[PATCH] Fix ICE in modified_type_die (PR debug/80461)

[Jakub Jelinek]

On Wed, Apr 19, 2017 at 09:55:19AM -0600, Jeff Law wrote:
> On 04/19/2017 09:10 AM, Jakub Jelinek wrote:
> > On Wed, Apr 19, 2017 at 08:57:52AM -0600, Jeff Law wrote:
> > > > 2017-04-19  Jakub Jelinek  <jakub@redhat.com>
> > > > 
> > > > 	PR debug/80461
> > > > 	* dwarf2out.c (modified_type_die, gen_type_die_with_usage):
> > > > 	Check for t with zero TYPE_QUALS_NO_ADDR_SPACE.
> > > > 
> > > > 	* g++.dg/debug/pr80461.C: New test.
> > > I'm going to assume your use of TYPE_QUALS_NO_ADDR_SPACE vs TYPE_QUALS or
> > > TYPE_QUALS_NO_ADDR_SPACE_NO_ATOMIC is correct.
> > 
> > I don't really know.  For address space quals I think one would need to have
> > pointer-to-members in different code address spaces, not sure if we support
> > anything like that.  And atomic is C only which doesn't have
> > pointer-to-members.
> To put it another way, in your message you indicated that modified_type_die
> expects either an unqualified type or the type itself and that your patch
> makes sure we only pick unqualified types.
> 
> Using TYPE_QUALS_NO_ADDR_SPACE like you have seems to conflict with those
> statements.  So I'm curious why you allow address space qualifiers to pass
> through, but no others.   It just seems odd.

I used TYPE_QUALS_NO_ADDR_SPACE because that seems to be used in
modified_type_die elsewhere (dwarf2out.c has only one use of TYPE_QUALS and
even that one ignores addr space bits, as it is masked with qual_mask;
the rest just TYPE_QUALS_NO_ADDR_SPACE).  I think with FUNCTION/METHOD types
with addr space quals we end up in grossly untested territory that most
likely will just not work at all.  I think we don't do anything with the
address space quals right now, in the future DWARF has segment identifiers
and something like that could be emitted, but there needs to be ABI
agreement on what it means.

	Jakub