--- a/toolchain-funcs.eclass	
+++ a/toolchain-funcs.eclass	
@@ -483,6 +483,8 @@ tc-endian() {
 # Query the preprocessor to improve compatibility across different
 # compilers rather than maintaining a --version flag matrix. #335943
 _gcc_fullversion() {
+	local opt=""
+	[[ $(tc-getCPP) == clang-cpp ]] || opt="-E"
 	local ver="$1"; shift
 	set -- `$(tc-getCPP "$@") -E -P - <<<"__GNUC__ __GNUC_MINOR__ __GNUC_PATCHLEVEL__"`
 	eval echo "$ver"