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This commit is contained in:
Ralf Jung 2022-08-02 20:43:28 -04:00
parent c4aca2bc88
commit da3e11fc42
1 changed files with 4 additions and 2 deletions
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6
library/core/src/intrinsics.rs
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@ -1212,8 +1212,8 @@ extern "rust-intrinsic" {
/// `transmute` is semantically equivalent to a bitwise move of one type /// `transmute` is semantically equivalent to a bitwise move of one type
/// into another. It copies the bits from the source value into the /// into another. It copies the bits from the source value into the
/// destination value, then forgets the original. Note that source and destination /// destination value, then forgets the original. Note that source and destination
/// are passed by-value, which means if `T` or `U` contains padding, that padding /// are passed by-value, which means if `T` or `U` contain padding, that padding
/// might *not* be preserved by `transmute`. /// is *not* guaranteed to be preserved by `transmute`.
/// ///
/// Both the argument and the result must be [valid](../../nomicon/what-unsafe-does.html) at /// Both the argument and the result must be [valid](../../nomicon/what-unsafe-does.html) at
/// their given type. Violating this condition leads to [undefined behavior][ub]. The compiler /// their given type. Violating this condition leads to [undefined behavior][ub]. The compiler
@ -1225,6 +1225,8 @@ extern "rust-intrinsic" {
/// ///
/// Transmuting pointers to integers in a `const` context is [undefined behavior][ub]. /// Transmuting pointers to integers in a `const` context is [undefined behavior][ub].
/// Any attempt to use the resulting value for integer operations will abort const-evaluation. /// Any attempt to use the resulting value for integer operations will abort const-evaluation.
/// (And even outside `const`, such transmutation is touching on many unspecified aspects of the
/// Rust memory model and should be avoided. See below for alternatives.)
/// ///
/// Because `transmute` is a by-value operation, alignment of the *transmuted values /// Because `transmute` is a by-value operation, alignment of the *transmuted values
/// themselves* is not a concern. As with any other function, the compiler already ensures /// themselves* is not a concern. As with any other function, the compiler already ensures