[erlang-questions] make_ref bug or feature?

Kenneth Lundin <>
Fri Mar 27 13:18:43 CET 2009


The node name is included in the encoding of a ref so if you have 2
unnamed nodes they will be able to create
the same values with make_ref.

If you have node a and node b they will create different values with make_ref.

/Kenneth

On Fri, Mar 27, 2009 at 12:52 PM, Kenneth Lundin
<> wrote:
> The reference is unique within one Erlang VM.
>
> I don't think you started 2 shells towards the same VM.
>
> /Kenneth
>
> On Fri, Mar 27, 2009 at 12:43 PM, Joe Armstrong <> wrote:
>> I got a question from Ivo Danihelka about make_ref().
>>
>> Isn't make_ref() supposed to generate "an almost unique reference" the
>> manual says
>>
>>    "Returns an almost unique reference.
>>     The returned reference will re-occur after approximately 2^82
>> calls; therefore it is unique enough for practical purposes."
>>
>> If I start two erlang shells and evaluate the following in both shells:
>>
>> 1> io:format("~p~n",[term_to_binary(make_ref())]).
>> <<131,114,0,3,100,0,13,110,111,110,111,100,101,64,110,111,104,111,115,116,0,0,
>>  0,0,34,0,0,0,0,0,0,0,0>>
>>
>> They *both* print the same thing - this violates the principle of
>> least astonishment.
>> (I thought I'd have to start 2^82 shells :-)
>>
>> Is this a bug or a feature?
>>
>> /Joe
>> _______________________________________________
>> erlang-questions mailing list
>> 
>> http://www.erlang.org/mailman/listinfo/erlang-questions
>>
>



More information about the erlang-questions mailing list