From: Ara.T.Howard@...
Date: 2005-05-17T08:50:30+09:00
Subject: Re: rb_gc_mark question

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On Tue, 17 May 2005, Nikolai Weibull wrote:

> Ara.T.Howard wrote:
>
>>   static VALUE
>>   convertgslmatrixToRubyMatrix (gsl_matrix * dm)
>>   {
>>     int i, j;
>>     VALUE result;
>>     VALUE rows =3D rb_ary_new ();
>>     for (i =3D 0; i < dm->size1; i +=3D 1)
>>       {
>>         VALUE currow =3D rb_ary_new ();
>>         rb_gc_mark (currow);
>>         rb_ary_push (rows, currow);
>>         for (j =3D 0; j < dm->size2; j +=3D 1)
>>           {
>>             double val =3D gsl_matrix_get (dm, i, j);
>>             VALUE rval =3D rb_float_new (val);
>>             rb_ary_push (currow, rval);
>>           }
>>       }
>>     result =3D rb_funcall (cMatrix, rb_intern ("rows"), 2, rows, Qnil);
>>     return result;
>>   }
>
> I don=E2=80=99t understand why you need to rb_gc_mark those values.  They=
=E2=80=99re
> pointed to by objects on the stack, so a GC sweep won=E2=80=99t remove th=
em.
> Neither of the volatile specifiers in the original are needed either, as
> you write (or I am definitely missing something).  I don=E2=80=99t see ho=
w they
> would be optimized away anyway.  Well, actually, the 'result' variable
> should be optimized away :-), just return the result of the rb_funcall
> immediately.
>
> Perhaps I don=E2=80=99t understand what you want to do here,
>        nikolai

just wanting you to confirm exactly what i was thinking.  the code was so
aggressive with rb_gc_mark that i started thinking i might be missing
something!  you'll note my version didn't have them at all...

so we are in total agreement - i'm reading the code for someone else and ju=
st
trying to figure out what they thought they were doing.  needless to say th=
is
extension has some memory issues ;-)

thanks for the clarification.

cheers.

-a
--=20
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| email :: ara [dot] t [dot] howard [at] noaa [dot] gov
| phone :: 303.497.6469
| renunciation is not getting rid of the things of this world, but acceptin=
g
| that they pass away. --aitken roshi
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