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Document raw pointer <-> usize casts. #970

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Merged
merged 10 commits into from
May 17, 2021
Merged

Document raw pointer <-> usize casts. #970

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d65e590
Document raw pointer <-> usize casts.
Feb 28, 2021
ec33e2b
Address to pointer cast: hint at provenance.
Mar 8, 2021
b144532
Pointer<->address cast: stylistic changes.
Mar 8, 2021
f41e1a8
Reformat cast expression details.
ben0x539 Apr 28, 2021
b794f8a
Expand on pointer<->address casts without mentioning provenance.
ben0x539 Apr 28, 2021
96a811a
Fix warning block for pointer<->integer cast expression.
ben0x539 Apr 28, 2021
c11c649
Fix reformatting mishap.
ben0x539 Apr 28, 2021
a2cae39
Make the pointer to address cast example sounder.
ben0x539 Apr 28, 2021
771cce3
Justify "4".
ben0x539 Apr 28, 2021
dc1931a
Use markdown link instead of HTML.
ehuss May 17, 2021
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8 changes: 8 additions & 0 deletions src/expressions/operator-expr.md
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Expand Up @@ -360,6 +360,12 @@ Here `*T` means either `*const T` or `*mut T`.
* `char` casts to the value of the code point, then uses a numeric cast if needed.
* `u8` to `char` cast
* Casts to the `char` with the corresponding code point.
* Pointer to address cast
* Casting from a valid raw pointer to `usize` will produce the address that is pointed to. Note that the pointer's provenance is lost in this conversion.
* Address to pointer cast
* Casting from `usize` to a raw pointer will produce a raw pointer to the same location as the original pointer, if the `usize` was obtained through a pointer to address cast of a valid pointer.

Note that the two pointers are not equivalent. Dereferencing the pointer obtained from the address to pointer cast may be [undefined behavior] if aliasing rules are not followed.

\* if integer-to-float casts with this rounding mode and overflow behavior are
not supported natively by the hardware, these casts will likely be slower than
Expand All @@ -373,6 +379,8 @@ expected.
number, preferring the one with an even least significant digit if exactly
halfway between two floating point numbers.

[undefined behavior]: ../behavior-considered-undefined.md

## Assignment expressions

> **<sup>Syntax</sup>**\
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