[Minor] do not pass invalid C warnings to C++ flags

cc1plus: warning: command line option ‘-Wno-pointer-sign’ is valid for C/ObjC but not for C++
cc1plus: warning: command line option ‘-Wstrict-prototypes’ is valid for C/ObjC but not for C++

diff --git a/cmake/CompilerWarnings.cmake b/cmake/CompilerWarnings.cmake
index b9bb7ffde2350397515c88cf49a8f1aa117839d5..4dd011d9887846a4cca635671cd4ccf18e5435e8 100644 (file)
--- a/cmake/CompilerWarnings.cmake
+++ b/cmake/CompilerWarnings.cmake
@@ -35,10 +35,12 @@ IF(SUPPORT_WUNUSED_VAR)
     ADD_COMPILE_OPTIONS("-Wunused-variable")
 ENDIF(SUPPORT_WUNUSED_VAR)
 IF(SUPPORT_WPOINTER_SIGN)
-    ADD_COMPILE_OPTIONS("-Wno-pointer-sign")
+    # only valid for C
+    ADD_COMPILE_OPTIONS($<$<COMPILE_LANGUAGE:C>:-Wno-pointer-sign>)
 ENDIF(SUPPORT_WPOINTER_SIGN)
 IF(SUPPORT_WSTRICT_PROTOTYPES)
-    ADD_COMPILE_OPTIONS("-Wstrict-prototypes")
+    # only valid for C
+    ADD_COMPILE_OPTIONS($<$<COMPILE_LANGUAGE:C>:-Wstrict-prototypes>)
 ENDIF(SUPPORT_WSTRICT_PROTOTYPES)
 IF(SUPPORT_WSTRICT_ALIASING)
     ADD_COMPILE_OPTIONS("-Wno-strict-aliasing")