Subject: Re: [BUG?] git range-diff -Ix @{1}... segfaults

From: Junio C Hamano <[email-masked]>
Date: Tue, 07 Sep 2021 13:05:12 -0700

René Scharfe <[email-masked]> writes:

> range-diff.c::output() calls diff.c::diff_flush() in a loop with the
> same struct diff_options (via range-diff.c::patch_diff()).

Woooo, that's, eh, unexpected.

> So the second iteration of that loop tries to use the already freed
> ignore regexes.  Here's a patch for that:

Thanks.

>
> --- >8 ---
> Subject: [PATCH] range-diff: avoid segfault with -I
>
> output() reuses the same struct diff_options for multiple calls of
> diff_flush().  Set the option no_free to instruct it to keep the
> ignore regexes between calls and release them explicitly at the end.
>
> Signed-off-by: René Scharfe <[email-masked]>
> ---
> Test missing because I couldn't see any effect of -I on range-diff.

I wanted to omit my sign-off when comparing a previous series and
the new series (iow, I expected -I"^Signed-off-by: me" to apply to
the outer diff, not the inner "generation of patches to be compared").

>  range-diff.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/range-diff.c b/range-diff.c
> index e731525e66..cac89a2f4f 100644
> --- a/range-diff.c
> +++ b/range-diff.c
> @@ -482,6 +482,7 @@ static void output(struct string_list *a, struct string_list *b,
>  	else
>  		diff_setup(&opts);
>
> +	opts.no_free = 1;
>  	if (!opts.output_format)
>  		opts.output_format = DIFF_FORMAT_PATCH;
>  	opts.flags.suppress_diff_headers = 1;
> @@ -542,6 +543,8 @@ static void output(struct string_list *a, struct string_list *b,
>  	strbuf_release(&buf);
>  	strbuf_release(&dashes);
>  	strbuf_release(&indent);
> +	opts.no_free = 0;
> +	diff_free(&opts);
>  }
>
>  int show_range_diff(const char *range1, const char *range2,
> --
> 2.33.0