std::experi...que_resource(3)

🌸 NAME 🌸

Okay so bestie, this is the std::experimental::unique_resource::unique_resource page from the C++ Standard Libary manual — yes, that’s the cppreference one, and yes, the title is literally std::experimental::unique_resource::unique_resource twice because we love a dramatic repetition. 💅 It’s giving RAII royalty, no cap.

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✨ Synopsis ✨

Here’s the whole constructor family, looking iconic:

unique_resource();                                  (1) (library
fundamentals TS v3)
template< class RR, class DD >
unique_resource( RR&& r, DD&& d ) noexcept(/*see    (2) (library
fundamentals TS v3)
below*/)
unique_resource( unique_resource&& other );         (3) (library
fundamentals TS v3)

These follow items are used for explanatory purpose, bestie — lil shorthand names so we don’t lose our minds:

• RS is the type of stored resource handle.
• The expression res_ refers the underlying resource handle.
• del_ refers the deleter object.

💖 Overload (1) — default constructor

Default constructor. Value-initializes the stored resource handle and the deleter. The constructed unique_resource does not own the resource.

This overload participates in overload resolution only if both std::is_default_constructible_v<R> and std::is_default_constructible_v<D> are true.

🦋 Overload (2) — the ( RR&& r, DD&& d ) one

The stored resource handle is initialized with std::forward<RR>(r) if std::is_nothrow_constructible_v<RS, RR> is true, otherwise r. If initialization of the stored resource handle throws an exception, calls d(r).

Then, the deleter is initialized with std::forward<DD>(d) if std::is_nothrow_constructible_v<D, DD> is true, otherwise d. If initialization of deleter throws an exception, calls d(res_).

The constructed unique_resource owns the resource.

This overload participates in overload resolution only if all of these are true:

• std::is_constructible_v<RS, RR>
• std::is_constructible_v<D, DD>
• std::is_nothrow_constructible_v<RS, RR> || std::is_constructible_v<RS, RR&>
• std::is_nothrow_constructible_v<D, DD> || std::is_constructible_v<D, DD&>

The program is ill-formed if any of the expressions d(r), d(res_) and del_(res_) is ill-formed.

🚨 Bestie, this is UB territory: the behavior is undefined if any of the expressions d(r), d(res_) and del_(res_) results in undefined behavior or throws an exception.

🎀 Overload (3) — move constructor

Move constructor. The stored resource handle is initialized from the one of other, using std::move if std::is_nothrow_move_constructible_v<RS> is true. If initialization of the stored resource handle throws an exception, other is not modified.

Then, the deleter is initialized with the one of other, using std::move if std::is_nothrow_move_constructible_v<D> is true. If initialization of the deleter throws an exception and std::is_nothrow_move_constructible_v<RS> is true and other owns the resource, calls the deleter of other with res_ to dispose the resource, then calls other.release().

After construction, the constructed unique_resource owns its resource if and only if other owned the resource before the construction, and other is set to not own the resource.

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🌈 Parameters 🌈

• r — a resource handle.
• d — a deleter to use to dispose the resource.
• other — another unique_resource to acquire the ownership from.

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😭 Exceptions 😭

Any exception thrown during initialization of the stored resource handle or the deleter.

2) noexcept specification:

noexcept((
    std::is_nothrow_constructible_v<RS, RR> || std::is_nothrow_constructible_v<RS, RR&>
) &&
(
    std::is_nothrow_constructible_v<D, DD> || std::is_nothrow_constructible_v<D, DD&>
))

3) noexcept specification:

noexcept(
    std::is_nothrow_move_constructible_v<R1> &&
    std::is_nothrow_move_constructible_v<D>
)

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💜 Notes 💜

The mechanism of these constructors ensures no leaking of resources. Literally the whole point, and it ate. 🔥

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🍓 Example 🍓

This section is incomplete.

Reason: no example — not me crying over the missing example 😭.

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🫶 See also 🫶

• constructor — constructs a new unique_ptr (public member function of std::unique_ptr<T,Deleter>).

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👑 Categories 👑

• conditionally noexcept
• Todo no example

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💖 source: http://cppreference.com · version/date: 2024.06.10 · page: std::experi...que_resource(3) — bye bestie, go construct something iconic! 💅✨