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 <section id="cmake-compile-features-7">
<h1><a class="toc-backref" href="#id3" role="doc-backlink">cmake-compile-features(7)</a><a class="headerlink" href="#cmake-compile-features-7" title="Permalink to this heading">¶</a></h1>
<nav class="contents" id="contents">
Contents
<ul class="simple">
<li><a class="reference internal" href="#cmake-compile-features-7" id="id3">cmake-compile-features(7)</a>
<ul>
<li><a class="reference internal" href="#introduction" id="id4">Introduction</a></li>
<li><a class="reference internal" href="#compile-feature-requirements" id="id5">Compile Feature Requirements</a>
<ul>
<li><a class="reference internal" href="#requiring-language-standards" id="id6">Requiring Language Standards</a></li>
<li><a class="reference internal" href="#availability-of-compiler-extensions" id="id7">Availability of Compiler Extensions</a></li>
</ul>
</li>
<li><a class="reference internal" href="#optional-compile-features" id="id8">Optional Compile Features</a></li>
<li><a class="reference internal" href="#conditional-compilation-options" id="id9">Conditional Compilation Options</a></li>
<li><a class="reference internal" href="#supported-compilers" id="id10">Supported Compilers</a></li>
<li><a class="reference internal" href="#language-standard-flags" id="id11">Language Standard Flags</a></li>
</ul>
</li>
</ul>
</nav>
<section id="introduction">
<h2><a class="toc-backref" href="#id4" role="doc-backlink">Introduction</a><a class="headerlink" href="#introduction" title="Permalink to this heading">¶</a></h2>
Project source code may depend on, or be conditional on, the availability
of certain features of the compiler. There are three use-cases which arise:
<a class="reference internal" href="#compile-feature-requirements">Compile Feature Requirements</a>, <a class="reference internal" href="#optional-compile-features">Optional Compile Features</a>
and <a class="reference internal" href="#conditional-compilation-options">Conditional Compilation Options</a>.
While features are typically specified in programming language standards,
CMake provides a primary user interface based on granular handling of
the features, not the language standard that introduced the feature.
The <a class="reference internal" href="../prop_gbl/CMAKE_C_KNOWN_FEATURES.html#prop_gbl:CMAKE_C_KNOWN_FEATURES" title="CMAKE_C_KNOWN_FEATURES"><code class="xref cmake cmake-prop_gbl docutils literal notranslate">CMAKE_C_KNOWN_FEATURES</code></a>, <a class="reference internal" href="../prop_gbl/CMAKE_CUDA_KNOWN_FEATURES.html#prop_gbl:CMAKE_CUDA_KNOWN_FEATURES" title="CMAKE_CUDA_KNOWN_FEATURES"><code class="xref cmake cmake-prop_gbl docutils literal notranslate">CMAKE_CUDA_KNOWN_FEATURES</code></a>,
and <a class="reference internal" href="../prop_gbl/CMAKE_CXX_KNOWN_FEATURES.html#prop_gbl:CMAKE_CXX_KNOWN_FEATURES" title="CMAKE_CXX_KNOWN_FEATURES"><code class="xref cmake cmake-prop_gbl docutils literal notranslate">CMAKE_CXX_KNOWN_FEATURES</code></a> global properties contain all the
features known to CMake, regardless of compiler support for the feature.
The <a class="reference internal" href="../variable/CMAKE_C_COMPILE_FEATURES.html#variable:CMAKE_C_COMPILE_FEATURES" title="CMAKE_C_COMPILE_FEATURES"><code class="xref cmake cmake-variable docutils literal notranslate">CMAKE_C_COMPILE_FEATURES</code></a>, <a class="reference internal" href="../variable/CMAKE_CUDA_COMPILE_FEATURES.html#variable:CMAKE_CUDA_COMPILE_FEATURES" title="CMAKE_CUDA_COMPILE_FEATURES"><code class="xref cmake cmake-variable docutils literal notranslate">CMAKE_CUDA_COMPILE_FEATURES</code></a>
, and <a class="reference internal" href="../variable/CMAKE_CXX_COMPILE_FEATURES.html#variable:CMAKE_CXX_COMPILE_FEATURES" title="CMAKE_CXX_COMPILE_FEATURES"><code class="xref cmake cmake-variable docutils literal notranslate">CMAKE_CXX_COMPILE_FEATURES</code></a> variables contain all features
CMake knows are known to the compiler, regardless of language standard
or compile flags needed to use them.
