std::allocator_traits<Alloc>::construct

 

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std::allocator_traits

成员类型

成员函数

allocator_traits::allocate

allocator_traits::allocate_at_least (C++23)

allocator_traits::deallocate

allocator_traits::construct

allocator_traits::destroy

allocator_traits::max_size

allocator_traits::select_on_container_copy_construction

 

定义于头文件 <memory>
template< class T, class... Args > static void construct( Alloc& a, T* p, Args&&... args );		(since C++11) (constexpr since C++20)

如果可能，通过调用 a.construct(p, std::forward<Args>(args)...)，在 p 指向的已分配但未初始化的存储中构造类型 T 的对象。

如果上述方法不可行（例如，Alloc 没有成员函数 construct()），则调用

::new (static_cast<void*>(p)) T(std::forward<Args>(args)...)	(until C++20)
std::construct_at(p, std::forward<Args>(args)...)	(since C++20)

参数

a	-	用于构造的分配器
p	-	指向将在其上构造 T 对象的未初始化存储的指针
args...	-	要传递给 a.construct() 或 placement-new(until C++20)std::construct_at()(since C++20) 的构造函数参数

返回值

(无)

注解

标准库容器在插入、复制或移动元素时使用此函数。

由于此函数提供了自动回退到 placement new 的机制，因此成员函数 construct() 是 C++11 之后可选的 Allocator 要求。

参见

operator newoperator new[]	分配函数 (函数)
construct (until C++20)	在已分配的存储中构造对象 (std::allocator<T> 的公共成员函数)
construct_at (C++20)	在给定地址创建对象 (函数模板)