Clean up command argument assembly

Several commands internally assemble command lines to call other
commands.  This includes initdb, pg_dumpall, and pg_regress.  (Also
pg_ctl, but that is different enough that I didn't consider it here.)
This has all evolved a bit organically, with fixed-size buffers, and
various optional command-line arguments being injected with
confusing-looking code, and the spacing between options handled in
inconsistent ways.  Clean all this up a bit to look clearer and be
more easily extensible with new arguments and options.  We start each
command with printfPQExpBuffer(), and then append arguments as
necessary with appendPQExpBuffer().  Also standardize on using
initPQExpBuffer() over createPQExpBuffer() where possible.  pg_regress
uses StringInfo instead of PQExpBuffer, but many of the same ideas
apply.

Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Discussion: https://www.postgresql.org/message-id/flat/16d0beac-a141-e5d3-60e9-323da75f49bf@eisentraut.org

src/bin/initdb/initdb.c

@@ -309,16 +309,16 @@ void		initialize_data_directory(void);
 /*
  * macros for running pipes to postgres
  */
-#define PG_CMD_DECL		char cmd[MAXPGPATH]; FILE *cmdfd
+#define PG_CMD_DECL		FILE *cmdfd
 
-#define PG_CMD_OPEN \
+#define PG_CMD_OPEN(cmd) \
 do { \
 	cmdfd = popen_check(cmd, "w"); \
 	if (cmdfd == NULL) \
 		exit(1); /* message already printed by popen_check */ \
 } while (0)
 
-#define PG_CMD_CLOSE \
+#define PG_CMD_CLOSE() \
 do { \
 	if (pclose_check(cmdfd)) \
 		exit(1); /* message already printed by pclose_check */ \
@@ -1138,13 +1138,15 @@ test_config_settings(void)
 static bool
 test_specific_config_settings(int test_conns, int test_buffs)
 {
-	PQExpBuffer cmd = createPQExpBuffer();
+	PQExpBufferData cmd;
 	_stringlist *gnames,
 			   *gvalues;
 	int			status;
 
+	initPQExpBuffer(&cmd);
+
 	/* Set up the test postmaster invocation */
-	printfPQExpBuffer(cmd,
+	printfPQExpBuffer(&cmd,
 					  "\"%s\" --check %s %s "
 					  "-c max_connections=%d "
 					  "-c shared_buffers=%d "
@@ -1158,18 +1160,18 @@ test_specific_config_settings(int test_conns, int test_buffs)
 		 gnames != NULL;		/* assume lists have the same length */
 		 gnames = gnames->next, gvalues = gvalues->next)
 	{
-		appendPQExpBuffer(cmd, " -c %s=", gnames->str);
+		appendPQExpBuffer(&cmd, " -c %s=", gnames->str);
-		appendShellString(cmd, gvalues->str);
+		appendShellString(&cmd, gvalues->str);
 	}
 
-	appendPQExpBuffer(cmd,
+	appendPQExpBuffer(&cmd,
 					  " < \"%s\" > \"%s\" 2>&1",
 					  DEVNULL, DEVNULL);
 
 	fflush(NULL);
-	status = system(cmd->data);
+	status = system(cmd.data);
 
-	destroyPQExpBuffer(cmd);
+	termPQExpBuffer(&cmd);
 
 	return (status == 0);
 }
@@ -1469,6 +1471,7 @@ static void
 bootstrap_template1(void)
 {
 	PG_CMD_DECL;
+	PQExpBufferData cmd;
 	char	  **line;
 	char	  **bki_lines;
 	char		headerline[MAXPGPATH];
@@ -1530,16 +1533,17 @@ bootstrap_template1(void)
 	/* Also ensure backend isn't confused by this environment var: */
 	unsetenv("PGCLIENTENCODING");
 
-	snprintf(cmd, sizeof(cmd),
+	initPQExpBuffer(&cmd);
-			 "\"%s\" --boot -X %d %s %s %s %s",
+
-			 backend_exec,
+	printfPQExpBuffer(&cmd, "\"%s\" --boot %s %s", backend_exec, boot_options, extra_options);
-			 wal_segment_size_mb * (1024 * 1024),
+	appendPQExpBuffer(&cmd, " -X %d", wal_segment_size_mb * (1024 * 1024));
-			 data_checksums ? "-k" : "",
+	if (data_checksums)
-			 boot_options, extra_options,
+		appendPQExpBuffer(&cmd, " -k");
-			 debug ? "-d 5" : "");
+	if (debug)
+		appendPQExpBuffer(&cmd, " -d 5");
 
 
-	PG_CMD_OPEN;
+	PG_CMD_OPEN(cmd.data);
 
 	for (line = bki_lines; *line != NULL; line++)
 	{
@@ -1547,8 +1551,9 @@ bootstrap_template1(void)
 		free(*line);
 	}
 
-	PG_CMD_CLOSE;
+	PG_CMD_CLOSE();
 
+	termPQExpBuffer(&cmd);
 	free(bki_lines);
 
 	check_ok();
@@ -2951,6 +2956,7 @@ void
 initialize_data_directory(void)
 {
 	PG_CMD_DECL;
+	PQExpBufferData cmd;
 	int			i;
 
 	setup_signals();
@@ -3014,12 +3020,11 @@ initialize_data_directory(void)
 	fputs(_("performing post-bootstrap initialization ... "), stdout);
 	fflush(stdout);
 
