Hi! As I've mentioned on Saturday, the CWG3130 patchset fail to bootstrap. The problem is that we try to call build_value_init on anonymous unions or structs, which doesn't work well when they don't have a default constructor. Now, if some non-trivial construction is needed, type will already have either a user-provided constructor or at least non-trivial one, in that case build_value_init_noctor isn't called at all. So, this patch just zero-initializes the anonymous aggregate members.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2026-05-25 Jakub Jelinek <[email protected]> * init.cc (build_value_init_noctor): Zero initialize anonymous union/struct subobjects. Formatting fix. --- gcc/cp/init.cc.jj 2026-04-03 10:18:16.808121758 +0200 +++ gcc/cp/init.cc 2026-05-25 11:01:59.409845336 +0200 @@ -445,6 +445,20 @@ build_value_init_noctor (tree type, tsub && integer_zerop (DECL_SIZE (field))) continue; + /* Zero-initialize anonymous union and struct members. The + default constructor doesn't exist for those and if NSDMIs + are used, the containing type's default constructor is + non-trivial. */ + if (ANON_AGGR_TYPE_P (ftype)) + { + value = build_zero_init (ftype, NULL_TREE, + /*static_storage_p=*/false); + if (value == error_mark_node) + return error_mark_node; + CONSTRUCTOR_APPEND_ELT (v, field, value); + continue; + } + /* We could skip vfields and fields of types with user-defined constructors, but I think that won't improve performance at all; it should be simpler in general just @@ -461,7 +475,7 @@ build_value_init_noctor (tree type, tsub if (value == error_mark_node) return error_mark_node; - CONSTRUCTOR_APPEND_ELT(v, field, value); + CONSTRUCTOR_APPEND_ELT (v, field, value); /* We shouldn't have gotten here for anything that would need non-trivial initialization, and gimplify_init_ctor_preeval Jakub