Features known to CMake are named mostly following the same convention
as the Clang feature test macros. There are some exceptions, such as
CMake using <code class="docutils literal notranslate">cxx_final</code> and <code class="docutils literal notranslate">cxx_override</code> instead of the single
<code class="docutils literal notranslate">cxx_override_control</code> used by Clang.
Note that there are no separate compile features properties or variables for
the <code class="docutils literal notranslate">OBJC</code> or <code class="docutils literal notranslate">OBJCXX</code> languages. These are based off <code class="docutils literal notranslate">C</code> or <code class="docutils literal notranslate">C++</code>
respectively, so the properties and variables for their corresponding base
language should be used instead.
</section>
<section id="compile-feature-requirements">
<h2><a class="toc-backref" href="#id5" role="doc-backlink">Compile Feature Requirements</a><a class="headerlink" href="#compile-feature-requirements" title="Permalink to this heading">¶</a></h2>
Compile feature requirements may be specified with the
<a class="reference internal" href="../command/target_compile_features.html#command:target_compile_features" title="target_compile_features"><code class="xref cmake cmake-command docutils literal notranslate">target_compile_features()</code></a> command. For example, if a target must
be compiled with compiler support for the
<a class="reference internal" href="../prop_gbl/CMAKE_CXX_KNOWN_FEATURES.html#prop_gbl:CMAKE_CXX_KNOWN_FEATURES" title="CMAKE_CXX_KNOWN_FEATURES"><code class="xref cmake cmake-prop_gbl docutils literal notranslate">cxx_constexpr</code></a> feature:
<div class="highlight-cmake notranslate"><div class="highlight"><pre>add_library(mylib requires_constexpr.cpp)
target_compile_features(mylib PRIVATE cxx_constexpr)
</pre></div>
</div>
In processing the requirement for the <code class="docutils literal notranslate">cxx_constexpr</code> feature,
<a class="reference internal" href="cmake.1.html#manual:cmake(1)" title="cmake(1)"><code class="xref cmake cmake-manual docutils literal notranslate">cmake(1)</code></a> will ensure that the in-use C++ compiler is capable
of the feature, and will add any necessary flags such as <code class="docutils literal notranslate">-std=gnu++11</code>
to the compile lines of C++ files in the <code class="docutils literal notranslate">mylib</code> target. A
<code class="docutils literal notranslate">FATAL_ERROR</code> is issued if the compiler is not capable of the
feature.
The exact compile flags and language standard are deliberately not part
of the user interface for this use-case. CMake will compute the
appropriate compile flags to use by considering the features specified
for each target.
Such compile flags are added even if the compiler supports the
particular feature without the flag. For example, the GNU compiler
supports variadic templates (with a warning) even if <code class="docutils literal notranslate">-std=gnu++98</code> is
used. CMake adds the <code class="docutils literal notranslate">-std=gnu++11</code> flag if <code class="docutils literal notranslate">cxx_variadic_templates</code>
is specified as a requirement.
In the above example, <code class="docutils literal notranslate">mylib</code> requires <code class="docutils literal notranslate">cxx_constexpr</code> when it
is built itself, but consumers of <code class="docutils literal notranslate">mylib</code> are not required to use a
compiler which supports <code class="docutils literal notranslate">cxx_constexpr</code>. If the interface of
<code class="docutils literal notranslate">mylib</code> does require the <code class="docutils literal notranslate">cxx_constexpr</code> feature (or any other
known feature), that may be specified with the <code class="docutils literal notranslate">PUBLIC</code> or
<code class="docutils literal notranslate">INTERFACE</code> signatures of <a class="reference internal" href="../command/target_compile_features.html#command:target_compile_features" title="target_compile_features"><code class="xref cmake cmake-command docutils literal notranslate">target_compile_features()</code></a>:
<div class="highlight-cmake notranslate"><div class="highlight"><pre>add_library(mylib requires_constexpr.cpp)
# cxx_constexpr is a usage-requirement
target_compile_features(mylib PUBLIC cxx_constexpr)

# main.cpp will be compiled with -std=gnu++11 on GNU for cxx_constexpr.
add_executable(myexe main.cpp)
target_link_libraries(myexe mylib)
</pre></div>
</div>
Feature requirements are evaluated transitively by consuming the link
implementation. See <a class="reference internal" href="cmake-buildsystem.7.html#manual:cmake-buildsystem(7)" title="cmake-buildsystem(7)"><code class="xref cmake cmake-manual docutils literal notranslate">cmake-buildsystem(7)</code></a> for more on
transitive behavior of build properties and usage requirements.
