Messages in this thread | | | From | Miguel Ojeda <> | Date | Fri, 16 Apr 2021 23:39:00 +0200 | Subject | Re: [PATCH 04/13] Kbuild: Rust support |
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On Fri, Apr 16, 2021 at 10:58 PM Willy Tarreau <w@1wt.eu> wrote: > > No, two: > - ok in %rax (seems like it's "!ok" technically speaking since it > returns 1 on !ok and 0 on ok) > - foo_or_err in %rdx
Yes, but that is the implementation -- conceptually you only have one or the other, and Rust won't allow you to use the wrong one.
> However then I'm bothered because Miguel's example showed that regardless > of OK, EINVAL was always returned in foo_or_err, so maybe it's just > because his example was not well chosen but it wasn't very visible from > the source:
That is the optimizer being fancy since the error can be put unconditionally in `rdx`.
If you compile:
pub fn it_is_ok() -> KernelResult<Bar> { Ok(Bar) }
you will see it just clears `rax`.
Cheers, Miguel
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