https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98463
--- Comment #14 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:2127d2c3ee23bbd03f02d88fd82403408696ee4a commit r10-9314-g2127d2c3ee23bbd03f02d88fd82403408696ee4a Author: Jason Merrill <ja...@redhat.com> Date: Fri Jan 22 13:17:10 2021 -0500 c++: [[no_unique_address]] in empty base [PR98463] In this testcase, cxx_eval_store_expression got confused trying to build up CONSTRUCTORs for initializing a subobject because the subobject is a member of an empty base. In C++14 mode and below we don't build FIELD_DECLs for empty bases, so the CONSTRUCTOR skipped the empty base, and treated the member as a member of the derived class, which breaks. Fixed by recognizing this situation and giving up on trying to build a CONSTRUCTOR for the inner target at that point; since it doesn't have any data, we don't need to actually store anything. gcc/cp/ChangeLog: PR c++/98463 * constexpr.c (get_or_insert_ctor_field): Add check. (cxx_eval_store_expression): Handle discontinuity of refs. gcc/testsuite/ChangeLog: PR c++/98463 * g++.dg/cpp2a/no_unique_address8.C: New test.
