On Wed, 8 Nov 2000, Brian Paul wrote:
> Jon Leech wrote:
> >
> > On Fri, Nov 03, 2000 at 10:19:37AM -0800, Ron Bielaski wrote:
> > > Can someone help refresh my memory about what happens when an
> > > extension function exists in the library and is called but is
> > > not supported by the device?
> >
> > If you mean specifically WRT the Linux ABI, the correct answer at
> > this point is "whatever Brian's implementation in XFree86 4 does".
>
> It'll be a no-op. Both in XFree86/DRI and stand-alone Mesa.
I don't think you should rely on that. It's "undefined" - which
means anything from a No-op to a core dump.
> > It's an application error; making such an invalid call doesn't even
> > necessarily fall under the "will not terminate the GL" caveat in the
> > Specification IMO. More benign failure modes, such as returning
> > GL_UNSUPPORTED_OPERATION or generating a GLX error, are probably
> > desirable when possible - but they aren't always possible.
Exactly.
> I found it to be a simple matter to initialize all dispatch tables
> with pointers to no-op functions. The no-op function could easily
> be modified to abort or print an error message, but I'd like to
> keep it a plain no-op.
I think it should abort - otherwise people will write programs
(badly) using Mesa and wonder why they crash on other OpenGL's.
I'm not a great fan of (potentially) burdening drivers with
the need to operate correctly in the face of a broken application.
Whilst it's nice to hear that Mesa can provide a clean fallback
for missing functions - I don't think we should require other
OpenGL implementations to do the same.
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