Re: [RFC PATCH 09/15] add-patch: assert parse_diff() expectations with BUG()

> On 03 June 2022 at 19:37 Ævar Arnfjörð Bjarmason <avarab@gmail.com> wrote:
> 
> 
> Assert that this code added in [1], [2] and other related commits
> expects that once we see a "diff " line we should have a non-NULL
> "file_diff" and "hunk".
> 
> In practice this would have always been the case, as we are parsing
> our own "diff" output, but e.g. GCC v12's -fanalyzer doesn't know
> that, and will alert us that in the "else if" and below in this
> function we could be dereferencing NULL if we were processing anything
> except our expected input.

> 1. f6aa7ecc343 (built-in add -i: start implementing the `patch`
>    functionality in C, 2019-12-13)
> 2. 80399aec5ab (built-in add -p: support multi-file diffs, 2019-12-13)
> 
> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
> ---
>  add-patch.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/add-patch.c b/add-patch.c
> index 55d719f7845..087bf317b07 100644
> --- a/add-patch.c
> +++ b/add-patch.c
> @@ -478,11 +478,16 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
>  	while (p != pend) {
>  		char *eol = memchr(p, '\n', pend - p);
>  		const char *deleted = NULL, *mode_change = NULL;
> +		const char *const diff_l = "diff ";
> +		int is_diff_line = starts_with(p, diff_l);
>  
>  		if (!eol)
>  			eol = pend;
>  
> -		if (starts_with(p, "diff ")) {
> +		if (!is_diff_line && (!file_diff || !hunk))
> +			BUG("expected '%s' line to follow a '%s' line", p, diff_l);
> +
> +		if (is_diff_line) {
>  			complete_file(marker, hunk);
>  			ALLOC_GROW_BY(s->file_diff, s->file_diff_nr, 1,
>  				   file_diff_alloc);
> -- 
> 2.36.1.1124.g577fa9c2ebd
>