[Mesa-dev] [Bug 106833] glLinkProgram is expected to fail when vertex attribute aliasing happens on ES3.0 context or later

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=106833

xinghua <xinghua.cao at intel.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yang.gu at intel.com,
                   |                            |yunchao.he at intel.com

--- Comment #2 from xinghua <xinghua.cao at intel.com> ---
(In reply to Tapani Pälli from comment #1)
> FYI I noticed this test prints out following before failing tests:
> 
> "Testing with shader that has entirely unused attributes".
> 
> IMO the issue here is that Mesa does not assign a location to entirely
> unused attributes (their location will be -1) and therefore checks for
> overlapping/aliasing locations are not done. I've proven this by skipping
> opt_dead_code for certain variables in the test and that makes it pass as we
> run the appropriate check in linker.
> 
> I'm not sure if this testing overlapping locations of unused attributes
> makes actually sense or how to fix the situation.

The  original target of these cases are surely testing with shader that has
entirely unused attributes. These cases are used to verify whether GLES
implementation follows the spec, and spec defines that "The existence of
aliasing is determined by declarations present after preprocessing", "not
depend on compiler optimizations which might be implementation-dependent".

I do also know nothing why spec defines aliasing like above. Does OpenGL 4.5
defines aliasing the same as OpenGL ES 3.0?(I had not found related information
in OpenGL spec) And Do other OpenGL ES 3.0 implementations(intel or non-intel)
of attribute aliasing also depend on compiler optimizations?
Thank you.

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