fixup! cmake: Add TryAppendCXXFlags module

Author: hebasto

cmake/module/TryAppendCXXFlags.cmake

@@ -8,24 +8,28 @@ include(CheckCXXSourceCompiles)
 #[=[
 Usage examples:
 
-  try_append_cxx_flags(warn_cxx_flags "-Wformat -Wformat-security")
+  try_append_cxx_flags("-Wformat -Wformat-security" VAR warn_cxx_flags)
 
 
-  try_append_cxx_flags(warn_cxx_flags "-Wsuggest-override"
+  try_append_cxx_flags("-Wsuggest-override" VAR warn_cxx_flags
     SOURCE "struct A { virtual void f(); }; struct B : A { void f() final; };"
   )
 
 
-  try_append_cxx_flags(sanitizers_cxx_flags "-fsanitize=${SANITIZERS}" RESULT_VAR cxx_supports_sanitizers)
+  try_append_cxx_flags("-fsanitize=${SANITIZERS}" TARGET core
+    RESULT_VAR cxx_supports_sanitizers
+  )
   if(NOT cxx_supports_sanitizers)
     message(FATAL_ERROR "Compiler did not accept requested flags.")
   endif()
 
 
-  try_append_cxx_flags(warn_cxx_flags "-Wunused-parameter" IF_CHECK_PASSED "-Wno-unused-parameter")
+  try_append_cxx_flags("-Wunused-parameter" TARGET core
+    IF_CHECK_PASSED "-Wno-unused-parameter"
+  )
 
 
-  try_append_cxx_flags(error_cxx_flags "-Werror=return-type"
+  try_append_cxx_flags("-Werror=return-type" TARGET core
     IF_CHECK_FAILED "-Wno-error=return-type"
     SOURCE "#include <cassert>\nint f(){ assert(false); }"
   )
@@ -37,49 +41,67 @@ In configuration output, this function prints a string by the following pattern:
   -- Performing Test CXX_SUPPORTS_[flags] - Success
 
 ]=]
-function(try_append_cxx_flags flags_var flags)
-  cmake_parse_arguments(PARSE_ARGV 2
+function(try_append_cxx_flags flags)
+  cmake_parse_arguments(PARSE_ARGV 1
     TACXXF                            # prefix
     ""                                # options
-    "SOURCE;RESULT_VAR"               # one_value_keywords
+    "TARGET;VAR;SOURCE;RESULT_VAR"    # one_value_keywords
     "IF_CHECK_PASSED;IF_CHECK_FAILED" # multi_value_keywords
   )
 
   string(MAKE_C_IDENTIFIER "${flags}" result)
   string(TOUPPER "${result}" result)
-  set(result "CXX_SUPPORTS_${result}")
-
-  # Every subsequent check_cxx_source_compiles((<code> <resultVar>) run will re-use
-  # the cached result rather than performing the check again, even if the <code> changes.
-  # Removing the cached result in order to force the check to be re-evaluated.
-  unset(${result} CACHE)
-
-  if(NOT DEFINED TACXXF_SOURCE)
-    set(TACXXF_SOURCE "int main() { return 0; }")
+  string(PREPEND result CXX_SUPPORTS_)
+
+  set(source "int main() { return 0; }")
+  if(DEFINED TACXXF_SOURCE AND NOT TACXXF_SOURCE STREQUAL source)
+    set(source "${TACXXF_SOURCE}")
+    string(SHA256 source_hash "${source}")
+    string(SUBSTRING ${source_hash} 0 4 source_hash_head)
+    string(APPEND result _${source_hash_head})
   endif()
 
   # This avoids running a linker.
   set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
   set(CMAKE_REQUIRED_FLAGS "${flags} ${working_compiler_werror_flag}")
-  check_cxx_source_compiles("${TACXXF_SOURCE}" ${result})
+  check_cxx_source_compiles("${source}" ${result})
 
   if(${result})
     if(DEFINED TACXXF_IF_CHECK_PASSED)
-      string(STRIP "${${flags_var}} ${TACXXF_IF_CHECK_PASSED}" ${flags_var})
+      if(DEFINED TACXXF_TARGET)
+        target_compile_options(${TACXXF_TARGET} INTERFACE ${TACXXF_IF_CHECK_PASSED})
+      endif()
+      if(DEFINED TACXXF_VAR)
+        string(STRIP "${${TACXXF_VAR}} ${TACXXF_IF_CHECK_PASSED}" ${TACXXF_VAR})
+      endif()
     else()
-      string(STRIP "${${flags_var}} ${flags}" ${flags_var})
+      if(DEFINED TACXXF_TARGET)
+        target_compile_options(${TACXXF_TARGET} INTERFACE ${flags})
+      endif()
+      if(DEFINED TACXXF_VAR)
+        string(STRIP "${${TACXXF_VAR}} ${flags}" ${TACXXF_VAR})
+      endif()
     endif()
   elseif(DEFINED TACXXF_IF_CHECK_FAILED)
-    string(STRIP "${${flags_var}} ${TACXXF_IF_CHECK_FAILED}" ${flags_var})
+    if(DEFINED TACXXF_TARGET)
+      target_compile_options(${TACXXF_TARGET} INTERFACE ${TACXXF_IF_CHECK_FAILED})
+    endif()
+    if(DEFINED TACXXF_VAR)
+      string(STRIP "${${TACXXF_VAR}} ${TACXXF_IF_CHECK_FAILED}" ${TACXXF_VAR})
+    endif()
+  endif()
+
+  if(DEFINED TACXXF_VAR)
+    set(${TACXXF_VAR} "${${TACXXF_VAR}}" PARENT_SCOPE)
+  endif()
+
+  if(DEFINED TACXXF_RESULT_VAR)
+    set(${TACXXF_RESULT_VAR} "${${result}}" PARENT_SCOPE)
   endif()
-  set(${flags_var} "${${flags_var}}" PARENT_SCOPE)
-  set(${TACXXF_RESULT_VAR} "${${result}}" PARENT_SCOPE)
 endfunction()
 
 if(MSVC)
-  set(warning_as_error_flag /WX)
+  try_append_cxx_flags("/WX /options:strict" VAR working_compiler_werror_flag)
 else()
-  set(warning_as_error_flag -Werror)
+  try_append_cxx_flags("-Werror" VAR working_compiler_werror_flag)
 endif()
-try_append_cxx_flags(working_compiler_werror_flag ${warning_as_error_flag})
-unset(warning_as_error_flag)