[vlc-devel] [PATCH 09/12] network: io: Remove VLA usages

Rémi Denis-Courmont remi at remlab.net
Thu Dec 10 11:00:07 CET 2020


Hi,

The point of Linus (and Microsoft, if it's the same point as you seem to imply) is that VLAs are slower than FLAs. At least in GCC and LLVM, it's undeniably true. Hence why I okayed the input stream patch.

But heap allocations are vastly slower than VLAs.

Le 10 décembre 2020 09:25:17 GMT+02:00, Steve Lhomme <robux4 at ycbcr.xyz> a écrit :
>On 2020-12-09 17:49, Rémi Denis-Courmont wrote:
>> Le mercredi 9 décembre 2020, 17:47:18 EET Hugo Beauzée-Luyssen a
>écrit :
>>> On Wed, Dec 9, 2020, at 4:12 PM, Rémi Denis-Courmont wrote:
>>>> Le mercredi 9 décembre 2020, 11:38:42 EET Thomas Guillem a écrit :
>>>> Likewise, production builds must be done with GCC or Clang again
>for the
>>>> optimisations, as well as for licensing reasons (which we've
>covered
>>>> multiple times in the past already).
>>>
>>> Who said anything about changing anything about the release builds?
>> 
>> I don't think anybody said anything but what's the point in
>supporting a
>> compiler that won't be used for releases?
>
>* To have more Windows developers by making it easy for them to just 
>open Visual Studio and start hacking in VLC.
>* To get different compiler diagnostic. Just like having clang in 
>addition to GCC is helping find issues GCC doesn't report.
>* Possibly have more code analysis tools
>
>>>> just to support "incomplete" C11 compilers. It's open-source so you
>are
>>>> free to fork if you want to but I don't want to have to deal with
>it.
>>>
>>> This sounds a lot like "If you disagree with me, get out", with
>which I'd
>>> have to disagree.
>> 
>> I'm saying that nobody, not me, not other developers, and especially
>not those
>> who expressed a desire to allow GCCisms/Clangisms in the code base,
>should
>> have to deal with the extra effort from VLAs being systematically
>removed and
>> forbidden, except those few who care to play with MSVC.
>> 
>> I'm saying that users of non-MSVC builds should not have to suffer
>bugs or
>> worse performance because a few want to play with MSVC without having
>to
>> maintain their own branch.
>
>The point of Linus and Microsoft not to support VLA is mainly 
>performance based. We're not getting slower code here.
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