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Note the layout of pointers to T:Sized matches that of C pointers #100

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Merged
RalfJung merged 2 commits into from
Apr 11, 2019
Merged

Note the layout of pointers to T:Sized matches that of C pointers #100

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Note the layout of pointers to T:Sized matches that of C pointers
gnzlbg Mar 14, 2019
228a0fd
Add warning about reference validity
gnzlbg Mar 15, 2019
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8 changes: 8 additions & 0 deletions reference/src/layout/pointers.md
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Expand Up @@ -31,6 +31,14 @@ and are at least one word.

The layouts of `&T`, `&mut T` and `*T` are the same.

If `T` is sized, references and pointers to `T` have a size and alignment of one
word and have therefore the same layout as C pointers.

> **warning**: while the layout of references and pointers is compatible with
> the layout of C pointers, references come with a _validity_ invariant that
> does not allow them to be used when they could be `NULL`, unaligned, dangling,
> or, in the case of `&mut T`, aliasing.

We do not make any guarantees about the layout of
multi-trait objects `&(dyn T + U)` or references to other dynamically sized types,
other than that they are at least word-aligned, and have size at least one word.
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