NAME¶

std::experimental::scope_success - std::experimental::scope_success

Synopsis¶

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

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

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

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

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

A scope_success effectively holds an EF and a bool flag indicating if it is active,
alongwith a counter of uncaught exceptions used for detecting whether the destructor
is called during stack unwinding.

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_success
(public member function)
calls the exit function when the scope is exited normally if the
destructor scope_success is active, then destroys the scope_success
(public member function)
operator= scope_success is not assignable
[deleted] (public member function)

Modifiers¶

release makes the scope_success inactive
(public member function)

Deduction guides

Notes¶

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

Constructing a scope_success is constructed from another scope_success created in a
different thread might also lead to unexpected behavior since the count of uncaught
exceptions obtained in different threads may be compared during the destruction.

If the EF stored in a scope_success 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_success's destructor executes, calling the
exit function. This can lead to surprising behavior.

Example¶

This section is incomplete
Reason: no example

See also¶

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