Use a more effective approach to handling GCC compatible flags in GoogleBenchmark

Author: christopherbate

third-party/benchmark/CMakeLists.txt

@@ -147,15 +147,6 @@ endif()
 set(CMAKE_CXX_STANDARD ${BENCHMARK_CXX_STANDARD})
 set(CMAKE_CXX_STANDARD_REQUIRED YES)
 set(CMAKE_CXX_EXTENSIONS OFF)
-option(BENCHMARK_ENABLE_EXPENSIVE_CMAKE_CHECKS "Enable use of expensive CMake checks for unused source files" ON)
-
-macro(handle_flag flag)
-  if(LLVM_COMPILER_IS_GCC_COMPATIBLE AND NOT BENCHMARK_ENABLE_EXPENSIVE_CMAKE_CHECKS)
-    list(APPEND CMAKE_CXX_FLAGS ${flag})
-  else()
-    add_cxx_compiler_flag(${flag})
-  endif()
-endmacro()
 
 if (MSVC)
   # Turn compiler warnings up to 11
@@ -194,49 +185,49 @@ else()
   add_definitions(-D_LARGEFILE64_SOURCE)
   add_definitions(-D_LARGEFILE_SOURCE)
   # Turn compiler warnings up to 11
-  handle_flag(-Wall)
-  handle_flag(-Wextra)
-  handle_flag(-Wshadow)
-  handle_flag(-Wfloat-equal)
-  handle_flag(-Wold-style-cast)
+  add_cxx_compiler_flag(-Wall)
+  add_cxx_compiler_flag(-Wextra)
+  add_cxx_compiler_flag(-Wshadow)
+  add_cxx_compiler_flag(-Wfloat-equal)
+  add_cxx_compiler_flag(-Wold-style-cast)
   if(BENCHMARK_ENABLE_WERROR)
-      handle_flag(-Werror)
+      add_cxx_compiler_flag(-Werror)
   endif()
   if (NOT BENCHMARK_ENABLE_TESTING)
     # Disable warning when compiling tests as gtest does not use 'override'.
-    handle_flag(-Wsuggest-override)
+    add_cxx_compiler_flag(-Wsuggest-override)
   endif()
-  handle_flag(-pedantic)
-  handle_flag(-pedantic-errors)
-  handle_flag(-Wshorten-64-to-32)
-  handle_flag(-fstrict-aliasing)
+  add_cxx_compiler_flag(-pedantic)
+  add_cxx_compiler_flag(-pedantic-errors)
+  add_cxx_compiler_flag(-Wshorten-64-to-32)
+  add_cxx_compiler_flag(-fstrict-aliasing)
   # Disable warnings regarding deprecated parts of the library while building
   # and testing those parts of the library.
-  handle_flag(-Wno-deprecated-declarations)
+  add_cxx_compiler_flag(-Wno-deprecated-declarations)
   if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel" OR CMAKE_CXX_COMPILER_ID STREQUAL "IntelLLVM")
     # Intel silently ignores '-Wno-deprecated-declarations',
     # warning no. 1786 must be explicitly disabled.
     # See #631 for rationale.
-    handle_flag(-wd1786)
-    handle_flag(-fno-finite-math-only)
+    add_cxx_compiler_flag(-wd1786)
+    add_cxx_compiler_flag(-fno-finite-math-only)
   endif()
   # Disable deprecation warnings for release builds (when -Werror is enabled).
   if(BENCHMARK_ENABLE_WERROR)
-      handle_flag(-Wno-deprecated)
+      add_cxx_compiler_flag(-Wno-deprecated)
   endif()
   if (NOT BENCHMARK_ENABLE_EXCEPTIONS)
-    handle_flag(-fno-exceptions)
+    add_cxx_compiler_flag(-fno-exceptions)
   endif()
 