<section id="requiring-language-standards">
<h3><a class="toc-backref" href="#id6" role="doc-backlink">Requiring Language Standards</a><a class="headerlink" href="#requiring-language-standards" title="Permalink to this heading">¶</a></h3>
In projects that use a large number of commonly available features from
a particular language standard (e.g. C++ 11) one may specify a
meta-feature (e.g. <code class="docutils literal notranslate">cxx_std_11</code>) that requires use of a compiler mode
that is at minimum aware of that standard, but could be greater.
This is simpler than specifying all the features individually, but does
not guarantee the existence of any particular feature.
Diagnosis of use of unsupported features will be delayed until compile time.
For example, if C++ 11 features are used extensively in a project's
header files, then clients must use a compiler mode that is no less
than C++ 11. This can be requested with the code:
<div class="highlight-cmake notranslate"><div class="highlight"><pre>target_compile_features(mylib PUBLIC cxx_std_11)
</pre></div>
</div>
In this example, CMake will ensure the compiler is invoked in a mode
of at-least C++ 11 (or C++ 14, C++ 17, ...), adding flags such as
<code class="docutils literal notranslate">-std=gnu++11</code> if necessary. This applies to sources within <code class="docutils literal notranslate">mylib</code>
as well as any dependents (that may include headers from <code class="docutils literal notranslate">mylib</code>).
<div class="admonition note">
Note
If the compiler's default standard level is at least that
of the requested feature, CMake may omit the <code class="docutils literal notranslate">-std=</code> flag.
The flag may still be added if the compiler's default extensions mode
does not match the <a class="reference internal" href="../prop_tgt/LANG_EXTENSIONS.html#prop_tgt:&lt;LANG&gt;_EXTENSIONS" title="&lt;LANG&gt;_EXTENSIONS"><code class="xref cmake cmake-prop_tgt docutils literal notranslate">&lt;LANG&gt;_EXTENSIONS</code></a> target property,
or if the <a class="reference internal" href="../prop_tgt/LANG_STANDARD.html#prop_tgt:&lt;LANG&gt;_STANDARD" title="&lt;LANG&gt;_STANDARD"><code class="xref cmake cmake-prop_tgt docutils literal notranslate">&lt;LANG&gt;_STANDARD</code></a> target property is set.
</div>
</section>
<section id="availability-of-compiler-extensions">
<h3><a class="toc-backref" href="#id7" role="doc-backlink">Availability of Compiler Extensions</a><a class="headerlink" href="#availability-of-compiler-extensions" title="Permalink to this heading">¶</a></h3>
The <a class="reference internal" href="../prop_tgt/LANG_EXTENSIONS.html#prop_tgt:&lt;LANG&gt;_EXTENSIONS" title="&lt;LANG&gt;_EXTENSIONS"><code class="xref cmake cmake-prop_tgt docutils literal notranslate">&lt;LANG&gt;_EXTENSIONS</code></a> target property defaults to the compiler's
default (see <a class="reference internal" href="../variable/CMAKE_LANG_EXTENSIONS_DEFAULT.html#variable:CMAKE_&lt;LANG&gt;_EXTENSIONS_DEFAULT" title="CMAKE_&lt;LANG&gt;_EXTENSIONS_DEFAULT"><code class="xref cmake cmake-variable docutils literal notranslate">CMAKE_&lt;LANG&gt;_EXTENSIONS_DEFAULT</code></a>). Note that because
most compilers enable extensions by default, this may expose portability bugs
in user code or in the headers of third-party dependencies.
