core::mem::ManuallyDrop - Rust
Description: API documentation for the Rust `ManuallyDrop` struct in crate `core`.
Keywords: rust, rustlang, rust-lang, ManuallyDrop

# 1.20.0[−][src]Struct core::mem::ManuallyDrop

    #[lang = "manually_drop"]
    #[repr(transparent)]
    pub struct ManuallyDrop<T: ?Sized> { /* fields omitted */ }

A wrapper to inhibit compiler from automatically calling `T`’s destructor.

This wrapper is 0-cost.

# Examples

This wrapper helps with explicitly documenting the drop order dependencies between fields of the type:

    use std::mem::ManuallyDrop;
    struct Peach;
    struct Banana;
    struct Melon;
    struct FruitBox {
        // Immediately clear there’s something non-trivial going on with these fields.
        peach: ManuallyDrop<Peach>,
        melon: Melon, // Field that’s independent of the other two.
        banana: ManuallyDrop<Banana>,
    }

    impl Drop for FruitBox {
        fn drop(&mut self) {
            unsafe {
                // Explicit ordering in which field destructors are run specified in the intuitive
                // location – the destructor of the structure containing the fields.
                // Moreover, one can now reorder fields within the struct however much they want.
                ManuallyDrop::drop(&mut self.peach);
                ManuallyDrop::drop(&mut self.banana);
            }
            // After destructor for `FruitBox` runs (this function), the destructor for Melon gets
            // invoked in the usual manner, as it is not wrapped in `ManuallyDrop`.
        }
    }Run

## Methods

###

`impl<T> ManuallyDrop<T>`

[src]

####

`pub const fn new(value: T) -> ManuallyDrop<T>`

[src]

Wrap a value to be manually dropped.

# Examples

    use std::mem::ManuallyDrop;
    ManuallyDrop::new(Box::new(()));Run

####

`pub fn into_inner(slot: ManuallyDrop<T>) -> T`

[src]

Extract the value from the `ManuallyDrop` container.

This allows the value to be dropped again.

# Examples

    use std::mem::ManuallyDrop;
    let x = ManuallyDrop::new(Box::new(()));
    let _: Box<()> = ManuallyDrop::into_inner(x); // This drops the `Box`.Run

###

`impl<T: ?Sized> ManuallyDrop<T>`

[src]

####

`pub unsafe fn drop(slot: &mut ManuallyDrop<T>)`

[src]

Manually drops the contained value.

If you have ownership of the value, you can use `ManuallyDrop::into_inner` instead.

# Safety

This function runs the destructor of the contained value and thus the wrapped value now represents uninitialized data. It is up to the user of this method to ensure the uninitialized data is not actually used.

## Trait Implementations

###

`impl<T: Copy + ?Sized> Copy for ManuallyDrop<T>`

[src]

###

`impl<T: ?Sized> Deref for ManuallyDrop<T>`

[src]

#### `type Target = T`

The resulting type after dereferencing.

####

`fn deref(&self) -> &Self::Target`

[src]

Dereferences the value.

###

`impl<T: ?Sized> DerefMut for ManuallyDrop<T>`

[src]

####

`fn deref_mut(&mut self) -> &mut Self::Target`

[src]

Mutably dereferences the value.

###

`impl<T: PartialEq + ?Sized> PartialEq<ManuallyDrop<T>> for ManuallyDrop<T>`

[src]

####

`fn eq(&self, other: &ManuallyDrop<T>) -> bool`

[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

####

`fn ne(&self, other: &ManuallyDrop<T>) -> bool`

[src]

This method tests for `!=`.

