# std::experimental::scope_exit

From cppreference.com
< cpp‎ | experimental

Defined in header `<experimental/scope>` |  |
template< class EF > class scope_exit; |  | (library fundamentals TS v3)

The class template `scope_exit` is a general-purpose scope guard intended to call its exit function when a scope is exited.

`scope_exit` is not CopyConstructible, CopyAssignable or MoveAssignable, however, it may be MoveConstructible if `EF` meets some requirements, which permits wrapping a `scope_exit` into another object.

A `scope_exit` may be either active, i.e. calls its exit function on destruction, or inactive, i.e. does nothing on destruction. A `scope_exit` is active after constructed from an exit function.

A `scope_exit` can become inactive by calling release() on it either manually or automatically (by the move constructor). An inactive `scope_exit` may also be obtained by initializing with another inactive `scope_exit`. Once a `scope_exit` is inactive, it cannot become active again.

A `scope_exit` effectively holds an `EF` and a bool flag indicating if it is active.

### Template parameters

EF | - | type of stored exit function
Type requirements
- `EF` shall be either: a Destructible FunctionObject type, an lvalue reference to FunctionObject, an lvalue reference to function.
- Calling an lvalue of std::remove_reference_t<EF> with no argument shall be well-formed.

### Member functions

(constructor) | constructs a new `scope_exit` (public member function)
(destructor) | calls the exit function when the scope is exited if the `scope_exit` is active, then destroys the `scope_exit` (public member function)
operator= [deleted] | `scope_exit` is not assignable (public member function)
##### Modifiers
release | makes the `scope_exit` inactive (public member function)

### Deduction guides

### Notes

Constructing a `scope_exit` of dynamic storage duration might lead to unexpected behavior.

If the `EF` stored in a `scope_exit` object refers to a local variable of the function where it is defined, e.g., as a lambda capturing the variable by reference, and that variable is used as a return operand in that function, that variable might have already been returned when the `scope_exit`'s destructor executes, calling the exit function. This can lead to surprising behavior.

### Example

| This section is incomplete Reason: no example

### See also

scope_fail | wraps a function object and invokes it on exiting the scope through an exception (class template)
scope_success | wraps a function object and invokes it on exiting the scope normally (class template)
default_delete (C++11) | default deleter for unique_ptr (class template)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/experimental/scope_exit&oldid=131177"