[VDPAU] Should we export these functions ? (Re: Exporting the flash workaround functions)

[José Hiram Soltren]

Hi Emil:

Inline.

On 07/01/2014 05:06 PM, Emil Velikov wrote:
> José Hiram Soltren wrote:
>> As for the DRI2 functions referenced in src/vdpau_wrapper.c: I don't see a
>> reason for these to be non-static either. We implement our own mesa_dri2.c
>> in libvdpau and only use this internally. I've CC'd Aaron who might be able
>> to comment further. You are probably correct here as well.
> 
> José,
> 
> Thanks for the input. Yet, I do not see how one can define a function as
> static and then use it in another source file. Perhaps I'm missing something ?

As implemented in http://cgit.freedesktop.org/~aplattner/libvdpau/tree/ as of
the tag 'libvdpau-0.8':

src/mesa_dri2.h - VDPAU specific version of mesa_dri2.h, defines:

_vdp_DRI2QueryExtension
_vdp_DRI2QueryVersion
_vdp_DRI2Connect
_vdp_DRI2RemoveExtension

src/mesa_dri2.c - implements these symbols.

src/vdpau_wrapper.c - uses these symbols through '#include "mesa_dri2.h"'.

As implemented, these four symbols in mesa_dri2.h must not be flagged with the
'static' keyword, since they are used in a different source file, as you
correctly noted.

In my reply, "non-static" should have read "exported by VDPAU in a .so". Since
we go out of our way to implement VDPAU specific DRI functions for internal
use, there is no good reason to export them.

I agree with Aaron's proposal to use '-fvisibility=hidden'. This also agrees with:

https://www.gnu.org/software/gnulib/manual/html_node/Exported-Symbols-of-Shared-Libraries.html

I hope that clarifies any confusion.

--José

> Aaron Plattner wrote:
>> Correct, those symbols should not be exported.  -fvisibility=hidden or
>> equivalent options sound like the right way to go there on sufficiently
>> new compilers, though there are also no prototypes for them in the
>> public API headers so it should be obvious that they're not part of the
>> exported ABI...
> 
> That's exactly what I had planned Aaron. Check if the compiler supports
> -fvisibility... and add a couple of symbols (PUBLIC & PRIVATE) in a private
> header. Then explicitly annotate the symbols where required. Thanks for the
> confirmation.
> 
> Will try to find some time over the weekend.
> 
> Thanks gents,
> Emil
> 
> P.S. Was not subscribed to the list, so I had to butcher your replies from the
> ML archive. Just subscribed so I won't miss any replies :)
>