Enable GNU GCC type checking of format arguments for our functions

errormsg.h

@@ -35,7 +35,14 @@ typedef struct {
  *  \return the new error message list head
  */
 
-void ErrPutMsg(ErrList *list, char *fmt, ...);
+#if __GNUC__ > 2
+#define G_GNUC_PRINTF( format_idx, arg_idx )    \
+  __attribute__((__format__ (__printf__, format_idx, arg_idx)))
+#else
+#define G_GNUC_PRINTF( format_idx, arg_idx )
+#endif
+void ErrPutMsg(ErrList *list, char *fmt, ...) G_GNUC_PRINTF (2, 3);
+#undef G_GNUC_PRINTF
 
 /** \brief Get the most recent error message
  *  \param list the error list