Module mem 

Basic functions for dealing with memory, values, and types.

The contents of this module can be seen as belonging to a few families:

• drop, replace, swap, and take are safe functions for moving values in particular ways. They are useful in everyday Rust code.

• size_of, size_of_val, align_of, align_of_val, and offset_of give information about the representation of values in memory.

• discriminant allows comparing the variants of enum values while ignoring their fields.

• forget and ManuallyDrop prevent destructors from running, which is used in certain kinds of ownership transfer. needs_drop tells you whether a type’s destructor even does anything.

• transmute, transmute_copy, and MaybeUninit convert and construct values in unsafe ways.

See also the alloc and ptr modules for more primitive operations on memory.

Re-exports

pub use manually_drop::ManuallyDrop;

pub use maybe_uninit::MaybeUninit;

pub use drop_guard::DropGuard;

pub use alignment::Alignment;Experimental

pub use maybe_dangling::MaybeDangling;Experimental

pub use transmutability::Assume;Experimental

pub use transmutability::TransmuteFrom;Experimental

Modules

alignment 🔒

drop_guard 🔒

manually_drop 🔒

maybe_uninit 🔒

transmutability 🔒

maybe_dangling 🔒 Experimental

type_infoExperimental

MVP for exposing compile-time information about types in a runtime or const-eval processable way.

Macros

offset_of

Expands to the offset in bytes of a field from the beginning of the given type.

Structs

Discriminant

Opaque type representing the discriminant of an enum.

Traits

SizedTypeProperties 👻 Experimental

Provides associated constants for various useful properties of types, to give them a canonical form in our code and make them easier to read.

Functions

align_of

Returns the ABI-required minimum alignment of a type, in bytes.

align_of_val

Returns the ABI-required minimum alignment of the type of the value that val points to, in bytes.

align_of_val_raw^⚠

Returns the ABI-required minimum alignment of the type of the value that val points to, in bytes.

conjure_zst^⚠

Create a fresh instance of the inhabited ZST type T.

discriminant

Returns a value uniquely identifying the enum variant in v.

drop

Disposes of a value.

forget

Takes ownership and “forgets” about the value without running its destructor.

min_align_ofDeprecated

Returns the ABI-required minimum alignment of a type in bytes.

min_align_of_valDeprecated

Returns the ABI-required minimum alignment of the type of the value that val points to in bytes.

needs_drop

Returns true if dropping values of type T matters.

replace

Moves src into the referenced dest, returning the previous dest value.

size_of

Returns the size of a type in bytes.

size_of_val

Returns the size of the pointed-to value in bytes.

size_of_val_raw^⚠

Returns the size of the pointed-to value in bytes.

swap

Swaps the values at two mutable locations, without deinitializing either one.

take

Replaces dest with the default value of T, returning the previous dest value.

transmute^⚠

Reinterprets the bits of a value of one type as another type.

transmute_copy^⚠

Interprets src as having type &Dst, and then reads src without moving the contained value.

uninitialized^⚠Deprecated

Bypasses Rust’s normal memory-initialization checks by pretending to produce a value of type T, while doing nothing at all.

zeroed^⚠

Returns the value of type T represented by the all-zero byte-pattern.

copyExperimental

Bitwise-copies a value.

forget_unsizedExperimental

Like forget, but also accepts unsized values.

transmute_neo^⚠Experimental

New version of transmute, exposed under this name so it can be iterated upon without risking breakage to uses of “real” transmute.

transmute_prefix^⚠Experimental

Like transmute, but only initializes the “common prefix” of the first min(size_of::<Src>(), size_of::<Dst>()) bytes of the destination from the corresponding bytes of the source.

variant_countExperimental

Returns the number of variants in the enum type T.