https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93711
--- Comment #12 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-10 branch has been updated by Jason Merrill <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:97014e4ada448aa8978b3cd14ed95e0e56f375d9 commit r10-9168-g97014e4ada448aa8978b3cd14ed95e0e56f375d9 Author: Jason Merrill <ja...@redhat.com> Date: Wed Aug 12 05:45:02 2020 -0400 c++: Copy elision and [[no_unique_address]]. [PR93711] We don't elide a copy from a function returning a class by value into a base because that can overwrite data laid out in the tail padding of the base class; we need to handle [[no_unique_address]] fields the same way, or we ICE when the middle-end wants to create a temporary object of a TYPE_NEEDS_CONSTRUCTING type. This means that we can't always express initialization of a field with INIT_EXPR from a TARGET_EXPR the way we usually do, so I needed to change several places that were assuming that was sufficient. This also fixes 90254, the same problem with C++17 aggregate initialization of a base. gcc/cp/ChangeLog: PR c++/90254 PR c++/93711 * cp-tree.h (unsafe_return_slot_p): Declare. * call.c (is_base_field_ref): Rename to unsafe_return_slot_p. (build_over_call): Check unsafe_return_slot_p. (build_special_member_call): Likewise. * init.c (expand_default_init): Likewise. * typeck2.c (split_nonconstant_init_1): Likewise. gcc/testsuite/ChangeLog: PR c++/90254 PR c++/93711 * g++.dg/cpp1z/aggr-base10.C: New test. * g++.dg/cpp2a/no_unique_address7.C: New test. * g++.dg/cpp2a/no_unique_address7a.C: New test.
