internal/CheckCompilerFlag: rely on common configuration

Extract configuration step from the CheckCompilerFlag command
to enable to share it with future CheckLinkerFlag implementation

Modules/Internal/CheckCompilerFlag.cmake

@@ -2,71 +2,15 @@
 # file Copyright.txt or https://cmake.org/licensing for details.
 
 include_guard(GLOBAL)
+include(Internal/CheckFlagCommonConfig)
 include(Internal/CheckSourceCompiles)
 include(CMakeCheckCompilerFlagCommonPatterns)
 
-cmake_policy(PUSH)
-cmake_policy(SET CMP0054 NEW) # if() quoted variables not dereferenced
-cmake_policy(SET CMP0057 NEW) # if() supports IN_LIST
-
 function(CMAKE_CHECK_COMPILER_FLAG _lang _flag _var)
-
-  if(_lang STREQUAL "C")
-    set(_lang_src "int main(void) { return 0; }")
-    set(_lang_fail_regex FAIL_REGEX "command[ -]line option .* is valid for .* but not for C"
-                         FAIL_REGEX "-Werror=.* argument .* is not valid for C")
-  elseif(_lang STREQUAL "CXX")
-    set(_lang_src "int main() { return 0; }")
-    set(_lang_fail_regex FAIL_REGEX "command[ -]line option .* is valid for .* but not for C\\+\\+"
-                         FAIL_REGEX "-Werror=.* argument .* is not valid for C\\+\\+")
-  elseif(_lang STREQUAL "CUDA")
-    set(_lang_src "__host__ int main() { return 0; }")
-    set(_lang_fail_regex FAIL_REGEX "command[ -]line option .* is valid for .* but not for C\\+\\+" # Host GNU
-                         FAIL_REGEX "argument unused during compilation: .*") # Clang
-  elseif(_lang STREQUAL "Fortran")
-    set(_lang_src "       program test\n       stop\n       end program")
-    set(_lang_fail_regex FAIL_REGEX "command[ -]line option .* is valid for .* but not for Fortran")
-  elseif(_lang STREQUAL "HIP")
-    set(_lang_src "__host__ int main() { return 0; }")
-    set(_lang_fail_regex FAIL_REGEX "argument unused during compilation: .*") # Clang
-  elseif(_lang STREQUAL "OBJC")
-    set(_lang_src [=[
-#ifndef __OBJC__
-#  error "Not an Objective-C compiler"
-#endif
-int main(void) { return 0; }]=])
-    set(_lang_fail_regex FAIL_REGEX "command[ -]line option .* is valid for .* but not for Objective-C" # GNU
-                         FAIL_REGEX "argument unused during compilation: .*") # Clang
-  elseif(_lang STREQUAL "OBJCXX")
-    set(_lang_src [=[
-#ifndef __OBJC__
-#  error "Not an Objective-C++ compiler"
-#endif
-int main(void) { return 0; }]=])
-    set(_lang_fail_regex FAIL_REGEX "command[ -]line option .* is valid for .* but not for Objective-C\\+\\+" # GNU
-                         FAIL_REGEX "argument unused during compilation: .*") # Clang
-  elseif(_lang STREQUAL "ISPC")
-    set(_lang_src "float func(uniform int32, float a) { return a / 2.25; }")
-  else()
-    message (SEND_ERROR "check_compiler_flag: ${_lang}: unknown language.")
-    return()
-  endif()
-
-  get_property (_supported_languages GLOBAL PROPERTY ENABLED_LANGUAGES)
-  if (NOT _lang IN_LIST _supported_languages)
-    message (SEND_ERROR "check_compiler_flag: ${_lang}: needs to be enabled before use.")
-    return()
-  endif()
+  cmake_check_flag_common_init("check_compiler_flag" ${_lang} _lang_src _lang_fail_regex)
 
   set(CMAKE_REQUIRED_DEFINITIONS ${_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()
-
   check_compiler_flag_common_patterns(_common_patterns)
   cmake_check_source_compiles(${_lang}
     "${_lang_src}"
@@ -75,9 +19,5 @@ int main(void) { return 0; }]=])
     ${_common_patterns}
     )
 
-  foreach(v IN LISTS _locale_vars)
-    set(ENV{${v}} ${_locale_vars_saved_${v}})
-  endforeach()
-endfunction ()
-
-cmake_policy(POP)
+  cmake_check_flag_common_finish()
+endfunction()

