tests: check --always-show-pid option

* tests/strace--always-show-pid.c: New file.
* tests/pure_executables.list: Add strace--always-show-pid.
* tests/.gitignore: Likewise.
* tests/gen_tests.in (strace--always-show-pid): New test.

tests/.gitignore

@@ -1085,6 +1085,7 @@ status-successful-threads
 status-unfinished
 status-unfinished-threads
 statx
+strace--always-show-pid
 strace--decode-pids-comm
 strace--strings-in-hex
 strace--strings-in-hex-all

tests/gen_tests.in

@@ -1068,6 +1068,7 @@ strace--absolute-timestamps-format-unix-precision-ms +strace-ttt.test 3 --absolu
 strace--absolute-timestamps-format-unix-precision-ns +strace-ttt.test 9 --absolute-timestamps=format:unix --absolute-timestamps=precision:ns
 strace--absolute-timestamps-format-unix-precision-s +strace-ttt.test 0 --absolute-timestamps=format:unix --absolute-timestamps=precision:s
 strace--absolute-timestamps-format-unix-precision-us +strace-ttt.test 6 --absolute-timestamps=precision:us --absolute-timestamps=format:unix
+strace--always-show-pid	--always-show-pid --trace=fchdir -a15
 strace--decode-pids-comm	--decode-pids=comm --trace=getppid,tgkill --signal='!SIGCHLD,SIGCONT' -q -f -a 18
 strace--follow-forks-output-separately +strace-ff.test --follow-forks --output-separately
 strace--relative-timestamps +strace-r.test --relative-timestamps

tests/pure_executables.list

@@ -784,6 +784,7 @@ status-successful-long
 status-successful-status
 status-unfinished
 statx
+strace--always-show-pid
 strace--strings-in-hex
 strace--strings-in-hex-all
 strace--strings-in-hex-non-ascii

tests/strace--always-show-pid.c

@@ -0,0 +1,22 @@
+/*
+ * Check the PID prefix output with --always-show-pid option.
+ *
+ * Copyright (c) 2024 The strace developers.
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "tests.h"
+#include <stdio.h>
+#include <unistd.h>
+
+int
+main(void)
+{
+	const int pid = getpid();
+	printf("%-5u fchdir(-1) = %s\n", pid, sprintrc(fchdir(-1)));
+
+	printf("%-5u +++ exited with 0 +++\n", pid);
+	return 0;
+}