<a class="reference internal" href="../prop_tgt/LANG_EXTENSIONS.html#prop_tgt:&lt;LANG&gt;_EXTENSIONS" title="&lt;LANG&gt;_EXTENSIONS"><code class="xref cmake cmake-prop_tgt docutils literal notranslate">&lt;LANG&gt;_EXTENSIONS</code></a> used to default to <code class="docutils literal notranslate">ON</code>. See <a class="reference internal" href="../policy/CMP0128.html#policy:CMP0128" title="CMP0128"><code class="xref cmake cmake-policy docutils literal notranslate">CMP0128</code></a>.
</section>
</section>
<section id="optional-compile-features">
<h2><a class="toc-backref" href="#id8" role="doc-backlink">Optional Compile Features</a><a class="headerlink" href="#optional-compile-features" title="Permalink to this heading">¶</a></h2>
Compile features may be preferred if available, without creating a hard
requirement. This can be achieved by not specifying features with
<a class="reference internal" href="../command/target_compile_features.html#command:target_compile_features" title="target_compile_features"><code class="xref cmake cmake-command docutils literal notranslate">target_compile_features()</code></a> and instead checking the compiler
capabilities with preprocessor conditions in project code.
In this use-case, the project may wish to establish a particular language
standard if available from the compiler, and use preprocessor conditions
to detect the features actually available. A language standard may be
established by <a class="reference internal" href="#requiring-language-standards">Requiring Language Standards</a> using
<a class="reference internal" href="../command/target_compile_features.html#command:target_compile_features" title="target_compile_features"><code class="xref cmake cmake-command docutils literal notranslate">target_compile_features()</code></a> with meta-features like <code class="docutils literal notranslate">cxx_std_11</code>,
or by setting the <a class="reference internal" href="../prop_tgt/CXX_STANDARD.html#prop_tgt:CXX_STANDARD" title="CXX_STANDARD"><code class="xref cmake cmake-prop_tgt docutils literal notranslate">CXX_STANDARD</code></a> target property or
<a class="reference internal" href="../variable/CMAKE_CXX_STANDARD.html#variable:CMAKE_CXX_STANDARD" title="CMAKE_CXX_STANDARD"><code class="xref cmake cmake-variable docutils literal notranslate">CMAKE_CXX_STANDARD</code></a> variable.
See also policy <a class="reference internal" href="../policy/CMP0120.html#policy:CMP0120" title="CMP0120"><code class="xref cmake cmake-policy docutils literal notranslate">CMP0120</code></a> and legacy documentation on
<a class="reference internal" href="../module/WriteCompilerDetectionHeader.html#wcdh-example-usage">Example Usage</a> of the deprecated
<a class="reference internal" href="../module/WriteCompilerDetectionHeader.html#module:WriteCompilerDetectionHeader" title="WriteCompilerDetectionHeader"><code class="xref cmake cmake-module docutils literal notranslate">WriteCompilerDetectionHeader</code></a> module.
</section>
<section id="conditional-compilation-options">
<h2><a class="toc-backref" href="#id9" role="doc-backlink">Conditional Compilation Options</a><a class="headerlink" href="#conditional-compilation-options" title="Permalink to this heading">¶</a></h2>
Libraries may provide entirely different header files depending on
requested compiler features.
For example, a header at <code class="docutils literal notranslate">with_variadics/interface.h</code> may contain:
<div class="highlight-c++ notranslate"><div class="highlight"><pre>template&lt;int I, int... Is&gt;
struct Interface;

template&lt;int I&gt;
struct Interface&lt;I&gt;
{
 static int accumulate()
 {
 return I;
 }
};

template&lt;int I, int... Is&gt;
struct Interface
{
 static int accumulate()
 {
 return I + Interface&lt;Is...&gt;::accumulate();
 }
};
</pre></div>
</div>
while a header at <code class="docutils literal notranslate">no_variadics/interface.h</code> may contain:
<div class="highlight-c++ notranslate"><div class="highlight"><pre>template&lt;int I1, int I2 = 0, int I3 = 0, int I4 = 0&gt;
struct Interface
{
 static int accumulate() { return I1 + I2 + I3 + I4; }
};
</pre></div>
</div>
It may be possible to write an abstraction <code class="docutils literal notranslate">interface.h</code> header
containing something like:
<div class="highlight-c++ notranslate"><div class="highlight"><pre>#ifdef HAVE_CXX_VARIADIC_TEMPLATES
#include &quot;with_variadics/interface.h&quot;
#else
#include &quot;no_variadics/interface.h&quot;
#endif
</pre></div>
</div>
However this could be unmaintainable if there are many files to
abstract. What is needed is to use alternative include directories
depending on the compiler capabilities.
