From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeff King <peff@peff.net>
Subject: Re: [PATCH] general style: replaces memcmp() with proper
 starts_with()
Date: Thu, 13 Mar 2014 13:55:15 -0400
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Cc: David Kastrup <dak@gnu.org>,
	Quint Guvernator <quintus.public@gmail.com>,
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To: Junio C Hamano <gitster@pobox.com>
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On Thu, Mar 13, 2014 at 10:47:28AM -0700, Junio C Hamano wrote:

> >> --- a/builtin/cat-file.c
> >> +++ b/builtin/cat-file.c
> >> @@ -82,7 +82,7 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name)
> >>  				enum object_type type;
> >>  				unsigned long size;
> >>  				char *buffer = read_sha1_file(sha1, &type, &size);
> >> -				if (memcmp(buffer, "object ", 7) ||
> >> +				if (!starts_with(buffer, "object ") ||
> >
> > [...]
> >
> >> The original hunks show that the code knows and relies on magic
> >> numbers 7 and 8 very clearly and there are rooms for improvement.
> >
> > Like: what if the file is empty?
> 
> Yes.

I think this one is actually OK. The result of read_sha1_file is
NUL-terminated, and we know that starts_with reads byte-by-byte (the
prior memcmp is wrong, but only if you care about accessing bytes past
the end of the NUL).

That whole piece of code seems silly, though, IMHO. It should be using
parse_tag or peel_to_type.

-Peff