Modules/Internal/CheckFlagCommonConfig.cmake

@@ -0,0 +1,75 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+
+# Do NOT include this module directly into any of your code. It is meant as
+# a library for Check*CompilerFlag.cmake and Check*LinkerFlag.cma modules.
+# It's content may change in any way between releases.
+
+include_guard(GLOBAL)
+cmake_policy(PUSH)
+cmake_policy(SET CMP0054 NEW) # if() quoted variables not dereferenced
+cmake_policy(SET CMP0057 NEW) # if() supports IN_LIST
+
+macro(CMAKE_CHECK_FLAG_COMMON_INIT _FUNC _LANG _SRC _PATTERNS)
+  if("${_LANG}" STREQUAL "C")
+    set(${_SRC} "int main(void) { return 0; }")
+    set(${_PATTERNS} FAIL_REGEX "command[ -]line option .* is valid for .* but not for C"
+      FAIL_REGEX "-Werror=.* argument .* is not valid for C")
+  elseif("${_LANG}" STREQUAL "CXX")
+    set(${_SRC} "int main() { return 0; }")
+    set(${_PATTERNS} FAIL_REGEX "command[ -]line option .* is valid for .* but not for C\\+\\+"
+      FAIL_REGEX "-Werror=.* argument .* is not valid for C\\+\\+")
+  elseif("${_LANG}" STREQUAL "CUDA")
+    set(${_SRC} "__host__ int main() { return 0; }")
+    set(${_PATTERNS} FAIL_REGEX "command[ -]line option .* is valid for .* but not for C\\+\\+" # Host GNU
+      FAIL_REGEX "argument unused during compilation: .*") # Clang
+  elseif("${_LANG}" STREQUAL "Fortran")
+    set(${_SRC} "       program test\n       stop\n       end program")
+    set(${_PATTERNS} FAIL_REGEX "command[ -]line option .* is valid for .* but not for Fortran")
+  elseif("${_LANG}" STREQUAL "HIP")
+    set(${_SRC} "__host__ int main() { return 0; }")
+    set(${_PATTERNS} FAIL_REGEX "argument unused during compilation: .*") # Clang
+  elseif("${_LANG}" STREQUAL "OBJC")
+    set(${_SRC} [=[
+      #ifndef __OBJC__
+      #  error "Not an Objective-C compiler"
+      #endif
+      int main(void) { return 0; }]=])
+    set(${_PATTERNS} FAIL_REGEX "command[ -]line option .* is valid for .* but not for Objective-C" # GNU
+      FAIL_REGEX "argument unused during compilation: .*") # Clang
+  elseif("${_LANG}" STREQUAL "OBJCXX")
+    set(${_SRC} [=[
+      #ifndef __OBJC__
+      #  error "Not an Objective-C++ compiler"
+      #endif
+      int main(void) { return 0; }]=])
+    set(${_PATTERNS} FAIL_REGEX "command[ -]line option .* is valid for .* but not for Objective-C\\+\\+" # GNU
+      FAIL_REGEX "argument unused during compilation: .*") # Clang
+  elseif("${_LANG}" STREQUAL "ISPC")
+    set(${_SRC} "float func(uniform int32, float a) { return a / 2.25; }")
+  else()
+    message (SEND_ERROR "${_FUNC}: ${_LANG}: unknown language.")
+    return()
+  endif()
+
+  get_property (_supported_languages GLOBAL PROPERTY ENABLED_LANGUAGES)
+  if (NOT "${_LANG}" IN_LIST _supported_languages)
+    message (SEND_ERROR "${_FUNC}: ${_LANG}: needs to be enabled before use.")
+    return()
+  endif()
+  # Normalize locale during test compilation.
+  set(_locale_vars LC_ALL LC_MESSAGES LANG)
+  foreach(v IN LISTS _locale_vars)
+    set(_CMAKE_CHECK_FLAG_COMMON_CONFIG_locale_vars_saved_${v} "$ENV{${v}}")
+    set(ENV{${v}} C)
+  endforeach()
+endmacro()
+
+macro(CMAKE_CHECK_FLAG_COMMON_FINISH)
+  foreach(v IN LISTS _CFCC_locale_vars)
+    set(ENV{${v}} ${_CMAKE_CHECK_FLAG_COMMON_CONFIG_locale_vars_saved_${v}})
+  endforeach()
+endmacro()
+
+cmake_policy(POP)

Tests/RunCMake/CheckCompilerFlag/NonExistentLanguage-stderr.txt

@@ -1,2 +1,2 @@
-CMake Error at .*CheckCompilerFlag\.cmake:[0-9]+ \(message\):
+CMake Error at .*CheckFlagCommonConfig\.cmake:[0-9]+ \(message\):
   check_compiler_flag: FAKE_LANG: unknown language.

Tests/RunCMake/CheckCompilerFlag/NotEnabledLanguage-stderr.txt

@@ -1,2 +1,2 @@
-CMake Error at .*CheckCompilerFlag\.cmake:[0-9]+ \(message\):
+CMake Error at .*CheckFlagCommonConfig\.cmake:[0-9]+ \(message\):
   check_compiler_flag: C: needs to be enabled before use.