On 06/07/2017 02:12 PM, Martin Sebor wrote:
> On 06/07/2017 02:01 PM, Marc Glisse wrote:
>> On Wed, 7 Jun 2017, Bernhard Reutner-Fischer wrote:
>>
>>> On 7 June 2017 16:46:53 CEST, Martin Sebor <msebor@gmail.com> wrote:
>>>> On 06/07/2017 02:23 AM, Richard Biener wrote:
>>>>> On Wed, Jun 7, 2017 at 5:26 AM, Martin Sebor <msebor@gmail.com>
>>>> wrote:
>>>>>>> Note I'd be _much_ more sympathetic to simply canonicalizing all of
>>>>>>> bzero and bcopy
>>>>>>> to memset / memmove and be done with all the above complexity.
>>>>>>
>>>>>>
>>>>>> Attached is an updated patch along these lines.  Please let me
>>>>>> know if it matches your expectations.
>>>>>
>>>>> I think you attached the wrong patch.
>>>>
>>>> Yes I did, sorry.  The correct one is attached.
>>>
>>> Under POSIX.1-2008 "optimizing" bzero or bcmp is IMO plain wrong.
>>>
>>> It's like optimizing foo() to a random built-in but maybe that's just
>>> me. If your libc provides a define to a standard function for these
>>> under a compat knob then fine but otherwise you should fix that.
>>> *shrug*. Joseph?
>>
>> The patch optimizes __builtin_bzero, which should be ok. The question
>> (independent from this patch) is then under what conditions bzero should
>> be detected as a builtin.
>
> Yes.  The problem is that unlike for C and C++, GCC doesn't have
> a mechanism to select the target version of POSIX.  I think it
> should.
>
> But there is a subtle problem with the patch that needs fixing.
> Bcopy should not be transformed to memcpy but rather memmove.
> I'll fix that before committing.

Attached is an updated patch with this fix.  I also added a cast
from bcopy and bzero to void to detect accidental uses of the
return value.  Tested on x86_64-linux.

Martin