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| <div class="section" id="target-precompile-headers"> |
| <span id="command:target_precompile_headers"></span><h1>target_precompile_headers<a class="headerlink" href="#target-precompile-headers" title="Permalink to this headline">¶</a></h1> |
| <div class="versionadded"> |
| <p><span class="versionmodified added">New in version 3.16.</span></p> |
| </div> |
| <p>Add a list of header files to precompile.</p> |
| <p>Precompiling header files can speed up compilation by creating a partially |
| processed version of some header files, and then using that version during |
| compilations rather than repeatedly parsing the original headers.</p> |
| <div class="section" id="main-form"> |
| <h2>Main Form<a class="headerlink" href="#main-form" title="Permalink to this headline">¶</a></h2> |
| <div class="highlight-cmake notranslate"><div class="highlight"><pre><span></span><span class="nf">target_precompile_headers(</span><span class="nv"><target></span><span class="w"></span> |
| <span class="w"> </span><span class="o"><</span><span class="no">INTERFACE</span><span class="p">|</span><span class="no">PUBLIC</span><span class="p">|</span><span class="no">PRIVATE</span><span class="o">></span><span class="w"> </span><span class="p">[</span><span class="nb">header1...</span><span class="p">]</span><span class="w"></span> |
| <span class="w"> </span><span class="p">[</span><span class="o"><</span><span class="no">INTERFACE</span><span class="p">|</span><span class="no">PUBLIC</span><span class="p">|</span><span class="no">PRIVATE</span><span class="o">></span><span class="w"> </span><span class="p">[</span><span class="nb">header2...</span><span class="p">]</span><span class="w"> </span><span class="p">...]</span><span class="nf">)</span><span class="w"></span> |
| </pre></div> |
| </div> |
| <p>The command adds header files to the <span class="target" id="index-0-prop_tgt:PRECOMPILE_HEADERS"></span><a class="reference internal" href="../prop_tgt/PRECOMPILE_HEADERS.html#prop_tgt:PRECOMPILE_HEADERS" title="PRECOMPILE_HEADERS"><code class="xref cmake cmake-prop_tgt docutils literal notranslate"><span class="pre">PRECOMPILE_HEADERS</span></code></a> and/or |
| <span class="target" id="index-0-prop_tgt:INTERFACE_PRECOMPILE_HEADERS"></span><a class="reference internal" href="../prop_tgt/INTERFACE_PRECOMPILE_HEADERS.html#prop_tgt:INTERFACE_PRECOMPILE_HEADERS" title="INTERFACE_PRECOMPILE_HEADERS"><code class="xref cmake cmake-prop_tgt docutils literal notranslate"><span class="pre">INTERFACE_PRECOMPILE_HEADERS</span></code></a> target properties of <code class="docutils literal notranslate"><span class="pre"><target></span></code>. |
| The named <code class="docutils literal notranslate"><span class="pre"><target></span></code> must have been created by a command such as |
| <span class="target" id="index-0-command:add_executable"></span><a class="reference internal" href="add_executable.html#command:add_executable" title="add_executable"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">add_executable()</span></code></a> or <span class="target" id="index-0-command:add_library"></span><a class="reference internal" href="add_library.html#command:add_library" title="add_library"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">add_library()</span></code></a> and must not be an |
| <a class="reference internal" href="../manual/cmake-buildsystem.7.html#alias-targets"><span class="std std-ref">ALIAS target</span></a>.</p> |
| <p>The <code class="docutils literal notranslate"><span class="pre">INTERFACE</span></code>, <code class="docutils literal notranslate"><span class="pre">PUBLIC</span></code> and <code class="docutils literal notranslate"><span class="pre">PRIVATE</span></code> keywords are required to |
| specify the scope of the following arguments. <code class="docutils literal notranslate"><span class="pre">PRIVATE</span></code> and <code class="docutils literal notranslate"><span class="pre">PUBLIC</span></code> |
| items will populate the <span class="target" id="index-1-prop_tgt:PRECOMPILE_HEADERS"></span><a class="reference internal" href="../prop_tgt/PRECOMPILE_HEADERS.html#prop_tgt:PRECOMPILE_HEADERS" title="PRECOMPILE_HEADERS"><code class="xref cmake cmake-prop_tgt docutils literal notranslate"><span class="pre">PRECOMPILE_HEADERS</span></code></a> property of |
