wwa::utils::exit_action< ExitFunc > Class Template Reference

A scope guard that calls its exit function on destruction, when a scope is exited. More...

#include <scope_action.h>

Collaboration diagram for wwa::utils::exit_action< ExitFunc >:

Public Member Functions
	exit_action (exit_action &&other) noexcept(std::is_nothrow_move_constructible_v< ExitFunc >||std::is_nothrow_copy_constructible_v< ExitFunc >)
	Move constructor.
template<typename Func > requires (detail::can_move_construct_from_noexcept<exit_action, ExitFunc, Func>)
	exit_action (Func &&fn) noexcept
	Constructs a new exit_action from an exit function of type Func.
template<typename Func > requires (detail::can_construct_from<exit_action, ExitFunc, Func>)
	exit_action (Func &&fn) noexcept(std::is_nothrow_constructible_v< ExitFunc, Func >||std::is_nothrow_constructible_v< ExitFunc, Func & >)
	Constructs a new exit_action from an exit function of type Func.
	~exit_action () noexcept
	Calls the exit function if m_is_armed is active, then destroys the object.
void	release () noexcept
	Makes the exit_action object inactive.

Detailed Description

template<typename ExitFunc>
class wwa::utils::exit_action< ExitFunc >

A scope guard that calls its exit function on destruction, when a scope is exited.

An exit_action may be either active (i.e., it will calls its exit function on destruction), or inactive (it does nothing on destruction). An exit_action is active after construction from an exit function.

An exit_action becomes inactive by calling release() or a move constructor. An inactive exit_action may also be obtained by initializing with another inactive exit_action. Once an exit_action is inactive, it cannot become active again.

Usage example:

try {
    auto guard = wwa::utils::exit_action{[&exit_status]() { exit_status = true; }};
    maybe_throw();
}
catch (...) {
    did_throw = true;
}
print_exit_status("exit_action", exit_status, did_throw);

Template Parameters

ExitFunc

Exit function type. Func is either a Destructible FunctionObject type, or an lvalue reference to a FunctionObject or function.

See also

https://en.cppreference.com/w/cpp/experimental/scope_exit

https://github.com/microsoft/GSL/blob/main/docs/headers.md#user-content-H-util-final_action

Note

Constructing an exit_action of dynamic storage duration might lead to unexpected behavior.

If the exit function stored in an exit_action 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 exit_action's destructor executes, calling the exit function. This can lead to surprising behavior.

Examples

scope_action.cpp.

Definition at line 88 of file scope_action.h.

Constructor & Destructor Documentation

exit_action() [1/3]

template<typename ExitFunc >

template<typename Func >
requires (detail::can_construct_from<exit_action, ExitFunc, Func>)

wwa::utils::exit_action< ExitFunc >::exit_action ( Func && fn )

inlineexplicitnoexcept

Constructs a new exit_action from an exit function of type Func.

Initializes the exit function with a function or function object fn. The constructed exit_action is active. If Func is not an lvalue reference type, and std::is_nothrow_constructible_v<ExitFunc, Func> is true, the stored exit function is initialized with std::forward<Func>(fn); otherwise it is initialized with fn. If initialization of the stored exit function throws an exception, calls fn().

This overload participates in overload resolution only if:

• std::is_same_v<std::remove_cvref_t<Func>, exit_action> is false, and
• std::is_constructible_v<ExitFunc, Func> is true.

Template Parameters

Func	Exit function type. Must be constructible from ExitFunc.

Parameters

fn	Exit function.

Exceptions

anything

Any exception thrown during the initialization of the stored exit function.

See also

https://en.cppreference.com/w/cpp/experimental/scope_exit/scope_exit

Definition at line 109 of file scope_action.h.

exit_action() [2/3]

template<typename ExitFunc >

template<typename Func >
requires (detail::can_move_construct_from_noexcept<exit_action, ExitFunc, Func>)

wwa::utils::exit_action< ExitFunc >::exit_action ( Func && fn )

inlineexplicitnoexcept

Constructs a new exit_action from an exit function of type Func.

Initializes the exit function with a function or function object fn. The constructed exit_action is active. The stored exit function is initialized with std::forward<Func>(fn).

This overload participates in overload resolution only if:

• std::is_same_v<std::remove_cvref_t<Func>, exit_action> is false, and
• std::is_lvalue_reference_v<Func> is false, and
• std::is_nothrow_constructible_v<ExitFunc, Func> is true.

Template Parameters

Func	Exit function type. Must be constructible from ExitFunc.

Parameters

fn	Exit function.

See also

https://en.cppreference.com/w/cpp/experimental/scope_exit/scope_exit

Definition at line 142 of file scope_action.h.

exit_action() [3/3]

template<typename ExitFunc >

wwa::utils::exit_action< ExitFunc >::exit_action ( exit_action< ExitFunc > && other )

inlinenoexcept

Move constructor.

Initializes the stored exit function with the one in other. The constructed exit_action is active if and only if other is active before the construction.

If std::is_nothrow_move_constructible_v<ExitFunc> is true, initializes stored exit function (denoted by exitfun) with std::forward<ExitFunc>(other.exitfun), otherwise initializes it with other.exitfun.

After successful move construction, other becomes inactive.

This overload participates in overload resolution only if:

• std::is_nothrow_move_constructible_v<ExitFunc> is true, or
• std::is_copy_constructible_v<ExitFunc> is true.

Parameters

other

exit_action to move from.

Exceptions

anything

Any exception thrown during the initialization of the stored exit function.

See also

https://en.cppreference.com/w/cpp/experimental/scope_exit/scope_exit

Definition at line 164 of file scope_action.h.

~exit_action()

template<typename ExitFunc >

wwa::utils::exit_action< ExitFunc >::~exit_action ( )

inlinenoexcept

Calls the exit function if m_is_armed is active, then destroys the object.

See also

https://en.cppreference.com/w/cpp/experimental/scope_exit/%7Escope_exit

Definition at line 192 of file scope_action.h.

Member Function Documentation

release()

template<typename ExitFunc >

void wwa::utils::exit_action< ExitFunc >::release ( )

inlinenoexcept

Makes the exit_action object inactive.

Once an exit_action is inactive, it cannot become active again, and it will not call its exit function upon destruction.

See also

https://en.cppreference.com/w/cpp/experimental/scope_exit/release

Definition at line 207 of file scope_action.h.

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The documentation for this class was generated from the following file:

• scope_action.h