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

Structs

Alignment A type storing a usize which is a power of two, and thus represents a possible alignment in the Rust abstract machine.
Assume Configurable proof assumptions of TransmuteFrom.
Discriminant Opaque type representing the discriminant of an enum.
DropGuard Wrap a value and run a closure when dropped.
ManuallyDrop A wrapper to inhibit the compiler from automatically calling T’s destructor. This wrapper is 0-cost.
MaybeDangling Allows wrapped [references] and [boxes] to dangle.

Unions

MaybeUninit A wrapper type to construct uninitialized instances of T.

Traits

TransmuteFrom Marks that Src is transmutable into Self.

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.
copy Bitwise-copies a value.
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.
forget_unsized Like forget, but also accepts unsized values.
min_align_of Returns the [ABI]-required minimum alignment of a type in bytes.
min_align_of_val 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 Bypasses Rust's normal memory-initialization checks by pretending to produce a value of type T, while doing nothing at all.
variant_count Returns the number of variants in the enum type T.
zeroed Returns the value of type T represented by the all-zero byte-pattern.

Macros

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