| <code class="docutils literal notranslate"><span class="pre"><target></span></code>. <code class="docutils literal notranslate"><span class="pre">PUBLIC</span></code> and <code class="docutils literal notranslate"><span class="pre">INTERFACE</span></code> items will populate the |
| <span class="target" id="index-1-prop_tgt:INTERFACE_PRECOMPILE_HEADERS"></span><a class="reference internal" href="../prop_tgt/INTERFACE_PRECOMPILE_HEADERS.html#prop_tgt:INTERFACE_PRECOMPILE_HEADERS" title="INTERFACE_PRECOMPILE_HEADERS"><code class="xref cmake cmake-prop_tgt docutils literal notranslate"><span class="pre">INTERFACE_PRECOMPILE_HEADERS</span></code></a> property of <code class="docutils literal notranslate"><span class="pre"><target></span></code> |
| (<a class="reference internal" href="../manual/cmake-buildsystem.7.html#imported-targets"><span class="std std-ref">IMPORTED targets</span></a> only support <code class="docutils literal notranslate"><span class="pre">INTERFACE</span></code> items). |
| Repeated calls for the same <code class="docutils literal notranslate"><span class="pre"><target></span></code> will append items in the order called.</p> |
| <p>Projects should generally avoid using <code class="docutils literal notranslate"><span class="pre">PUBLIC</span></code> or <code class="docutils literal notranslate"><span class="pre">INTERFACE</span></code> for targets |
| that will be <a class="reference internal" href="install.html#install-export"><span class="std std-ref">exported</span></a>, or they should at least use |
| the <span class="target" id="index-0-genex:BUILD_INTERFACE"></span><a class="reference internal" href="../manual/cmake-generator-expressions.7.html#genex:BUILD_INTERFACE" title="BUILD_INTERFACE"><code class="xref cmake cmake-genex docutils literal notranslate"><span class="pre">$<BUILD_INTERFACE:...></span></code></a> generator expression to prevent precompile |
| headers from appearing in an installed exported target. Consumers of a target |
| should typically be in control of what precompile headers they use, not have |
| precompile headers forced on them by the targets being consumed (since |
| precompile headers are not typically usage requirements). A notable exception |
| to this is where an <a class="reference internal" href="../manual/cmake-buildsystem.7.html#interface-libraries"><span class="std std-ref">interface library</span></a> is created |
| to define a commonly used set of precompile headers in one place and then other |
| targets link to that interface library privately. In this case, the interface |
| library exists specifically to propagate the precompile headers to its |
| consumers and the consumer is effectively still in control, since it decides |
| whether to link to the interface library or not.</p> |
| <p>The list of header files is used to generate a header file named |
| <code class="docutils literal notranslate"><span class="pre">cmake_pch.h|xx</span></code> which is used to generate the precompiled header file |
| (<code class="docutils literal notranslate"><span class="pre">.pch</span></code>, <code class="docutils literal notranslate"><span class="pre">.gch</span></code>, <code class="docutils literal notranslate"><span class="pre">.pchi</span></code>) artifact. The <code class="docutils literal notranslate"><span class="pre">cmake_pch.h|xx</span></code> header |
| file will be force included (<code class="docutils literal notranslate"><span class="pre">-include</span></code> for GCC, <code class="docutils literal notranslate"><span class="pre">/FI</span></code> for MSVC) to |
| all source files, so sources do not need to have <code class="docutils literal notranslate"><span class="pre">#include</span> <span class="pre">"pch.h"</span></code>.</p> |
| <p>Header file names specified with angle brackets (e.g. <code class="docutils literal notranslate"><span class="pre"><unordered_map></span></code>) or |
