Bad error message

Robin Rosenberg (list subscriber)· May 4, 2006, 23:57 UTC · lore

Hi,

While playing with git I got the following "impossible" error message:

$ git commit --amend fatal: Ref HEAD is at 3cec3036287d6b24f7ad7f724f8bb9d4032fb1a3 but expected 3cec3036287d6b24f7ad7f724f8bb9d4032fb1a3

Since impossible things happen rarely, I was somewhat puzzled and it turned out not to be so impossible after all, but a rather typical C bug. Since I fixed my working directory using git-reset, I'm not sure how to verify the code (suggestions welcome), but I'm not sure if that's important since the code being replaced by this patch probably wasn't tested either. :/

Maybe someone could explain what might have been wrong with my work space (git status turned up nothing wrong or missing).

-- robin

--- git-1.3.1.orig/update-ref.c 2006-04-25 08:07:54.000000000 +0200 +++ git-1.3.1/update-ref.c 2006-05-04 16:30:04.000000000 +0200

@@ -43,8 +43,13 @@
                die("No such ref: %s", refname);

        if (oldval) {
-               if (memcmp(currsha1, oldsha1, 20))
-                       die("Ref %s is at %s but expected %s", refname, sha1_to_hex(currsha1), sha1_to_hex(oldsha1));
+               if (memcmp(currsha1, oldsha1, 20)) {
+                       char sha1str1[41];
+                       char sha1str2[41];
+                       strcpy(sha1str1, sha1_to_hex(currsha1));
+                       strcpy(sha1str2, sha1_to_hex(oldsha1));
+                       die("Ref %s is at %s but expected %s", refname, sha1str1, sha1str2);
+               }
                /* Nothing to do? */
                if (!memcmp(oldsha1, sha1, 20))
                        exit(0);

Junio C Hamano· May 5, 2006, 00:20 UTC · re: Robin Rosenberg (list subscriber) · lore

Re: Bad error message

"Robin Rosenberg (list subscriber)"  <robin.rosenberg.lists@dewire.com> writes:

Show 13 quoted lines

> @@ -43,8 +43,13 @@
>                 die("No such ref: %s", refname);
>
>         if (oldval) {
> -               if (memcmp(currsha1, oldsha1, 20))
> -                       die("Ref %s is at %s but expected %s", refname, sha1_to_hex(currsha1), sha1_to_hex(oldsha1));
> +               if (memcmp(currsha1, oldsha1, 20)) {
> +                       char sha1str1[41];
> +                       char sha1str2[41];
> +                       strcpy(sha1str1, sha1_to_hex(currsha1));
> +                       strcpy(sha1str2, sha1_to_hex(oldsha1));
> +                       die("Ref %s is at %s but expected %s", refname, sha1str1, sha1str2);
> +               }

Your patch looks correct, but probably is made unnecessary with the "you can use up to 4 sha1_to_hex() safely" patch Linus did.

We have it in "master" and my plan is to cherry-pick it to "maint" branch and included it in the next stale release 1.3.3, along with core.prefersymlinkrefs patch also only in "master", if we do not hear somebody scream in the next few days.