From: Tom de Vries <tdevries@suse.de>
To: Pedro Alves <pedro@palves.net>, Andrew Burgess <aburgess@redhat.com>
Cc: gdb-patches@sourceware.org
Subject: Re: [PATCH] [gdb/testsuite] Fix gdb.arch/i386-avx.exp with clang
Date: Fri, 5 Nov 2021 14:35:20 +0100 [thread overview]
Message-ID: <4a98d0ce-b473-7a44-f399-3a604a5b2516@suse.de> (raw)
In-Reply-To: <a687a8a2-3f53-739c-a022-bc2029bb1d04@palves.net>
On 11/5/21 2:20 PM, Pedro Alves wrote:
> On 2021-11-05 13:15, Tom de Vries wrote:
>> On 11/5/21 1:55 PM, Pedro Alves wrote:
>>> On 2021-11-05 12:23, Tom de Vries via Gdb-patches wrote:
>>>
>>>>> No, but in gdb/testsuite/lib/attribute.h we do setup a compatibility
>>>>> macro for 'noclone', so there's definitely precedent for using
>>>>> attributes that might not be supported everywhere.
>>>>>
>>>>
>>>> Right, I'm aware of this, but that's a typical case where we have no
>>>> portable alternative.
>>>
>>> We actually do -- _Alignas is standard C11. This fixes the test as well:
>>>
>>> _Alignas(32) v8sf_t data[] =
>>>
>>
>> I was referring to the noclone, but ok, I was not aware of the _Alignas,
>> good to know, thanks.
>>
>> Anyway, in the latest version this is not relevant anymore, since the
>> precise alignment implementation has an extra benefit, as explained in
>> the post.
>>
>
> OOC, is that benefit important here?
>
So, this is the post I mentioned (
https://sourceware.org/pipermail/gdb-patches/2021-November/183183.html ).
Well, the benefit is that it prevents accidental overalignment, which is
the reason that this problem escaped detection and/or fixing for so long.
Without that, I could do a thinko and specify too small an alignment and
have the test passing accidentally, only to fail in a different setup.
Thanks,
- Tom
next prev parent reply other threads:[~2021-11-05 13:35 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-04 13:55 Tom de Vries
2021-11-05 9:33 ` Andrew Burgess
2021-11-05 9:43 ` Tom de Vries
2021-11-05 11:54 ` Andrew Burgess
2021-11-05 12:23 ` Tom de Vries
2021-11-05 12:55 ` Pedro Alves
2021-11-05 13:15 ` Tom de Vries
2021-11-05 13:20 ` Pedro Alves
2021-11-05 13:35 ` Tom de Vries [this message]
2021-11-05 13:52 ` Andrew Burgess
2021-12-06 15:27 ` Tom de Vries
2021-11-05 13:54 ` Pedro Alves
2021-12-06 15:25 ` Tom de Vries
2021-11-05 12:24 ` Pedro Alves
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