libvisual-devel

[Libvisual-devel] lvdisplay news

[Vitaly V. B. <vit...@us...>]

Hi! :)

lvdisplay now supports multiple screens :)

...but before you start demo program...
there's a problem.

=======
*** glibc detected *** double free or corruption: 0x0810a338 ***
    [ that's my new glibc :) I like it! ]
Program received signal SIGABRT, Aborted.
[Switching to Thread 1083998352 (LWP 4063)]
0xffffe410 in ?? ()
(gdb) bt
    [ snip ]
#8  0x40029df1 in visual_mem_free (ptr=0x0) at lv_mem.c:49
#9  0x40026c41 in visual_plugin_unload (plugin=0x1fa) at lv_plugin.c:504
#10 0x40022e1e in visual_input_destroy (input=0x805fd40) at lv_input.c:163
#11 0x40023c08 in visual_bin_destroy (bin=0x805fcc8) at lv_bin.c:91
#12 0x40018bf5 in lvdisplay_finalize (v=0x8057300) at lv_display.c:326
#13 0x08048de5 in main (argc=1, argv=0xbffff6a4) at main.c:243
=======

======= example/main.c
	VisInput *input = visual_input_new("alsa");
 [snip]
	visual_bin_connect(bin, actor, input);
	visual_bin_connect(bin2, actor2, input);
 [snip]
	lvdisplay_finalize(v);
	lvdisplay_finalize(v2);
========

yup, "input" gets free()'d 2 times. How we're going to fix it?

a. forbid such kind of code. Add input->is_used field to debug it.
b. add refcounting to input and alike structures and free it accordingly

I think b. is nice here. Because we have a reentrant design, plugin
can be used multiple times.... or not?

and BTW, why not to move -O3 flag to configure scripts and use it only
when --enable-debug is not passed?

-- 
Vitaly
GPG Key ID: F95A23B9

Re: [Libvisual-devel] lvdisplay news

[Dennis S. <sy...@yo...>]

On Sun, 2004-11-21 at 22:38 +0200, Vitaly V. Bursov wrote:
> Hi! :)

HI!! where have you been!, I'm so glad to see that you're back !!!
*YAY!*

> lvdisplay now supports multiple screens :)

Neat! :)


> ======= example/main.c
> 	VisInput *input = visual_input_new("alsa");
>  [snip]
> 	visual_bin_connect(bin, actor, input);
> 	visual_bin_connect(bin2, actor2, input);
>  [snip]
> 	lvdisplay_finalize(v);
> 	lvdisplay_finalize(v2);
> ========

> yup, "input" gets free()'d 2 times. How we're going to fix it?

Ai, I see the problem!

> a. forbid such kind of code. Add input->is_used field to debug it.
> b. add refcounting to input and alike structures and free it accordingly
> 
> I think b. is nice here. Because we have a reentrant design, plugin
> can be used multiple times.... or not?

I agree, we should introduce refcounting. I've got to add something to 
this. What about introducing a VisObject structure, from which every
structure can 'inheritent' by making sure it's allocated in the top of
the struct like I did in VisUI and do ref counting things on a global
scale, something like visual_object_ref, visual_object_unref etc...

We could introduce cast macros so you get something like

VisInput *input = blahblah;
visual_object_unref (VISUAL_OBJECT (input)); to decrease the ref count.

What do you think ?, and are there things I should keep in mind, I
never implemented ref counting before, but I understand the idea...


> and BTW, why not to move -O3 flag to configure scripts and use it only
> when --enable-debug is not passed?

Please go ahead and do this, if you'd like :)

Cheers,
Dennis