-	snprintf(cmd, sizeof(cmd),
+	initPQExpBuffer(&cmd);
-			 "\"%s\" %s %s template1 >%s",
+	printfPQExpBuffer(&cmd, "\"%s\" %s %s template1 >%s",
-			 backend_exec, backend_options, extra_options,
+					  backend_exec, backend_options, extra_options, DEVNULL);
-			 DEVNULL);
 
-	PG_CMD_OPEN;
+	PG_CMD_OPEN(cmd.data);
 
 	setup_auth(cmdfd);
 
@@ -3054,7 +3059,8 @@ initialize_data_directory(void)
 
 	make_postgres(cmdfd);
 
-	PG_CMD_CLOSE;
+	PG_CMD_CLOSE();
+	termPQExpBuffer(&cmd);
 
 	check_ok();
 }

src/bin/pg_dump/pg_dumpall.c

@@ -1564,11 +1564,14 @@ dumpDatabases(PGconn *conn)
 static int
 runPgDump(const char *dbname, const char *create_opts)
 {
-	PQExpBuffer connstrbuf = createPQExpBuffer();
+	PQExpBufferData connstrbuf;
-	PQExpBuffer cmd = createPQExpBuffer();
+	PQExpBufferData cmd;
 	int			ret;
 
-	appendPQExpBuffer(cmd, "\"%s\" %s %s", pg_dump_bin,
+	initPQExpBuffer(&connstrbuf);
+	initPQExpBuffer(&cmd);
+
+	printfPQExpBuffer(&cmd, "\"%s\" %s %s", pg_dump_bin,
 					  pgdumpopts->data, create_opts);
 
 	/*
@@ -1576,27 +1579,27 @@ runPgDump(const char *dbname, const char *create_opts)
 	 * format.
 	 */
 	if (filename)
-		appendPQExpBufferStr(cmd, " -Fa ");
+		appendPQExpBufferStr(&cmd, " -Fa ");
 	else
-		appendPQExpBufferStr(cmd, " -Fp ");
+		appendPQExpBufferStr(&cmd, " -Fp ");
 
 	/*
 	 * Append the database name to the already-constructed stem of connection
 	 * string.
 	 */
-	appendPQExpBuffer(connstrbuf, "%s dbname=", connstr);
+	appendPQExpBuffer(&connstrbuf, "%s dbname=", connstr);
-	appendConnStrVal(connstrbuf, dbname);
+	appendConnStrVal(&connstrbuf, dbname);
 
-	appendShellString(cmd, connstrbuf->data);
+	appendShellString(&cmd, connstrbuf.data);
 
-	pg_log_info("running \"%s\"", cmd->data);
+	pg_log_info("running \"%s\"", cmd.data);
 
 	fflush(NULL);
 
-	ret = system(cmd->data);
+	ret = system(cmd.data);
 
-	destroyPQExpBuffer(cmd);
+	termPQExpBuffer(&cmd);
-	destroyPQExpBuffer(connstrbuf);
+	termPQExpBuffer(&connstrbuf);
 
 	return ret;
 }

src/test/regress/pg_regress.c

@@ -2293,6 +2293,7 @@ regression_main(int argc, char *argv[],
 
 	if (temp_instance)
 	{
+		StringInfoData cmd;
 		FILE	   *pg_conf;
 		const char *env_wait;
 		int			wait_seconds;
@@ -2318,23 +2319,28 @@ regression_main(int argc, char *argv[],
 			make_directory(buf);
 
 		/* initdb */
-		snprintf(buf, sizeof(buf),
+		initStringInfo(&cmd);
-				 "\"%s%sinitdb\" -D \"%s/data\" --no-clean --no-sync%s%s > \"%s/log/initdb.log\" 2>&1",
+		appendStringInfo(&cmd,
-				 bindir ? bindir : "",
+						 "\"%s%sinitdb\" -D \"%s/data\" --no-clean --no-sync",
-				 bindir ? "/" : "",
+						 bindir ? bindir : "",
-				 temp_instance,
+						 bindir ? "/" : "",
-				 debug ? " --debug" : "",
+						 temp_instance);
-				 nolocale ? " --no-locale" : "",
+		if (debug)
-				 outputdir);
+			appendStringInfo(&cmd, " --debug");
+		if (nolocale)
+			appendStringInfo(&cmd, " --no-locale");
+		appendStringInfo(&cmd, " > \"%s/log/initdb.log\" 2>&1", outputdir);
 		fflush(NULL);
-		if (system(buf))
+		if (system(cmd.data))
 		{
 			bail("initdb failed\n"
 				 "# Examine \"%s/log/initdb.log\" for the reason.\n"
 				 "# Command was: %s",
-				 outputdir, buf);
+				 outputdir, cmd.data);
 		}
 
+		pfree(cmd.data);
+
 		/*
 		 * Adjust the default postgresql.conf for regression testing. The user
 		 * can specify a file to be appended; in any case we expand logging