From af96c0f4faf5bf9f4a4dbc958b09a1dfc58dab38 Mon Sep 17 00:00:00 2001
From: Marc Chevrier <marc.chevrier@gmail.com>
Date: Sat, 16 May 2020 17:01:23 +0200
Subject: CheckLinkerFlag: Add module to check validity of linker flags

Fixes: #15934
---
 Modules/CheckLinkerFlag.cmake | 81 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 Modules/CheckLinkerFlag.cmake

(limited to 'Modules/CheckLinkerFlag.cmake')

diff --git a/Modules/CheckLinkerFlag.cmake b/Modules/CheckLinkerFlag.cmake
new file mode 100644
index 0000000000..beda5fe3c3
--- /dev/null
+++ b/Modules/CheckLinkerFlag.cmake
@@ -0,0 +1,81 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+#[=======================================================================[.rst:
+CheckLinkerFlag
+---------------
+
+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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