[Mesa-dev] Request to revert commit [3d81e11b49366b5636b8524ba0f8c7076e3fdf34] mesa: remove, unnecessary, 'sort by year' for the GL extensions

Roland Scheidegger sroland at vmware.com
Thu Sep 20 14:22:35 UTC 2018

Am 20.09.2018 um 16:10 schrieb Ian Romanick:
> On 09/20/2018 07:04 AM, Roland Scheidegger wrote:
>> Am 20.09.2018 um 15:09 schrieb Ian Romanick:
>>> On 09/19/2018 11:36 PM, Federico Dossena wrote:
>>>> As most of you are probably aware of, id2 and id3 games store GL
>>>> extensions in a buffer that's too small for modern systems. This usually
>>>> leads to a crash when MESA_EXTENSION_MAX_YEAR is not set, but what the
>>>> creator of this commit didn't know is that some id3 games (the more
>>>> "recent" ones) don't crash, they just truncate the string. As a result
>>>> of this commit, these games can't detect some extensions and therefore
>>>> don't work properly.
>>> It sounds like the problem is still that MESA_EXTENSION_MAX_YEAR is not
>>> set, so why not just set it?  Doesn't that fix the problem?
>> Yes it does.
>> It is however not really obvious why an app is failing (in this case the
>> game still ran, just shadows were broken - I suppose they were not
>> tested without some extensions being available).
>> I suppose we could try detecting affected apps by name, but I have no
>> idea which are (possibly some later published games using id tech 3 have
>> it fixed for real, I have no idea).
>> It is not a mesa specific problem neither, since apparently windows AMD
>> drivers suffer from the same issue. Maybe nvidia always reorders
>> extensions (or recognizes affected apps).
> Or maybe NVIDIA changes the extension string based on the app?
Yes, that's what I basically meant. They could reorder (or cut down) the
string based on app detection. Or they do it always.


>> Roland
>>>> I discovered this while trying to figure out why dynamic lights in Star
>>>> Trek Voyager Elite Force (2000) suddenly broke with Mesa 18. I discussed
>>>> this with Ronald Scheidegger, who's been very helpful and helped me
>>>> figure out what was going on.
>>>> Personally, I see nothing wrong with reverting this commit and keeping
>>>> the extensions sorted by year, it doesn't impact performance and it
>>>> doesn't break anything modern. What do you think about it?

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