+/* gcc supports the "unused" attribute on possibly unused labels, and
+ g++ has since version 4.5. */
+#if !defined __cplusplus || __GNUC__ > 4 \
+ || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
+# define _GL_UNUSED_LABEL _GL_UNUSED
+#else
+# define _GL_UNUSED_LABEL
+#endif
+