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Remove confusing comment about ideally using ! for c_void #56594

Merged
merged 2 commits into from
Jan 18, 2019
Merged

Remove confusing comment about ideally using ! for c_void #56594

merged 2 commits into from
Jan 18, 2019

Commits on Dec 13, 2018

  1. Remove confusing comment about ideally using ! for c_void 

    Using `!` for `c_void` would have the problem that pointers and
potentially references to an uninhabited type would be created, and at
least for references this is UB.

Also document in addition that newtype wrappers around `c_void` are not
recommended for representing opaque types (as a workaround for `extern
type` not being stable) but instead refer to the Nomicon.
    @sdroege
    sdroege committed Dec 13, 2018
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  2. Update code comments of c_void to explain the reasoning for its cur… 

    …rent implementation

We need at least two variants of the enum as otherwise the compiler
complains about the #[repr(u8)] attribute and we also need at least one
variant as otherwise the enum would be uninhabitated and dereferencing
pointers to it would be UB.

As such, mark the variants not unstable because they should not actually
exist but because they are temporary implementation details until
`extern type` is stable and can be used instead.
    @sdroege
    sdroege committed Dec 13, 2018
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