CMake: Allow user build flags to override default build flags

Autotools has the very useful feature by design of allowing the user
to override the default build flags (you break it you keep it).

Apparently CMake applies COMPILE_OPTIONS target property after
CMAKE_{C,CXX}_FLAGS so that doesn't work here. Prepend our flags to those
variables instead to make it work then.

Specific target flag overrides can still be added with COMPILER_OPTIONS
(e.g: generated files with -Wno-warning) but this is less effective and
then we're back at the point where this overrides user flags. It's less
of a concern though.

Change-Id: I44761a79be4289238e02d4e781fef0099628817b
Reviewed-on: https://code.wireshark.org/review/23675
Petri-Dish: João Valverde <j@v6e.pt>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: João Valverde <j@v6e.pt>
Reviewed-by: Peter Wu <peter@lekensteyn.nl>

1 files changed, 18 insertions, 21 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7bafe80dec..9ceeaf4520 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -693,10 +693,10 @@ foreach(THIS_FLAG ${C_WARN_TESTS})
 	message(STATUS "Checking for c-compiler flag: ${THIS_FLAG}")
 	check_c_compiler_flag("${C_FLAG_TESTS} ${${F}}" ${V})
 	if (${${V}})
-		set(ADDED_WARN_C_FLAGS ${ADDED_WARN_C_FLAGS} ${${F}})
+		set(ADDED_WARN_C_FLAGS "${ADDED_WARN_C_FLAGS} ${${F}}")
 	endif()
 endforeach()
-set(WS_WARNINGS_C_FLAGS ${ADDED_WARN_C_FLAGS})
+set(CMAKE_C_FLAGS "${ADDED_WARN_C_FLAGS} ${CMAKE_C_FLAGS}")
 
 foreach(THIS_FLAG ${CXX_WARN_TESTS})
 	string( REGEX REPLACE "[^a-zA-Z0-9_]+" "_" F ${THIS_FLAG} )
@@ -705,10 +705,10 @@ foreach(THIS_FLAG ${CXX_WARN_TESTS})
 	message(STATUS "Checking for c++-compiler flag: ${THIS_FLAG}")
 	check_cxx_compiler_flag("${CXX_FLAG_TESTS} ${${F}}" ${V})
 	if (${${V}})
-		set(ADDED_WARN_CXX_FLAGS ${ADDED_WARN_CXX_FLAGS} ${${F}})
+		set(ADDED_WARN_CXX_FLAGS "${ADDED_WARN_CXX_FLAGS} ${${F}}")
 	endif()
 endforeach()
-set(WS_WARNINGS_CXX_FLAGS ${ADDED_WARN_CXX_FLAGS})
+set(CMAKE_CXX_FLAGS "${ADDED_WARN_CXX_FLAGS} ${CMAKE_CXX_FLAGS}")
 
 include(CMakePushCheckState)
 
@@ -773,14 +773,14 @@ if( NOT CMAKE_C_COMPILER_ID MATCHES "MSVC")
 	#
 	check_c_compiler_flag(-fvisibility=hidden FVHIDDEN)
 	if(FVHIDDEN)
-		set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fvisibility=hidden")
+		set(CMAKE_C_FLAGS "-fvisibility=hidden ${CMAKE_C_FLAGS}")
 	else()
 		#
 		# OK, try the Sun^WOracle C -xldscope=hidden
 		#
 		check_c_compiler_flag(-xldscope=hidden XLDSCOPEHIDDEN)
 		if(XLDSCOPEHIDDEN)
-			set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -xldscope=hidden")
+			set(CMAKE_C_FLAGS "-xldscope=hidden ${CMAKE_C_FLAGS}")
 		else()
 			#
 			# Anything else?
@@ -1203,9 +1203,9 @@ if (Qt5Widgets_FOUND)
 		if(NOT CXX__std_c__11_VALID)
 			message(FATAL_ERROR "Qt ${Qt5Widgets_VERSION} requires C++ 11")
 		endif()
-		set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
+		set(CMAKE_CXX_FLAGS "-std=c++11 ${CMAKE_CXX_FLAGS}")
 	endif()
-	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${Qt5Widgets_EXECUTABLE_COMPILE_FLAGS}")
+	set(CMAKE_CXX_FLAGS "${Qt5Widgets_EXECUTABLE_COMPILE_FLAGS} ${CMAKE_CXX_FLAGS}")
 	set (QT_FOUND ON)
 	set (QT_LIBRARIES ${Qt5Widgets_LIBRARIES} ${Qt5PrintSupport_LIBRARIES})
 	if(Qt5Multimedia_FOUND)
@@ -1550,10 +1550,8 @@ set_package_properties(NGHTTP2 PROPERTIES
 	PURPOSE "Header decompression in HTTP2"
 )
 
