Re: [bug-patch] two different hunks erroneously get applied to the very same spot

[Benno Schulenberg]

Andreas,

Op  4-09-2017 om 14:15 schreef Andreas Grünbacher:
> I'm getting the following result with current patch, which differs
> from what you are getting:
>
> $ patch -i goes-wrong.patch -o testor.c.out testor.c
> patching file testor.c.out (read from testor.c)
> Hunk #1 succeeded at 7 with fuzz 1.
> Hunk #2 succeeded at 56 with fuzz 2 (offset 8 lines).

That is what I get when I apply the patch a second time.  I'm pretty
sure your testor.c file has already been patched/modified -- because
if not, and the first hunk applies with fuzz 1, the second one should
apply with no fuzz and offset 0 lines.  The offset of 8 lines means
that already two hunks of 4 lines have been inserted.

The original testor.c has this:
$ wc testor.c
  95  388 2719 testor.c

> The algorithm patch uses for matching hunks is rather crude: it tries
> to match a hunk anywhere in the file with fuzz 0, then with fuzz 1,
> etc. When a hunk matches, it is applied and the remaining hunks are
> matched against the rest of the file (that is, the second hunk will
> not be applied before the first one). There is no global optimization
> of fuzz or anything like that. When a patch applies with fuzz, it is
> best to check the result rather than relying on patch to do the right
> thing.
>
> Apart from fixing bugs, we cannot easily change this behavior: people
> have come to expect patch to behave the way it does.

I know.  I was merely "philosophying".  :)

Benno