Report postmaster.pid file as empty if it is empty, rather than

reporting in contains invalid data.

src/backend/utils/init/miscinit.c

@@ -766,6 +766,14 @@ CreateLockFile(const char *filename, bool amPostmaster,
 							filename)));
 		close(fd);
 
+		if (len == 0)
+		{
+			ereport(FATAL,
+					(errcode(ERRCODE_LOCK_FILE_EXISTS),
+					 errmsg("lock file \"%s\" is empty", filename),
+					 errhint("Either another server is starting, or the lock file is the remnant of a previous server startup crash.")));
+		}
+
 		buffer[len] = '\0';
 		encoded_pid = atoi(buffer);
 

src/bin/pg_ctl/pg_ctl.c

@@ -292,8 +292,13 @@ get_pgpid(void)
 	}
 	if (fscanf(pidf, "%ld", &pid) != 1)
 	{
-		write_stderr(_("%s: invalid data in PID file \"%s\"\n"),
-					 progname, pid_file);
+		/* Is the file empty? */
+		if (ftell(pidf) == 0 && feof(pidf))
+			write_stderr(_("%s: the PID file \"%s\" is empty\n"),
+						 progname, pid_file);
+		else
+			write_stderr(_("%s: invalid data in PID file \"%s\"\n"),
+						 progname, pid_file);
 		exit(1);
 	}
 	fclose(pidf);