From: David Brown <david@westcontrol.com>
To: gcc@gcc.gnu.org
Subject: Re: Volatile qualification on pointer and data
Date: Wed, 21 Sep 2011 10:20:00 -0000 [thread overview]
Message-ID: <j5cdok$3ol$1@dough.gmane.org> (raw)
In-Reply-To: <j5c6qa$jcm$1@dough.gmane.org>
On 21/09/2011 10:21, Paulo J. Matos wrote:
> On 21/09/11 08:03, David Brown wrote:
>> Asking to read it by a volatile read does not
>> change the nature of "foo" - the compiler can still implement it as a
>> compile-time constant.
>
> But since I am accessing the data through the pointer and the pointer
> qualifies the data as volatile, shouldn't the compiler avoid this kind
> of optimization for reads through the pointer?
>
My thought is that the nature of "foo" is independent of how it is
accessed. On the other hand, some uses of a variable will affect its
implementation - if you take the address of "foo" and pass that on to an
external function or data, then the compiler would have to generate
"foo" in memory (but in read-only memory, and it can still assume its
value does not change). So I am not sure what the "correct" behaviour
is here - I merely ask the question.
Fortunately, this situation is not going to occur in real code.
> It still is a regression from GCC45, however it might be considered a
> feature instead of a bug as I already mentioned to Ian.
>
next prev parent reply other threads:[~2011-09-21 10:20 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-20 16:08 Paulo J. Matos
2011-09-20 16:36 ` Ian Lance Taylor
2011-09-21 7:07 ` David Brown
2011-09-21 8:22 ` Paulo J. Matos
2011-09-21 10:20 ` David Brown [this message]
2011-09-21 13:57 ` Ian Lance Taylor
2011-09-21 14:25 ` David Brown
2011-09-21 14:57 ` Paulo J. Matos
2011-09-22 8:39 ` David Brown
2011-09-22 21:15 ` Richard Guenther
2011-09-23 11:33 ` Paulo J. Matos
2011-09-23 11:51 ` Paulo J. Matos
2011-09-23 13:17 ` Paulo J. Matos
2011-09-21 18:51 ` Georg-Johann Lay
2011-09-22 8:53 ` David Brown
2011-09-24 15:10 ` John Regehr
2011-09-24 15:49 ` David Brown
2011-09-24 16:26 ` David Brown
2011-09-24 19:38 ` John Regehr
2011-09-25 13:03 ` David Brown
2011-09-25 15:15 ` Andreas Schwab
2011-09-25 16:33 ` David Brown
2011-09-25 16:36 ` David Brown
2011-09-25 16:06 ` Dave Korn
2011-09-25 22:05 ` David Brown
2011-09-25 22:05 ` David Brown
2011-09-26 7:14 ` Miles Bader
2011-09-26 8:53 ` David Brown
2011-09-26 8:58 ` David Brown
2011-09-21 8:14 ` Paulo J. Matos
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