Build: Use interface targets for inheriting flags and definitions

* Remove the usage of global flags and definitions
  set through the CMAKE_CXX_FLAGS variable.
* Use cmake target compile features for setting the
  CXX standard automatically.
* Make C++14 globally available in the project
* Closes #21033

1 files changed, 30 insertions, 18 deletions

diff --git a/cmake/compiler/gcc/settings.cmake b/cmake/compiler/gcc/settings.cmake
index b9d2e457df8..d854ff521ce 100644
--- a/cmake/compiler/gcc/settings.cmake
+++ b/cmake/compiler/gcc/settings.cmake
@@ -1,5 +1,7 @@
 # Set build-directive (used in core to tell which buildtype we used)
-add_definitions(-D_BUILD_DIRECTIVE='"${CMAKE_BUILD_TYPE}"')
+target_compile_definitions(trinity-compile-option-interface
+  INTERFACE
+    -D_BUILD_DIRECTIVE="${CMAKE_BUILD_TYPE}")
 
 set(GCC_EXPECTED_VERSION 6.3.0)
 
@@ -7,37 +9,47 @@ if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS GCC_EXPECTED_VERSION)
   message(FATAL_ERROR "GCC: TrinityCore requires version ${GCC_EXPECTED_VERSION} to build but found ${CMAKE_CXX_COMPILER_VERSION}")
 endif()
 
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
-message(STATUS "GCC: Enabled c++11 support")
-
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=gnu99")
-message(STATUS "GCC: Enabled C99 support")
-
 if(PLATFORM EQUAL 32)
   # Required on 32-bit systems to enable SSE2 (standard on x64)
-  set(SSE_FLAGS "-msse2 -mfpmath=sse")
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${SSE_FLAGS}")
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${SSE_FLAGS}")
+  target_compile_options(trinity-compile-option-interface
+    INTERFACE
+      -msse2
+      -mfpmath=sse)
 endif()
-add_definitions(-DHAVE_SSE2 -D__SSE2__)
+target_compile_definitions(trinity-compile-option-interface
+  INTERFACE
+    -DHAVE_SSE2
+    -D__SSE2__)
 message(STATUS "GCC: SFMT enabled, SSE2 flags forced")
 
 if( WITH_WARNINGS )
-  set(WARNING_FLAGS "-W -Wall -Wextra -Winit-self -Winvalid-pch -Wfatal-errors")
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${WARNING_FLAGS}")
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${WARNING_FLAGS} -Woverloaded-virtual")
+  target_compile_options(trinity-warning-interface
+    INTERFACE
+      -W
+      -Wall
+      -Wextra
+      -Winit-self
+      -Winvalid-pch
+      -Wfatal-errors
+      -Woverloaded-virtual)
+
   message(STATUS "GCC: All warnings enabled")
 endif()
 
 if( WITH_COREDEBUG )
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -g3")
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g3")
+  target_compile_options(trinity-compile-option-interface
+    INTERFACE
+      -g3)
+
   message(STATUS "GCC: Debug-flags set (-g3)")
 endif()
 
 if (BUILD_SHARED_LIBS)
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fPIC -fvisibility=hidden -Wno-attributes")
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC -fvisibility=hidden -Wno-attributes")
+  target_compile_options(trinity-compile-option-interface
+    INTERFACE
+      -fPIC
+      -fvisibility=hidden
+      -Wno-attributes)
 
   # Should break the build when there are TRINITY_*_API macros missing
   # but it complains about missing references in precompiled headers.