0: func_d
 at $DIR/backtrace-std.rs:LL:CC
   1: func_c
 at $DIR/backtrace-std.rs:LL:CC
   2: func_b
 at $DIR/backtrace-std.rs:LL:CC
   3: func_a
 at $DIR/backtrace-std.rs:LL:CC
   4: main
 at $DIR/backtrace-std.rs:LL:CC
   5: <fn() as std::ops::FnOnce<()>>::call_once - shim(fn())
 at rustc_src/src/ops/function.rs:LL:CC
   6: std::sys_common::backtrace::__rust_begin_short_backtrace
 at rustc_src/src/sys_common/backtrace.rs:LL:CC
   7: std::rt::lang_start::{closure#0}
 at rustc_src/src/rt.rs:LL:CC
   8: std::ops::function::impls::call_once
 at rustc_src/src/ops/function.rs:LL:CC
   9: std::panicking::r#try::do_call
 at rustc_src/src/panicking.rs:LL:CC
  10: std::panicking::r#try
 at rustc_src/src/panicking.rs:LL:CC
  11: std::panic::catch_unwind
 at rustc_src/src/panic.rs:LL:CC
  12: std::rt::lang_start_internal::{closure#2}
 at rustc_src/src/rt.rs:LL:CC
  13: std::panicking::r#try::do_call
 at rustc_src/src/panicking.rs:LL:CC
  14: std::panicking::r#try
 at rustc_src/src/panicking.rs:LL:CC
  15: std::panic::catch_unwind
 at rustc_src/src/panic.rs:LL:CC
  16: std::rt::lang_start_internal
 at rustc_src/src/rt.rs:LL:CC
  17: std::rt::lang_start
 at rustc_src/src/rt.rs:LL:CC