[erlang-questions] Recursive Heap Allocation

CGS <>
Tue Jul 24 06:40:43 CEST 2012


Sorry, I meant ipv4_addrs:test/1, not ipv4_addrs:next/1. As for how to
avoid this crash, I suppose it becomes obvious not to rely on writing the
addresses to the console, but to devise a test within ipv4_addrs:test/1
(either count the addresses, or check and report only errors which are
coming from reaching undesired values).

Good luck!
CGS




On Tue, Jul 24, 2012 at 6:25 AM, CGS <> wrote:

> Hi,
>
> I managed to reproduce the error and the problem is coming from
> io:format/2 (I suppose writing is too slow for the loop itself, so, the io
> buffer gets overflowed). Try this replacing ipv4_addrs:next/1 with this:
>
> test(done) -> done;
> test(Addr) -> test(next(Addrs)).
>
> CGS
>
>
>
>
> On Mon, Jul 23, 2012 at 11:50 PM, Greg Martin <>wrote:
>
>>  I think you're misunderstanding. It's like a 256 based number scheme.
>> 0.255
>> is followed by 1.0 not 1.255.
>>
>> -----Original Message-----
>> From: Ronny Meeus [mailto:]
>> Sent: Monday, July 23, 2012 2:00 PM
>> To: Bob Ippolito
>> Cc: Greg Martin; 
>> Subject: Re: [erlang-questions] Recursive Heap Allocation
>>
>> Hello
>>
>> I think there is an issue in the logic of your code:
>>
>> next( { First, Second, Third, 255 } ) -> { First, Second, Third + 1, 0 };
>> next( { First, Second, Third, Fourth } ) -> { First, Second, Third,
>> Fourth +
>> 1 }.
>>
>> If nothing matches, the last clause will do and the last number will be
>> incremented until 255 is reached.
>> If I understand you well, I would think that the looping continues with
>> the
>> last but 1 clause but here is the problem: you pass 0 instead of 255 so
>> there is no match and you end up in the last clause again.
>> Result is an endless loop.
>>
>> I think the code should be corrected like this:
>> next( { First, Second, Third, 255 } ) -> { First, Second, Third + 1, 255
>> };
>> next( { First, Second, Third, Fourth } ) -> { First, Second, Third,
>> Fourth +
>> 1 }.
>>
>> ---
>> Best regards,
>> Ronny
>>
>> On Mon, Jul 23, 2012 at 10:04 PM, Bob Ippolito <> wrote:
>> > You're probably generating output too fast, there's no flow control in
>> > io:format/2. You can generate things to print much faster than they
>> > get printed, which results in the io server accumulating so many
>> > messages in its mailbox that you eventually run out of memory and/or
>> > the machine grinds to a halt due to swapping.
>> >
>> >
>> > On Mon, Jul 23, 2012 at 12:50 PM, Greg Martin <>
>> wrote:
>> >>
>> >> I'm just learning erlang using Erlang R15B01 (erts-5.9.1) on Windows.
>> >> I'm wondering why ipv4_addrs:test(ipv4_addrs:first()) leads to the
>> >> crash below and how it can be called so that it doesn't. Thanks.
>> >>
>> >> {1,2,22,127}
>> >> {1,2,22,128}
>> >> {1,2,22,129}
>> >> {1,2,22,130}
>> >> {1,2,22,131}
>> >> {1,2,22,132}
>> >> {1,2,22,133}
>> >> {1,2,22,134}
>> >>
>> >> Crash dump was written to: erl_crash.dump
>> >> eheap_alloc: Cannot allocate 373662860 bytes of memory (of type
>> "heap").
>> >>
>> >>
>> >> Abnormal termination
>> >>
>> >>
>> >> -module(ipv4_addrs).
>> >>
>> >> -export([first/0, next/1, test/1]).
>> >>
>> >> first()->
>> >>         { 1,1,0,0 }.
>> >>
>> >> next( { 255, 255, 255, 255 } ) -> done; next( { 9, 255, 255, 255 } )
>> >> -> { 11, 0, 0, 0 }; next( { 172, 15, 255, 255 } ) -> { 172, 32, 0, 0
>> >> }; next( { 192, 167, 255, 255 } ) -> { 192, 169, 0, 0 }; next( {
>> >> First, 255, 255, 255 } ) -> { First + 1, 0, 0, 0 }; next( { First,
>> >> Second, 255, 255 } ) -> { First, Second + 1, 0, 0 }; next( { First,
>> >> Second, Third, 255 } ) -> { First, Second, Third + 1, 0 }; next( {
>> >> First, Second, Third, Fourth } ) -> { First, Second, Third, Fourth
>> >> +
>> >> 1 }.
>> >>
>> >> test(done) -> done;
>> >> test(Addr) ->
>> >>         io:format("~p~n", [Addr]),
>> >>         Next = next(Addr),
>> >>         test(Next).
>> >>
>> >> _______________________________________________
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>> >> 
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>> >
>> >
>> >
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