Clean up recent Coverity complaints.

Commit 5c649fe15 introduced a memory leak into pg_basebackup's
parse_compress_options.  (I simplified nearby code while at it.)

Commit 9a974cbcb introduced a memory leak into pg_dump's
binary_upgrade_set_pg_class_oids.

Coverity also complained about a call of SnapBuildProcessChange that
ignored the result, unlike every other call of that function.  This
is evidently intentional, so add a (void) cast to indicate that.
(It's also old, dating to b89e15105; I suppose the reason it showed
up now is 7a5f6b474's recent rearrangement of nearby code.)

src/backend/replication/logical/decode.c

@@ -498,7 +498,7 @@ heap_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 			if (!TransactionIdIsValid(xid))
 				break;
 
-			SnapBuildProcessChange(builder, xid, buf->origptr);
+			(void) SnapBuildProcessChange(builder, xid, buf->origptr);
 			ReorderBufferXidSetCatalogChanges(ctx->reorder, xid, buf->origptr);
 			break;
 

src/bin/pg_basebackup/pg_basebackup.c

@@ -948,7 +948,7 @@ parse_compress_options(char *src, WalCompressionMethod *methodres,
 {
 	char	   *sep;
 	int			firstlen;
-	char	   *firstpart = NULL;
+	char	   *firstpart;
 
 	/* check if the option is split in two */
 	sep = strchr(src, ':');
@@ -959,7 +959,7 @@ parse_compress_options(char *src, WalCompressionMethod *methodres,
 	 */
 	firstlen = (sep != NULL) ? (sep - src) : strlen(src);
 	firstpart = pg_malloc(firstlen + 1);
-	strncpy(firstpart, src, firstlen);
+	memcpy(firstpart, src, firstlen);
 	firstpart[firstlen] = '\0';
 
 	/*
@@ -983,6 +983,8 @@ parse_compress_options(char *src, WalCompressionMethod *methodres,
 
 		*methodres = (*levelres > 0) ?
 			COMPRESSION_GZIP : COMPRESSION_NONE;
+
+		free(firstpart);
 		return;
 	}
 
@@ -992,6 +994,7 @@ parse_compress_options(char *src, WalCompressionMethod *methodres,
 		 * The caller specified a method without a colon separator, so let any
 		 * subsequent checks assign a default level.
 		 */
+		free(firstpart);
 		return;
 	}
 
@@ -1010,6 +1013,8 @@ parse_compress_options(char *src, WalCompressionMethod *methodres,
 	if (!option_parse_int(sep, "-Z/--compress", 0, INT_MAX,
 						  levelres))
 		exit(1);
+
+	free(firstpart);
 }
 
 /*

src/bin/pg_dump/pg_dump.c

@@ -4714,7 +4714,6 @@ binary_upgrade_set_pg_class_oids(Archive *fout,
 		}
 
 		PQclear(upgrade_res);
-		destroyPQExpBuffer(upgrade_query);
 	}
 	else
 	{
@@ -4728,6 +4727,8 @@ binary_upgrade_set_pg_class_oids(Archive *fout,
 	}
 
 	appendPQExpBufferChar(upgrade_buffer, '\n');
+
+	destroyPQExpBuffer(upgrade_query);
 }
 
 /*