std::experi...ointer_cast,(3)

💖 NAME 💖

okay so this is the std::experi...ointer_cast,(3) page from the C++ Standard Libary manual — yes, Libary is exactly how it’s spelled on the page, no cap. It’s the library-fundamentals-TS pointer-cast girlies, and the NAME section is literally:

std::experimental::static_pointer_cast,std::experimental::dynamic_pointer_cast,
-
std::experimental::static_pointer_cast,std::experimental::dynamic_pointer_cast,

🌸 Synopsis 🌸

Four overloads, every one of them (library fundamentals TS) and noexcept. Here they are, signature by signature:

(1) — (library fundamentals TS)

template< class T, class U >
std::experimental::shared_ptr<T> static_pointer_cast( const std::experimental::shared_ptr<U>& r ) noexcept;

(2) — (library fundamentals TS)

template< class T, class U >
std::experimental::shared_ptr<T> dynamic_pointer_cast( const std::experimental::shared_ptr<U>& r ) noexcept;

(3) — (library fundamentals TS)

template< class T, class U >
std::experimental::shared_ptr<T> const_pointer_cast( const std::experimental::shared_ptr<U>& r ) noexcept;

(4) — (library fundamentals TS)

template< class T, class U >
std::experimental::shared_ptr<T> reinterpret_pointer_cast( const std::experimental::shared_ptr<U>& r ) noexcept;

okay so what do they actually do? They create a new instance of std::experimental::shared_ptr whose stored pointer is obtained from r’s stored pointer using a cast expression. If r is empty, so is the new shared_ptr (but its stored pointer is not necessarily null). 🫶

Otherwise, the new shared_ptr will share ownership with r, except that it is empty if the dynamic_cast performed by dynamic_pointer_cast returns a null pointer.

Let Y be typename std::experimental::shared_ptr<T>::element_type, then the resulting std::experimental::shared_ptr’s stored pointer will be obtained by calling (in respective order):

1. static_cast<Y*>(r.get()).
2. dynamic_cast<Y*>(r.get()) (if the result of the dynamic_cast is a null pointer value, the returned shared_ptr will be empty).
3. const_cast<Y*>(r.get()).
4. reinterpret_cast<Y*>(r.get()).

🚨 undefined behavior alert, bestie 🚨 The behavior of these functions is undefined unless the corresponding cast from U* to T* is well formed:

1. The behavior is undefined unless static_cast<T*>((U*)nullptr) is well formed.
2. The behavior is undefined unless dynamic_cast<T*>((U*)nullptr) is well formed.
3. The behavior is undefined unless const_cast<T*>((U*)nullptr) is well formed.
4. The behavior is undefined unless reinterpret_cast<T*>((U*)nullptr) is well formed.

💖 Parameters 💖

• r — the pointer to convert

🎀 Example 🎀

This section is incomplete. Reason: no example 😭

🦋 See also 🦋

• constructor — constructs new shared_ptr (public member function)
• static_pointer_cast
• dynamic_pointer_cast
• const_pointer_cast
• reinterpret_pointer_cast (function template) (C++17)
• and the pointer-cast functions apply static_cast, dynamic_cast, const_cast, or reinterpret_cast to the stored pointer

🌈 Categories: 🌈

• Noindexed pages
• Todo no example

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Source/version/date, bestie: http://cppreference.com, 2024.06.10, and the page is std::experi...ointer_cast,(3). Mwah 💋✨