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.

Modules

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

Discriminantvalidated

Opaque type representing the discriminant of an enum.

ManuallyDropvalidated

A wrapper to inhibit the compiler from automatically calling T’s destructor. This wrapper is 0-cost.

AlignmentExperimentalvalidated

A type storing a usize which is a power of two, and thus represents a possible alignment in the Rust abstract machine.

AssumeExperimental

Configurable proof assumptions of TransmuteFrom.

DropGuardExperimental

Wrap a value and run a closure when dropped.

MaybeDanglingExperimentalvalidated

Allows wrapped references and boxes to dangle.

Traits

TransmuteFromExperimental

Marks that Src is transmutable into Self.

Functions

align_ofvalidated

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

align_of_valvalidated

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

discriminantvalidated

Returns a value uniquely identifying the enum variant in v.

dropvalidated

Disposes of a value.

forgetvalidated

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_dropvalidated

Returns true if dropping values of type T matters.

replacevalidated

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

size_ofvalidated

Returns the size of a type in bytes.

size_of_valvalidated

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

swapvalidated

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

takevalidated

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

transmute^⚠validated

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

transmute_copy^⚠validated

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^⚠validated

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

align_of_val_raw^⚠Experimental

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

conjure_zst^⚠Experimentalvalidated

Create a fresh instance of the inhabited ZST type T.

copyExperimental

Bitwise-copies a value.

forget_unsizedExperimental

Like forget, but also accepts unsized values.

size_of_val_raw^⚠Experimentalvalidated

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

variant_countExperimental

Returns the number of variants in the enum type T.

Unions

MaybeUninit

A wrapper type to construct uninitialized instances of T.