GNU bug report logs - #20087
'gensym' is not guaranteed to return a fresh symbol

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Message #32 received at 20087 <at> debbugs.gnu.org (full text, mbox):

From: ludo <at> gnu.org (Ludovic Courtès)
To: Andy Wingo <wingo <at> pobox.com>
Cc: Mark H Weaver <mhw <at> netris.org>, 20087 <at> debbugs.gnu.org,
 rain1 <at> openmailbox.org
Subject: Re: bug#20087: gensym
Date: Thu, 23 Jun 2016 16:13:57 +0200

Andy Wingo <wingo <at> pobox.com> skribis:

> On Thu 24 Mar 2016 09:45, ludo <at> gnu.org (Ludovic Courtès) writes:
>
>> Mark H Weaver <mhw <at> netris.org> skribis:
>>
>>> It turns out the manual already has the following text in the ‘gensym’
>>> entry, which I think is sufficient.
>>>
>>>      The symbols generated by ‘gensym’ are _likely_ to be unique, since
>>>   their names begin with a space and it is only otherwise possible to
>>>   generate such symbols if a programmer goes out of their way to do so.
>>>   Uniqueness can be guaranteed by instead using uninterned symbols
>>>   (*noteSymbol Uninterned::), though they can’t be usefully written out
>>>   and read back in.
>>>
>>> What do you think?
>>
>> Oh indeed, I guess I had overlooked that.
>
> I just pushed something to master to error when serializing an
> uninterned symbol.  Otherwise compiling an uninterned symbol effectively
> interns it!  I am not sure that we can apply such a fix in 2.0 though as
> who knows, maybe someone is compiling something with symbols made with
> make-symbol.  WDYT?  If you agree we can close this bug.

That makes sense to me.

Thanks!
Ludo’.

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