https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89422
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- Confirmed. Program received signal SIGSEGV, Segmentation fault. 0x0000000000e33f81 in field_byte_offset (decl=0x7ffff699d7b8, ctx=0x7fffffffb5e0, cst_offset=0x7fffffffb4a8) at /space/rguenther/src/svn/trunk2/gcc/dwarf2out.c:19086 19086 if (TREE_CODE (DECL_FIELD_BIT_OFFSET (decl)) != INTEGER_CST) (gdb) p decl $1 = (const_tree) 0x7ffff699d7b8 (gdb) p debug_tree (decl) <field_decl 0x7ffff699d7b8 b type <integer_type 0x7ffff68985e8 int asm_written public type_6 SI size <integer_cst 0x7ffff689c078 constant 32> unit-size <integer_cst 0x7ffff689c090 constant 4> align:32 warn_if_not_align:0 symtab:-158767472 alias-set -1 canonical-type 0x7ffff68985e8 precision:32 min <integer_cst 0x7ffff689c030 -2147483648> max <integer_cst 0x7ffff689c048 2147483647> pointer_to_this <pointer_type 0x7ffff68a19d8>> decl_3 VOID t.C:4:11 align:1 warn_if_not_align:0 offset_align 1 context <record_type 0x7ffff69d1690 S> chain <type_decl 0x7ffff699d720 S>> $2 = void (gdb) p decl->field_decl.bit_offset $3 = (tree) 0x0 (gdb) p decl->field_decl.offset $4 = (tree) 0x0 that's not a valid FIELD_DECL. The aggregate is <record_type 0x7ffff69d1690 S asm_written type_0 type_5 type_6 VOID size <integer_cst 0x7ffff687aea0 type <integer_type 0x7ffff68980a8 bitsizetype> constant 0> unit-size <integer_cst 0x7ffff687ae58 type <integer_type 0x7ffff6898000 sizetype> constant 0> align:8 warn_if_not_align:0 symtab:-158767632 alias-set -1 canonical-type 0x7ffff69d1690 fields <using_decl 0x7ffff699d850 operator= decl_0 VOID t.C:1:23 align:1 warn_if_not_align:0 context <record_type 0x7ffff69d1690 S> result <record_type 0x7ffff69d1690 S> chain <field_decl 0x7ffff699d7b8 b type <integer_type 0x7ffff68985e8 int> decl_3 VOID t.C:4:11 align:1 warn_if_not_align:0 offset_align 1 context <record_type 0x7ffff69d1690 S> chain <type_decl 0x7ffff699d720 S>>> context <translation_unit_decl 0x7ffff6887168 t.C> full-name "struct S<<anonymous> >" n_parents=0 use_template=0 interface-unknown chain <type_decl 0x7ffff699d688 S>> and we call debug_hooks->type_decl on the __lambda1 TYPE_DECL.