std::experimental::scope_exit

 

C++

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Technical Specifications

 

Technical specifications

Filesystem library (filesystem TS)

Library fundamentals (library fundamentals TS)

Library fundamentals 2 (library fundamentals TS v2)

Library fundamentals 3 (library fundamentals TS v3)

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Extensions for parallelism 2 (parallelism TS v2)

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Library fundamentals v3

experimental::scope_exit

experimental::scope_fail

experimental::scope_success

experimental::unique_resource

 

std::experimental::scope_exit

Member functions

scope_exit::scope_exit

scope_exit::~scope_exit

Modifiers

scope_exit::release

Deduction guides

 

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)

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.

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)