std::experi...::scope_fail(3)

✨ NAME ✨

okay so this page is for std::experimental::scope_fail, and the manual name up top is std::experi...::scope_fail(3). Bestie, we're getting into scope-guard territory 💅

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🌸 Synopsis 🌸

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

The class template scope_fail is a general-purpose scope guard intended to call its exit function when a scope is exited via an exception. It’s giving “I have one job, and that job happens when things go sideways” energy 😭

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

A scope_fail may be either active — i.e. it calls its exit function on destruction — or inactive — i.e. it does nothing on destruction. A scope_fail is active after it’s constructed from an exit function.

A scope_fail can become inactive by calling release() on it either manually or automatically (by the move constructor). An inactive scope_fail may also be obtained by initializing with another inactive scope_fail. Once a scope_fail is inactive, it cannot become active again. No take-backs, no encore, periodt 🎤

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

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🎀 Template parameters 🎀

• EF — type of stored exit function.

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💖 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.

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🦋 Member functions 🦋

• constructor — constructs a new scope_fail (public member function).
• destructor — calls the exit function when the scope is exited via an exception if the scope_fail is active, then destroys the scope_fail (public member function).
• operator= — scope_fail is not assignable — [deleted] (public member function).

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🌈 Modifiers 🌈

• release — makes the scope_fail inactive (public member function).

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🧚 Deduction guides 🧚

The page says Deduction guides and then just leaves it there — mysterious, lowkey iconic, no extra details listed here ✨

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💜 Notes 💜

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

Constructing a scope_fail from another scope_fail 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.

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🍓 Example 🍓

This section is incomplete.

Reason: no example.

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👑 See also 👑

• scope_exit — wraps a function object and invokes it on exiting the scope (class template).
• scope_success — wraps a function object and invokes it on exiting the scope normally (class template).
• default_delete — default deleter for unique_ptr (C++11) (class template).

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🌟 Category 🌟

• Todo no example

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footer vibe, folded into a cute sign-off: source/version is http://cppreference.com, dated 2024.06.10 — bye bestie, stay scoped and stay slaying 🫶💖