CMake provides a <code class="docutils literal notranslate">COMPILE_FEATURES</code>
<a class="reference internal" href="cmake-generator-expressions.7.html#manual:cmake-generator-expressions(7)" title="cmake-generator-expressions(7)"><code class="xref cmake cmake-manual docutils literal notranslate">generator expression</code></a> to implement
such conditions. This may be used with the build-property commands such as
<a class="reference internal" href="../command/target_include_directories.html#command:target_include_directories" title="target_include_directories"><code class="xref cmake cmake-command docutils literal notranslate">target_include_directories()</code></a> and <a class="reference internal" href="../command/target_link_libraries.html#command:target_link_libraries" title="target_link_libraries"><code class="xref cmake cmake-command docutils literal notranslate">target_link_libraries()</code></a>
to set the appropriate <a class="reference internal" href="cmake-buildsystem.7.html#manual:cmake-buildsystem(7)" title="cmake-buildsystem(7)"><code class="xref cmake cmake-manual docutils literal notranslate">buildsystem</code></a>
properties:
<div class="highlight-cmake notranslate"><div class="highlight"><pre>add_library(foo INTERFACE)
set(with_variadics ${CMAKE_CURRENT_SOURCE_DIR}/with_variadics)
set(no_variadics ${CMAKE_CURRENT_SOURCE_DIR}/no_variadics)
target_include_directories(foo
 INTERFACE
 &quot;$&lt;$&lt;COMPILE_FEATURES:cxx_variadic_templates&gt;:${with_variadics}&gt;&quot;
 &quot;$&lt;$&lt;NOT:$&lt;COMPILE_FEATURES:cxx_variadic_templates&gt;&gt;:${no_variadics}&gt;&quot;
 )
</pre></div>
</div>
Consuming code then simply links to the <code class="docutils literal notranslate">foo</code> target as usual and uses
the feature-appropriate include directory
<div class="highlight-cmake notranslate"><div class="highlight"><pre>add_executable(consumer_with consumer_with.cpp)
target_link_libraries(consumer_with foo)
set_property(TARGET consumer_with CXX_STANDARD 11)

add_executable(consumer_no consumer_no.cpp)
target_link_libraries(consumer_no foo)
</pre></div>
</div>
</section>
<section id="supported-compilers">
<h2><a class="toc-backref" href="#id10" role="doc-backlink">Supported Compilers</a><a class="headerlink" href="#supported-compilers" title="Permalink to this heading">¶</a></h2>
CMake is currently aware of the <a class="reference internal" href="../prop_tgt/CXX_STANDARD.html#prop_tgt:CXX_STANDARD" title="CXX_STANDARD"><code class="xref cmake cmake-prop_tgt docutils literal notranslate">C++ standards</code></a>
and <a class="reference internal" href="../prop_gbl/CMAKE_CXX_KNOWN_FEATURES.html#prop_gbl:CMAKE_CXX_KNOWN_FEATURES" title="CMAKE_CXX_KNOWN_FEATURES"><code class="xref cmake cmake-prop_gbl docutils literal notranslate">compile features</code></a> available from
the following <a class="reference internal" href="../variable/CMAKE_LANG_COMPILER_ID.html#variable:CMAKE_&lt;LANG&gt;_COMPILER_ID" title="CMAKE_&lt;LANG&gt;_COMPILER_ID"><code class="xref cmake cmake-variable docutils literal notranslate">compiler ids</code></a> as of the
versions specified for each:
<ul class="simple">
<li><code class="docutils literal notranslate">AppleClang</code>: Apple Clang for Xcode versions 4.4+.</li>
<li><code class="docutils literal notranslate">Clang</code>: Clang compiler versions 2.9+.</li>
<li><code class="docutils literal notranslate">GNU</code>: GNU compiler versions 4.4+.</li>
<li><code class="docutils literal notranslate">MSVC</code>: Microsoft Visual Studio versions 2010+.</li>
<li><code class="docutils literal notranslate">SunPro</code>: Oracle SolarisStudio versions 12.4+.</li>
<li><code class="docutils literal notranslate">Intel</code>: Intel compiler versions 12.1+.</li>
</ul>
