@@ -48,4 +48,4 @@ nlohmann::json_abi_v3_12_0
## 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`, and `_dufio` in version 3.13.0; see [`nlohmann` Namespace](https://json.nlohmann.me/features/namespace/#structure).
- 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`, `_vns`, and `_vssse3` in version 3.13.0 unreleased; see [`nlohmann` Namespace](https://json.nlohmann.me/features/namespace/#structure).
@@ -1,4 +1,4 @@
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URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmann_json_namespace_begin-nlohmann_json_namespace_end class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default 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12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 Line truncated
<span class=cp>#define NLOHMANN_JSON_NAMESPACE_END </span><span class=cm>/* value */</span><span class=cp> </span><span class=c1>// (2)</span>
</code></pre></div> <p>These macros can be used to open and close the <code>nlohmann</code> namespace. See <a href=../../../features/namespace/#structure><code>nlohmann</code> Namespace</a> for details.</p> <ol> <li>Opens the namespace.</li> <li>Closes the namespace.</li> </ol> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default definitions open and close the <code>nlohmann</code> namespace. The precise definition of <code>NLOHMANN_JSON_NAMESPACE_BEGIN</code> varies as described <a href=../../../features/namespace/#structure>here</a>.</p> <ol> <li> <p>Default definition of <code>NLOHMANN_JSON_NAMESPACE_BEGIN</code>:</p> <div class=highlight><pre><span></span><code><span class=k>namespace</span><span class=w> </span><span class=nn>nlohmann</span>
<span class=p>{</span>
@@ -1,4 +1,4 @@
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_json_namespace_no_version/" rel="canonical"><link href=../nlohmann_json_namespace_begin/ rel=prev><link href=../nlohmann_json_serialize_enum/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_JSON_NAMESPACE_NO_VERSION - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> NLOHMANN_JSON_NAMESPACE_NO_VERSION </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo 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6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_json_namespace_no_version/" rel="canonical"><link href=../nlohmann_json_namespace_begin/ rel=prev><link href=../nlohmann_json_serialize_enum/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_JSON_NAMESPACE_NO_VERSION - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 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</code></pre></div> <p>If defined to <code>1</code>, the version component is omitted from the inline namespace. See <a href=../../../features/namespace/#structure><code>nlohmann</code> Namespace</a> for details.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define NLOHMANN_JSON_NAMESPACE_NO_VERSION 0</span>
</code></pre></div> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The example shows how to use <code>NLOHMANN_JSON_NAMESPACE_NO_VERSION</code> to disable the version component of the inline namespace.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
@@ -1,4 +1,4 @@
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_json_serialize_enum/" rel="canonical"><link href=../nlohmann_json_namespace_no_version/ rel=prev><link href=../nlohmann_json_serialize_enum_strict/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_JSON_SERIALIZE_ENUM - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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</code></pre></div> <p>By default, enum values are serialized to <abbr title="JavaScript Object Notation">JSON</abbr> as integers. In some cases, this could result in undesired behavior. If an enum is modified or re-ordered after data has been serialized to <abbr title="JavaScript Object Notation">JSON</abbr>, the later deserialized <abbr title="JavaScript Object Notation">JSON</abbr> data may be undefined or a different enum value than was originally intended.</p> <p>The <code>NLOHMANN_JSON_SERIALIZE_ENUM</code> allows to define a user-defined serialization for every enumerator.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>type</code> (in)</dt> <dd>name of the enum to serialize/deserialize</dd> <dt><code>conversion</code> (in)</dt> <dd>a pair of an enumerator and a <abbr title="JavaScript Object Notation">JSON</abbr> serialization; arbitrary pairs can be given as a comma-separated list</dd> </dl> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The macro adds two functions to the namespace which take care of the serialization and deserialization:</p> <div class=highlight><pre><span></span><code><span class=k>template</span><span class=o>&lt;</span><span class=k>typename</span><span class=w> </span><span class=nc>BasicJsonType</span><span class=o>&gt;</span>
<span class=kr>inline</span><span class=w> </span><span class=kt>void</span><span class=w> </span><span class=n>to_json</span><span class=p>(</span><span class=n>BasicJsonType</span><span class=o>&amp;</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>type</span><span class=o>&amp;</span><span class=w> </span><span class=n>e</span><span class=p>);</span>
<span class=k>template</span><span class=o>&lt;</span><span class=k>typename</span><span class=w> </span><span class=nc>BasicJsonType</span><span class=o>&gt;</span>
@@ -1,4 +1,4 @@
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</code></pre></div> <p>By default, enum values are serialized to <abbr title="JavaScript Object Notation">JSON</abbr> as integers. In some cases, this could result in undesired behavior. If an enum is modified or re-ordered after data has been serialized to <abbr title="JavaScript Object Notation">JSON</abbr>, the later deserialized <abbr title="JavaScript Object Notation">JSON</abbr> data may be undefined or a different enum value than was originally intended.</p> <p><code>NLOHMANN_JSON_SERIALIZE_ENUM_STRICT</code> allows to define a user-defined serialization for every enumerator that throws an exception on undefined input.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>type</code> (in)</dt> <dd>name of the enum to serialize/deserialize</dd> <dt><code>conversion</code> (in)</dt> <dd>a pair of an enumerator and a <abbr title="JavaScript Object Notation">JSON</abbr> serialization; arbitrary pairs can be given as a comma-separated list</dd> </dl> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The macro adds two functions to the namespace which take care of the serialization and deserialization:</p> <div class=highlight><pre><span></span><code><span class=k>template</span><span class=o>&lt;</span><span class=k>typename</span><span class=w> </span><span class=nc>BasicJsonType</span><span class=o>&gt;</span>
<span class=kr>inline</span><span class=w> </span><span class=kt>void</span><span class=w> </span><span class=n>to_json</span><span class=p>(</span><span class=n>BasicJsonType</span><span class=o>&amp;</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>type</span><span class=o>&amp;</span><span class=w> </span><span class=n>e</span><span class=p>);</span>
<span class=k>template</span><span class=o>&lt;</span><span class=k>typename</span><span class=w> </span><span class=nc>BasicJsonType</span><span class=o>&gt;</span>
@@ -1,4 +1,4 @@
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_json_version_major/" rel="canonical"><link href=../nlohmann_json_serialize_enum_strict/ rel=prev><link href=../../../community/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_JSON_VERSION_MAJOR, NLOHMANN_JSON_VERSION_MINOR, NLOHMANN_JSON_VERSION_PATCH - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_json_version_major/" rel="canonical"><link href=../nlohmann_json_serialize_enum_strict/ rel=prev><link href=../../../community/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_JSON_VERSION_MAJOR, NLOHMANN_JSON_VERSION_MINOR, NLOHMANN_JSON_VERSION_PATCH - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet 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<span class=cp>#define NLOHMANN_JSON_VERSION_MINOR </span><span class=cm>/* value */</span>
<span class=cp>#define NLOHMANN_JSON_VERSION_PATCH </span><span class=cm>/* value */</span>
</code></pre></div> <p>These macros are defined by the library and contain the version numbers according to <a href="https://semver.org/spec/v2.0.0.html">Semantic Versioning 2.0.0</a>.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The macros are defined according to the current library version.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The example below shows how <code>NLOHMANN_JSON_VERSION_MAJOR</code>, <code>NLOHMANN_JSON_VERSION_MINOR</code>, and <code>NLOHMANN_JSON_VERSION_PATCH</code> are defined by the library.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>