Re: [C++ PATCH] Fix alignment handling in build_cplus_array_type/cp_build_qualified_type_real (PR c++/65690)

[Jan Hubicka <hubicka@ucw.cz>]

> On Wed, Apr 08, 2015 at 06:22:10PM +0200, Jan Hubicka wrote:
> > > On 04/08/2015 06:02 AM, Jakub Jelinek wrote:
> > > >	(cp_build_qualified_type_real): Use check_base_type.  Build a
> > > >	variant and copy over even TYPE_CONTEXT and
> > > >	TYPE_ALIGN/TYPE_USER_ALIGN if any of those are different.
> > > 
> > > This seems wrong.  If there is an array with the same name,
> > > attributes and element type, it should have the same alignment; if
> > 
> > One of problems is that cp_build_qualified_type rebuilds the array from
> > scratch and never copies the attribute list around (as oposed to
> > build_qualified_type that just memcpy the type node)
> 
> As I said earlier, TYPE_ATTRIBUTES is NULL here anyway, because the
> attributes hang in DECL_ATTRIBUTES of TYPE_DECL.  And, except for
> config/sol2.c (which looks wrong), nothing ever calls lookup_attribute for
> "aligned" anyway, the user aligned stuff is encoded in TYPE_USER_ALIGN
> and/or DECL_USER_ALIGN and TYPE_ALIGN/DECL_ALIGN.

This is interesting too.  I did know that alignment is "lowered" into
TYPE_USER_ALIGN/TYPE_ALIGN values, but there is a lot of other code
that looks for type attributes by searching TYPE_ATTRIBUTES, not DECL_ATTRIBUTES
of TYPE_DECL (such as nonnul_arg_p in tree-vrp) or alloc_object_size.
Does it mean that those attributes are ignored for C++ produced types?

Honza
> 
> 	Jakub