[PATCH v2 02/11] clean: do not pass strbuf by value
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Jul 31, 2025, 22:54 UTC
- Message-ID
- <20250731225433.4028872-3-gitster@pobox.com>
- In-Reply-To
- <20250731225433.4028872-1-gitster@pobox.com>
When you pass a structure by value, the callee can modify the contents of the structure that was passed in without having to worry about changing the structure the caller has. Passing structure by value sometimes (but not very often) can be a valid way to give callee a temporary variable it can freely modify.
But not a structure with members that are pointers, like a strbuf.
builtin/clean.c:list_and_choose() reads a line interactively from the user, and passes the line (in a strbuf) to parse_choice() by value, which then munges by replacing ',' with ' ' (to accept both comma and space separated list of choices). But because the strbuf passed by value still shares the underlying character array buf[], this ends up munging the caller's strbuf contents.
This is a catastrophe waiting to happen. If the callee causes the strbuf to be reallocated, the buf[] the caller has will become dangling, and when the caller does strbuf_release(), it would result in double-free.
Stop calling the function with misleading call-by-value with strbuf.
Signed-off-by: Junio C Hamano <gitster@pobox.com> --- builtin/clean.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/builtin/clean.c b/builtin/clean.c index 053c94fc6b..224551537e 100644 --- a/builtin/clean.c +++ b/builtin/clean.c @@ -477,7 +477,7 @@ static int find_unique(const char *choice, struct menu_stuff *menu_stuff) */ static int parse_choice(struct menu_stuff *menu_stuff, int is_single, - struct strbuf input, + struct strbuf *input, int **chosen) { struct strbuf **choice_list, **ptr; @@ -485,14 +485,14 @@ static int parse_choice(struct menu_stuff *menu_stuff, int i; if (is_single) { - choice_list = strbuf_split_max(&input, '\n', 0); + choice_list = strbuf_split_max(input, '\n', 0); } else { - char *p = input.buf; + char *p = input->buf; do { if (*p == ',') *p = ' '; } while (*p++); - choice_list = strbuf_split_max(&input, ' ', 0); + choice_list = strbuf_split_max(input, ' ', 0); } for (ptr = choice_list; *ptr; ptr++) { @@ -630,7 +630,7 @@ static int *list_and_choose(struct menu_opts *opts, struct menu_stuff *stuff) nr = parse_choice(stuff, opts->flags & MENU_OPTS_SINGLETON, - choice, + &choice, &chosen); if (opts->flags & MENU_OPTS_SINGLETON) {
-- 2.50.1-618-g45d530d26b