Re: [PATCH 2/5] http: use `size_t` for byte position in fwrite_sha1_file

From: Junio C Hamano <gitster@pobox.com>
Date: Oct 17, 2026, 04:11 UTC
Message-ID: <xmqqv771aruf.fsf@gitster.g>
In-Reply-To: <395b47c0-6dc7-4a1b-b547-e5e68e7356f5@hogyros.de>

Simon Richter <Simon.Richter@hogyros.de> writes:

Show 5 quoted lines

>> I agree that changing the type of posn from int to size_t is the
>> right move.
>
> It is a position in a file that is being read as binary data[1], so 
> off_t would be the best choice I think.

Interesting.

The function writes out eltsize * nmemb bytes (both of type size_t), which means the product could theoretically exceed the range of size_t. However, posn is used in xwrite() to offset into a contiguous in-core buffer starting at ptr:

        ssize_t retval = xwrite(freq->localfile,
                                (char *) ptr + posn,
                                size - posn);

Because we are indexing into an allocated in-core region, any valid offset must fit within size_t. If posn were to exceed the bounds of size_t, the pointer arithmetic ptr + posn would already be invalid. As posn only runs up to the allocation size of the region, it indeed should be measured in size_t, no?