https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70297
Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Component|debug |c --- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> --- So duplicate_decls ggc_free()s newdecl which is still used as TYPE_NAME. #1 0x000000000075a2fe in duplicate_decls ( newdecl=<type_decl 0x7ffff68abda8 target_ulong>, olddecl=<type_decl 0x7ffff68abd10 target_ulong>) at /space/rguenther/src/svn/trunk3/gcc/c/c-decl.c:2731 2731 ggc_free (newdecl); (gdb) p olddecl->typed.type $13 = <integer_type 0x7ffff698b540 target_ulong> (gdb) p olddecl->typed.type->type_common.name $14 = <type_decl 0x7ffff68abda8 target_ulong> (gdb) p newdecl $15 = <type_decl 0x7ffff68abda8 target_ulong> C frontend issue. merge_decls copies everything from new to old, including type which can self-reference new.