[erlang-bugs] io_list_to_binary returns wrong result for iolist of length 2^32

Paul Davis <>
Wed Apr 13 17:47:31 CEST 2011


On Wed, Apr 13, 2011 at 11:17 AM, Erik Søe Sørensen <> wrote:
>
>
> That would defeat the purpose of testing how iolist_to_binary handles large outputs though... :-)
>
> ----- Reply message -----
> Fra: "Paul Davis" <>
> Dato: ons., apr. 13, 2011 16:28
> Emne: [erlang-bugs] io_list_to_binary returns wrong result for iolist of length 2^32
> Til: "Erik Søe Sørensen" <>
> Cc: "" <>
>
> On Wed, Apr 13, 2011 at 9:38 AM, Erik Søe Sørensen <> wrote:
>> To reproduce:
>>
>>   $ erl
>>   Erlang R14B (erts-5.8.1) [source] [64-bit] [smp:8:8] [rq:8]
>>   [async-threads:0] [kernel-poll:false]
>>
>>   Eshell V5.8.1  (abort with ^G)
>>   [snip]
>>   6> iolist_to_binary(lists:foldl(fun(_,A) -> [A|A] end, [64],
>>   lists:seq(1,32))).
>>   <<>>
>>   7>
>>   size(v(-1)).
>>       0
>>   8> iolist_to_binary(lists:foldl(fun(_,A) -> [A|A] end, [64],
>>   lists:seq(1,31))).
>>   HUGE size (8589934632)
>>   Aborted
>>
>>
>> -- So, length 2^31 aborts the VM while 2^32 "simply" returns a wrong result.
>>
>> For size 2^31, I hypothesized that something went wrong when Eshell
>> memorizes the result, but that does not appear to be the case:
>>
>>   :riak_kv-basho$ erl
>>   Erlang R14B (erts-5.8.1) [source] [64-bit] [smp:8:8] [rq:8]
>>   [async-threads:0] [kernel-poll:false]
>>
>>   Eshell V5.8.1  (abort with ^G)
>>   1> iolist_to_binary(lists:foldl(fun(_,A) -> [A|A] end, [64],
>>   lists:seq(1,31))), ok.
>>   HUGE size (8589934632)
>>   Aborted
>>
>> These tests were run on:
>> $ uname -a
>> Linux flitwick 2.6.31-22-generic #73-Ubuntu SMP Fri Feb 11 19:18:05 UTC 2011
>> x86_64 GNU/Linux
>>
>>
>> /Erik
>> _______________________________________________
>> erlang-bugs mailing list
>> 
>> http://erlang.org/mailman/listinfo/erlang-bugs
>>
>
> My guess is that this is that your lists are recursive. Try changing:
>
> fun(_,A) -> [A|A] end
>
> into:
>
> fun(V,A) -> [V|A] end
>

Touché.

I can confirm that I'm getting the same results with R14B on OS X 10.6.7.


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