Dbg: trace rendering of recursive functions, for example. indent

Question

I have a problem debugging a complex recursive function. I use the idiom:

dbg:tracer(),dbg:p(all,c),dbg:tpl(Mod,Fun1,x),dbg:tpl(Mod,Fun2,x)...

This gives me a flat list of calls to all functions where it is very difficult to figure out which return belongs to which call.

Is there an easy way to make this more readable, for example? indentation.

I could just post the processed text and indentation for each call as well as for each return, but that doesn't sound very elegant to me.

Answer 1

, , . , dbg:trace/2,3 , .

, dbg:trace:

-module(trtool).
-export([nested/2]).

nested({trace, _Pid, call, {Mod, Fun, Param}}, Level) ->
    io:format("~s~p:~p ~p\n", 
              [lists:duplicate(Level, "|   "), Mod, Fun, Param]),
    Level + 1;
nested({trace, _Pid, return_from, {Mod, Fun, Arity}, Rval}, Level) ->
    L = Level - 1,
    io:format("~s~p:~p/~b -> ~p\n", 
              [lists:duplicate(L, "|   "), Mod, Fun, Arity, Rval]),
    L;
nested(Any, Level) ->
    io:format("trace_msg: ~p\n", [Any]),
    Level.

, , . , , , , , , .

- , . dbg:trace .

nested , call return_from.

, dbg:tracer/2, process, - , .

1> dbg:tracer(process, {fun trtool:nested/2, 0}).                         
{ok,<0.70.0>}

, :

2> dbg:p(all, c), dbg:tpl(user_default,hop,x),dbg:tpl(user_default,rec,x).
{ok,[{matched,nonode@nohost,2},{saved,x}]}

, :

3> rec(3).                                                                
user_default:rec [3]
|   user_default:rec [3,1,3]
|   |   user_default:rec [3,1,2]
|   |   |   user_default:rec [3,1,1]
|   |   |   |   user_default:rec [3,1,0]
|   |   |   |   |   user_default:hop [3,1,0]
|   |   |   |   |   user_default:hop/3 -> {3,21}
|   |   |   |   user_default:rec/3 -> {3,21,1}
|   |   |   |   user_default:rec [6,2,-1]
|   |   |   |   |   user_default:hop [6,2,1]
|   |   |   |   |   user_default:hop/3 -> {2,46}
|   |   |   |   user_default:rec/3 -> {2,46,1}
|   |   |   user_default:rec/3 -> {5,67,2}
|   |   |   user_default:rec [8,3,0]
|   |   |   |   user_default:hop [8,3,0]
|   |   |   |   user_default:hop/3 -> {3,144}
|   |   |   user_default:rec/3 -> {3,144,1}
|   |   user_default:rec/3 -> {8,211,3}
|   |   user_default:rec [11,4,1]
|   |   |   user_default:rec [11,4,0]
|   |   |   |   user_default:hop [11,4,0]
|   |   |   |   user_default:hop/3 -> {3,258}
|   |   |   user_default:rec/3 -> {3,258,1}
|   |   |   user_default:rec [14,5,-1]
|   |   |   |   user_default:hop [14,5,1]
|   |   |   |   user_default:hop/3 -> {2,260}
|   |   |   user_default:rec/3 -> {2,260,1}
|   |   user_default:rec/3 -> {5,518,2}
|   user_default:rec/3 -> {13,729,5}
user_default:rec/1 -> {15,729}
{15,729}
4>

Answer 2

dbg, . dbg: tracer/2 , , .

, , ( ) .