   if (HAVE_CXX_FLAG_FSTRICT_ALIASING)
     if (NOT CMAKE_CXX_COMPILER_ID STREQUAL "Intel" AND NOT CMAKE_CXX_COMPILER_ID STREQUAL "IntelLLVM") #ICC17u2: Many false positives for Wstrict-aliasing
-      handle_flag(-Wstrict-aliasing)
+      add_cxx_compiler_flag(-Wstrict-aliasing)
     endif()
   endif()
   # ICC17u2: overloaded virtual function "benchmark::Fixture::SetUp" is only partially overridden
   # (because of deprecated overload)
-  handle_flag(-wd654)
-  handle_flag(-Wthread-safety)
+  add_cxx_compiler_flag(-wd654)
+  add_cxx_compiler_flag(-Wthread-safety)
   if (HAVE_CXX_FLAG_WTHREAD_SAFETY)
     cxx_feature_check(THREAD_SAFETY_ATTRIBUTES "-DINCLUDE_DIRECTORIES=${PROJECT_SOURCE_DIR}/include")
   endif()
@@ -255,8 +246,8 @@ else()
 
   # Link time optimisation
   if (BENCHMARK_ENABLE_LTO)
-    handle_flag(-flto)
-    handle_flag(-Wno-lto-type-mismatch)
+    add_cxx_compiler_flag(-flto)
+    add_cxx_compiler_flag(-Wno-lto-type-mismatch)
     if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
       find_program(GCC_AR gcc-ar)
       if (GCC_AR)
@@ -287,7 +278,7 @@ else()
     BENCHMARK_SHARED_LINKER_FLAGS_COVERAGE)
   set(CMAKE_BUILD_TYPE "${CMAKE_BUILD_TYPE}" CACHE STRING
     "Choose the type of build, options are: None Debug Release RelWithDebInfo MinSizeRel Coverage.")
-  handle_flag(--coverage COVERAGE)
+  add_cxx_compiler_flag(--coverage COVERAGE)
 endif()
 
 if (BENCHMARK_USE_LIBCXX)

third-party/benchmark/cmake/AddCXXCompilerFlag.cmake

@@ -27,20 +27,45 @@ function(mangle_compiler_flag FLAG OUTPUT)
   set(${OUTPUT} "${SANITIZED_FLAG}" PARENT_SCOPE)
 endfunction(mangle_compiler_flag)
 
+set(BENCHMARK_GCC_COMPATIBLE_FLAGS
+  -fno-exceptions
+  -fstrict-aliasing
+  -pedantic
+  -pedantic-errors
+  -Wall
+  -Werror
+  -Wextra
+  -Wfloat-equal
+  -Wno-deprecated
+  -Wno-deprecated-declarations
+  -Wold-style-cast
+  -Wshadow
+  -Wstrict-aliasing
+  -Wsuggest-override
+  )
+
+macro(_benchmark_populate_cxx_compiler_flag)
+  if(ARGC GREATER 1)
+    set(VARIANT ${ARGV1})
+    string(TOUPPER "_${VARIANT}" VARIANT)
+  else()
+    set(VARIANT "")
+  endif()
+  set(CMAKE_CXX_FLAGS${VARIANT} "${CMAKE_CXX_FLAGS${VARIANT}} ${BENCHMARK_CXX_FLAGS${VARIANT}} ${FLAG}" PARENT_SCOPE)
+endmacro()
+
 function(add_cxx_compiler_flag FLAG)
   mangle_compiler_flag("${FLAG}" MANGLED_FLAG)
+  if(LLVM_COMPILER_IS_GCC_COMPATIBLE AND "${FLAG}" IN_LIST BENCHMARK_GCC_COMPATIBLE_FLAGS)
+    _benchmark_populate_cxx_compiler_flag(${FLAG} ${VARIANT})
+    return()
+  endif()
   set(OLD_CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS}")
   set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${FLAG}")
   check_cxx_compiler_flag("${FLAG}" ${MANGLED_FLAG})
   set(CMAKE_REQUIRED_FLAGS "${OLD_CMAKE_REQUIRED_FLAGS}")
   if(${MANGLED_FLAG})
-    if(ARGC GREATER 1)
-      set(VARIANT ${ARGV1})
-      string(TOUPPER "_${VARIANT}" VARIANT)
-    else()
-      set(VARIANT "")
-    endif()
-    set(CMAKE_CXX_FLAGS${VARIANT} "${CMAKE_CXX_FLAGS${VARIANT}} ${BENCHMARK_CXX_FLAGS${VARIANT}} ${FLAG}" PARENT_SCOPE)
+    _benchmark_populate_cxx_compiler_flag(${FLAG} ${VARIANT})
   endif()
 endfunction()