[cmake] add default compiler flags

CMakeLists.txt

@@ -77,6 +77,7 @@ if(WITH_CLANG_FORMAT)
 	include(ClangFormat)
 endif()
 
+include(CompilerFlags)
 include(DetectBSD)
 include(CheckIncludeFiles)
 include(CheckLibraryExists)
@@ -392,19 +393,7 @@ if(${CMAKE_C_COMPILER_ID} STREQUAL "Clang" OR CMAKE_COMPILER_IS_GNUCC)
 endif()
 
 if(MSVC)
-	# Remove previous warning definitions,
-	# NMake is otherwise complaining.
-	foreach (flags_var_to_scrub
-		CMAKE_C_FLAGS
-		CMAKE_C_FLAGS_RELEASE
-		CMAKE_C_FLAGS_RELWITHDEBINFO
-		CMAKE_C_FLAGS_MINSIZEREL)
-		string (REGEX REPLACE "(^| )[/-]W[ ]*[1-9]" " "
-		"${flags_var_to_scrub}" "${${flags_var_to_scrub}}")
-	endforeach()
-
 	set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /Gd")
-	set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /W3")
 
 	set(EXECUTABLE_OUTPUT_PATH ${PROJECT_BINARY_DIR})
 	set(LIBRARY_OUTPUT_PATH ${PROJECT_BINARY_DIR})

cmake/CompilerFlags.cmake

@@ -0,0 +1,45 @@
+include(CheckCCompilerFlag)
+
+macro (checkCFlag FLAG)
+	CHECK_C_COMPILER_FLAG("${FLAG}" CFLAG${FLAG})
+	if(CFLAG${FLAG})
+		string(APPEND CMAKE_C_FLAGS " ${FLAG}")
+	else()
+		message(WARNING "compiler does not support ${FLAG}")
+	endif()
+endmacro()
+
+option(ENABLE_WARNING_VERBOSE "enable -Weveryting (and some exceptions) for compile" ON)
+option(ENABLE_WARNING_ERROR "enable -Werror for compile" OFF)
+
+if (ENABLE_WARNING_VERBOSE)
+	if (MSVC)
+		set(C_WARNING_FLAGS
+			/Wall
+		)
+	else()
+		set(C_WARNING_FLAGS
+			-Weverything
+			-Wall
+			-Wpedantic
+			-Wno-padded
+			-Wno-cast-align
+			-Wno-declaration-after-statement
+			-Wno-unsafe-buffer-usage
+			-Wno-reserved-identifier
+			-Wno-covered-switch-default
+		)
+	endif()
+
+	foreach(FLAG ${C_WARNING_FLAGS})
+		CheckCFlag(${FLAG})
+	endforeach()
+endif()
+
+
+if (ENABLE_WARNING_ERROR)
+	CheckCFlag(-Werror)
+endif()
+
+set(CMAKE_C_FLAGS ${CMAKE_C_FLAGS} CACHE STRING "default CFLAGS")
+message("Using CFLAGS ${CMAKE_C_FLAGS}")