https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113919
--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I suppose this should fix it but there are testsuite FAILs.
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -5522,6 +5522,12 @@ fixup_anonymous_aggr (tree t)
}
}
}
+ /* [class.union.anon]/1: Nested types, anonymous unions, and functions
+ shall not be declared within an anonymous union. */
+ else if (ANON_UNION_TYPE_P (TREE_TYPE (probe)))
+ pedwarn (DECL_SOURCE_LOCATION (probe), OPT_Wpedantic,
+ "anonymous unions cannot be declared within an anonymous "
+ "union");
}
/* Splice all functions out of CLASSTYPE_MEMBER_VEC. */
