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From: Duy Nguyen <pclouds@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: René Scharfe <l.s.r@web.de>, Git List <git@vger.kernel.org>,
	Johannes Schindelin <johannes.schindelin@gmx.de>
Subject: Re: [PATCH] fast-export: avoid NULL pointer arithmetic
Date: Fri, 11 May 2018 08:19:59 +0200
Message-ID: <CACsJy8AN4nssu1+x0x9Kmz1BB1aXO7_UBFCjpyULMeC5K-Fzvw@mail.gmail.com> (raw)
In-Reply-To: <xmqq7eoahk49.fsf@gitster-ct.c.googlers.com>

On Fri, May 11, 2018 at 6:49 AM, Junio C Hamano <gitster@pobox.com> wrote:
> Junio C Hamano <gitster@pobox.com> writes:
>
>> René Scharfe <l.s.r@web.de> writes:
>>
>>>> But it somehow feels backwards in spirit to me, as the reason why we
>>>> use "void *" there in the decoration field is because we expect that
>>>> we'd have a pointer to some struture most of the time, and we have
>>>> to occasionally store a small integer there.
>>>
>>> Yes, fast-export seems to be the only place that stores an integer as
>>> a decoration.
>>
>> With the decoration subsystem that might be the case, but I think
>> we have other codepaths where "void * .util" field in the structure
>> is used to store (void *)1, expecting that a normal allocation will
>> never yield a pointer that is indistinguishable from that value.
>
> I was looking at a different topic and noticed that bisect.c uses
> commit->util (which is of type "void *") to always store an int (it
> never stores a pointer and there is no mixing).  This one is equally
> unportable as fast-export after your fix.
>

In both cases we should be able to use commit-slab instead of
commit->util. We could go even further and kill "util" pointer but
that's more work.
-- 
Duy

  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-09 21:06 René Scharfe
2018-05-09 21:43 ` Johannes Schindelin
2018-05-10  9:24 ` René Scharfe
2018-05-10 10:51   ` Junio C Hamano
2018-05-10 19:47     ` René Scharfe
2018-05-11  2:16       ` Junio C Hamano
2018-05-11  4:49         ` Junio C Hamano
2018-05-11  6:19           ` Duy Nguyen [this message]
2018-05-11  8:56             ` Jeff King
2018-05-11 13:11               ` Duy Nguyen
2018-05-11 13:34                 ` Duy Nguyen
2018-05-11 17:42                   ` Jeff King
2018-05-12  8:45                     ` René Scharfe
2018-05-12  8:49                       ` René Scharfe
2018-05-14  1:37                       ` Junio C Hamano
2018-05-15 19:36                         ` René Scharfe

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