[erlang-questions] make_ref bug or feature?

Kenneth Lundin <>
Fri Mar 27 12:52:25 CET 2009


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
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