[erlang-questions] Strange Socket Behaviour Was:Parents always take children with them?

Ulf Wiger <>
Sun Apr 29 11:00:53 CEST 2007


It can be tricky to detect crashes in processes created using spawn().
One way to do it is to run SASL, and use proc_lib:spawn() instead:

1> application:start(sasl).
ok
...
=PROGRESS REPORT==== 29-Apr-2007::10:54:20 ===
         application: sasl
          started_at: 
2> spawn(fun() -> 1=2 end).
<0.43.0>
=ERROR REPORT==== 29-Apr-2007::10:54:32 ===
Error in process <0.43.0> with exit value:
{{badmatch,2},[{erl_eval,expr,3}]}

   (now that particular error message was reported by the shell.)

3> proc_lib:spawn(fun() -> 1=2 end).
<0.45.0>
=CRASH REPORT==== 29-Apr-2007::10:55:11 ===
  crasher:
    pid: <0.45.0>
    registered_name: []
    error_info: {{badmatch,2},[{erl_eval,expr,3}]}
    initial_call: #Fun<erl_eval.20.112921583>
    ancestors: [<0.30.0>]
    messages: []
    links: []
    dictionary: []
    trap_exit: false
    status: running
    heap_size: 233
    stack_size: 21
    reductions: 83
  neighbours:

BR,
Ulf W

2007/4/29, Matthias Lang <>:
>
> Ludovic Coquelle writes:
>
> > ... so the normal behavior is that gen_recv doesn't block, which is
> probably
> > intended since you request 0 byte with infinity timeout
>
> More precisely, gen_tcp:recv(P, 0) will block until at least one octet
> of data is available, with the options Andrew is using.
>
> But yes, Andrew's problem is as you diagnosed:  his "critical" line of
> code will crash the process because the second argument to io:format
> must be a list.
>
> Matthias
> _______________________________________________
> erlang-questions mailing list
> 
> http://www.erlang.org/mailman/listinfo/erlang-questions
>
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