From: Junio C Hamano <gitster@pobox.com>
Date: Fri, 19 Aug 2011 06:22:12 GMT
Subject: Re: [PATCH 1/1] clone: replace relative paths in the alternates
Message-ID: <7vy5yp53aj.fsf@alter.siamese.dyndns.org>
In-Reply-To: <1313731396-10458-2-git-send-email-jason77.wang@gmail.com>

Hui Wang <jason77.wang@gmail.com> writes:

> +	mapsz = xsize_t(st.st_size);
> +	map = xmmap(NULL, mapsz, PROT_READ, MAP_PRIVATE, fd, 0);
> +	close(fd);
> +
> +	tmpbuf = mapsz > 4096 ? xmalloc(mapsz * 2) : xmalloc(mapsz + 4096);

Where do these magic numbers come from, and what guarantee do we have that
these magic numbers give safe upper bound for pathnames that are expanded
to be absolute?

Wouldn't it be a lot cleaner and much less error prone if you open the
original, read from it with strbuf_readline(), convert the path using
strbuf manipulation functions and write the resulting line out to the
lockfile you obtained to update it, line by line?