> On Mon, 8 Jun 2015, Richard Biener wrote:
>
> > On Mon, 8 Jun 2015, Joseph Myers wrote:
> >
> > > On Mon, 8 Jun 2015, Richard Biener wrote:
> > >
> > > > I'm not sure the C standard mandates compatibility between
> > > >
> > > > struct { int i; } and struct { unsigned i; } for purposes of TBAA.
> > > > Joseph?
> > >
> > > I don't think they are necessarily compatible for TBAA.
> >
> > Ok, but as int and unsigned are reading either structs element
> > via a pointer to int or a pointer to unsigned must be supported?
>
> Yes. The questionable case would be taking an object of one of those
> structure types, casting a pointer to it to point to the other structure
> type and then dereferencing.
Are "struct { int i; }" and "struct { unsigned i; }" compatible when one is
defined
in one unit and other in another?
In any cae, I suppose if int and unsigned int pointers can be used
interchangeably,
we want to ignore TYPE_UNSGINED for purposes of canonical type calculation for
LTO.
So is the second variant of patch OK with a comment update that this is also
required
by C?
Honza
>
> --
> Joseph S. Myers
> jos...@codesourcery.com
