Test optimization flags only when CMAKE_CXX_FLAGS is set

Author: alandefreitas

cmake/functions/project_flags.cmake

@@ -50,15 +50,17 @@ endmacro()
 # @brief Set the default optimization flags in case the user didn't
 #        explicitly choose it with -DCMAKE_CXX_FLAGS
 macro(set_optimization_flags)
-    set(OPT_FLAGS /O1 /O2 /Ob /Od /Og /Oi /Os /Ot /Ox /Oy /favor -O0 -O1 -O -O2 -O3 -Os -Ofast -Og)
     set(OPTIMIZATION_FLAG_IS_SET OFF)
-    string(REPLACE " " ";" CMAKE_CXX_FLAGS_LIST ${CMAKE_CXX_FLAGS})
-    foreach(FLAG ${CMAKE_CXX_FLAGS_LIST})
-        if (${FLAG} IN_LIST OPT_FLAGS)
-            message("CXX optimization flag is already set to ${FLAG}")
-            set(OPTIMIZATION_FLAG_IS_SET ON)
-        endif()
-    endforeach()
+    if (CMAKE_CXX_FLAGS)
+        set(OPT_FLAGS /O1 /O2 /Ob /Od /Og /Oi /Os /Ot /Ox /Oy /favor -O0 -O1 -O -O2 -O3 -Os -Ofast -Og)
+        string(REPLACE " " ";" CMAKE_CXX_FLAGS_LIST ${CMAKE_CXX_FLAGS})
+        foreach(FLAG ${CMAKE_CXX_FLAGS_LIST})
+            if (${FLAG} IN_LIST OPT_FLAGS)
+                message("CXX optimization flag is already set to ${FLAG}")
+                set(OPTIMIZATION_FLAG_IS_SET ON)
+            endif()
+        endforeach()
+    endif()
 
     if (NOT OPTIMIZATION_FLAG_IS_SET)
         if (CMAKE_BUILD_TYPE STREQUAL "Debug")