[Mesa-dev] [RFC] glsl: bump default glsl version to 130 if EXT_gpu_shader4 used

[Timothy Arceri]

On 16/05/18 09:41, Marek Olšák wrote:
> On Tue, May 15, 2018 at 4:59 PM, Jason Ekstrand <jason at jlekstrand.net 
> <mailto:jason at jlekstrand.net>> wrote:
> 
>     On Tue, May 15, 2018 at 1:38 PM, Marek Olšák <maraeo at gmail.com
>     <mailto:maraeo at gmail.com>> wrote:
> 
>         On Tue, May 15, 2018 at 4:09 PM, Ilia Mirkin
>         <imirkin at alum.mit.edu <mailto:imirkin at alum.mit.edu>> wrote:
> 
>             On Tue, May 15, 2018 at 3:54 PM, Marek Olšák
>             <maraeo at gmail.com <mailto:maraeo at gmail.com>> wrote:
>             > On Tue, May 15, 2018 at 3:36 PM, Ilia Mirkin <imirkin at alum.mit.edu <mailto:imirkin at alum.mit.edu>> wrote:
>             >>
>             >> The extension is totally different... it adds things like "unsigned
>             >> int", and a ton of texture*/shadow* variants. If it helps this one
>             >> shader compile, that's a coincidence. IMO it's dangerous to start
>             >> throwing things like this in.
>             >
>             >
>             > That's why it prints a warning. The extension isn't exposed.
> 
>             It bumps the GLSL version to 1.30 though, which e.g. makes
>             "in" and
>             "out" a keyword. And a bunch of other stuff like that. Just
>             seems
>             dangerous.
> 
> 
>         It may seem dangerous, but not after you consider that it
>         changes a compile failure into "some behavior" and a warning.
>         That is pretty safe, because you'll either get a compile failure
>         again, or you'll get correct behavior as if a subset of the
>         extension was exposed. Either case is harmless.
> 
> 
>     This does seem really sketchy.  It's a spec violation because we are
>     required to fail the shader compile for unknown extensions.  And
>     it's letting a shader through even though we know it's likely to die
>     in a fire later on due to the fact that we only implement 30% of
>     gpu_shader4.  On top of that, the best justification we can come up
>     with is a broken app that assumes gpu_shader4 but doesn't actually
>     use it.
> 
> 
> The best justification that we actually have is that there is an app 
> which uses GLSL 1.20 + EXT_gpu_shader4 but actually only needs GLSL 1.30.
> 
> Marek

I did consider just using force_glsl_version, maybe we should just do 
that for now. Old extensions like these are going to haunt us for a 
while I think. I was trying to get Doom (2016) running yesterday and it 
seems it uses bits from EXT_direct_state_access.