BUILD(cmake): Module to fetch compiler-dependent flags

Using a separate module instead of encoding the different flags for
different compilers into our own cmake source code should clean things
up a bit and make the intention more clear (as the flags sometimes have
rather cryptic names).

This commit also contains a functional change in that it removes the
"fast-math" compile option (from optimized builds) as this is
incompatible with at least Opus.

CMakeLists.txt

@@ -44,6 +44,7 @@ list(APPEND CMAKE_MODULE_PATH
 	"${CMAKE_SOURCE_DIR}/cmake"
 	"${CMAKE_SOURCE_DIR}/cmake/FindModules"
 	"${3RDPARTY_DIR}/FindPythonInterpreter"
+	"${3RDPARTY_DIR}/cmake-compiler-flags"
 )
 
 

cmake/compiler.cmake

@@ -3,6 +3,7 @@
 # that can be found in the LICENSE file at the root of the
 # Mumble source tree or at <https://www.mumble.info/LICENSE>.
 
+include(CompilerFlags)
 include(CheckCXXCompilerFlag)
 
 if(${CMAKE_SIZEOF_VOID_P} EQUAL 8)
@@ -20,15 +21,26 @@ if(WIN32)
 	add_compile_definitions(_WIN32_WINNT=0x0601)
 endif()
 
-if(MSVC)
-	add_compile_options(
-		"$<$<CONFIG:Release>:/Ox>"
-		"$<$<CONFIG:Release>:/fp:fast>"
-	)
+set(WANTED_FEATURES "ENABLE_MOST_WARNINGS")
+
+if(CMAKE_BUILD_TYPE STREQUAL "Release")
+	list(APPEND WANTED_FEATURES "OPTIMIZE_FOR_SPEED")
+elseif(CMAKE_BUILD_TYPE STREQUAL "Debug")
+	list(APPEND WANTED_FEATURES "OPTIMIZE_FOR_DEBUG")
+endif()
 
-	# Needed in order to not run into C1128: number of sections exceeded object file format limit
-	add_compile_options(/bigobj)
+if(warnings-as-errors)
+	list(APPEND WANTED_FEATURES "ENABLE_WARNINGS_AS_ERRORS")
+endif()
+
+get_compiler_flags(
+	${WANTED_FEATURES}
+	OUTPUT_VARIABLE MUMBLE_COMPILER_FLAGS
+)
+
+message(STATUS "Using (among others) the following compiler flags: ${MUMBLE_COMPILER_FLAGS}")
 
+if(MSVC)
 	if(32_BIT)
 		# SSE2 code is generated by default, unless an explicit arch is set.
 		# Our 32 bit binaries should not contain any SSE2 code, so override the default.
@@ -54,35 +66,17 @@ if(MSVC)
 			"/ignore:4099"
 		)
 	endif()
-
-	if(warnings-as-errors)
-		add_compile_options("/WX")
-		add_link_options("/WX")
-	endif()
 elseif(UNIX OR MINGW)
 	add_compile_options(
 		"-fvisibility=hidden"
-		"-Wall"
-		"-Wextra"
 	)
 
-	# Avoid "File too big" error
-	check_cxx_compiler_flag("-Wa,-mbig-obj" COMPILER_HAS_MBIG_OBJ)
-	if (${COMPILER_HAS_MBIG_OBJ})
-		add_compile_options("-Wa,-mbig-obj")
-	endif()
-
 	if(optimize)
 		add_compile_options(
-			"-O3"
 			"-march=native"
 		)
 	endif()
 
-	if(warnings-as-errors)
-		add_compile_options("-Werror")
-	endif()
-
 	if(APPLE)
 		add_link_options("-Wl,-dead_strip")
 
@@ -129,9 +123,11 @@ elseif(UNIX OR MINGW)
 endif()
 
 function(target_disable_warnings TARGET)
-	if(MSVC)
-		target_compile_options(${TARGET} PRIVATE "/w")
-	else()
-		target_compile_options(${TARGET} PRIVATE "-w")
-	endif()
+	get_compiler_flags(
+		DISABLE_ALL_WARNINGS
+		DISABLE_DEFAULT_FLAGS
+		OUTPUT_VARIABLE NO_WARNING_FLAGS
+	)
+
+	target_compile_options(${TARGET} PRIVATE ${NO_WARNING_FLAGS})
 endfunction()

overlay/CMakeLists.txt

@@ -14,6 +14,7 @@ if(BUILD_OVERLAY_XCOMPILE)
 		LANGUAGES CXX
 	)
 
+	list(APPEND CMAKE_MODULE_PATH "${3RDPARTY_DIR}/cmake-compiler-flags")
 	include("${MUMBLE_SOURCE_ROOT}/cmake/compiler.cmake")
 endif()
 
@@ -162,6 +163,7 @@ if(64_BIT AND MSVC)
 				"-DMUMBLE_SOURCE_ROOT=${CMAKE_SOURCE_DIR}"
 				"-DMUMBLE_BINARY_DIR=${CMAKE_BINARY_DIR}"
 				"-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}"
+				"-D3RDPARTY_DIR=${3RDPARTY_DIR}"
 				# Force MSVC, because CMake prioritizes MinGW over it.
 				"-DCMAKE_C_COMPILER=cl.exe"
 				"-DCMAKE_CXX_COMPILER=cl.exe"
@@ -184,6 +186,7 @@ if(64_BIT AND MSVC)
 				"-DMUMBLE_SOURCE_ROOT=${CMAKE_SOURCE_DIR}"
 				"-DMUMBLE_BINARY_DIR=${CMAKE_BINARY_DIR}"
 				"-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}"
+				"-D3RDPARTY_DIR=${3RDPARTY_DIR}"
 				# Force MSVC, because CMake prioritizes MinGW over it.
 				"-DCMAKE_C_COMPILER=cl.exe"
 				"-DCMAKE_CXX_COMPILER=cl.exe"

src/CMakeLists.txt

@@ -34,6 +34,8 @@ find_pkg(OpenSSL
 
 find_pkg(Protobuf REQUIRED)
 
+add_compile_options(${MUMBLE_COMPILER_FLAGS})
+
 add_library(shared STATIC)
 
 protobuf_generate(LANGUAGE cpp TARGET shared PROTOS ${PROTO_FILE} OUT_VAR BUILT_PROTO_FILES)