Check whether the C compiler supports a given flag.
check_c_compiler_flag check_c_compiler_flag(<flag> <var>)
Check that the <flag> is accepted by the compiler without a diagnostic. Stores the result in an internal cache entry named <var>.
This command temporarily sets the CMAKE_REQUIRED_DEFINITIONS variable and calls the check_c_source_compiles macro from the CheckCSourceCompiles module. See documentation of that module for a listing of variables that can otherwise modify the build.
A positive result from this check indicates only that the compiler did not issue a diagnostic message when given the flag. Whether the flag has any effect or even a specific one is beyond the scope of this module.
Note
Since the try_compile() command forwards flags from variables like CMAKE_C_FLAGS, unknown flags in such variables may cause a false negative for this check.
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Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.19/module/CheckCCompilerFlag.html