| explicit double quotes (escaped for the <span class="target" id="index-0-manual:cmake-language(7)"></span><a class="reference internal" href="../manual/cmake-language.7.html#manual:cmake-language(7)" title="cmake-language(7)"><code class="xref cmake cmake-manual docutils literal notranslate"><span class="pre">cmake-language(7)</span></code></a>, |
| e.g. <code class="docutils literal notranslate"><span class="pre">[["other_header.h"]]</span></code>) will be treated as is, and include directories |
| must be available for the compiler to find them. Other header file names |
| (e.g. <code class="docutils literal notranslate"><span class="pre">project_header.h</span></code>) are interpreted as being relative to the current |
| source directory (e.g. <span class="target" id="index-0-variable:CMAKE_CURRENT_SOURCE_DIR"></span><a class="reference internal" href="../variable/CMAKE_CURRENT_SOURCE_DIR.html#variable:CMAKE_CURRENT_SOURCE_DIR" title="CMAKE_CURRENT_SOURCE_DIR"><code class="xref cmake cmake-variable docutils literal notranslate"><span class="pre">CMAKE_CURRENT_SOURCE_DIR</span></code></a>) and will be |
| included by absolute path. For example:</p> |
| <div class="highlight-cmake notranslate"><div class="highlight"><pre><span></span><span class="nf">target_precompile_headers(</span><span class="nb">myTarget</span><span class="w"></span> |
| <span class="w"> </span><span class="no">PUBLIC</span><span class="w"></span> |
| <span class="w"> </span><span class="nb">project_header.h</span><span class="w"></span> |
| <span class="w"> </span><span class="no">PRIVATE</span><span class="w"></span> |
| <span class="w"> </span><span class="p">[[</span><span class="s">"other_header.h"</span><span class="p">]]</span><span class="w"></span> |
| <span class="w"> </span><span class="nv"><unordered_map></span><span class="w"></span> |
| <span class="nf">)</span><span class="w"></span> |
| </pre></div> |
| </div> |
| <p>Arguments to <code class="docutils literal notranslate"><span class="pre">target_precompile_headers()</span></code> may use "generator expressions" |
| with the syntax <code class="docutils literal notranslate"><span class="pre">$<...></span></code>. |
| See the <span class="target" id="index-0-manual:cmake-generator-expressions(7)"></span><a class="reference internal" href="../manual/cmake-generator-expressions.7.html#manual:cmake-generator-expressions(7)" title="cmake-generator-expressions(7)"><code class="xref cmake cmake-manual docutils literal notranslate"><span class="pre">cmake-generator-expressions(7)</span></code></a> manual for available |
| expressions. |
| The <span class="target" id="index-0-genex:COMPILE_LANGUAGE"></span><a class="reference internal" href="../manual/cmake-generator-expressions.7.html#genex:COMPILE_LANGUAGE" title="COMPILE_LANGUAGE"><code class="xref cmake cmake-genex docutils literal notranslate"><span class="pre">$<COMPILE_LANGUAGE:...></span></code></a> generator expression is particularly |
| useful for specifying a language-specific header to precompile for |
| only one language (e.g. <code class="docutils literal notranslate"><span class="pre">CXX</span></code> and not <code class="docutils literal notranslate"><span class="pre">C</span></code>). In this case, header |
| file names that are not explicitly in double quotes or angle brackets |
| must be specified by absolute path. Also, when specifying angle brackets |
| inside a generator expression, be sure to encode the closing <code class="docutils literal notranslate"><span class="pre">></span></code> as |
| <code class="docutils literal notranslate"><span class="pre">$<ANGLE-R></span></code>. For example:</p> |
| <div class="highlight-cmake notranslate"><div class="highlight"><pre><span></span><span class="nf">target_precompile_headers(</span><span class="nb">mylib</span><span class="w"> </span><span class="no">PRIVATE</span><span class="w"></span> |
| <span class="w"> </span><span class="s">"$<$<COMPILE_LANGUAGE:CXX>:${CMAKE_CURRENT_SOURCE_DIR}/cxx_only.h>"</span><span class="w"></span> |
| <span class="w"> </span><span class="s">"$<$<COMPILE_LANGUAGE:C>:<stddef.h$<ANGLE-R>>"</span><span class="w"></span> |
| <span class="w"> </span><span class="s">"$<$<COMPILE_LANGUAGE:CXX>:<cstddef$<ANGLE-R>>"</span><span class="w"></span> |
| <span class="nf">)</span><span class="w"></span> |
| </pre></div> |
| </div> |
| </div> |
