std::pmr::p...c_allocator(3)

💖 NAME 💖

okay bestie, this page is all about std::pmr::polymorphic_allocator::polymorphic_allocator — yes, that’s the same name twice, because it’s the constructor page for std::pmr::polymorphic_allocator. It lives in the C++ Standard Libary manual (and yes, that’s how the manual name is spelled — I’m not fixing it, I’m just reporting the vibes 😭).

🌸 Synopsis 🌸

Here’s the whole constructor squad, laid out exactly like the page does it:

polymorphic_allocator() noexcept;
(1)
polymorphic_allocator( const polymorphic_allocator& other ) = default;   (2)
template< class U >
(3)
polymorphic_allocator( const polymorphic_allocator<U>& other ) noexcept;
polymorphic_allocator( std::pmr::memory_resource* r );
(4)

Constructs a new polymorphic_allocator. That’s the main character job, periodt 💅

1. (1) — Constructs a polymorphic_allocator using the return value of std::pmr::get_default_resource() as the underlying memory resource.
2. (2), (3) — Constructs a polymorphic_allocator using other.resource() as the underlying memory resource.
3. (4) — Constructs a polymorphic_allocator using r as the underlying memory resource. This constructor provides an implicit conversion from std::pmr::memory_resource*.

🎀 Parameters 🎀

• other — another polymorphic_allocator to copy from. 💖
• r — pointer to the memory resource to use. May not be null. fr fr do not pass null 🔥

💀 Exceptions 💀

• (4) — Throws nothing. Iconic. No drama, no chaos, just quiet slay.

🧚 Notes 🧚

Copying a container using a polymorphic_allocator will not call the allocator’s copy constructor. Nope, that’s not the move.

Instead, the new container will use the return value of select_on_container_copy_construction (a default-constructed polymorphic_allocator) as its allocator. That’s the lowkey important plot twist 👑

👑 See also 👑

• select_on_container_copy_construction — create a new polymorphic_allocator for use by a container’s copy constructor (public member function). 🫶

mwah 💋 source: http://cppreference.com · version/date: 2024.06.10 · page title: std::pmr::p...c_allocator(3)