Messages in this thread | | | From | Linus Torvalds <> | Date | Fri, 18 Sep 2020 10:23:54 -0700 | Subject | Re: [GIT PULL] percpu fix for v5.9-rc6 |
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On Fri, Sep 18, 2020 at 9:17 AM Gustavo A. R. Silva <gustavoars@kernel.org> wrote: > > This bug could have been prevented by either adopting better > coding practices or through the use[3] of the recent struct_size() helper.
Well, my unspoken point was that coding practices are just theoretical. Coding practices don't help - actual *checking* of them helps.
I realize that structures with flexible-array member are allowed to use sizeof() in standard C, but if we want to make sure this doesn't happen, we would need to have a stricter model than that. But a quick google didn't find any flag to enable such a stricter mode.
I guess a sparse warning would work, but sparse already has too many warnings and as a result most people don't care - even if they were to run sparse in the first place.
Is there some gcc option that I didn't find to help find any questionable cases?
Because if we have a coding practice that you should use 'struct_size()', then we should also have a way to _verify_ that.
The whole - and really ONLY - point of using flexible arrays was that it would protect against these things. And as things are now, it simply doesn't. It's not an actual improvement over just using a zero-sized array.
(Slightly related: copying a struct has the exact same issue. A flexible array is no better than a zero-sized array, and generates the same code and the same lack of any warnings, afaik).
Linus
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