[LTP] [PATCH] lib: tst_test: Add reproducible output.

[Cyril Hrubis]

This commit adds an environment variable LTP_REPRODUCIBLE_OUTPUT that
when set skips printing parts of the test messages that may contain data
that differ on subsequent runs (e.g. pids).

With this you can run a test twice under a different conditions and
check if the test codeflow was identical by simply doing diff of the
outputs from the two runs.

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
Suggested-by: Martin Doucha <mdoucha@suse.cz>
CC: valgrind-developers@lists.sourceforge.net
---
 lib/tst_test.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/lib/tst_test.c b/lib/tst_test.c
index 2bb4519dd..3f94a1607 100644
--- a/lib/tst_test.c
+++ b/lib/tst_test.c
@@ -64,6 +64,7 @@ static int mntpoint_mounted;
 static int ovl_mounted;
 static struct timespec tst_start_time; /* valid only for test pid */
 static int tdebug;
+static int reproducible_output;
 
 struct results {
 	int passed;
@@ -304,6 +305,9 @@ static void print_result(const char *file, const int lineno, int ttype,
 	str += ret;
 	size -= ret;
 
+	if (reproducible_output)
+		goto print;
+
 	if (tst_color_enabled(STDERR_FILENO))
 		ret = snprintf(str, size, "%s%s: %s", tst_ttype2color(ttype),
 			       res, ANSI_COLOR_RESET);
@@ -329,6 +333,7 @@ static void print_result(const char *file, const int lineno, int ttype,
 				"Next message is too long and truncated:");
 	}
 
+print:
 	snprintf(str, size, "\n");
 
 	/* we might be called from signal handler, so use write() */
@@ -1312,6 +1317,8 @@ static void do_setup(int argc, char *argv[])
 	if (tst_test->supported_archs && !tst_is_on_arch(tst_test->supported_archs))
 		tst_brk(TCONF, "This arch '%s' is not supported for test!", tst_arch.name);
 
+	reproducible_output = !!getenv("LTP_REPRODUCIBLE_OUTPUT");
+
 	assert_test_fn();
 
 	TCID = tid = get_tid(argv);
-- 
2.49.0