[erlang-questions] Weird behavior with the visual debugger.

Dan Gudmundsson <>
Tue Nov 25 09:19:58 CET 2014


First one is problematic, I would make a debug macro for timeouts and set
it to infinity when debug
compiled.

The second one looks like a bug in the interpreter.

/Dan

On Mon, Nov 24, 2014 at 10:23 PM, Matthieu Tourne <
> wrote:

> I'm using Erlang/OTP 17 on Mac OS, and I'm seeing a weird behavior with
> the debugger.
>
> I'm pretty new to the Erlang world, so not sure what is expected or not ..
>
> So here is what I'm doing :
>
> $> ii(module_to_debug).
> $> im().
>
> This will launch the visual debugger with the module I want to debug.
> I've been trying to do 2 different things :
>
> 1. Set up a break point in my code
> I'm setting a break point, and setting up the option "Auto attach - On
> Break".
>
> My problem is that what I want to step through is behind a gen_server
> call, and the whole thing times out before I can do any meaningful
> debugging.
> Is there a way to prevent the timeouts *without* having to change the code
> that does the call ?
>
> 2. Inspecting the call stack on exception
> In this case I'm just setting the option "Auto attach - On Exit".
>
> That is where the weirdest behaviors lies, upon reaching the exception I
> get 2 blank debugger windows, one saying "State: uninterpreted" at the
> bottom and the other one "Loading module..."
> In my Erlang console I get the following message (which only ever happen
> if I'm trying to attach the debugger this way) :
>
> $> 13:08:38.300 [error] gen_server dbg_iserver terminated with reason: no
> match of right hand value [] in dbg_iserver:handle_call/3 line 287
> (I'm using lager, hence the formatting).
>
> All subsequent calls to what leads to the exception behave weirdly :
>
> ** exception exit: {noproc,{gen_server,call,
>
>  [undefined,{get_meta,<0.14874.0>},infinity]}}
> $> 13:20:22.337 [error] CRASH REPORT Process <0.14874.0> with 2 neighbours
> exited with reason: no such process or port in call to
> gen_server:call(undefined, {get_meta,<0.14874.0>}, infinity) in
> gen_server:init_it/6 line 330
>
>
> I'm not sure what I'm doing wrong here, or if there is a real problem.
> If you can eventually point me to an article that explains how to make my
> two possible workflows above work, that would be great too.
>
>
> Thank you,
> Matthieu
>
>
> ps: Yes I already know "dbg:tracer(),dbg:p(all,c),dbg:tpl(ess_tcp, x)."
> Which doesn't entirely solve my problem.
>
>
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