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From: Christopher Li <sparse@chrisli.org>
To: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Linux-Sparse <linux-sparse@vger.kernel.org>,
	Dibyendu Majumdar <mobile@majumdar.org.uk>
Subject: Re: [PATCH] fix expansion of constant bitfield dereference
Date: Mon, 21 Aug 2017 12:46:00 -0400	[thread overview]
Message-ID: <CANeU7QkWUDxpmm2ZsAdNsa4OsP3xGUhyJfRaZYRRoWU_2orghQ@mail.gmail.com> (raw)
In-Reply-To: <CAMHZB6FaVescSVFrZK4x_=47Rs_zF=WNbgbSWhjgHhqUK9FXEw@mail.gmail.com>

On Mon, Aug 21, 2017 at 12:14 PM, Luc Van Oostenryck
<luc.vanoostenryck@gmail.com> wrote:
> On Mon, Aug 21, 2017 at 6:06 PM, Christopher Li <sparse@chrisli.org> wrote:
>>
>> I am referenitng to your email reply to Dibyendu:
>>
>> ===========================
>> It's a very surprising bug. It's not a linearization or
>> an optimization bug as the AST is already wrong.
>> With a simpler test case, like:
>>         struct s {
>>                 char a:4;
>>                 char b:4;
>>         };
>>
>>         int foo(void)
>>         {
>>                 struct s x = { .a = 2, .b = 4 };
>>
>>                 return x.b;
>>         }
>>
>> you can see that the linearization produce correct
>> code for the initializer.
>> You can also see that the return statement to be
>> linearized is something like
>>         STMT_RETURN
>>                 ret_value: EXPR_VALUE (value = 2)
>
>
> It's precisely this bug that this patch fixes.

Oh, I see. I misunderstand what bug the patch fix.
Let me go back to read it again.

Sorry about that.

Thanks for the explain.

Chris

      reply	other threads:[~2017-08-21 16:46 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-20 22:16 [PATCH] fix expansion of constant bitfield dereference Luc Van Oostenryck
2017-08-20 22:19 ` Dibyendu Majumdar
2017-08-21 12:26 ` Christopher Li
2017-08-21 13:32   ` Dibyendu Majumdar
2017-08-21 13:41     ` Christopher Li
2017-08-21 13:42   ` Luc Van Oostenryck
2017-08-21 16:06     ` Christopher Li
2017-08-21 16:14       ` Luc Van Oostenryck
2017-08-21 16:46         ` Christopher Li [this message]

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