Re: Possible segfault introduced in commit.c

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Am 25.04.2012 13:14, schrieb Jeff King:
On Wed, Apr 25, 2012 at 12:59:28AM -0700, Michael Mueller wrote:

As you might already know, we analyze git regularly with Sentry (our
static analysis tool).  Today it picked up a new NULL pointer
dereference in commit.c:366:

     void commit_list_reverse(struct commit_list **list_p)
         struct commit_list *prev = NULL, *curr = *list_p, *next;

         if (!list_p)
         /* function continues... */

list_p is dereferenced on the first line, then tested for NULL on
the very next statement.  If it's possible that list_p is NULL, this
will be a segfault.  If it can't be NULL, then the check is
unnecessary (and probably misleading).

Yes, you're right. There is only one caller currently, and it can never
be NULL (it passes the address-of a pointer variable). I think dropping
the NULL-check is the right thing; even an empty list will still have a
pointer to its NULL head.

More often then not, a mistake like that is surrounded by other issues. No, I didn't put it there intentionally to prove this point. ;-)

Having to reverse the list at all is unfortunate and I only did that because I thought appending would be more complicated and because we are going to replace the linked list with a different data structure soon anyway. Turns out appending is easy. Patches to follow.

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