[Mesa-dev] [Bug 30172] GL_EXT_framebuffer_blit function required

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Thu Sep 16 18:31:37 PDT 2010


--- Comment #18 from Tom Fogal <tfogal at alumni.unh.edu> 2010-09-16 18:31:37 PDT ---
bugzilla-daemon at freedesktop.org writes:
> --- Comment #17 from Brian Paul <brianp at vmware.com> 2010-09-16 12:08:29 PDT -
> --
> (In reply to comment #16)
> > Perhaps a sensible resolution is to only export those symbols if
> > a binary-only application is found requiring them, which works on
> > another GL implementation.
> I agree that if there's an existing application that fails out of the
> box w/ Mesa but not NVIDIA or AMD for this reason, we should then
> export the functio n too.  There's no sense in punishing end users
> like that.

FWIW, as an app developer, I'd vote that OGL 1.2, GLX 1.3, and
ARB_multitexture be the only statically exported functions.  It sucks
that some apps break, but they'll be fixed eventually.

Further, this is the only behavior that I know is guaranteed, and I
think windows behaves as above anyway.  It gives me warm fuzzy feelings
when my nightly test builds prove something good -- i.e. in this case
that I'm accessing functions via fqn pointer, as designed, and not
relying on undefined behavior.

> > Although I'm personally for preventive action, following the
> > "liberal" part of "be conservative in what you do, be liberal in
> > what you accept from others" .
> >
> > And yes, that does encourage applications to be broken, but the
> > fault fort hat lies in AMD and nVidia.
> >
> > At a more fundamental level, it lies in whoever reinvented the
> > wheel by add ing glXGetProcAddress instead of just using ELF weak
> > symbols (or dlsym if you somehow insist on querying symbols by
> > string).

ELF weak symbols do not allow one to decide behavior (OpenGL library)
at runtime -- mangling aside.

> I was involved in developing glXGetProcAddress.  Back then, I'm not
> sure that dlsym() was widely available on all the flavors of Unix
> having OpenGL.  There was also the possibility of using X/GLX on
> non-Unix systems.

We *still* have to support systems that do not have dlsym  =(

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