[MPlayer-G2-dev] Re: About final cfg.h (config layer 0 discussion)

[D Richard Felker III]

On Mon, May 26, 2003 at 05:48:53PM +0300, Andriy N. Gritsenko wrote:
> >This is total nonsense since some of vf->cfg may be pointers to other
> >dynamically allocated stuff. With all this confusion about who will
> >allocate, free, and update what, you're bound to create memory leaks.
> 
>     Where did you find memory leak in lines above? Caller (upper level of
> application) allocate memory, use it as temporal and then free it. No
> other level (core or other application layer) doesn't know what is that
> memory. No leaks at all!

vf->cfg may be full of string pointers.

>     On other hand, if you will change vf->cfg directly in multithreaded
> application, you will get a memory leak - you don't know if some of
> parameters there are static or allocated and don't know if it will be
> reallocated or freed while you changing it. So don't touch that vf->cfg
> directly if you don't want memory leaks! :)
>     About dinamically allocated data as string parameters - when you'll
> call VFCTRL_GET_PARAMS control you'll get only copy of parameters then
> only module itself may allocate and free own copies. Just let's have all
> documented well.
> 
> >IMO you should just let the program modify vf->cfg directly. If the
> >module needs an untouchable copy of the 'current value' of some param
> >to use when deciding whether a runtime change it allowed, it should
> >make its own copy of the data in vf->priv. Otherwise it should expect
> >the program to call VFCTRL_SET_PARAMS immediately after changing
> >vf->cfg.
> 
>     How will you know if filter allowed set some parameter only on filter
> opening? If your application will change some parameter (for example,
> size of frame) which is critical for the filter then would you guarantee
> that _any_ filter will work correctly (think, please, about multitasking
> or multithreading application) until you say VFCTRL_SET_PARAMS for it? I

No, it's nonsense to allow setting filter options in a separate
thread. MPlayer will not be polluted with such thread/locking/etc.
crap. It's even a problem with your design unless the filters do some
sort of locking during VFCTRL_SET_PARAMS, and filters MUST NOT have to
be thread-aware!! If the calling program wants to do such idiocy, it
should have to make its thread exclusive before setting vf->cfg and
calling VFCTRL_SET_PARAMS.

> would to say you may have a big mess if you will change some parameter
> directly. BTW, on running application you may have that vf->cfg already
> dinamically allocated and changed right when you trying to modify it. I'm
> against it very much and I've against have that vf->cfg visible for
> higher level of application at all - it's _private_ area of variables.

No. vf->priv is private. vf->cfg is totally public. This is clean C
code, not some object-oriented encapsulated bullshit with data-hiding.

Rich