From: Sigurd <cu9ypd@...>
Date: 2012-02-10T23:37:06+09:00
Subject: Re: Symbol garbage collection

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Hi,
Ruby store all object, method and variable names as a symbols. That's =
why symbol GC might be dangerous.
The only thing i'm not clear about is the rb_gc_mark_symbols method that =
is implemented in parse.y and is called for every GC round.
Can someone explain what's its purpose?

On Feb 10, 2012, at 3:52 PM, Jes=FAs Gabriel y Gal=E1n wrote:

> On Fri, Feb 10, 2012 at 1:48 PM, Robert Klemme
> <shortcutter@googlemail.com> wrote:
>> 2012/2/10 Jes=FAs Gabriel y Gal=E1n <jgabrielygalan@gmail.com>:
>>> On Fri, Feb 10, 2012 at 11:07 AM, Robert Klemme
>>> <shortcutter@googlemail.com> wrote:
>>>> On Fri, Feb 10, 2012 at 8:28 AM, Dido Sevilla =
<dido.sevilla@gmail.com> wrote:
>>>>> I've always wondered why Ruby didn't do garbage collection of =
symbols,
>>>>> when Lisp implementations here and there did so, and in fact they =
are
>>>>> essential in macro programming because Lisp programs tend to =
create a
>>>>> lot of unique symbols at runtime, especially in macro code, with =
such
>>>>> contrivances as gensym in Scheme and Common Lisp and uniq in Arc.
>>>>=20
>>>> In Ruby the idea is rather to only use a fixed amount of Symbols in
>>>> the program and use Strings for everything that changes often.
>>>=20
>>> I have a question about this rule of thumb: did this rule came to
>>> existence precisely due to the fact that Symbols are not GCed, or =
was
>>> it the other way around?
>>=20
>> I can't speak for Matz but from what I have gathered it was his very
>> conscious design decision to have Symbols not GC'ed.
>>=20
>>> Maybe if Symbols' garbage collection wasn't a problem, that rule =
about
>>> using them just in a limited and fixed amount would have never
>>> existed.
>>=20
>> But without this distinction there is really no point in having =
String
>> AND Symbol any more.  A Symbol then would merely be a String which is
>> frozen by default.  I prefer the current situation because it makes
>> much more sense in my opinion.  With a symbol we denote a fixed
>> identifier which is used in multiple locations of an application and
>> with a String we denote arbitrary text content.
>=20
> Makes sense, thanks.
>=20
> Jesus.
>=20


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