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SubjectRe: [GIT PULL] usercopy structs for v5.4-rc2
On Fri, Oct 04, 2019 at 10:53:41AM -0700, Linus Torvalds wrote:
> On Fri, Oct 4, 2019 at 3:42 AM Christian Brauner
> <christian.brauner@ubuntu.com> wrote:
> >
> > The only separate fix we we had to apply
> > was for a warning by clang when building the tests for using the result of
> > an assignment as a condition without parantheses.
>
> Hmm. That code is ugly, both before and after the fix.
>
> This just doesn't make sense for so many reasons:
>
> if ((ret |= test(umem_src == NULL, "kmalloc failed")))
>
> where the insanity comes from
>
> - why "|=" when you know that "ret" was zero before (and it had to
> be, for the test to make sense)
>
> - why do this as a single line anyway?
>
> - don't do the stupid "double parenthesis" to hide a warning. Make it
> use an actual comparison if you add a layer of parentheses.
>
> So
>
> if ((x = y))
>
> is *wrong*. I know the compiler suggests that, but the compiler is
> just being stupid, and the suggestion comes from people who don't have
> any taste.
>
> If you want to test an assignment, you should just use
>
> if ((x = y) != 0)
>
> instead, at which point it's not syntactic noise mind-games any more,
> but the parenthesis actually make sense.
>
> However, you had no reason to use an assignment in the conditional in
> the first place.
>
> IOW, the code should have just been
>
> ret = test(umem_src == NULL, "kmalloc failed");
> if (ret) ...

Yes, I had this as the original fix but I tried to keep the same
intention as the original author. I should have gone with my gut. Sorry
for the ugliness, I'll try to be better in the future.

Cheers,
Nathan

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