From the GL_OES_texture_buffer spec:
"If no buffer object is bound to the buffer texture, the results
of the texel access are undefined."
this can be interpreted as allowing any result to come back, but not
terminate the program.
The current solution is not entirely complete, as it could still try to
get a wrong address for the shader state address.
This can be checked with piglit test
arb_texture_buffer_object-render-no-bo; the test is skip because it
requires OpenGL 3.1, but if overriding the version then it will crash.
Signed-off-by: Alejandro Piñeiro <apinheiro@igalia.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13409>
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