On Tue, Mar 14, 2017 at 02:34:30PM -0400, Jason Merrill wrote: > On Tue, Mar 14, 2017 at 2:33 PM, Jason Merrill <ja...@redhat.com> wrote: > > On Tue, Mar 7, 2017 at 12:10 PM, Marek Polacek <pola...@redhat.com> wrote: > >> In this testcase we have > >> C c = bar (X{1}); > >> which store_init_value sees as > >> c = TARGET_EXPR <D.2332, bar (TARGET_EXPR <D.2298, {.i=1, > >> .n=(&<PLACEHOLDER_EXPR struct X>)->i}>)> > >> i.e. we're initializing "c" with a TARGET_EXPR. We call > >> replace_placeholders > >> that walks the whole tree to substitute the placeholders. Eventually we > >> find > >> the nested <PLACEHOLDER_EXPR struct X> but that's for another object, so we > >> crash. Seems that we shouldn't have stepped into the second TARGET_EXPR at > >> all; it has nothing to with "c", it's bar's argument. > >> > >> It occurred to me that we shouldn't step into CALL_EXPRs and leave the > >> placeholders in function arguments to cp_gimplify_init_expr which calls > >> replace_placeholders for constructors. Not sure if it's enough to handle > >> CALL_EXPRs like this, anything else? > > > > Hmm, we might have a DMI containing a call with an argument referring > > to *this, i.e. > > > > struct A > > { > > int i; > > int j = frob (this->i); > > }; > > > > The TARGET_EXPR seems like a more likely barrier, but even there we > > could have something like > > > > struct A { int i; }; > > struct B > > { > > int i; > > A a = A{this->i}; > > }; > > > > I think we need replace_placeholders to keep a stack of objects, so > > that when we see a TARGET_EXPR we add it to the stack and therefore > > can properly replace a PLACEHOLDER_EXPR of its type. > > Or actually, avoid replacing such a PLACEHOLDER_EXPR, but rather leave > it for later when we lower the TARGET_EXPR.
Sorry, I don't really follow. I have a patch that puts TARGET_EXPRs on a stack, but I don't know how that helps. E.g. with nsdmi-aggr3.C we have B b = TARGET_EXPR <D1, {.a = TARGET_EXPR <D2, (struct A *) &<PLACEHOLDER_EXPR struct B>>}> so when we get to that PLACEHOLDER_EXPR, on the stack there's TARGET_EXPR with type struct A TARGET_EXPR with type struct B so the type of the PLACEHOLDER_EXPR doesn't match the type of the current TARGET_EXPR, but we still want to replace it in this case. So -- could you expand a bit on what you had in mind, please? Thanks, Marek