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| <div class="section" id="checkcxxsymbolexists"> |
| <span id="module:CheckCXXSymbolExists"></span><h1>CheckCXXSymbolExists<a class="headerlink" href="#checkcxxsymbolexists" title="Permalink to this headline">¶</a></h1> |
| <p>Check if a symbol exists as a function, variable, or macro in <code class="docutils literal notranslate"><span class="pre">C++</span></code>.</p> |
| <dl class="cmake command"> |
| <dt class="sig sig-object cmake" id="command:check_cxx_symbol_exists"> |
| <span class="sig-name descname"><span class="pre">check_cxx_symbol_exists</span></span><a class="headerlink" href="#command:check_cxx_symbol_exists" title="Permalink to this definition">¶</a></dt> |
| <dd><div class="highlight-cmake notranslate"><div class="highlight"><pre><span></span><span class="nf">check_cxx_symbol_exists(</span><span class="nv"><symbol></span><span class="w"> </span><span class="nv"><files></span><span class="w"> </span><span class="nv"><variable></span><span class="nf">)</span><span class="w"></span> |
| </pre></div> |
| </div> |
| <p>Check that the <code class="docutils literal notranslate"><span class="pre"><symbol></span></code> is available after including given header |
| <code class="docutils literal notranslate"><span class="pre"><files></span></code> and store the result in a <code class="docutils literal notranslate"><span class="pre"><variable></span></code>. Specify the list of |
| files in one argument as a semicolon-separated list. |
| <code class="docutils literal notranslate"><span class="pre">check_cxx_symbol_exists()</span></code> can be used to check for symbols as seen by |
| the C++ compiler, as opposed to <span class="target" id="index-0-command:check_symbol_exists"></span><a class="reference internal" href="CheckSymbolExists.html#command:check_symbol_exists" title="check_symbol_exists"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">check_symbol_exists()</span></code></a>, which always |
| uses the <code class="docutils literal notranslate"><span class="pre">C</span></code> compiler.</p> |
| <p>If the header files define the symbol as a macro it is considered |
| available and assumed to work. If the header files declare the symbol |
| as a function or variable then the symbol must also be available for |
| linking. If the symbol is a type, enum value, or C++ template it will |
| not be recognized: consider using the <span class="target" id="index-0-module:CheckTypeSize"></span><a class="reference internal" href="CheckTypeSize.html#module:CheckTypeSize" title="CheckTypeSize"><code class="xref cmake cmake-module docutils literal notranslate"><span class="pre">CheckTypeSize</span></code></a> |
| or <span class="target" id="index-0-module:CheckSourceCompiles"></span><a class="reference internal" href="CheckSourceCompiles.html#module:CheckSourceCompiles" title="CheckSourceCompiles"><code class="xref cmake cmake-module docutils literal notranslate"><span class="pre">CheckSourceCompiles</span></code></a> module instead.</p> |
| </dd></dl> |
| |
| <div class="admonition note"> |
| <p class="admonition-title">Note</p> |
| <p>This command is unreliable when <code class="docutils literal notranslate"><span class="pre"><symbol></span></code> is (potentially) an overloaded |
| function. Since there is no reliable way to predict whether a given function |
| in the system environment may be defined as an overloaded function or may be |
| an overloaded function on other systems or will become so in the future, it |
| is generally advised to use the <span class="target" id="index-0-module:CheckCXXSourceCompiles"></span><a class="reference internal" href="CheckCXXSourceCompiles.html#module:CheckCXXSourceCompiles" title="CheckCXXSourceCompiles"><code class="xref cmake cmake-module docutils literal notranslate"><span class="pre">CheckCXXSourceCompiles</span></code></a> module for |
| checking any function symbol (unless somehow you surely know the checked |
| function is not overloaded on other systems or will not be so in the |
| future).</p> |
| </div> |
| <p>The following variables may be set before calling this macro to modify |
| the way the check is run:</p> |
| <dl> |
| <dt><code class="docutils literal notranslate"><span class="pre">CMAKE_REQUIRED_FLAGS</span></code></dt><dd><p>string of compile command line flags.</p> |
| </dd> |
| <dt><code class="docutils literal notranslate"><span class="pre">CMAKE_REQUIRED_DEFINITIONS</span></code></dt><dd><p>a <a class="reference internal" href="../manual/cmake-language.7.html#cmake-language-lists"><span class="std std-ref">;-list</span></a> of macros to define (-DFOO=bar).</p> |
| </dd> |
| <dt><code class="docutils literal notranslate"><span class="pre">CMAKE_REQUIRED_INCLUDES</span></code></dt><dd><p>a <a class="reference internal" href="../manual/cmake-language.7.html#cmake-language-lists"><span class="std std-ref">;-list</span></a> of header search paths to pass to |
| the compiler.</p> |
| </dd> |
| <dt><code class="docutils literal notranslate"><span class="pre">CMAKE_REQUIRED_LINK_OPTIONS</span></code></dt><dd><div class="versionadded"> |
| <p><span class="versionmodified added">New in version 3.14: </span>a <a class="reference internal" href="../manual/cmake-language.7.html#cmake-language-lists"><span class="std std-ref">;-list</span></a> of options to add to the link command.</p> |
| </div> |
| </dd> |
| <dt><code class="docutils literal notranslate"><span class="pre">CMAKE_REQUIRED_LIBRARIES</span></code></dt><dd><p>a <a class="reference internal" href="../manual/cmake-language.7.html#cmake-language-lists"><span class="std std-ref">;-list</span></a> of libraries to add to the link |
| command. See policy <span class="target" id="index-0-policy:CMP0075"></span><a class="reference internal" href="../policy/CMP0075.html#policy:CMP0075" title="CMP0075"><code class="xref cmake cmake-policy docutils literal notranslate"><span class="pre">CMP0075</span></code></a>.</p> |
| </dd> |
| <dt><code class="docutils literal notranslate"><span class="pre">CMAKE_REQUIRED_QUIET</span></code></dt><dd><div class="versionadded"> |
| <p><span class="versionmodified added">New in version 3.1: </span>execute quietly without messages.</p> |
| </div> |
| </dd> |
| </dl> |
| <p>For example:</p> |
| <div class="highlight-cmake notranslate"><div class="highlight"><pre><span></span><span class="nf">include(</span><span class="nb">CheckCXXSymbolExists</span><span class="nf">)</span><span class="w"></span> |
| |
| <span class="c"># Check for macro SEEK_SET</span> |
| <span class="nf">check_cxx_symbol_exists(</span><span class="no">SEEK_SET</span><span class="w"> </span><span class="s">"cstdio"</span><span class="w"> </span><span class="no">HAVE_SEEK_SET</span><span class="nf">)</span><span class="w"></span> |
| <span class="c"># Check for function std::fopen</span> |
| <span class="nf">check_cxx_symbol_exists(</span><span class="nb">std</span><span class="o">::</span><span class="nb">fopen</span><span class="w"> </span><span class="s">"cstdio"</span><span class="w"> </span><span class="no">HAVE_STD_FOPEN</span><span class="nf">)</span><span class="w"></span> |
| </pre></div> |
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