On Thu, Feb 21, 2019 at 11:22:41AM -1000, Jason Merrill wrote: > On 2/21/19 10:56 AM, Marek Polacek wrote: > > On Wed, Feb 20, 2019 at 01:53:18PM -1000, Jason Merrill wrote: > > > On 2/20/19 10:31 AM, Marek Polacek wrote: > > > > Here we ICE when substituting a deferred noexcept-specifier, because it > > > > contains 'this', a PARM_DECL, in an evaluated context. This is > > > > different > > > > from "noexcept(noexcept(this))" where the noexcept operator's operand is > > > > an unevaluated operand. We crash within tsubst_copy's PARM_DECL > > > > handling > > > > of a 'this' PARM_DECL: > > > > 15488 gcc_assert (cp_unevaluated_operand != 0) > > > > It'd be wrong to mess with cp_unevaluated_operand (or current_class_*), > > > > and > > > > since we only check the expression's constness after substituting in > > > > maybe_instantiate_noexcept, one fix would be the following. > > > > > > > > This is not just about 'this', as the 87844 test shows: here we also > > > > have > > > > a parameter whose value we're trying to determine -- it's a template arg > > > > of a late-specified return type. Returning the original value in > > > > tsubst_copy > > > > and leaving the later code to complain seems to work here as well. Just > > > > removing the assert should work as well. > > > > > > I'm reluctant to mess with this assert, as it catches a lot of lambda > > > bugs. > > > > Makes sense -- I wasn't aware of that. > > > > > I think we want to register_parameter_specializations when instantiating > > > deferred noexcept, so that tsubst_copy can find the right decls. > > > > Thanks for the suggestion -- that works with one catch: we need to replace > > the > > fake 'this' in the noexcept- specifier with a real 'this' (the template > > one), > > one that has DECL_CONTEXT set. The fake one comes from > > inject_this_parameter, > > when we were parsing the noexcept-specifier. The real one was set in > > grokfndecl. > > If you set current_class_ptr appropriately tsubst_copy will use it, so you > shouldn't need to do a walk_tree.
Unfortunately that broke a lot of libstdc++ tests. I can poke at it more if you feel stronly about it. Marek
