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

Ian Romanick idr at freedesktop.org
Fri Sep 21 12:55:59 UTC 2018

On 09/21/2018 05:36 AM, Federico Dossena wrote:
> Do you know of other applications that are affected by the order or
> extensions? This is the first time I encounter this problem.

Just the idTech2 and idTech3 games.  One thing I think we can do... for
the game where you hit this, can you provide the output of 'strings
game_executable | grep 'GL_[A-Z3]' ?  I'll make a piglit test that
verifies that all the supported extensions from that list occur in the
first 4k of the extension string.  Having tests will help prevent this
issue from coming back.

> On 2018-09-21 13:56, Ian Romanick wrote:
>> On 09/20/2018 04:42 PM, Timothy Arceri wrote:
>>> On 20/9/18 11:09 pm, Ian Romanick wrote:
>>>> 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?
>>> There is no driconfig option for this currently. Personally I'd rather
>>> just sort the extensions (even if it was only for 32bit builds of Mesa)
>>> rather than adding a bunch of code and extra entry's into driconfig.
>>> Or are you saying you would prefer we do nothing and people should use
>>> MESA_EXTENSION_MAX_YEAR be required to use?
>> I was mostly trying to feel out the current (and possible future) extent
>> of the problem space.  I've never been fond of the by-year sorting, but
>> I don't hate it either.  My biggest annoyance is that it feels like
>> we've made a bunch of changes to this area over the years without really
>> thinking it through... and now we're back here.  I don't want to be back
>> here in another 2 years. :)
>>>>> 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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