Messages in this thread | | | From | Linus Torvalds <> | Date | Tue, 21 Nov 2023 12:54:57 -0800 | Subject | Re: [PATCH 2/2] zstd: Backport Huffman speed improvement from upstream |
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On Tue, 21 Nov 2023 at 12:35, Nick Terrell <terrelln@meta.com> wrote: > > > > Honestly, any coding rule that includes "don't use the do-while-zero > > construct" is actively broken shit. > > > > Please just fix your upstream rules. Because they are incredible garbage. > > Yeah, that’s the plan. Visual Studios fixed that compiler bug in VS2015 [0], > so we should be safe to migrate to safer macros.
I don't even use MSVS, but a minute of googling shows that you should never have done that silly "avoid sane C", and you should always just have done
#pragma warning (disable: 4127)
for MSVC.
Honestly, the fact that the result was instead to disable that standard - and required - construct in the project makes me worry about the whole zstd thing. WTF?
The do-while-zero construct is _so_ important that there are (sane) projects that literally *require* the use of it. See for example MISRA code safety rules.
The kernel rules aren't quite that strict, but yes, do-while-zero is very much "you should *absolutely* do this" along with all the usual "make sure you have parentheses around macro arguments" rules.
We had some RFC patches for this area:
https://lore.kernel.org/all/20230511152951.1970870-1-mathieu.desnoyers@efficios.com/
And on that note, when I googled for the solution to the MSVC brain damage, I was distressed by how many hits I saw where people thought the do-while-zero pattern was some "legacy pattern".
That just shows that there are lots of incompetent people simply do not understand why it's actually *required* for reliable parsing of macros. This is not some "historical stylistic" issue, it's literally a correctness issue for generic macro usage.
Linus
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