Define DEBUG and _DEBUG on debug build

CMakeLists.txt

@@ -42,6 +42,14 @@ if(WIN32)
 	add_definitions(-DUNICODE -D_UNICODE)
 endif()
 
+if(MSVC)
+	set(CMAKE_C_FLAGS_DEBUG "/DDEBUG=1 /D_DEBUG=1 ${CMAKE_C_FLAGS_DEBUG}")
+	set(CMAKE_CXX_FLAGS_DEBUG "/DDEBUG=1 /D_DEBUG=1 ${CMAKE_C_FLAGS_DEBUG}")
+else()
+	set(CMAKE_C_FLAGS_DEBUG "-DDEBUG=1 -D_DEBUG=1 ${CMAKE_C_FLAGS_DEBUG}")
+	set(CMAKE_CXX_FLAGS_DEBUG "-DDEBUG=1 -D_DEBUG=1 ${CMAKE_C_FLAGS_DEBUG}")
+endif()
+
 if(APPLE)
 	set(CMAKE_MACOSX_RPATH TRUE)
 	set(CMAKE_BUILD_WITH_INSTALL_RPATH TRUE)