mirror of
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ac67631b02
- Added intro code blocks showing how to include these modules.
- Used word "command" instead of "macro".
- Added examples sections.
- Updated and synced descriptions of commands and arguments.
- Added a rubric title for variables that affect the checks.
- Listed CMAKE_TRY_COMPILE_TARGET_TYPE variable in the rubric together
with CMAKE_REQUIRED_* variables.
- Added link to CheckCompilerFlag module in the target_compile_options()
docs.
- Used lowercase style for check_fortran_compiler_flag() command.
- Added a link to `$<COMPILE_LANGUAGE:languages>` generator expression
so it can be linked from other pages (See commit
2e37a20f02 for more info on the initial
style used).
- Fixed the GENEX_NOTE inclusion (starting with line after the 2nd line)
where part of the sentence was rendered in the output.
111 lines
3.5 KiB
CMake
111 lines
3.5 KiB
CMake
# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
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# file LICENSE.rst or https://cmake.org/licensing for details.
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#[=======================================================================[.rst:
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CheckCCompilerFlag
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------------------
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This module provides a command to check whether the C compiler supports a
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given flag.
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Load this module in a CMake project with:
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.. code-block:: cmake
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include(CheckCCompilerFlag)
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Commands
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^^^^^^^^
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This module provides the following command:
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.. command:: check_c_compiler_flag
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Checks once whether the C compiler supports a given flag:
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.. code-block:: cmake
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check_c_compiler_flag(<flag> <variable>)
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This command checks once that the ``<flag>`` is accepted by the C compiler
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without producing a diagnostic message. Multiple flags can be specified
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in one argument as a string using a :ref:`semicolon-separated list
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<CMake Language Lists>`.
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The result of the check is stored in the internal cache variable specified
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by ``<variable>``, with boolean true for success and boolean false for
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failure.
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A successful result only indicates that the compiler did not report an
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error when given the flag. Whether the flag has any effect, or the
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intended one, is outside the scope of this module.
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.. note::
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Since the underlying :command:`try_compile` command also uses flags from
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variables like :variable:`CMAKE_<LANG>_FLAGS`, unknown or unsupported
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flags in those variables may result in a false negative for this check.
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.. rubric:: Variables Affecting the Check
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The following variables may be set before calling this command to modify
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the way the check is run:
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.. include:: /module/include/CMAKE_REQUIRED_FLAGS.rst
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.. include:: /module/include/CMAKE_REQUIRED_DEFINITIONS.rst
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.. include:: /module/include/CMAKE_REQUIRED_INCLUDES.rst
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.. include:: /module/include/CMAKE_REQUIRED_LINK_OPTIONS.rst
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.. include:: /module/include/CMAKE_REQUIRED_LIBRARIES.rst
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.. include:: /module/include/CMAKE_REQUIRED_LINK_DIRECTORIES.rst
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.. include:: /module/include/CMAKE_REQUIRED_QUIET.rst
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.. include:: /module/include/CMAKE_TRY_COMPILE_TARGET_TYPE.rst
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Examples
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^^^^^^^^
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The following example demonstrates how to use this module to check support
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for the C compiler flag ``-fno-optimize-strlen``, which disables
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optimizations related to the ``strlen()`` C function in GCC and Clang
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compilers. The result of the check is stored in the internal cache
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variable ``HAVE_FNO_OPTIMIZE_STRLEN``, and the flag is conditionally enabled
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using the :command:`target_compile_options` command. The
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:genex:`$<COMPILE_LANGUAGE:...> <COMPILE_LANGUAGE:languages>` generator
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expression ensures that the flag is added only to ``C`` source files.
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.. code-block:: cmake
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include(CheckCCompilerFlag)
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check_c_compiler_flag(-fno-optimize-strlen HAVE_FNO_OPTIMIZE_STRLEN)
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if(HAVE_FNO_OPTIMIZE_STRLEN)
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target_compile_options(
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example
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PRIVATE $<$<COMPILE_LANGUAGE:C>:-fno-optimize-strlen>
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)
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endif()
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See Also
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^^^^^^^^
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* The :module:`CheckCompilerFlag` module for a more general command to check
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whether a compiler flag is supported.
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#]=======================================================================]
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include_guard(GLOBAL)
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include(Internal/CheckCompilerFlag)
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macro (CHECK_C_COMPILER_FLAG _FLAG _RESULT)
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cmake_check_compiler_flag(C "${_FLAG}" ${_RESULT})
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endmacro ()
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# FIXME(#24994): The following module is included only for compatibility
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# with projects that accidentally relied on it with CMake 3.26 and below.
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include(CheckCSourceCompiles)
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