Difference between revisions of "cpp/experimental/scope exit"
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{{include page|cpp/experimental/scope_guard|scope_exit}} | {{include page|cpp/experimental/scope_guard|scope_exit}} | ||
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Latest revision as of 10:23, 6 July 2021
| Defined in header <experimental/scope>
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| 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.
Contents |
[edit] Template parameters
| EF | - | type of stored exit function |
| Type requirements | ||
-EF shall be either:
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| -Calling an lvalue of std::remove_reference_t<EF> with no argument shall be well-formed. | ||
[edit] Member functions
constructs a new scope_exit (public member function) | |
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 | |
makes the scope_exit inactive (public member function) | |
[edit] Deduction guides
[edit] 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.
[edit] Example
| This section is incomplete Reason: no example |
[edit] See also
| wraps a function object and invokes it on exiting the scope through an exception (class template) | |
| wraps a function object and invokes it on exiting the scope normally (class template) | |
| (C++11) |
default deleter for unique_ptr (class template) |
