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From: David Kastrup <dak@gnu•org>
To: git@vger•kernel.org
Subject: Re: [PATCH] builtin/blame.c::prepare_lines: fix allocation size of sb->lineno
Date: Sat, 08 Feb 2014 10:49:40 +0100	[thread overview]
Message-ID: <87lhxmc4sr.fsf@fencepost.gnu.org> (raw)
In-Reply-To: <1391851166-10393-1-git-send-email-dak@gnu.org> (David Kastrup's message of "Sat, 8 Feb 2014 10:19:26 +0100")

David Kastrup <dak@gnu•org> writes:

> If we are calling xrealloc on every single line, the least we can do
> is get the right allocation size.
>
> Signed-off-by: David Kastrup <dak@gnu•org>
> ---
> This should be less contentious than the patch in
> <URL:http://permalink.gmane.org/gmane.comp.version-control.git/241561>,
> Message-ID: <1391550392-17118-1-git-send-email-dak@gnu•org> as it
> makes no stylistic decisions whatsoever and only fixes a clear bug.
>
> builtin/blame.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/builtin/blame.c b/builtin/blame.c
> index e44a6bb..29eb31c 100644
> --- a/builtin/blame.c
> +++ b/builtin/blame.c
> @@ -1779,7 +1779,7 @@ static int prepare_lines(struct scoreboard *sb)
>  	while (len--) {
>  		if (bol) {
>  			sb->lineno = xrealloc(sb->lineno,
> -					      sizeof(int *) * (num + 1));
> +					      sizeof(int) * (num + 1));

But please note that since sb->lineno originally comes from a zeroed
memory area and is passed to xrealloc, this requires that after

int *p;
memset(&p, 0, sizeof(p));

the equivalence

((void *)p == NULL)

will hold.  While this is true on most platforms, and while the C
standard guarantees the slightly different
((void *)0 == NULL)
is true, it makes no statement concerning the memory representation of
the NULL pointer.

I have not bothered addressing this non-compliance with the C standard
as it would be polishing a turd.  A wholesale replacement has already
been proposed, and it's likely that this assumption is prevalent in the
Git codebase elsewhere anyway.

-- 
David Kastrup

next prev parent reply	other threads:[~2014-02-08  9:49 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-02-08  9:19 [PATCH] builtin/blame.c::prepare_lines: fix allocation size of sb->lineno David Kastrup
2014-02-08  9:49 ` David Kastrup [this message]
2014-02-08 21:21   ` Jeff King
2014-02-08 21:34     ` David Kastrup

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