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

A scope guard that calls its exit function when a scope is exited via an exception. More...

#include <scope_action.h>

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

Public Member Functions
	fail_action (fail_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<fail_action, ExitFunc, Func>)
	fail_action (Func &&fn) noexcept
	Constructs a new fail_action from an exit function of type Func.
template<typename Func > requires (detail::can_construct_from<fail_action, ExitFunc, Func>)
	fail_action (Func &&fn) noexcept(std::is_nothrow_constructible_v< ExitFunc, Func >||std::is_nothrow_constructible_v< ExitFunc, Func & >)
	Constructs a new fail_action from an exit function of type Func.
	~fail_action () noexcept
	Calls the exit function if the scope is exited via an exception and destroys the object.
void	release () noexcept
	Makes the fail_action object inactive.

Detailed Description

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

A scope guard that calls its exit function when a scope is exited via an exception.

Like exit_action, a fail_action may be active or inactive. A fail_action is active after construction from an exit function.

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

Usage example:

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

Note

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

Constructing a fail_action from another fail_action 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.

Examples

scope_action.cpp.

Definition at line 246 of file scope_action.h.

Constructor & Destructor Documentation

fail_action() [1/3]

template<typename ExitFunc >

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

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

inlineexplicitnoexcept

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

Initializes the exit function with a function or function object, and initializes the counter of uncaught exceptions as if with std::uncaught_exceptions(). The constructed fail_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>, fail_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_fail/scope_fail

Definition at line 270 of file scope_action.h.

fail_action() [2/3]

template<typename ExitFunc >

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

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

inlineexplicitnoexcept

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

Initializes the exit function with a function or function object fn. The constructed fail_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>, fail_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_fail/scope_fail

Definition at line 303 of file scope_action.h.

fail_action() [3/3]

template<typename ExitFunc >

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

inlinenoexcept

Move constructor.

Initializes the stored exit function with the one in other, and initializes the counter of uncaught exceptions with the one in other. The constructed fail_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.release() is called and 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

fail_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_fail/scope_fail

Definition at line 326 of file scope_action.h.

~fail_action()

template<typename ExitFunc >

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

inlinenoexcept

Calls the exit function if the scope is exited via an exception and destroys the object.

Calls the exit function if the result of std::uncaught_exceptions() is greater than the counter of uncaught exceptions (typically on stack unwinding) and the fail_action is active; then destroys the object.

See also

https://en.cppreference.com/w/cpp/experimental/scope_fail/%7Escope_fail

Definition at line 358 of file scope_action.h.

Member Function Documentation

release()

template<typename ExitFunc >

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

inlinenoexcept

Makes the fail_action object inactive.

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

Note

release() may be either manually called or automatically called by fail_action's move constructor.

See also

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

Definition at line 374 of file scope_action.h.

---

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

• scope_action.h