[gst-devel] [gst-cvs] ensonic gst-plugins-base: gst-plugins-base/ gst-plugins-base/docs/libs/ gst-plugins-base/gst-libs/gst/audio/ gst-plugins-base/gst-libs/gst/interfaces/ gst-plugins-base/gst-libs/gst/rtp/ gst-plugins-base/gst-libs/gst/sdp/

[Stefan Kost]

Hi Tim,

Tim Müller schrieb:
> On Tue, 2007-10-30 at 13:32 -0700, ensonic at kemper.freedesktop.org wrote:
> 
>> CVS Root:       /cvs/gstreamer
>> Module:         gst-plugins-base
>> Changes by:     ensonic
>> Date:           Tue Oct 30 2007  20:32:28 UTC
>>
>> Log message:
>> 	* docs/libs/gst-plugins-base-libs-sections.txt:
>> 	* gst-libs/gst/audio/gstaudiofilter.h:
>> 	* gst-libs/gst/interfaces/mixer.h:
>> 	* gst-libs/gst/rtp/gstbasertpdepayload.c:
>> 	* gst-libs/gst/rtp/gstbasertpdepayload.h:
>> 	* gst-libs/gst/sdp/gstsdpmessage.c:
>> 	  Fix the docs according to what gtk-doc complained about.
>> ...
>> http://freedesktop.org/cgi-bin/viewcvs.cgi/gstreamer/gst-plugins-base/gst-libs/gst/rtp/gstbasertpdepayload.h.diff?r1=1.20&r2=1.21
> 
> I wonder whether it's really a good idea to use GST_REMOVE_DEPRECATED in
> public header files, since it breaks ABI.

I though it is quite clear. This is from gstreamer/configure.ac:
# GST_DISABLE_DEPRECATED: hide the visibility of deprecated
# functionality from the API that gstreamer uses
# GST_REMOVE_DEPRECATED: don't compile deprecated functionality (breaks ABI)
DEPRECATED_CFLAGS="-DGST_DISABLE_DEPRECATED"
AC_SUBST(DEPRECATED_CFLAGS)

So people that actually use GST_REMOVE_DEPRECATED should be well aware that its
breaks binary compatibility. But then gstreamer is used in environment where you
have that under control and imho its a nice feature to be able to leave out
cruft with just one additional flag.

I mean even users on a distro like gentoo could use it, as they can recompile
their whole system if they want (not that it makes a lot sense there).

> 
> So far we've only been using GST_REMOVE_DEPRECATED in .c files to remove
> deprecated functions completely from our lib and guarded the declaration
> of those functions with GST_DISABLE_DEPRECATED.
> 
> What we've done in public headers last time this issue came up is use
> GST_DISABLE_DEPRECATED and then put differently-named dummy fields in
> the #else bracket, so code compiled with DISABLE_DEPRECATED couldn't use
> deprecated structure members any longer, but binary compatibility would
> still be maintained. See
> gst-plugins-base/gst-libs/gst/interfaces/mixer.h for an example.

For GST_DISABLE_DEPRECATED a dummy approach makes sense. But
GST_REMOVE_DEPRECATED means remove. So in theory we need:

#ifndef GST_DISABLE_DEPRECATED
#ifndef GST_REMOVE_DEPRECATED
/* this value can be modified by the child if needed, deprecated */
guint queue_delay;
#endif
#else
guint _deprecated;
#endif

(hopully I have not mixed up the neagtions).

> 
> I can see that there are reasons for wanting to remove those fields
> completely (ie. save a few bytes), but I wonder if it's not more
> desirable to maintain ABI/structure sizes, given that derived objects
> may sit in different modules.

Good that you brought it up. Lets decide and fix.

Stefan

> 
>  Cheers
>   -Tim
> 
> 
> 
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