[poojarysrujith]

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[poojarysrujith]

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[gitgitgadget]

Submitted as pull.2276.git.1792727808109.gitgitgadget@gmail.com

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[gitgitgadget]

Submitted as pull.2276.v2.git.1792734993812.gitgitgadget@gmail.com

To fetch this version into FETCH_HEAD:

git fetch https://github.com/gitgitgadget/git/ pr-2276/poojarysrujith/c-refactor-target-name-v2

To fetch this version to local tag pr-2276/poojarysrujith/c-refactor-target-name-v2:

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[gitgitgadget]

Junio C Hamano wrote on the Git mailing list (how to reply to this email):

"Srujith A Poojary via GitGitGadget" <gitgitgadget@gmail.com>
writes:

> From: Srujith A Poojary <poojarysrujith@gmail.com>
>
> Replace manual multiplication and addition in create_delta_index()
> with safe integer helpers (st_mult, st_add, st_add3) to prevent
> overflows while preserving NULL returns on failure.

I do not quite understand what the last part of this explanation
wants to say, i.e., "while preserving NULL returns on failure".  It
makes it sound as if the function would return NULL if the integer
helpers detect integer overflow, but I do not think that is what
actually the updated code does at all.  st_add() and friends will
simply die() when overflow happens, so you will not even reach
malloc(), let alone return NULL when the malloc fails.

And if you reply to this review message, please do not top-post.

Thanks.

>
> Signed-off-by: Srujith A Poojary <poojarysrujith@gmail.com>
> ---
>     [Outreachy PATCH] diff-delta: use safe integer arithmetic
>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2276%2Fpoojarysrujith%2Fc-refactor-target-name-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2276/poojarysrujith/c-refactor-target-name-v1
> Pull-Request: https://github.com/gitgitgadget/git/pull/2276
>
>  diff-delta.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/diff-delta.c b/diff-delta.c
> index 7cbedeb507..45df070ab9 100644
> --- a/diff-delta.c
> +++ b/diff-delta.c
> @@ -162,8 +162,8 @@ struct delta_index * create_delta_index(const void *buf, size_t bufsize)
>  	hmask = hsize - 1;
>  
>  	/* allocate lookup index */
> -	memsize = sizeof(*hash) * hsize +
> -		  sizeof(*entry) * entries;
> +	memsize = st_add(st_mult(sizeof(*hash), hsize),
> +				st_mult(sizeof(*entry), entries));
>  	mem = malloc(memsize);
>  	if (!mem)
>  		return NULL;
> @@ -258,9 +258,9 @@ struct delta_index * create_delta_index(const void *buf, size_t bufsize)
>  	 * Now create the packed index in array form
>  	 * rather than linked lists.
>  	 */
> -	memsize = sizeof(*index)
> -		+ sizeof(*packed_hash) * (hsize+1)
> -		+ sizeof(*packed_entry) * entries;
> +	memsize = st_add3(sizeof(*index),
> +			st_mult(sizeof(*packed_hash), hsize + 1),
> +			st_mult(sizeof(*packed_entry), entries));
>  	mem = malloc(memsize);
>  	if (!mem) {
>  		free(hash);
>
> base-commit: 47fdf2208c5b94c8cc01c106b8f7c85efb91c926

[gitgitgadget]

Srujith Poojary wrote on the Git mailing list (how to reply to this email):

On Fri, Oct 23, 2026 at 10:34 AM Junio C Hamano <gitster@pobox.com> wrote:
>
> "Srujith A Poojary via GitGitGadget" <gitgitgadget@gmail.com>
> writes:
>
> > From: Srujith A Poojary <poojarysrujith@gmail.com>
> >
> > Replace manual multiplication and addition in create_delta_index()
> > with safe integer helpers (st_mult, st_add, st_add3) to prevent
> > overflows while preserving NULL returns on failure.
>
> I do not quite understand what the last part of this explanation
> wants to say, i.e., "while preserving NULL returns on failure".  It
> makes it sound as if the function would return NULL if the integer
> helpers detect integer overflow, but I do not think that is what
> actually the updated code does at all.  st_add() and friends will
> simply die() when overflow happens, so you will not even reach
> malloc(), let alone return NULL when the malloc fails.
>
> And if you reply to this review message, please do not top-post.
>
> Thanks.
>
> >
> > Signed-off-by: Srujith A Poojary <poojarysrujith@gmail.com>
> > ---
> >     [Outreachy PATCH] diff-delta: use safe integer arithmetic
> >
> > Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2276%2Fpoojarysrujith%2Fc-refactor-target-name-v1
> > Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2276/poojarysrujith/c-refactor-target-name-v1
> > Pull-Request: https://github.com/gitgitgadget/git/pull/2276
> >
> >  diff-delta.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/diff-delta.c b/diff-delta.c
> > index 7cbedeb507..45df070ab9 100644
> > --- a/diff-delta.c
> > +++ b/diff-delta.c
> > @@ -162,8 +162,8 @@ struct delta_index * create_delta_index(const void *buf, size_t bufsize)
> >       hmask = hsize - 1;
> >
> >       /* allocate lookup index */
> > -     memsize = sizeof(*hash) * hsize +
> > -               sizeof(*entry) * entries;
> > +     memsize = st_add(st_mult(sizeof(*hash), hsize),
> > +                             st_mult(sizeof(*entry), entries));
> >       mem = malloc(memsize);
> >       if (!mem)
> >               return NULL;
> > @@ -258,9 +258,9 @@ struct delta_index * create_delta_index(const void *buf, size_t bufsize)
> >        * Now create the packed index in array form
> >        * rather than linked lists.
> >        */
> > -     memsize = sizeof(*index)
> > -             + sizeof(*packed_hash) * (hsize+1)
> > -             + sizeof(*packed_entry) * entries;
> > +     memsize = st_add3(sizeof(*index),
> > +                     st_mult(sizeof(*packed_hash), hsize + 1),
> > +                     st_mult(sizeof(*packed_entry), entries));
> >       mem = malloc(memsize);
> >       if (!mem) {
> >               free(hash);
> >
> > base-commit: 47fdf2208c5b94c8cc01c106b8f7c85efb91c926

Hi Junio,

Thank you for clarifying this. You are right—st_add() and st_mult()
call die() on overflow rather than returning NULL.
I will update the commit message to accurately reflect this behavior
and submit v2.

Best regards,
Srujith