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[PATCH v2 4/4] bisect--helper: double-check run command on exit code 126 and 127

From
René Scharfe <l.s.r@web.de>
Date
Jan 18, 2022, 12:46 UTC
Message-ID
<20987dc6-e0c7-6ca2-19fd-2b323b3f6d9f@web.de>
In-Reply-To
<fead25d6-6f5f-487a-ad4c-0657fe9785fd@www.fastmail.com>

When a run command cannot be executed or found, shells return exit code 126 or 127, respectively. Valid run commands are allowed to return these codes as well to indicate bad revisions, though, for historical reasons. This means typos can cause bogus bisect runs that go over the full distance and end up reporting invalid results.

The best solution would be to reserve exit codes 126 and 127, like 71b0251cdd (Bisect run: "skip" current commit if script exit code is 125., 2007-10-26) did for 125, and abort bisect run when we get them. That might be inconvenient for those who relied on the documentation stating that 126 and 127 can be used for bad revisions, though.

The workaround used by this patch is to run the command on a known-good revision and abort if we still get the same error code. This adds one step to runs with scripts that use exit codes 126 and 127, but keeps them supported, with one exception: It won't work with commands that cannot recognize the (manually marked) known-good revision as such.

Run commands that use low exit codes are unaffected. Typos are reported after executing the missing command twice and three checkouts (the first step, the known good revision and back to the revision of the first step).

Signed-off-by: René Scharfe <l.s.r@web.de>
---
 bisect.c                    |  3 +-
 bisect.h                    |  3 ++
 builtin/bisect--helper.c    | 63 +++++++++++++++++++++++++++++++++++++
 t/t6030-bisect-porcelain.sh |  4 +--
 4 files changed, 70 insertions(+), 3 deletions(-)
diff --git a/bisect.c b/bisect.c
index 888949fba6..9e6a2b7f20 100644
--- a/bisect.c
+++ b/bisect.c
@@ -724,7 +724,8 @@ static int is_expected_rev(const struct object_id *oid)
 	return res;
 }

-static enum bisect_error bisect_checkout(const struct object_id *bisect_rev, int no_checkout)
+enum bisect_error bisect_checkout(const struct object_id *bisect_rev,
+				  int no_checkout)
 {
 	char bisect_rev_hex[GIT_MAX_HEXSZ + 1];
 	struct commit *commit;
diff --git a/bisect.h b/bisect.h
index ec24ac2d7e..748adf0cff 100644
--- a/bisect.h
+++ b/bisect.h
@@ -69,4 +69,7 @@ void read_bisect_terms(const char **bad, const char **good);

 int bisect_clean_state(void);

+enum bisect_error bisect_checkout(const struct object_id *bisect_rev,
+				  int no_checkout);
+
 #endif
diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
index e529665d9f..50783a586c 100644
--- a/builtin/bisect--helper.c
+++ b/builtin/bisect--helper.c
@@ -1089,6 +1089,44 @@ static int bisect_visualize(struct bisect_terms *terms, const char **argv, int a
 	return res;
 }

+static int get_first_good(const char *refname, const struct object_id *oid,
+			  int flag, void *cb_data)
+{
+	oidcpy(cb_data, oid);
+	return 1;
+}
+
+static int verify_good(const struct bisect_terms *terms,
+		       const char **quoted_argv)
+{
+	int rc;
+	enum bisect_error res;
+	struct object_id good_rev;
+	struct object_id current_rev;
+	char *good_glob = xstrfmt("%s-*", terms->term_good);
+	int no_checkout = ref_exists("BISECT_HEAD");
+
+	for_each_glob_ref_in(get_first_good, good_glob, "refs/bisect/",
+			     &good_rev);
+	free(good_glob);
+
+	if (read_ref(no_checkout ? "BISECT_HEAD" : "HEAD", &current_rev))
+		return -1;
+
+	res = bisect_checkout(&good_rev, no_checkout);
+	if (res != BISECT_OK)
+		return -1;
+
+	printf(_("running %s\n"), quoted_argv[0]);
+	rc = run_command_v_opt(quoted_argv, RUN_USING_SHELL);
+
+	res = bisect_checkout(&current_rev, no_checkout);
+	if (res != BISECT_OK)
+		return -1;
+
+	return rc;
+}
+
 static int bisect_run(struct bisect_terms *terms, const char **argv, int argc)
 {
 	int res = BISECT_OK;
@@ -1096,6 +1134,7 @@ static int bisect_run(struct bisect_terms *terms, const char **argv, int argc)
 	struct strvec run_args = STRVEC_INIT;
 	const char *new_state;
 	int temporary_stdout_fd, saved_stdout;
+	int is_first_run = 1;

 	if (bisect_next_check(terms, NULL))
 		return BISECT_FAILED;
@@ -1113,6 +1152,30 @@ static int bisect_run(struct bisect_terms *terms, const char **argv, int argc)
 		printf(_("running %s\n"), command.buf);
 		res = run_command_v_opt(run_args.v, RUN_USING_SHELL);

