git commit the __attribute__ pragma is only for GCC

src/runtime/c/pgf/typechecker.h

@@ -101,7 +101,10 @@ class PGF_INTERNAL_DECL PgfTypechecker {
     };
 
     PgfDBMarshaller db_m;
-    bool type_error(const char *fmt, ...) __attribute__ ((format (printf, 2, 3)));
+    bool type_error(const char *fmt, ...)
+#ifdef __GNUC__
+    __attribute__ ((format (printf, 2, 3)));
+#endif
 
 public:
     PgfTypechecker(ref<PgfPGF> gr, PgfMarshaller *m, PgfUnmarshaller *u, PgfExn* err);