On Tue, Mar 22, 2016 at 6:12 PM, Patrick Palka <patr...@parcs.ath.cx> wrote: > On Tue, Mar 22, 2016 at 6:00 PM, Jason Merrill <ja...@redhat.com> wrote: >> On 03/22/2016 05:35 PM, Patrick Palka wrote: >>> >>> + if (cp_unevaluated_operand == 0 >> >> >> Why check this here? > > Just so that the change doesn't affect the behavior of tsubst_decl() > when cp_unevaluated_operand != 0. Presumably the existing code (10 > lines below) handles that case just fine.
Turns out that without the check we can trigger the cxx_dialect >= cxx14 assert because in c++11 mode we can reach the assert through get_defaulted_eh_spec() which increments cp_unevaluated_operand and then calls get_nsdmi (..., /*in_ctor=*/false) causing current_class_ref to get set to a PLACEHOLDER_EXPR. So for example g++.dg/cpp0x/nsdmi-template2.C regresses with an ICE. So it seems the cp_unevaluated_operand != 0 check is necessary as long as the assert stays. There are no regressions if both the cp_unevaluated_operand check and the assert are removed however.
