https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101073
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:b2287a4d9a640fdc2caef6a067830ea65044deb7 commit r13-6145-gb2287a4d9a640fdc2caef6a067830ea65044deb7 Author: Marek Polacek <pola...@redhat.com> Date: Wed Feb 8 19:13:18 2023 -0500 c++: ICE with -fno-elide-constructors and trivial fn [PR101073] In constexpr-nsdmi3.C, with -fno-elide-constructors, we don't elide the Y::Y(const Y&) call used to initialize o.c. So store_init_value -> cxx_constant_init must constexpr-evaluate the call to Y::Y(const Y&) in cxx_eval_call_expression. It's a trivial function, so we do the "Shortcut trivial constructor/op=" code and rather than evaluating the function, we just create an assignment o.c = *(const struct Y &) (const struct Y *) &(&<PLACEHOLDER_EXPR struct X>)->b which is a MODIFY_EXPR, so the preeval code in cxx_eval_store_expression clears .ctor and .object, therefore we can't replace the PLACEHOLDER_EXPR whereupon we crash at /* A placeholder without a referent. We can get here when checking whether NSDMIs are noexcept, or in massage_init_elt; just say it's non-constant for now. */ gcc_assert (ctx->quiet); The PLACEHOLDER_EXPR can also be on the LHS as in constexpr-nsdmi10.C. I don't think we can do much here, but I noticed that the whole trivial_fn_p (fun) block is only entered when -fno-elide-constructors. This is true since GCC 9; it wasn't easy to bisect what changes made it so, but r240845 is probably one of them. -fno-elide-constructors is an option for experiments only so it's not clear to me why we'd still want to shortcut trivial constructor/op=. I propose to remove the code and add a checking assert to make sure we're not getting a trivial_fn_p unless -fno-elide-constructors. PR c++/101073 gcc/cp/ChangeLog: * constexpr.cc (cxx_eval_call_expression): Replace shortcutting trivial constructor/op= with a checking assert. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/constexpr-nsdmi3.C: New test. * g++.dg/cpp1y/constexpr-nsdmi10.C: New test.
