[LTP] [PATCH v3] lib: tst_test: Add reproducible output.

[Cyril Hrubis]

This commit adds an environment variable LTP_REPRODUCIBLE_OUTPUT that
when set to 1 or y 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>
Reviewed-by: Martin Doucha <mdoucha@suse.cz>
Reviewed-by: Avinesh Kumar <akumar@suse.de>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
CC: valgrind-developers@lists.sourceforge.net
---
 doc/users/setup_tests.rst |  4 ++++
 lib/tst_test.c            | 33 ++++++++++++++++++++++-----------
 2 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/doc/users/setup_tests.rst b/doc/users/setup_tests.rst
index 2766ed719..2cce85fdf 100644
--- a/doc/users/setup_tests.rst
+++ b/doc/users/setup_tests.rst
@@ -42,6 +42,10 @@ users.
      - Path to the block device to be used. C Language: ``.needs_device = 1``.
        Shell language: ``TST_NEEDS_DEVICE=1``.
 
+   * - LTP_REPRODUCIBLE_OUTPUT
+     - When set to ``1`` or ``y`` discards the actual content of the messages
+       printed by the test (suitable for a reproducible output).
+
    * - LTP_SINGLE_FS_TYPE
      - Testing only - specifies filesystem instead all supported
        (for tests with ``.all_filesystems``).
diff --git a/lib/tst_test.c b/lib/tst_test.c
index 923ecf7be..297c376da 100644
--- a/lib/tst_test.c
+++ b/lib/tst_test.c
@@ -63,6 +63,7 @@ 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;
@@ -316,6 +317,9 @@ static void print_result(const char *file, const int lineno, int ttype,
 	str += ret;
 	size -= ret;
 
+	if (reproducible_output)
+		goto print;
+
 	ssize = size - 2;
 	ret = vsnprintf(str, size, fmt, va);
 	str += MIN(ret, ssize);
@@ -333,6 +337,7 @@ 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() */
@@ -606,17 +611,18 @@ static void print_help(void)
 	/* see doc/users/setup_tests.rst, which lists also shell API variables */
 	fprintf(stderr, "Environment Variables\n");
 	fprintf(stderr, "---------------------\n");
-	fprintf(stderr, "KCONFIG_PATH         Specify kernel config file\n");
-	fprintf(stderr, "KCONFIG_SKIP_CHECK   Skip kernel config check if variable set (not set by default)\n");
-	fprintf(stderr, "LTPROOT              Prefix for installed LTP (default: /opt/ltp)\n");
-	fprintf(stderr, "LTP_COLORIZE_OUTPUT  Force colorized output behaviour (y/1 always, n/0: never)\n");
-	fprintf(stderr, "LTP_DEV              Path to the block device to be used (for .needs_device)\n");
-	fprintf(stderr, "LTP_DEV_FS_TYPE      Filesystem used for testing (default: %s)\n", DEFAULT_FS_TYPE);
-	fprintf(stderr, "LTP_SINGLE_FS_TYPE   Testing only - specifies filesystem instead all supported (for .all_filesystems)\n");
-	fprintf(stderr, "LTP_TIMEOUT_MUL      Timeout multiplier (must be a number >=1)\n");
-	fprintf(stderr, "LTP_RUNTIME_MUL      Runtime multiplier (must be a number >=1)\n");
-	fprintf(stderr, "LTP_VIRT_OVERRIDE    Overrides virtual machine detection (values: \"\"|kvm|microsoft|xen|zvm)\n");
-	fprintf(stderr, "TMPDIR               Base directory for template directory (for .needs_tmpdir, default: %s)\n", TEMPDIR);
+	fprintf(stderr, "KCONFIG_PATH            Specify kernel config file\n");
+	fprintf(stderr, "KCONFIG_SKIP_CHECK      Skip kernel config check if variable set (not set by default)\n");
+	fprintf(stderr, "LTPROOT                 Prefix for installed LTP (default: /opt/ltp)\n");
+	fprintf(stderr, "LTP_COLORIZE_OUTPUT     Force colorized output behaviour (y/1 always, n/0: never)\n");
+	fprintf(stderr, "LTP_DEV                 Path to the block device to be used (for .needs_device)\n");
+	fprintf(stderr, "LTP_DEV_FS_TYPE         Filesystem used for testing (default: %s)\n", DEFAULT_FS_TYPE);
+	fprintf(stderr, "LTP_REPRODUCIBLE_OUTPUT When set to 1 or y discards the actual content of the messages printed by the test\n");
+	fprintf(stderr, "LTP_SINGLE_FS_TYPE      Testing only - specifies filesystem instead all supported (for .all_filesystems)\n");
+	fprintf(stderr, "LTP_TIMEOUT_MUL         Timeout multiplier (must be a number >=1)\n");
+	fprintf(stderr, "LTP_RUNTIME_MUL         Runtime multiplier (must be a number >=1)\n");
+	fprintf(stderr, "LTP_VIRT_OVERRIDE       Overrides virtual machine detection (values: \"\"|kvm|microsoft|xen|zvm)\n");
+	fprintf(stderr, "TMPDIR                  Base directory for template directory (for .needs_tmpdir, default: %s)\n", TEMPDIR);
 	fprintf(stderr, "\n");
 
 	fprintf(stderr, "Timeout and runtime\n");
@@ -1298,6 +1304,7 @@ static const char *default_fs_type(void)
 static void do_setup(int argc, char *argv[])
 {
 	char *tdebug_env = getenv("LTP_ENABLE_DEBUG");
+	char *reproducible_env = getenv("LTP_REPRODUCIBLE_OUTPUT");
 
 	if (!tst_test)
 		tst_brk(TBROK, "No tests to run");
@@ -1316,6 +1323,10 @@ 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);
 
+	if (reproducible_env &&
+	    (!strcmp(reproducible_env, "1") || !strcmp(reproducible_env, "y")))
+		reproducible_output = 1;
+
 	assert_test_fn();
 
 	TCID = tid = get_tid(argv);
-- 
2.49.0