pg_basebackup: Add a dummy return to bbsink_gzip_new().

Apparently, this is needed to avoid warnings on MVCC.

David Rowley

Discussion: http://postgr.es/m/CAApHDvosHkgyo_PZs7CSB4Kgs2ey4FdmFpcK0N_QOci9DJ=wnw@mail.gmail.com

src/backend/replication/basebackup_gzip.c

@@ -66,6 +66,7 @@ bbsink_gzip_new(bbsink *next, int compresslevel)
 	ereport(ERROR,
 			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 			 errmsg("gzip compression is not supported by this build")));
+	return NULL;				/* keep compiler quiet */
 #else
 	bbsink_gzip *sink;