[PATCH] Add a new type attribute always_alias (PR79671)

[Jakub Jelinek]

On Thu, Apr 06, 2017 at 04:51:01PM +0200, Florian Weimer wrote:
> On 04/06/2017 04:43 PM, Jonathan Wakely wrote:
> > On 06/04/17 16:23 +0200, Richard Biener wrote:
> > > On Thu, 6 Apr 2017, Florian Weimer wrote:
> > > 
> > > > On 04/06/2017 04:11 PM, Bernd Edlinger wrote:
> > > > 
> > > > > I think it is not too complicated to done in the C++ FE.
> > > > > The FE looks for array of std::byte and unsigned char,
> > > > > and sets the attribute when the final type is constructed.
> > > > >
> > > > > What I am trying to do is just extend the semantic of may_alias
> > > > > a bit, and then have the C++ FE use it in the way it has to.
> > > > 
> > > > We also need this for some POSIX and Linux kernel interfaces.  A
> > > > C++-only
> > > > solution would not help with that.
> > > 
> > > Example(s)?
> > 
> > sockaddr_storage comes to mind.
> 
> Right.  The kernel also has many APIs which return multiple variable-length
> data blocks, such as getdents64, and many more interfaces in combination

The kernel uses -fno-strict-aliasing I think, so it doesn't care.

	Jakub