+		/*
+		 * Exit code 126 and 127 can either come from the shell
+		 * if it was unable to execute or even find the script,
+		 * or from the script itself.  Check with a known-good
+		 * revision to avoid trashing the bisect run due to a
+		 * missing or non-executable script.
+		 */
+		if (is_first_run && (res == 126 || res == 127)) {
+			int rc = verify_good(terms, run_args.v);
+			is_first_run = 0;
+			if (rc < 0) {
+				error(_("unable to verify '%s' on good"
+					" revision"), command.buf);
+				res = BISECT_FAILED;
+				break;
+			}
+			if (rc == res) {
+				error(_("bogus exit code %d for good revision"),
+				      rc);
+				res = BISECT_FAILED;
+				break;
+			}
+		}
+
 		if (res < 0 || 128 <= res) {
 			error(_("bisect run failed: exit code %d from"
 				" '%s' is < 0 or >= 128"), res, command.buf);
diff --git a/t/t6030-bisect-porcelain.sh b/t/t6030-bisect-porcelain.sh
index fc18796517..5382e5d216 100755
--- a/t/t6030-bisect-porcelain.sh
+++ b/t/t6030-bisect-porcelain.sh
@@ -290,7 +290,7 @@ test_expect_success 'bisect run accepts exit code 126 as bad' '
 	grep "$HASH3 is the first bad commit" my_bisect_log.txt
 '

-test_expect_failure POSIXPERM 'bisect run fails with non-executable test script' '
+test_expect_success POSIXPERM 'bisect run fails with non-executable test script' '
 	test_when_finished "git bisect reset" &&
 	>not-executable.sh &&
 	chmod -x not-executable.sh &&
@@ -313,7 +313,7 @@ test_expect_success 'bisect run accepts exit code 127 as bad' '
 	grep "$HASH3 is the first bad commit" my_bisect_log.txt
 '

-test_expect_failure 'bisect run fails with missing test script' '
+test_expect_success 'bisect run fails with missing test script' '
 	test_when_finished "git bisect reset" &&
 	rm -f does-not-exist.sh &&
 	git bisect start &&
--
2.34.1
Previous: René ScharfeNext: Junio C Hamano
Message 24 of 31 in “git bisect bad @”
  1. Ramkumar RamachandraJan 9, 2022
  2. Junio C HamanoJan 9, 2022
  3. Ramkumar RamachandraJan 9, 2022
  4. bisect: report actual bisect_state() argument on errorRené Scharfe, Jan 10, 2022
  5. Ramkumar RamachandraJan 10, 2022
  6. Junio C HamanoJan 10, 2022
  7. Ramkumar RamachandraJan 10, 2022
  8. René ScharfeJan 12, 2022
  9. Junio C HamanoJan 12, 2022
  10. René ScharfeJan 12, 2022
  11. René ScharfeJan 13, 2022
  12. Ramkumar RamachandraJan 13, 2022
  13. Christian CouderJan 13, 2022
  14. René ScharfeJan 13, 2022
  15. Ramkumar RamachandraJan 13, 2022
  16. René ScharfeJan 14, 2022
  17. Ramkumar RamachandraJan 14, 2022
  18. René ScharfeJan 18, 2022
  19. Junio C HamanoJan 14, 2022
  20. Junio C HamanoJan 13, 2022
  21. 1/4 bisect--helper: report actual bisect_state() argument on errorRené Scharfe, Jan 18, 2022
  22. 2/4 bisect--helper: release strbuf and strvec on run errorRené Scharfe, Jan 18, 2022
  23. 3/4 bisect: document run behavior with exit codes 126 and 127René Scharfe, Jan 18, 2022
  24. 4/4 bisect--helper: double-check run command on exit code 126 and 127René Scharfe, Jan 18, 2022
  25. Junio C HamanoJan 19, 2022
  26. René ScharfeJan 19, 2022
  27. Junio C HamanoFeb 4, 2022
  28. René ScharfeFeb 4, 2022
  29. Ramkumar RamachandraFeb 4, 2022
  30. Junio C HamanoFeb 4, 2022
  31. Ramkumar RamachandraFeb 4, 2022

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