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64 lines
2.4 KiB
64 lines
2.4 KiB
# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
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# file Copyright.txt 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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Check whether the C compiler supports a given flag.
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.. command:: check_c_compiler_flag
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.. code-block:: cmake
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check_c_compiler_flag(<flag> <var>)
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Check that the ``<flag>`` is accepted by the compiler without
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a diagnostic. Stores the result in an internal cache entry
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named ``<var>``.
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This command temporarily sets the ``CMAKE_REQUIRED_DEFINITIONS`` variable
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and calls the ``check_c_source_compiles`` macro from the
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:module:`CheckCSourceCompiles` module. See documentation of that
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module for a listing of variables that can otherwise modify the build.
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A positive result from this check indicates only that the compiler did not
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issue a diagnostic message when given the flag. Whether the flag has any
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effect or even a specific one is beyond the scope of this module.
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.. note::
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Since the :command:`try_compile` command forwards flags from variables
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like :variable:`CMAKE_C_FLAGS <CMAKE_<LANG>_FLAGS>`, unknown flags
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in such variables may cause a false negative for this check.
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#]=======================================================================]
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include_guard(GLOBAL)
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include(CheckCSourceCompiles)
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include(CMakeCheckCompilerFlagCommonPatterns)
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macro (CHECK_C_COMPILER_FLAG _FLAG _RESULT)
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set(SAFE_CMAKE_REQUIRED_DEFINITIONS "${CMAKE_REQUIRED_DEFINITIONS}")
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set(CMAKE_REQUIRED_DEFINITIONS "${_FLAG}")
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# Normalize locale during test compilation.
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set(_CheckCCompilerFlag_LOCALE_VARS LC_ALL LC_MESSAGES LANG)
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foreach(v ${_CheckCCompilerFlag_LOCALE_VARS})
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set(_CheckCCompilerFlag_SAVED_${v} "$ENV{${v}}")
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set(ENV{${v}} C)
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endforeach()
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CHECK_COMPILER_FLAG_COMMON_PATTERNS(_CheckCCompilerFlag_COMMON_PATTERNS)
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CHECK_C_SOURCE_COMPILES("int main(void) { return 0; }" ${_RESULT}
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# Some compilers do not fail with a bad flag
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FAIL_REGEX "command line option .* is valid for .* but not for C" # GNU
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${_CheckCCompilerFlag_COMMON_PATTERNS}
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)
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foreach(v ${_CheckCCompilerFlag_LOCALE_VARS})
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set(ENV{${v}} ${_CheckCCompilerFlag_SAVED_${v}})
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unset(_CheckCCompilerFlag_SAVED_${v})
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endforeach()
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unset(_CheckCCompilerFlag_LOCALE_VARS)
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unset(_CheckCCompilerFlag_COMMON_PATTERNS)
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set (CMAKE_REQUIRED_DEFINITIONS "${SAFE_CMAKE_REQUIRED_DEFINITIONS}")
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endmacro ()
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