From: Richard Biener <rguenther@suse.de>
To: Bernd Edlinger <bernd.edlinger@hotmail.de>,Florian Weimer
<fweimer@redhat.com>,Jakub Jelinek <jakub@redhat.com>
Cc: Jonathan Wakely <jwakely@redhat.com>,GCC Patches
<gcc-patches@gcc.gnu.org>,Jason Merrill <jason@redhat.com>,Jeff
Law <law@redhat.com>
Subject: Re: [PATCH] Add a new type attribute always_alias (PR79671)
Date: Thu, 06 Apr 2017 19:14:00 -0000 [thread overview]
Message-ID: <0793C086-9DA4-4B21-9239-932916CAFF6B@suse.de> (raw)
In-Reply-To: <AM4PR0701MB2162C4BFB925AF1D4368AD2CE40D0@AM4PR0701MB2162.eurprd07.prod.outlook.com>
On April 6, 2017 7:39:14 PM GMT+02:00, Bernd Edlinger <bernd.edlinger@hotmail.de> wrote:
>On 04/06/17 16:17, Florian Weimer wrote:
>>> Here is what I want to write in the doc:
>>>
>>> @item typeless_storage
>>> @cindex @code{typeless_storage} type attribute
>>> A type declared with this attribute behaves like a character type
>>> with respect to aliasing semantics.
>>> This is attribute is similar to the @code{may_alias} attribute,
>>> except that it is not restricted to pointers.
>>
>> As Jakub pointed out, this is not what we need here. An object of
>type
>> char does *not* have untyped storage. Accessing it as a different
>type
>> is still undefined.
>>
>
>but, do you agree that this is valid in C11?
>
>typedef char char_a[4];
>
>int
>main (void)
>{
> char_a a = {1,2,3,4};
> short *b = (short *) &a;
>
> b[1] = 0;
>
> if (a[0] == 1 && a[1] == 2 && a[2] == 3 && a[3] == 4)
> abort();
>
> exit(0);
>}
>
>
>all I want to do is replace "char" with a different type.
Why?
Richard.
>Bernd.
>
>> The documentation says that the memory region is considered to by
>> untyped, like a memory region returned by malloc (but obviously not
>with
>> the implication that the memory region is separated from everything
>else).
>>
>> Thanks,
>> Florian
next prev parent reply other threads:[~2017-04-06 19:14 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-05 9:46 Bernd Edlinger
2017-04-05 13:28 ` Jakub Jelinek
2017-04-05 15:20 ` Richard Biener
2017-04-05 17:41 ` Bernd Edlinger
2017-04-05 20:18 ` Jason Merrill
2017-04-05 20:46 ` Bernd Edlinger
2017-04-05 22:54 ` Pedro Alves
2017-04-06 10:08 ` Jonathan Wakely
2017-04-06 7:23 ` Richard Biener
2017-04-05 15:27 ` Bernd Edlinger
2017-04-05 15:29 ` Jakub Jelinek
2017-04-05 14:50 ` Florian Weimer
2017-04-05 15:23 ` Richard Biener
2017-04-05 15:38 ` Bernd Edlinger
2017-04-05 16:03 ` Jonathan Wakely
2017-04-05 16:08 ` Jakub Jelinek
2017-04-05 17:23 ` Bernd Edlinger
2017-04-05 21:02 ` Bernd Edlinger
2017-04-05 23:17 ` Sandra Loosemore
2017-04-06 5:40 ` Jakub Jelinek
2017-04-06 7:47 ` Richard Biener
2017-04-06 7:51 ` Jakub Jelinek
2017-04-06 7:55 ` Richard Biener
2017-04-06 14:11 ` Bernd Edlinger
2017-04-06 14:17 ` Florian Weimer
2017-04-06 14:23 ` Richard Biener
2017-04-06 14:43 ` Jonathan Wakely
2017-04-06 14:51 ` Florian Weimer
2017-04-06 15:05 ` Jakub Jelinek
2017-04-06 15:10 ` Florian Weimer
2017-04-06 19:13 ` Richard Biener
2017-04-11 10:43 ` Florian Weimer
2017-04-11 10:48 ` Richard Biener
2017-04-06 17:39 ` Bernd Edlinger
2017-04-06 17:48 ` Florian Weimer
2017-04-06 18:12 ` Bernd Edlinger
2017-04-06 18:19 ` Florian Weimer
2017-04-06 18:49 ` Bernd Edlinger
2017-04-06 19:05 ` Florian Weimer
2017-04-06 19:20 ` Bernd Edlinger
2017-04-07 6:47 ` Richard Biener
2017-04-07 12:58 ` Bernd Edlinger
2017-04-06 19:16 ` Richard Biener
2017-04-07 6:56 ` Florian Weimer
2017-04-07 8:01 ` Richard Biener
2017-04-06 19:14 ` Richard Biener [this message]
2017-04-06 19:51 ` Bernd Edlinger
2017-04-06 14:22 ` Richard Biener
2017-04-06 21:00 ` Bernd Edlinger
2017-04-07 6:54 ` Richard Biener
2017-04-07 13:37 ` Bernd Edlinger
2017-04-07 15:10 ` Richard Biener
2017-04-07 15:33 ` Bernd Edlinger
2017-04-07 20:22 ` Jason Merrill
2017-04-10 12:50 ` Richard Biener
2017-04-10 14:41 ` Jason Merrill
2017-04-10 15:31 ` Richard Biener
2017-04-10 16:35 ` Jason Merrill
2017-04-11 10:32 ` Richard Biener
2017-04-11 11:53 ` Richard Biener
2017-04-11 13:35 ` Richard Biener
2017-04-11 18:47 ` Jason Merrill
2017-04-10 21:40 ` Pedro Alves
2017-04-11 7:37 ` Richard Biener
2017-04-06 20:20 ` Bernd Edlinger
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