core-trace-foo.log

$ bin/crystal build --debug foo.cr
Using compiled compiler at .build/crystal

$ ./foo 
BOOM (Exception)
0x0000000000434c20: *baz:NoReturn at /home/luis/code/crystal-lang/crystal/foo.cr 10:3
0x0000000000434c06: ??? at /home/luis/code/crystal-lang/crystal/foo.cr 6:3
0x0000000000434bf6: ??? at /home/luis/code/crystal-lang/crystal/foo.cr 2:3
0x00000000004306e1: ??? at /home/luis/code/crystal-lang/crystal/src/signal.cr 129:1
0x0000000000434ad9: main at /home/luis/.cache/crystal/macro70478608.cr 12:15
0x00007f87cf868ac0: __libc_start_main at ?? 0:0
0x0000000000430069: _start at ?? 0:0
0x0000000000000000: ??? at ?? 0:0

foo.cr

def foo
  bar
end

def bar
  baz
end

def baz
  raise "BOOM"
end

foo

lldb-foo.log

$ lldb foo
(lldb) target create "foo"
Current executable set to 'foo' (x86_64).
(lldb) b unwind
Breakpoint 1: where = foo`unwind + 9 at exception.cr:44, address = 0x000000000042a5d9
(lldb) r
Process 4030 launching
Process 4030 launched: '/home/luis/code/crystal-lang/crystal/foo' (x86_64)
Process 4030 stopped
* thread #1: tid = 4030, 0x000000000042a5d9 foo`unwind + 9 at exception.cr:44, name = 'foo', stop reason = breakpoint 1.1
    frame #0: 0x000000000042a5d9 foo`unwind + 9 at exception.cr:44
   41  	  {% end %}
   42  	
   43  	  protected def self.unwind
-> 44  	    callstack = [] of Void*
   45  	    backtrace_fn = ->(context : LibUnwind::Context, data : Void*) do
   46  	      bt = data.as(typeof(callstack))
   47  	      ip = Pointer(Void).new(LibUnwind.get_ip(context))
(lldb) bt
* thread #1: tid = 4030, 0x000000000042a5d9 foo`unwind + 9 at exception.cr:44, name = 'foo', stop reason = breakpoint 1.1
  * frame #0: 0x000000000042a5d9 foo`unwind + 9 at exception.cr:44
    frame #1: 0x000000000042a5ba foo`initialize + 10 at exception.cr:16
    frame #2: 0x000000000042a58a foo`new + 42 at exception.cr:15
    frame #3: 0x0000000000425478 foo`raise + 24 at raise.cr:98
    frame #4: 0x000000000042545e foo`raise + 14 at raise.cr:108
    frame #5: 0x0000000000428450 foo`baz + 16 at foo.cr:10
    frame #6: 0x0000000000428436 foo`bar + 6 at foo.cr:6
    frame #7: 0x0000000000428426 foo`foo + 6 at foo.cr:2
    frame #8: 0x0000000000424e20 foo`__crystal_main + 1104 at foo.cr:13
    frame #9: 0x0000000000428309 foo`main + 41 at macro67162880.cr:12
    frame #10: 0x00007ffff71eeac0 libc.so.6`__libc_start_main + 240
    frame #11: 0x00000000004248f9 foo`_start + 41
(lldb) 

run-foo.log

$ ./foo 
BOOM (Exception)
[4367911] *CallStack::unwind:Array(Pointer(Void)) +87
[4367802] *CallStack#initialize:Array(Pointer(Void)) +10
[4367754] *CallStack::new:CallStack +42
[4347000] *raise<Exception>:NoReturn +24
[4346974] ???
[4359248] *baz:NoReturn +16
[4359222] ???
[4359206] ???
[4345376] ???
[4358921] main +41
[140041657961152] __libc_start_main +240
[4344057] _start +41
[0] ???