From: Segher Boessenkool <segher@kernel.crashing.org>
To: Adrian Moreno <amorenoz@redhat.com>
Cc: Stefan Ring <stefanrin@gmail.com>, gcc-help <gcc-help@gcc.gnu.org>
Subject: Re: broken code only when optimized "-O2"
Date: Tue, 21 Dec 2021 10:39:50 -0600 [thread overview]
Message-ID: <20211221163950.GA614@gate.crashing.org> (raw)
In-Reply-To: <0210178a-c875-fcbd-009f-5f438a098709@redhat.com>
On Tue, Dec 21, 2021 at 05:13:08PM +0100, Adrian Moreno via Gcc-help wrote:
> On 12/21/21 17:05, Stefan Ring wrote:
> >On Tue, Dec 21, 2021 at 4:40 PM Adrian Moreno via Gcc-help
> ><gcc-help@gcc.gnu.org> wrote:
> >>
> >>I'd really appreciate any hint or idea to try to understand this problem.
> >
> >I guess the compiler doesn't like the dereferencing of uninitialized
> >pointers (in the sizeof expressions). I am not 100% sure that this
> >counts as dereferencing, but I would assume so. Because of this the
> >compiler will be free to behave however it likes to.
>
> I agree that doesn't look good. Replacing them by sizeof (struct ___)
> expressions does not change the behavior though.
As required by C. 6.3.2.1/2:
Except when it is the operand of the sizeof operator, [...], an lvalue
that does not have array type is converted to the value stored in the
designated object (and is no longer an lvalue); this is called lvalue
conversion.
There is no dereferencing.
Segher
next prev parent reply other threads:[~2021-12-21 16:40 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-21 15:40 Adrian Moreno
2021-12-21 16:05 ` Stefan Ring
2021-12-21 16:13 ` Adrian Moreno
2021-12-21 16:39 ` Segher Boessenkool [this message]
2021-12-21 17:05 ` David Brown
2021-12-22 9:24 ` Adrian Moreno
2021-12-22 10:27 ` Florian Weimer
2021-12-22 10:34 ` Adrian Moreno
2021-12-22 10:36 ` Xi Ruoyao
2021-12-22 16:05 ` Adrian Moreno
2021-12-22 15:32 ` LIU Hao
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