-string(REPLACE ";" " " _warnings_c_flags "${WS_WARNINGS_C_FLAGS}")
-message(STATUS "C-Flags: ${CMAKE_C_FLAGS} ${_warnings_c_flags}")
-string(REPLACE ";" " " _warnings_cxx_flags "${WS_WARNINGS_CXX_FLAGS}")
-message(STATUS "CXX-Flags: ${CMAKE_CXX_FLAGS} ${_warnings_cxx_flags}")
+message(STATUS "C-Flags: ${CMAKE_C_FLAGS}")
+message(STATUS "CXX-Flags: ${CMAKE_CXX_FLAGS}")
 message(STATUS "Warnings as errors: ${WERROR_COMMON_FLAGS}")
 
 feature_summary(WHAT ALL)
@@ -2213,9 +2211,10 @@ if(BUILD_wireshark AND QT_FOUND)
 	add_executable(wireshark WIN32 MACOSX_BUNDLE wireshark-qt.cpp ${wireshark_FILES} ${EXTRA_BUNDLE_FILES})
 	add_dependencies(wireshark version)
 	set(PROGLIST ${PROGLIST} wireshark)
-	set_target_properties(wireshark PROPERTIES COMPILE_OPTIONS "${WS_WARNINGS_CXX_FLAGS}")
-	set_target_properties(wireshark PROPERTIES LINK_FLAGS "${WS_LINK_FLAGS}")
-	set_target_properties(wireshark PROPERTIES FOLDER "Executables")
+	set_target_properties(wireshark PROPERTIES
+		LINK_FLAGS "${WS_LINK_FLAGS}"
+		FOLDER "Executables"
+	)
 	if(ENABLE_APPLICATION_BUNDLE OR WIN32)
 		set_target_properties(wireshark PROPERTIES OUTPUT_NAME Wireshark)
 	endif()
@@ -2293,7 +2292,6 @@ endif()
 # Common properties for CLI executables
 macro(set_extra_executable_properties _executable _folder)
 	set_target_properties(${_executable} PROPERTIES
-		COMPILE_OPTIONS "${WS_WARNINGS_C_FLAGS}"
 		LINK_FLAGS "${WS_LINK_FLAGS}"
 		FOLDER ${_folder}
 	)
@@ -2321,7 +2319,6 @@ macro(set_extcap_executable_properties _executable)
 
 	if(WIN32)
 		set_target_properties(${_executable} PROPERTIES
-			COMPILE_OPTIONS "${WS_WARNINGS_C_FLAGS}"
 			LINK_FLAGS "${WS_LINK_FLAGS}"
 			RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/run/extcap
 			RUNTIME_OUTPUT_DIRECTORY_DEBUG ${CMAKE_BINARY_DIR}/run/Debug/extcap
@@ -2331,7 +2328,6 @@ macro(set_extcap_executable_properties _executable)
 		)
 	else()
 		set_target_properties(${_executable} PROPERTIES
-			COMPILE_OPTIONS "${WS_WARNINGS_C_FLAGS}"
 			LINK_FLAGS "${WS_LINK_FLAGS}"
 			RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/run/extcap
 		)
@@ -2373,9 +2369,10 @@ if(BUILD_wireshark_gtk AND GTK_FOUND)
 	add_executable(wireshark-gtk WIN32 ${wireshark_FILES})
 	add_dependencies(wireshark-gtk version)
 	set(PROGLIST ${PROGLIST} wireshark-gtk)
-	set_target_properties(wireshark-gtk PROPERTIES COMPILE_OPTIONS "${WS_WARNINGS_C_FLAGS}")
-	set_target_properties(wireshark-gtk PROPERTIES LINK_FLAGS "${WS_LINK_FLAGS}")
-	set_target_properties(wireshark-gtk PROPERTIES FOLDER "Executables")
+	set_target_properties(wireshark-gtk PROPERTIES
+		LINK_FLAGS "${WS_LINK_FLAGS}"
+		FOLDER "Executables"
+	)
 	target_link_libraries(wireshark-gtk ${wireshark_gtk_LIBS})
 	install(TARGETS wireshark-gtk RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})