Remove arbitrary MAXPGPATH limit on command lengths in pg_ctl.

Replace fixed-length command buffers with psprintf() calls.  We didn't
have anything as convenient as psprintf() when this code was written,
but now that we do, there's little reason for the limitation to
stand.  Removing it eliminates some corner cases where (for example)
starting the postmaster with a whole lot of options fails.

Most individual file names that pg_ctl deals with are still restricted
to MAXPGPATH, but we've seldom had complaints about that limitation
so long as it only applies to one filename.

Back-patch to all supported branches.

Phil Krylov

Discussion: https://postgr.es/m/567e199c6b97ee19deee600311515b86@krylov.eu

src/bin/pg_ctl/pg_ctl.c

@@ -442,7 +442,7 @@ free_readfile(char **optlines)
 static pgpid_t
 start_postmaster(void)
 {
-	char		cmd[MAXPGPATH];
+	char	   *cmd;
 
 #ifndef WIN32
 	pgpid_t		pm_pid;
@@ -487,12 +487,12 @@ start_postmaster(void)
 	 * has the same PID as the current child process.
 	 */
 	if (log_file != NULL)
-		snprintf(cmd, MAXPGPATH, "exec \"%s\" %s%s < \"%s\" >> \"%s\" 2>&1",
-				 exec_path, pgdata_opt, post_opts,
-				 DEVNULL, log_file);
+		cmd = psprintf("exec \"%s\" %s%s < \"%s\" >> \"%s\" 2>&1",
+					   exec_path, pgdata_opt, post_opts,
+					   DEVNULL, log_file);
 	else
-		snprintf(cmd, MAXPGPATH, "exec \"%s\" %s%s < \"%s\" 2>&1",
-				 exec_path, pgdata_opt, post_opts, DEVNULL);
+		cmd = psprintf("exec \"%s\" %s%s < \"%s\" 2>&1",
+					   exec_path, pgdata_opt, post_opts, DEVNULL);
 
 	(void) execl("/bin/sh", "/bin/sh", "-c", cmd, (char *) NULL);
 
@@ -553,12 +553,12 @@ start_postmaster(void)
 		else
 			close(fd);
 
-		snprintf(cmd, MAXPGPATH, "\"%s\" /C \"\"%s\" %s%s < \"%s\" >> \"%s\" 2>&1\"",
-				 comspec, exec_path, pgdata_opt, post_opts, DEVNULL, log_file);
+		cmd = psprintf("\"%s\" /C \"\"%s\" %s%s < \"%s\" >> \"%s\" 2>&1\"",
+					   comspec, exec_path, pgdata_opt, post_opts, DEVNULL, log_file);
 	}
 	else
-		snprintf(cmd, MAXPGPATH, "\"%s\" /C \"\"%s\" %s%s < \"%s\" 2>&1\"",
-				 comspec, exec_path, pgdata_opt, post_opts, DEVNULL);
+		cmd = psprintf("\"%s\" /C \"\"%s\" %s%s < \"%s\" 2>&1\"",
+					   comspec, exec_path, pgdata_opt, post_opts, DEVNULL);
 
 	if (!CreateRestrictedProcess(cmd, &pi, false))
 	{
@@ -828,7 +828,7 @@ find_other_exec_or_die(const char *argv0, const char *target, const char *versio
 static void
 do_init(void)
 {
-	char		cmd[MAXPGPATH];
+	char	   *cmd;
 
 	if (exec_path == NULL)
 		exec_path = find_other_exec_or_die(argv0, "initdb", "initdb (PostgreSQL) " PG_VERSION "\n");
@@ -840,11 +840,11 @@ do_init(void)
 		post_opts = "";
 
 	if (!silent_mode)
-		snprintf(cmd, MAXPGPATH, "\"%s\" %s%s",
-				 exec_path, pgdata_opt, post_opts);
+		cmd = psprintf("\"%s\" %s%s",
+					   exec_path, pgdata_opt, post_opts);
 	else
-		snprintf(cmd, MAXPGPATH, "\"%s\" %s%s > \"%s\"",
-				 exec_path, pgdata_opt, post_opts, DEVNULL);
+		cmd = psprintf("\"%s\" %s%s > \"%s\"",
+					   exec_path, pgdata_opt, post_opts, DEVNULL);
 
 	if (system(cmd) != 0)
 	{
@@ -2175,9 +2175,9 @@ set_starttype(char *starttypeopt)
 static void
 adjust_data_dir(void)
 {
-	char		cmd[MAXPGPATH],
-				filename[MAXPGPATH],
-			   *my_exec_path;
+	char		filename[MAXPGPATH];
+	char	   *my_exec_path,
+			   *cmd;
 	FILE	   *fd;
 
 	/* do nothing if we're working without knowledge of data dir */
@@ -2207,10 +2207,10 @@ adjust_data_dir(void)
 		my_exec_path = pg_strdup(exec_path);
 
 	/* it's important for -C to be the first option, see main.c */
-	snprintf(cmd, MAXPGPATH, "\"%s\" -C data_directory %s%s",
-			 my_exec_path,
-			 pgdata_opt ? pgdata_opt : "",
-			 post_opts ? post_opts : "");
+	cmd = psprintf("\"%s\" -C data_directory %s%s",
+				   my_exec_path,
+				   pgdata_opt ? pgdata_opt : "",
+				   post_opts ? post_opts : "");
 
 	fd = popen(cmd, "r");
 	if (fd == NULL || fgets(filename, sizeof(filename), fd) == NULL)