On Fri, Mar 15, 2024 at 10:35:07AM -0400, Patrick Palka wrote:
> On Tue, 5 Mar 2024, Marek Polacek wrote:
> 
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> > 
> > -- >8 --
> > Here we ICE because we call register_local_specialization while
> > local_specializations is null, so
> > 
> >   local_specializations->put ();
> > 
> > crashes on null this.  It's null since maybe_instantiate_noexcept calls
> > push_to_top_level which creates a new scope.  Normally, I would have
> > guessed that we need a new local_specialization_stack.  But here we're
> > dealing with an operand of a noexcept, which is an unevaluated operand,
> > and those aren't registered in the hash map.  maybe_instantiate_noexcept
> > wasn't signalling that it's substituting an unevaluated operand though.
> 
> It thought it was noexcept-exprs rather than noexcept-specs that are
> unevaluated contexts?

Yes, sigh.  It would have to be noexcept(noexcept(x)).  I was looking at
cp_parser_unary_expression/RID_NOEXCEPT but that's a noexcept-expr.  So
what can we do here, set a new local_specialization_stack?  That wasn't
that straightforward when I tried.  Or maybe just

--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -15649,7 +15649,7 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain,
      {
        if (DECL_LANG_SPECIFIC (r))
          DECL_TEMPLATE_INFO (r) = NULL_TREE;
-       if (!cp_unevaluated_operand)
+       if (!cp_unevaluated_operand && local_specializations)
          register_local_specialization (r, t);
      }

?

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