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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><abbr title="Application Binary Interface">ABI</abbr> 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 (<abbr title="One Definition Rule">ODR</abbr>) 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>