[PATCH v3 11/12] bisect: check get_terms return at all call sites

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

Six callers of get_terms() silently discard its return value. When
get_terms fails (missing or truncated BISECT_TERMS file), the term
strings remain NULL or empty, causing confusing downstream
behavior: commands like "bisect next" or "bisect run" proceed with
empty term strings, producing nonsensical ref names (refs/bisect/
with no suffix) and misleading error messages.

Let's not discard the return value, but handle an error with the same
message `bisect_terms()` already uses when reading the terms failed.

Pointed out by Coverity.

There is one slight complication here: One caller _needs_ the return
value to indicate an error when the `BISECT_TERMS` file is absent, all
the other call sites are totally okay with a "missing" `BISECT_TERMS`
file. To address that, extend the function signature of `get_terms()` to
indicate which behavior the caller wants.

Assisted-by: Claude Opus 4.6
Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 builtin/bisect.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/builtin/bisect.c b/builtin/bisect.c
index 69ab7ea248..ceb60b0626 100644
--- a/builtin/bisect.c
+++ b/builtin/bisect.c
@@ -485,7 +485,7 @@ static int bisect_next_check(const struct bisect_terms *terms,
 	return decide_next(terms, current_term, !state.nr_good, !state.nr_bad);
 }
 
-static int get_terms(struct bisect_terms *terms)
+static int get_terms(struct bisect_terms *terms, int file_missing_is_ok)
 {
 	struct strbuf str = STRBUF_INIT;
 	FILE *fp = NULL;
@@ -493,7 +493,7 @@ static int get_terms(struct bisect_terms *terms)
 
 	fp = fopen(git_path_bisect_terms(), "r");
 	if (!fp) {
-		res = -1;
+		res = file_missing_is_ok ? 0 : -1;
 		goto finish;
 	}
 
@@ -519,7 +519,7 @@ finish:
 
 static int bisect_terms(struct bisect_terms *terms, const char *option)
 {
-	if (get_terms(terms))
+	if (get_terms(terms, 0))
 		return error(_("no terms defined"));
 
 	if (!option) {
@@ -1057,7 +1057,8 @@ static int process_replay_line(struct bisect_terms *terms, struct strbuf *line)
 	rev = word_end + strspn(word_end, " \t");
 	*word_end = '\0'; /* NUL-terminate the word */
 
-	get_terms(terms);
+	if (get_terms(terms, 1))
+		return error(_("no terms defined"));
 	if (check_and_set_terms(terms, p))
 		return -1;
 
@@ -1383,7 +1384,8 @@ static int cmd_bisect__next(int argc, const char **argv UNUSED, const char *pref
 	if (argc)
 		return error(_("'%s' requires 0 arguments"),
 			     "git bisect next");
-	get_terms(&terms);
+	if (get_terms(&terms, 1))
+		return error(_("no terms defined"));
 	res = bisect_next(&terms, prefix);
 	free_terms(&terms);
 	return res;
@@ -1417,7 +1419,8 @@ static int cmd_bisect__skip(int argc, const char **argv, const char *prefix UNUS
 	struct bisect_terms terms = { 0 };
 
 	set_terms(&terms, "bad", "good");
-	get_terms(&terms);
+	if (get_terms(&terms, 1))
+		return error(_("no terms defined"));
 	res = bisect_skip(&terms, argc, argv);
 	free_terms(&terms);
 	return res;
@@ -1429,7 +1432,8 @@ static int cmd_bisect__visualize(int argc, const char **argv, const char *prefix
 	int res;
 	struct bisect_terms terms = { 0 };
 
-	get_terms(&terms);
+	if (get_terms(&terms, 1))
+		return error(_("no terms defined"));
 	res = bisect_visualize(&terms, argc, argv);
 	free_terms(&terms);
 	return res;
@@ -1443,7 +1447,8 @@ static int cmd_bisect__run(int argc, const char **argv, const char *prefix UNUSE
 
 	if (!argc)
 		return error(_("'%s' failed: no command provided."), "git bisect run");
-	get_terms(&terms);
+	if (get_terms(&terms, 1))
+		return error(_("no terms defined"));
 	res = bisect_run(&terms, argc, argv);
 	free_terms(&terms);
 	return res;
@@ -1482,7 +1487,8 @@ int cmd_bisect(int argc,
 			usage_with_options(git_bisect_usage, options);
 
 		set_terms(&terms, "bad", "good");
-		get_terms(&terms);
+		if (get_terms(&terms, 1))
+			return error(_("no terms defined"));
 		if (check_and_set_terms(&terms, argv[0]) ||
 		    !one_of(argv[0], terms.term_good, terms.term_bad, NULL))
 			usage_msg_optf(_("unknown command: '%s'"), git_bisect_usage,
-- 
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