STD::ALIGNED_STORAGE(3)

💖 std::aligned_storage< _Len, _Align > 💖

okay bestie, this one's from the Library Functions Manual (section 3, we're in C++ template territory, iykyk) — it's a page about std::aligned_storage< _Len, _Align >, and honestly? it's giving "quietly important little struct that carries a whole lot of ✨alignment lore✨". let's get into it 🫶

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🌸 NAME 🌸

std::aligned_storage< _Len, _Align > — Aligned storage. that's it, that's the name, and it's iconic for it 💅

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🎀 SYNOPSIS 🎀

#include <type_traits>

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🦋 Detailed Description 🦋

template<size_t _Len, size_t _Align =
    __aligned_storage_default_alignment(_Len)>
struct std::aligned_storage< _Len, _Align >

Aligned storage. no cap, that's what it is 💖

so the member typedef type is a POD type that's suitable for use as uninitialized storage for any object whose size is at most _Len and whose alignment is a divisor of _Align. like, it's the raw, uninitialized little parking spot your object is gonna live in 🌈

MAJOR VIBE CHECK INCOMING 🚨 it is so important that you use the nested type as your uninitialized storage — not the std::aligned_storage type itself, because that one is an empty class with 1-byte alignment. and 1-byte alignment is NOT gonna cut it for your fancy over-aligned object, bestie. 💀

so THIS is correct:

typename std::aligned_storage<sizeof(X), alignof(X)>::type m_xobj;

and THIS is wrong:

std::aligned_storage<sizeof(X), alignof(X)> m_xobj;

not me stressing this distinction twice, but it's literally the whole point of the type 😭

in C++14 and later you can use std::aligned_storage_t<sizeof(X), alignof(X)> to refer to that type member typedef. shorter, cuter, same energy ⭐

and the default value of _Align? it's supposed to be the most stringent fundamental alignment requirement for any C++ object type whose size is no greater than _Len (see [basic.align] in the C++ standard, for the real ones who read the source material 📚).

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💅 Deprecated 💅

Deprecated in C++23. 🚨

uses can be replaced by an array std::byte[_Len] declared with alignas(_Align). so yeah, she's retired, she served her time, we move on, we grow 🌱

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👑 Author 👑

Generated automatically by Doxygen for libstdc++ from the source code. so technically the author is a robot and the robot ate, periodt 🤖✨

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and that's the whole page bestie!! thanks for coming to my TED talk about alignment 💖 this little legend lives in libstdc++ (the libstdc++ manual page, section 3 — std::align..., _Align >(3), she's got the cutest truncated title fr fr), and if you ever need her again just man 3 std::aligned_storage and she'll be right there, aligned and ready 🎀🦋🌸💜