From: Junio C Hamano <gitster@pobox.com>
Date: Fri, 23 Oct 2026 15:30:29 GMT
Subject: Re: [PATCH] [Outreachy PATCH] diff-delta: use safe integer arithmetic
Message-ID: <xmqqtsmca0yy.fsf@gitster.g>
In-Reply-To: <CABh_KWiKmXP4KTgF=k2gGdSvcZXkRipD61AVn+AS7ZgvhcjHWw@mail.gmail.com>

Srujith Poojary <poojarysrujith@gmail.com> writes:

> 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.

Please don't, before making sure if it can overflow.  With the
number of entries capped like this:

	if (bufsize >= 0xffffffffUL)
		entries = 0xfffffffeU / RABIN_WINDOW;

and then computed

	hsize = entries / 4;
	for (i = 4; (1u << i) < hsize; i++);
	hsize = 1 << i;
	/* allocate lookup index */
	memsize = sizeof(*hash) * hsize +
		  sizeof(*entry) * entries;

it may not be possible to overflow size_t even on 32-bit platforms.
I didn't have time to do math yet myself, though.