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Re: [C++ Patch] PR 84644 ("internal compiler error: in warn_misplaced_attr_for_class_type, at cp/decl.c:4718")


On 10/30/18 9:22 PM, Paolo Carlini wrote:
Hi,

On 30/10/18 21:37, Jason Merrill wrote:
On 10/26/18 2:02 PM, Paolo Carlini wrote:
On 26/10/18 17:18, Jason Merrill wrote:
On Fri, Oct 26, 2018 at 4:52 AM Paolo Carlini <paolo.carlini@oracle.com> wrote:
On 24/10/18 22:41, Jason Merrill wrote:
On 10/15/18 12:45 PM, Paolo Carlini wrote:
         && ((TREE_CODE (declspecs->type) != TYPENAME_TYPE
+       && TREE_CODE (declspecs->type) != DECLTYPE_TYPE
          && MAYBE_CLASS_TYPE_P (declspecs->type))
I would think that the MAYBE_CLASS_TYPE_P here should be CLASS_TYPE_P,
and then we can remove the TYPENAME_TYPE check.  Or do we want to
allow template type parameters for some reason?
Indeed, it would be nice to just use OVERLOAD_TYPE_P. However it seems
we at least want to let through TEMPLATE_TYPE_PARMs representing 'auto'
- otherwise Dodji's check a few lines below which fixed c++/51473
doesn't work anymore - and also BOUND_TEMPLATE_TEMPLATE_PARM, otherwise
we regress on template/spec32.C and template/ttp22.C because we don't
diagnose the shadowing anymore. Thus, I would say either we keep on
using MAYBE_CLASS_TYPE_P or we pick what we need, possibly we add a comment?
Aha.  I guess the answer is not to restrict that test any more, but
instead to fix the code further down so it gives a proper diagnostic
rather than call warn_misplaced_attr_for_class_type.

I see. Thus something like the below? It passes testing on x86_64-linux.

+  if ((!declared_type || TREE_CODE (declared_type) == DECLTYPE_TYPE)
+      && ! saw_friend && !error_p)
     permerror (input_location, "declaration does not declare anything");

I see no reason to make this specific to decltype.  Maybe move this diagnostic into the final 'else' block with the other declspec diagnostics and not look at declared_type at all?

I'm not sure to fully understand: if we do that we still want to at least minimally check that declared_type is null, like we already do, and then we simply accept the new testcase. Is that Ok? Because, as I probably mentioned at some point, all the other compilers I have at hand issue a "does not declare anything" diagnostic, and we likewise do that for the legacy __typeof. Not looking into declared_type *at all* doesn't work with plain class types and enums, of course. Or you meant something entirely different??

+  if (declspecs->attributes && warn_attributes && declared_type
+      && TREE_CODE (declared_type) != DECLTYPE_TYPE)

I think we do want to give a diagnostic about useless attributes, not skip it.

Agreed. FWIW the attached tests fine.

The problem here is that the code toward the bottom expects "declared_type" to be the tagged type declared by a declaration with no declarator, and in this testcase it's ending up as a DECLTYPE_TYPE.

I think once we've checked for 'auto' we don't want declared_type to be anything that isn't OVERLOAD_TYPE_P. We can arrange that either by checking for 'auto' first and then changing the code that sets declared_type to use OVERLOAD_TYPE_P, or by clearing declared_type after checking for 'auto' if it isn't OVERLOAD_TYPE_P.

Jason


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