From: Alex Gutteridge <alexg@...>
Date: 2010-11-25T19:13:15+09:00
Subject: Re: Ruby Programming

On Wed, 24 Nov 2010 13:02:09 +0900, Tridib Bandopadhyay
<tridib04@gmail.com> wrote:
> Alex Gutteridge wrote in post #962544:
>> On Fri, 19 Nov 2010 10:30:30 +0900, Tridib Bandopadhyay
>> <tridib04@gmail.com> wrote:
>>> which i tried to print out.?
>>>
>>> Regards
>>>
>>> Tridib
>>
>> Sure. There's also the GC_NOTIFY and GC_DEBUG defines in gc.c and
>> GC::Profiler which you can call from Ruby. As people have already
>> pointed
>> out *any* Ruby program will require memory allocation and hence GC.
> 
> Can you tell me how to call those two?...And do I need to write some 
> print statement within those one.??
> 
> Regards

There doesn't seem to be any mystery here, just search for GC_NOTIFY in
gc.c and set it to true rather than false. E.g.

#define GC_NOTIFY 0

becomes

#define GC_NOTIFY 1

That change alone prints "start garbage_collect()" whenever
garbage_collect() is run:

GUTTEA$ ./ruby -e 'GC.start'
start garbage_collect()
end garbage_collect()

Defining RUBY_MARK_FREE_DEBUG in gc.h gives lots more info as well:

GUTTEA$ ./ruby -e 'GC.start'
start garbage_collect()
mark: -> iseq (0x100624900)
 require @ <internal:lib/rubygems/custom_require>
 mark: -> iseq (0x100624cb0)
  rescue in require @ <internal:lib/rubygems/custom_require>
 mark: <- iseq (0x100624cb0)
mark: <- iseq (0x100624900)
mark: -> iseq (0x100612b90)
 gem @ <internal:gem_prelude>
mark: <- iseq (0x100612b90)
mark: -> iseq (0x10060c950)

[.......]

I don't see any problem with adding your own debug statements as well if
you want:

static int
garbage_collect(rb_objspace_t *objspace)
{
    struct gc_list *list;
    rb_thread_t *th = GET_THREAD();
    INIT_GC_PROF_PARAMS;

    if (GC_NOTIFY) printf("start garbage_collect()\n");

    printf("WoopWoop\n");

[....]

GUTTEA$ ./ruby -e 'GC.start'
start garbage_collect()
WoopWoop

[....]

-- 
Alex Gutteridge