On Wed, Apr 08, 2015 at 06:32:29PM +0200, Jan Hubicka wrote:
> > 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?
I don't think this has anything to do with C++. c-common.c has an attribute
table, for each attribute it has 3 flags, whether a decl is required, type
is required and/or fn type is required, and that determines to what the
attributes go.
These flags have the following combinations (decl/type/fntype # of attributes):
TFF 51 (i.e. decl required)
FTT 12 (i.e. function type required)
FTF 9 (i.e. some type required)
FFF 7 (applies to both types and decls)
Which means most of the attributes require a decl and thus go into
DECL_ATTRIBUTES, then some require function types and go to the
TYPE_ATTRIBUTES of the function, then others go solely to TYPE_ATTRIBUTES.
The last row are attributes that don't really care where they apply to, and
that is
{ "packed", 0, 0, false, false, false,
{ "unused", 0, 0, false, false, false,
{ "transparent_union", 0, 0, false, false, false,
{ "aligned", 0, 1, false, false, false,
{ "deprecated", 0, 1, false, false, false,
{ "visibility", 1, 1, false, false, false,
{ "warn_unused", 0, 0, false, false, false,
where the first 6 really don't care about what is stored in
{TYPE,DECL}_ATTRIBUTES because the attributes are encoded differently in
generic, and the last one sounds like a mistake (perhaps one that can't be
undone anymore) where it doesn't require a type, but only stores it on types
and warns otherwise.
Jakub
