How to show Erlang call stack?

Question

I need to debug some module in foreign system. The module has public function foo() - how can I know place (module and function name) from which foo() given module

Answer 1

This might work:

where_am_i() ->
    try throw(a)
    catch throw:a ->
            erlang:get_stacktrace()
    end.

Except that it doesn't work for tail calls. For example, given these two functions:

foo() ->
    where_am_i().

bar() ->
    X = where_am_i(),
    {ok, X}.

I get these results:

4> foo:foo().
[{foo,where_am_i,0},
 {erl_eval,do_apply,5},
 {shell,exprs,6},
 {shell,eval_exprs,6},
 {shell,eval_loop,3}]
5> foo:bar().
{ok,[{foo,where_am_i,0},
     {foo,bar,0},
     {erl_eval,do_apply,5},
     {shell,exprs,6},
     {shell,eval_exprs,6},
     {shell,eval_loop,3}]}

That is, I can only see bar, since foo's call frame has been left already when where_am_i is called.