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Pool.inner_mut() and other mut methods are UB #2

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seanmonstar opened this issue Apr 11, 2015 · 3 comments
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Pool.inner_mut() and other mut methods are UB #2

seanmonstar opened this issue Apr 11, 2015 · 3 comments

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@seanmonstar
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According to this doc page http://doc.rust-lang.org/1.0.0-beta/std/cell/struct.UnsafeCell.html, transmuting &T to &mut T is undefined behavior. I believe rustc tells llvm they are readonly unless the unsafe lang item is used, which is UnsafeCell.
@carllerche
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Hmmm.... so what about transmuting *mut T -> &mut T, is that permitted? Should PoolInner be wrapped in an UnsafeCell?

@seanmonstar
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I do not know if that's safe. However, you can easily do let a = &mut *ptr; to get &mut T from a *mut T.

@seanmonstar
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Finally filed that PR for a lint as well: rust-lang/rust#24392

@seanmonstar seanmonstar mentioned this issue Apr 30, 2015
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@carllerche @seanmonstar