Comment # 2 on bug 102797 from Samuel Pitoiset

[..] then Mesa reports the following errors:

Mesa: User error: GL_INVALID_OPERATION in glBeginTransformFeedback(no varyings
to record)
358502: message: major api error 4: GL_INVALID_OPERATION in
glBeginTransformFeedback(no varyings to record)

and the GPU hangs.

If you try the "special varying hack" patch from #101731 it fixes the issue.

*** This bug has been marked as a duplicate of bug 101731 ***