threads / patch / 65072

patchfetch: fix wrong evaluation order in URL trailing-slash trimming

Subject: [PATCH] fetch: fix wrong evaluation order in URL trailing-slash trimming

## tl;dr

3 messages between Feb 25, 2026 and Feb 25, 2026. Diffs are folded; open one to read it.

replies: 2people: 3as markdown or json

cui via GitGitGadget· Feb 25, 2026, 02:00 UTC · lore
From: cuiweixie <cuiweixie@gmail.com>
if i == -1, url[i] will be UB.
Signed-off-by: cuiweixie <cuiweixie@gmail.com>
---
    fetch: fix wrong evaluation order in URL trailing-slash trimming
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2211%2Fcuiweixie%2Fbugfix-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2211/cuiweixie/bugfix-v1
Pull-Request: https://github.com/git/git/pull/2211
 builtin/fetch.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
Show changes to builtin/fetch.c +1 −1
diff --git a/builtin/fetch.c b/builtin/fetch.c
index a3bc7e9380..306138c6e5 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -722,7 +722,7 @@ static void display_state_init(struct display_state *display_state, struct ref *
 		display_state->url = xstrdup("foreign");
 
 	display_state->url_len = strlen(display_state->url);
-	for (i = display_state->url_len - 1; display_state->url[i] == '/' && 0 <= i; i--)
+	for (i = display_state->url_len - 1; 0 <= i && display_state->url[i] == '/'; i--)
 		;
 	display_state->url_len = i + 1;
 	if (4 < i && !strncmp(".git", display_state->url + i - 3, 4))

base-commit: 7c02d39fc2ed2702223c7674f73150d9a7e61ba4
-- 
gitgitgadget
Jeff King· Feb 25, 2026, 14:10 UTC · re: cui via GitGitGadget · lore

Re: [PATCH] fetch: fix wrong evaluation order in URL trailing-slash trimming

On Wed, Feb 25, 2026 at 02:00:57AM +0000, cui via GitGitGadget wrote:
Show 8 quoted lines
> if i == -1, url[i] will be UB.
> [...]
>  	display_state->url_len = strlen(display_state->url);
> -	for (i = display_state->url_len - 1; display_state->url[i] == '/' && 0 <= i; i--)
> +	for (i = display_state->url_len - 1; 0 <= i && display_state->url[i] == '/'; i--)
>  		;
>  	display_state->url_len = i + 1;
>  	if (4 < i && !strncmp(".git", display_state->url + i - 3, 4))

Yeah, the original is obviously nonsense. Probably it is not worth too much effort to add a test here, but I wondered if this can even be triggered in practice.

We would hit it when there is no non-slash character in the URL. I'm not sure it's possible to get this far with that, but it makes sense to me to write it as you have.

I can't help but think this would be easier to read without an empty loop body, like:

  for (len = strlen(display_state->url); len > 0; len--) {
	if (display_state->url[len-1] != '/')
		break;
  }

which makes it much more clear we never leave the bounds of the string (and also works with a size_t, which is a more appropriate type than int here).

But it may not be worth polishing this bit of code too much (if we did, I'd also suggest strip_suffix_mem() to drop ".git" rather than all of those magic numbers. Or even stuffing it in a strbuf and using strbuf_setlen() and strbuf_strip_suffix().

But anyway, your patch seems like an obvious improvement in the meantime.

-Peff
Junio C Hamano· Feb 25, 2026, 15:36 UTC · re: Jeff King · lore

Re: [PATCH] fetch: fix wrong evaluation order in URL trailing-slash trimming

Jeff King <peff@peff.net> writes:
Show 11 quoted lines
> I can't help but think this would be easier to read without an empty
> loop body, like:
>
>   for (len = strlen(display_state->url); len > 0; len--) {
> 	if (display_state->url[len-1] != '/')
> 		break;
>   }
>
> which makes it much more clear we never leave the bounds of the string
> (and also works with a size_t, which is a more appropriate type than int
> here).

Yes, this is vastly more readable, even though what it does is exactly the same as the original.

Or instead of having strlen() to scan the entire string once and then ourselves scan backwards from the end, scan forward ourselves only once while noting where the last non-slash byte was, or something.

> But it may not be worth polishing this bit of code too much (if we did,
> I'd also suggest strip_suffix_mem() to drop ".git" rather than all of
> those magic numbers. Or even stuffing it in a strbuf and using
> strbuf_setlen() and strbuf_strip_suffix().

True. None of these "we could do it this way too" bikeshedding has much value. The patch posted is an obvious and trivial enough improvement.

Thanks.

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