CMake is currently aware of the <a class="reference internal" href="../prop_tgt/C_STANDARD.html#prop_tgt:C_STANDARD" title="C_STANDARD"><code class="xref cmake cmake-prop_tgt docutils literal notranslate">C standards</code></a>
and <a class="reference internal" href="../prop_gbl/CMAKE_C_KNOWN_FEATURES.html#prop_gbl:CMAKE_C_KNOWN_FEATURES" title="CMAKE_C_KNOWN_FEATURES"><code class="xref cmake cmake-prop_gbl docutils literal notranslate">compile features</code></a> available from
the following <a class="reference internal" href="../variable/CMAKE_LANG_COMPILER_ID.html#variable:CMAKE_&lt;LANG&gt;_COMPILER_ID" title="CMAKE_&lt;LANG&gt;_COMPILER_ID"><code class="xref cmake cmake-variable docutils literal notranslate">compiler ids</code></a> as of the
versions specified for each:
<ul class="simple">
<li>all compilers and versions listed above for C++.</li>
<li><code class="docutils literal notranslate">GNU</code>: GNU compiler versions 3.4+</li>
</ul>
CMake is currently aware of the <a class="reference internal" href="../prop_tgt/CXX_STANDARD.html#prop_tgt:CXX_STANDARD" title="CXX_STANDARD"><code class="xref cmake cmake-prop_tgt docutils literal notranslate">C++ standards</code></a> and
their associated meta-features (e.g. <code class="docutils literal notranslate">cxx_std_11</code>) available from the
following <a class="reference internal" href="../variable/CMAKE_LANG_COMPILER_ID.html#variable:CMAKE_&lt;LANG&gt;_COMPILER_ID" title="CMAKE_&lt;LANG&gt;_COMPILER_ID"><code class="xref cmake cmake-variable docutils literal notranslate">compiler ids</code></a> as of the
versions specified for each:
<ul class="simple">
<li><code class="docutils literal notranslate">Cray</code>: Cray Compiler Environment version 8.1+.</li>
<li><code class="docutils literal notranslate">Fujitsu</code>: Fujitsu HPC compiler 4.0+.</li>
<li><code class="docutils literal notranslate">PGI</code>: PGI version 12.10+.</li>
<li><code class="docutils literal notranslate">NVHPC</code>: NVIDIA HPC compilers version 11.0+.</li>
<li><code class="docutils literal notranslate">TI</code>: Texas Instruments compiler.</li>
<li><code class="docutils literal notranslate">XL</code>: IBM XL version 10.1+.</li>
</ul>
CMake is currently aware of the <a class="reference internal" href="../prop_tgt/C_STANDARD.html#prop_tgt:C_STANDARD" title="C_STANDARD"><code class="xref cmake cmake-prop_tgt docutils literal notranslate">C standards</code></a> and
their associated meta-features (e.g. <code class="docutils literal notranslate">c_std_99</code>) available from the
following <a class="reference internal" href="../variable/CMAKE_LANG_COMPILER_ID.html#variable:CMAKE_&lt;LANG&gt;_COMPILER_ID" title="CMAKE_&lt;LANG&gt;_COMPILER_ID"><code class="xref cmake cmake-variable docutils literal notranslate">compiler ids</code></a> as of the
versions specified for each:
<ul class="simple">
<li>all compilers and versions listed above with only meta-features for C++.</li>
</ul>
CMake is currently aware of the <a class="reference internal" href="../prop_tgt/CUDA_STANDARD.html#prop_tgt:CUDA_STANDARD" title="CUDA_STANDARD"><code class="xref cmake cmake-prop_tgt docutils literal notranslate">CUDA standards</code></a> and
their associated meta-features (e.g. <code class="docutils literal notranslate">cuda_std_11</code>) available from the
following <a class="reference internal" href="../variable/CMAKE_LANG_COMPILER_ID.html#variable:CMAKE_&lt;LANG&gt;_COMPILER_ID" title="CMAKE_&lt;LANG&gt;_COMPILER_ID"><code class="xref cmake cmake-variable docutils literal notranslate">compiler ids</code></a> as of the
versions specified for each:
<ul class="simple">
<li><code class="docutils literal notranslate">Clang</code>: Clang compiler 5.0+.</li>
<li><code class="docutils literal notranslate">NVIDIA</code>: NVIDIA nvcc compiler 7.5+.</li>
