std::experimental:: scope_exit

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)