https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112580
--- Comment #10 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:f931bd7725f5cea948dd55ac370b5b9fd9a00198 commit r14-8900-gf931bd7725f5cea948dd55ac370b5b9fd9a00198 Author: Patrick Palka <ppa...@redhat.com> Date: Fri Feb 9 12:40:28 2024 -0500 c++/modules: anon union member of as-base class [PR112580] Here when streaming in the fields of the as-base version of _Formatting_scanner<int> we end up overwriting ANON_AGGR_TYPE_FIELD of the anonymous union type, since it turns out this type is shared between the original FIELD_DECL and the as-base FIELD_DECL copy (copied during layout_class_type). ANON_AGGR_TYPE_FIELD first gets properly set to the original FIELD_DECL when streaming in the canonical definition of _Formatting_scanner<int>, and then gets overwritten to the as-base FIELD_DECL when streaming in the the as-base definition. This leads to lookup_anon_field later giving the wrong answer when resolving the _M_values use at instantiation time. This patch makes us avoid overwriting ANON_AGGR_TYPE_FIELD when streaming in an as-base class definition; it should already be properly set at that point. PR c++/112580 gcc/cp/ChangeLog: * module.cc (trees_in::read_class_def): When streaming in an anonymous union field of an as-base class, don't overwrite ANON_AGGR_TYPE_FIELD. gcc/testsuite/ChangeLog: * g++.dg/modules/anon-3_a.H: New test. * g++.dg/modules/anon-3_b.C: New test. Reviewed-by: Jason Merrill <ja...@redhat.com>
