std::experimental::scope_success
| Defined in header <experimental/scope>
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| template< class EF > class scope_success; |
(library fundamentals TS v3) | |
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:
| ||
| -Calling an lvalue of std::remove_reference_t<EF> with no argument shall be well-formed. | ||
Member functions
constructs a new scope_success (public member function) | |
calls the exit function when the scope is exited normally if the scope_success is active, then destroys the scope_success (public member function) | |
| operator= [deleted] |
scope_success is not assignable (public member function) |
Modifiers | |
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
| 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 an exception (class template) | |
| (C++11) |
default deleter for unique_ptr (class template) |