| <div class="section" id="reusing-precompile-headers"> |
| <h2>Reusing Precompile Headers<a class="headerlink" href="#reusing-precompile-headers" title="Permalink to this headline">¶</a></h2> |
| <p>The command also supports a second signature which can be used to specify that |
| one target re-uses a precompiled header file artifact from another target |
| instead of generating its own:</p> |
| <div class="highlight-cmake notranslate"><div class="highlight"><pre><span></span><span class="nf">target_precompile_headers(</span><span class="nv"><target></span><span class="w"> </span><span class="no">REUSE_FROM</span><span class="w"> </span><span class="nv"><other_target></span><span class="nf">)</span><span class="w"></span> |
| </pre></div> |
| </div> |
| <p>This form sets the <span class="target" id="index-0-prop_tgt:PRECOMPILE_HEADERS_REUSE_FROM"></span><a class="reference internal" href="../prop_tgt/PRECOMPILE_HEADERS_REUSE_FROM.html#prop_tgt:PRECOMPILE_HEADERS_REUSE_FROM" title="PRECOMPILE_HEADERS_REUSE_FROM"><code class="xref cmake cmake-prop_tgt docutils literal notranslate"><span class="pre">PRECOMPILE_HEADERS_REUSE_FROM</span></code></a> property to |
| <code class="docutils literal notranslate"><span class="pre"><other_target></span></code> and adds a dependency such that <code class="docutils literal notranslate"><span class="pre"><target></span></code> will depend |
| on <code class="docutils literal notranslate"><span class="pre"><other_target></span></code>. CMake will halt with an error if the |
| <span class="target" id="index-2-prop_tgt:PRECOMPILE_HEADERS"></span><a class="reference internal" href="../prop_tgt/PRECOMPILE_HEADERS.html#prop_tgt:PRECOMPILE_HEADERS" title="PRECOMPILE_HEADERS"><code class="xref cmake cmake-prop_tgt docutils literal notranslate"><span class="pre">PRECOMPILE_HEADERS</span></code></a> property of <code class="docutils literal notranslate"><span class="pre"><target></span></code> is already set when |
| the <code class="docutils literal notranslate"><span class="pre">REUSE_FROM</span></code> form is used.</p> |
| <div class="admonition note"> |
| <p class="admonition-title">Note</p> |
| <p>The <code class="docutils literal notranslate"><span class="pre">REUSE_FROM</span></code> form requires the same set of compiler options, |
| compiler flags and compiler definitions for both <code class="docutils literal notranslate"><span class="pre"><target></span></code> and |
| <code class="docutils literal notranslate"><span class="pre"><other_target></span></code>. Some compilers (e.g. GCC) may issue a warning if the |
| precompiled header file cannot be used (<code class="docutils literal notranslate"><span class="pre">-Winvalid-pch</span></code>).</p> |
| </div> |
| </div> |
| <div class="section" id="see-also"> |
| <h2>See Also<a class="headerlink" href="#see-also" title="Permalink to this headline">¶</a></h2> |
| <p>To disable precompile headers for specific targets, see the |
| <span class="target" id="index-0-prop_tgt:DISABLE_PRECOMPILE_HEADERS"></span><a class="reference internal" href="../prop_tgt/DISABLE_PRECOMPILE_HEADERS.html#prop_tgt:DISABLE_PRECOMPILE_HEADERS" title="DISABLE_PRECOMPILE_HEADERS"><code class="xref cmake cmake-prop_tgt docutils literal notranslate"><span class="pre">DISABLE_PRECOMPILE_HEADERS</span></code></a> target property.</p> |
| <p>To prevent precompile headers from being used when compiling a specific |
| source file, see the <span class="target" id="index-0-prop_sf:SKIP_PRECOMPILE_HEADERS"></span><a class="reference internal" href="../prop_sf/SKIP_PRECOMPILE_HEADERS.html#prop_sf:SKIP_PRECOMPILE_HEADERS" title="SKIP_PRECOMPILE_HEADERS"><code class="xref cmake cmake-prop_sf docutils literal notranslate"><span class="pre">SKIP_PRECOMPILE_HEADERS</span></code></a> source file property.</p> |
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| <li><a class="reference internal" href="#">target_precompile_headers</a><ul> |
| <li><a class="reference internal" href="#main-form">Main Form</a></li> |
| <li><a class="reference internal" href="#reusing-precompile-headers">Reusing Precompile Headers</a></li> |
| <li><a class="reference internal" href="#see-also">See Also</a></li> |
| </ul> |
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