</ul>
</section>
<section id="language-standard-flags">
<h2><a class="toc-backref" href="#id11" role="doc-backlink">Language Standard Flags</a><a class="headerlink" href="#language-standard-flags" title="Permalink to this heading">¶</a></h2>
In order to satisfy requirements specified by the
<a class="reference internal" href="../command/target_compile_features.html#command:target_compile_features" title="target_compile_features"><code class="xref cmake cmake-command docutils literal notranslate">target_compile_features()</code></a> command or the
<a class="reference internal" href="../variable/CMAKE_LANG_STANDARD.html#variable:CMAKE_&lt;LANG&gt;_STANDARD" title="CMAKE_&lt;LANG&gt;_STANDARD"><code class="xref cmake cmake-variable docutils literal notranslate">CMAKE_&lt;LANG&gt;_STANDARD</code></a> variable, CMake may pass a
language standard flag to the compiler, such as <code class="docutils literal notranslate">-std=c++11</code>.
For <a class="reference internal" href="cmake-generators.7.html#visual-studio-generators">Visual Studio Generators</a>, CMake cannot precisely control
the placement of the language standard flag on the compiler command line.
For <a class="reference internal" href="cmake-generators.7.html#ninja-generators">Ninja Generators</a>, <a class="reference internal" href="cmake-generators.7.html#makefile-generators">Makefile Generators</a>, and
<a class="reference internal" href="../generator/Xcode.html#generator:Xcode" title="Xcode"><code class="xref cmake cmake-generator docutils literal notranslate">Xcode</code></a>, CMake places the language standard flag just after
the language-wide flags from <a class="reference internal" href="../variable/CMAKE_LANG_FLAGS.html#variable:CMAKE_&lt;LANG&gt;_FLAGS" title="CMAKE_&lt;LANG&gt;_FLAGS"><code class="xref cmake cmake-variable docutils literal notranslate">CMAKE_&lt;LANG&gt;_FLAGS</code></a>
and <a class="reference internal" href="../variable/CMAKE_LANG_FLAGS_CONFIG.html#variable:CMAKE_&lt;LANG&gt;_FLAGS_&lt;CONFIG&gt;" title="CMAKE_&lt;LANG&gt;_FLAGS_&lt;CONFIG&gt;"><code class="xref cmake cmake-variable docutils literal notranslate">CMAKE_&lt;LANG&gt;_FLAGS_&lt;CONFIG&gt;</code></a>.
<div class="versionchanged">
Changed in version 3.26: The language standard flag is placed before flags specified by other
abstractions such as the <a class="reference internal" href="../command/target_compile_options.html#command:target_compile_options" title="target_compile_options"><code class="xref cmake cmake-command docutils literal notranslate">target_compile_options()</code></a> command.
Prior to CMake 3.26, the language standard flag was placed after them.
</div>
</section>
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<li><a class="reference internal" href="#">cmake-compile-features(7)</a><ul>
<li><a class="reference internal" href="#introduction">Introduction</a></li>
<li><a class="reference internal" href="#compile-feature-requirements">Compile Feature Requirements</a><ul>
<li><a class="reference internal" href="#requiring-language-standards">Requiring Language Standards</a></li>
<li><a class="reference internal" href="#availability-of-compiler-extensions">Availability of Compiler Extensions</a></li>
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<li><a class="reference internal" href="#optional-compile-features">Optional Compile Features</a></li>
<li><a class="reference internal" href="#conditional-compilation-options">Conditional Compilation Options</a></li>
<li><a class="reference internal" href="#supported-compilers">Supported Compilers</a></li>
<li><a class="reference internal" href="#language-standard-flags">Language Standard Flags</a></li>
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