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# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
# file Copyright.txt or https://cmake.org/licensing for details.
#[=======================================================================[.rst:
CheckLinkerFlag
---------------
.. versionadded:: 3.18
Check whether the compiler supports a given link flag.
.. command:: check_linker_flag
.. code-block:: cmake
check_linker_flag(<lang> <flag> <var>)
Check that the link ``<flag>`` is accepted by the ``<lang>`` compiler without
a diagnostic. Stores the result in an internal cache entry named ``<var>``.
This command temporarily sets the ``CMAKE_REQUIRED_LINK_OPTIONS`` variable
and calls the ``check_<lang>_source_compiles`` macro from the
``Check<lang>SourceCompiles`` module (:module:`CheckCSourceCompiles`,
:module:`CheckCSourceCompiles`, :module:`CheckCXXSourceCompiles`,
:module:`CheckOBJCSourceCompiles`, :module:`CheckOBJCXXSourceCompiles` or
:module:`CheckFortranSourceCompiles`). See documentation of these
modules for a listing of variables that can otherwise modify the build.
The underlying implementation rely on :prop_tgt:`LINK_OPTIONS` property to
check the specified flag. The ``LINKER:`` prefix, as described in
:command:`target_link_options` command, can be used as well.
A positive result from this check indicates only that the compiler did not
issue a diagnostic message when given the link flag. Whether the flag has any
effect or even a specific one is beyond the scope of this module.
.. note::
Since the :command:`try_compile` command forwards flags from variables
like :variable:`CMAKE_<LANG>_FLAGS`, unknown flags in such variables may
cause a false negative for this check.
#]=======================================================================]
include_guard(GLOBAL)
include(CMakeCheckCompilerFlagCommonPatterns)
function(CHECK_LINKER_FLAG _lang _flag _var)
get_property (_supported_languages GLOBAL PROPERTY ENABLED_LANGUAGES)
if (NOT _lang IN_LIST _supported_languages)
message (SEND_ERROR "check_linker_flag: ${_lang}: unknown language.")
return()
endif()
include (Check${_lang}SourceCompiles)
set(CMAKE_REQUIRED_LINK_OPTIONS "${_flag}")
# Normalize locale during test compilation.
set(_locale_vars LC_ALL LC_MESSAGES LANG)
foreach(v IN LISTS _locale_vars)
set(_locale_vars_saved_${v} "$ENV{${v}}")
set(ENV{${v}} C)
endforeach()
if (_lang MATCHES "^(C|CXX)$")
set (_source "int main() { return 0; }")
elseif (_lang STREQUAL "Fortran")
set (_source " program test\n stop\n end program")
elseif (_lang MATCHES "^(OBJC|OBJCXX)$")
set (_source "#ifndef __OBJC__\n# error \"Not an Objective-C++ compiler\"\n#endif\nint main(void) { return 0; }")
else()
message (SEND_ERROR "check_linker_flag: ${_lang}: unsupported language.")
return()
endif()
check_compiler_flag_common_patterns(_common_patterns)
cmake_language (CALL check_${_lang}_source_compiles "${_source}" ${_var} ${_common_patterns})
foreach(v IN LISTS _locale_vars)
set(ENV{${v}} ${_locale_vars_saved_${v}})
endforeach()
set(${_var} "${${_var}}" PARENT_SCOPE)
endfunction()
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