###

`impl<T: Eq + ?Sized> Eq for ManuallyDrop<T>`

[src]

###

`impl<T: Ord + ?Sized> Ord for ManuallyDrop<T>`

[src]

####

`fn cmp(&self, other: &ManuallyDrop<T>) -> Ordering`

[src]

This method returns an `Ordering` between `self` and `other`. Read more

####

`fn max(self, other: Self) -> Self where Self: Sized,`

1.21.0
[src]

Compares and returns the maximum of two values. Read more

####

`fn min(self, other: Self) -> Self where Self: Sized,`

1.21.0
[src]

Compares and returns the minimum of two values. Read more

###

`impl<T: PartialOrd + ?Sized> PartialOrd<ManuallyDrop<T>> for ManuallyDrop<T>`

[src]

####

`fn partial_cmp(&self, other: &ManuallyDrop<T>) -> Option<Ordering>`

[src]

This method returns an ordering between `self` and `other` values if one exists. Read more

####

`fn lt(&self, other: &ManuallyDrop<T>) -> bool`

[src]

This method tests less than (for `self` and `other`) and is used by the `<` operator. Read more

####

`fn le(&self, other: &ManuallyDrop<T>) -> bool`

[src]

This method tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more

####

`fn gt(&self, other: &ManuallyDrop<T>) -> bool`

[src]

This method tests greater than (for `self` and `other`) and is used by the `>` operator. Read more

####

`fn ge(&self, other: &ManuallyDrop<T>) -> bool`

[src]

This method tests greater than or equal to (for `self` and `other`) and is used by the `>=` operator. Read more

###

`impl<T: Clone + ?Sized> Clone for ManuallyDrop<T>`

[src]

####

`fn clone(&self) -> ManuallyDrop<T>`

[src]

Returns a copy of the value. Read more

####

`fn clone_from(&mut self, source: &Self)`

1.0.0
[src]

Performs copy-assignment from `source`. Read more

###

`impl<T: Default + ?Sized> Default for ManuallyDrop<T>`

[src]

####

`fn default() -> ManuallyDrop<T>`

[src]

Returns the "default value" for a type. Read more

###

`impl<T: Hash + ?Sized> Hash for ManuallyDrop<T>`

[src]

####

`fn hash<__HT: Hasher>(&self, state: &mut __HT)`

[src]

Feeds this value into the given [`Hasher`]. Read more

####

`fn hash_slice<H: Hasher>(data: &[Self], state: &mut H) where Self: Sized,`

1.3.0
[src]

Feeds a slice of this type into the given [`Hasher`]. Read more

###

`impl<T: Debug + ?Sized> Debug for ManuallyDrop<T>`

[src]

####

`fn fmt(&self, f: &mut Formatter) -> Result`

[src]

Formats the value using the given formatter. Read more

## Auto Trait Implementations

###

`impl<T: ?Sized> Send for ManuallyDrop<T> where T: Send,`

###

`impl<T: ?Sized> Sync for ManuallyDrop<T> where T: Sync,`

## Blanket Implementations

###

`impl<T, U> Into for T where U: From<T>,`

[src]

####

`fn into(Self) -> U`

[src]

Performs the conversion.

###

`impl<T> From for T`

[src]

####

`fn from(T) -> T`

[src]

Performs the conversion.

###

`impl<T, U> TryInto for T where U: TryFrom<T>,`

[src]

#### `type Error = <U as TryFrom<T>>::Error`

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

####

`fn try_into(Self) -> Result<U, <U as TryFrom<T>>::Error>`

[src]

🔬 This is a nightly-only experimental API. (`try_from` #33417)

Performs the conversion.

###

`impl<T, U> TryFrom for T where T: From<U>,`

[src]

#### `type Error = !`

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

####

`fn try_from(U) -> Result<T, <T as TryFrom<U>>::Error>`

[src]

🔬 This is a nightly-only experimental API. (`try_from` #33417)

Performs the conversion.

###

`impl<T> Borrow for T where T: ?Sized,`

[src]

####

`fn borrow(&Self) -> &T`

[src]

Immutably borrows from an owned value. Read more

###

`impl<T> BorrowMut for T where T: ?Sized,`

[src]

####

`fn borrow_mut(&mut Self) -> &mut T`

[src]

Mutably borrows from an owned value. Read more

###

`impl<T> Any for T where T: 'static + ?Sized,`

[src]

####

`fn get_type_id(&Self) -> TypeId`

[src]

🔬 This is a nightly-only experimental API. (`get_type_id` #27745)

this method will likely be replaced by an associated static

Gets the `TypeId` of `self`. Read more

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