0: main
 at tests/pass/backtrace/backtrace-global-alloc.rs:LL:CC
   1: <fn() as std::ops::FnOnce<()>>::call_once - shim(fn())
 at RUSTLIB/core/src/ops/function.rs:LL:CC
   2: std::sys::backtrace::__rust_begin_short_backtrace
 at RUSTLIB/std/src/sys/backtrace.rs:LL:CC
   3: std::rt::lang_start::{closure#0}
 at RUSTLIB/std/src/rt.rs:LL:CC
   4: std::ops::function::impls::call_once
 at RUSTLIB/core/src/ops/function.rs:LL:CC
   5: std::panicking::catch_unwind::do_call
 at RUSTLIB/std/src/panicking.rs:LL:CC
   6: std::panicking::catch_unwind
 at RUSTLIB/std/src/panicking.rs:LL:CC
   7: std::panic::catch_unwind
 at RUSTLIB/std/src/panic.rs:LL:CC
   8: std::rt::lang_start_internal::{closure#0}
 at RUSTLIB/std/src/rt.rs:LL:CC
   9: std::panicking::catch_unwind::do_call
 at RUSTLIB/std/src/panicking.rs:LL:CC
  10: std::panicking::catch_unwind
 at RUSTLIB/std/src/panicking.rs:LL:CC
  11: std::panic::catch_unwind
 at RUSTLIB/std/src/panic.rs:LL:CC
  12: std::rt::lang_start_internal
 at RUSTLIB/std/src/rt.rs:LL:CC
  13: std::rt::lang_start
 at RUSTLIB/std/src/rt.rs:LL:CC