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| <div class="section" id="include-guard"> |
| <span id="command:include_guard"></span><h1>include_guard<a class="headerlink" href="#include-guard" title="Permalink to this headline">ΒΆ</a></h1> |
| <div class="versionadded"> |
| <p><span class="versionmodified added">New in version 3.10.</span></p> |
| </div> |
| <p>Provides an include guard for the file currently being processed by CMake.</p> |
| <div class="highlight-cmake notranslate"><div class="highlight"><pre><span></span><span class="nf">include_guard(</span><span class="p">[</span><span class="no">DIRECTORY</span><span class="p">|</span><span class="no">GLOBAL</span><span class="p">]</span><span class="nf">)</span><span class="w"></span> |
| </pre></div> |
| </div> |
| <p>Sets up an include guard for the current CMake file (see the |
| <span class="target" id="index-0-variable:CMAKE_CURRENT_LIST_FILE"></span><a class="reference internal" href="../variable/CMAKE_CURRENT_LIST_FILE.html#variable:CMAKE_CURRENT_LIST_FILE" title="CMAKE_CURRENT_LIST_FILE"><code class="xref cmake cmake-variable docutils literal notranslate"><span class="pre">CMAKE_CURRENT_LIST_FILE</span></code></a> variable documentation).</p> |
| <p>CMake will end its processing of the current file at the location of the |
| <span class="target" id="index-0-command:include_guard"></span><a class="reference internal" href="#command:include_guard" title="include_guard"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">include_guard()</span></code></a> command if the current file has already been |
| processed for the applicable scope (see below). This provides functionality |
| similar to the include guards commonly used in source headers or to the |
| <code class="docutils literal notranslate"><span class="pre">#pragma</span> <span class="pre">once</span></code> directive. If the current file has been processed previously |
| for the applicable scope, the effect is as though <span class="target" id="index-0-command:return"></span><a class="reference internal" href="return.html#command:return" title="return"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">return()</span></code></a> had been |
| called. Do not call this command from inside a function being defined within |
| the current file.</p> |
| <p>An optional argument specifying the scope of the guard may be provided. |
| Possible values for the option are:</p> |
| <dl class="simple"> |
| <dt><code class="docutils literal notranslate"><span class="pre">DIRECTORY</span></code></dt><dd><p>The include guard applies within the current directory and below. The file |
| will only be included once within this directory scope, but may be included |
| again by other files outside of this directory (i.e. a parent directory or |
| another directory not pulled in by <span class="target" id="index-0-command:add_subdirectory"></span><a class="reference internal" href="add_subdirectory.html#command:add_subdirectory" title="add_subdirectory"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">add_subdirectory()</span></code></a> or |
| <span class="target" id="index-0-command:include"></span><a class="reference internal" href="include.html#command:include" title="include"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">include()</span></code></a> from the current file or its children).</p> |
| </dd> |
| <dt><code class="docutils literal notranslate"><span class="pre">GLOBAL</span></code></dt><dd><p>The include guard applies globally to the whole build. The current file |
| will only be included once regardless of the scope.</p> |
| </dd> |
| </dl> |
| <p>If no arguments given, <code class="docutils literal notranslate"><span class="pre">include_guard</span></code> has the same scope as a variable, |
| meaning that the include guard effect is isolated by the most recent |
| function scope or current directory if no inner function scopes exist. |
| In this case the command behavior is the same as:</p> |
| <div class="highlight-cmake notranslate"><div class="highlight"><pre><span></span><span class="nf">if(</span><span class="nb">__CURRENT_FILE_VAR__</span><span class="nf">)</span><span class="w"></span> |
| <span class="w"> </span><span class="nf">return()</span><span class="w"></span> |
| <span class="nf">endif()</span><span class="w"></span> |
| <span class="nf">set(</span><span class="nb">__CURRENT_FILE_VAR__</span><span class="w"> </span><span class="no">TRUE</span><span class="nf">)</span><span class="w"></span> |
| </pre></div> |
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