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[Brianp-h <905456@xxxxxxxxxxxxxxxxxx>]

(In reply to comment #3)
> (In reply to comment #2)
> > Sounds like a bug in the application to me. From the GLX 1.4 spec (though
> > that's certainly not new in 1.4):
> > 
> > "A non-NULL return value for glXGetProcAddress does not guarantee that an
> > extension function is actually supported at runtime. The client must also query
> > glGetString() or glXQueryExtensionsString to determine if an extension is
> > supported by a particular context."
> 
> I'm not sure what behaviour is correct. I relied on the the description of
> glXGetProcAddress:
> http://www.opengl.org/sdk/docs/man/xhtml/glXGetProcAddress.xml
> 
> "A NULL pointer is returned if function requested is not suported in the
> implementation being queried."

There's no conflict between the quotes above.  Getting a non-NULL
pointer is no indication whatsoever about whether the extension is
supported or not supported.

The reason is this:  suppose the very first call in main() is
glXGetProcAddress("glGenTransformFeedbacks").  At this point, the GL
library can't determine whether the extension is supported because it
hasn't even opened an X display connection.  Depending on which
display/GPU is used, the extension may or may not be supported.  So if
libGL implements the function (or can generate a dispatch stub for it)
it must return the pointer for it right away.

Later on, the app has to check GL_EXTENSIONS to see if
GL_ARB_transform_feedback2 is really supported.  If the extension is not
supported and the function is called anyway, things might blow up.

This is an application bug.

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https://bugs.launchpad.net/bugs/905456

Title:
  needs to be built with --disable-asm for super meat boy to work

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