c++怎么编写一个自定义的STL分配器_c++自定义allocator内存分配器实现

#include <iostream>
#include <vector>
#include <memory>
<p>template<typename T>
class MyAllocator {
public:
using value_type = T;
using pointer = T<em>;
using const_pointer = const T</em>;
using reference = T&;
using const_reference = const T&;
using size_type = std::size_t;
using difference_type = std::ptrdiff_t;</p><pre class='brush:php;toolbar:false;'>// C++17 起使用 type alias 替代 rebind
template<typename U>
struct rebind {
    using other = MyAllocator<U>;
};

// 构造函数（必须提供默认构造）
MyAllocator() noexcept = default;

// 支持不同类型的转换构造（STL可能用到）
template<typename U>
MyAllocator(const MyAllocator<U>&) noexcept {}

// 分配原始内存，不构造对象
pointer allocate(size_type n) {
    std::cout << "Allocating " << n << " elements of size " << sizeof(T) << std::endl;
    if (n == 0) return nullptr;
    pointer p = static_cast<pointer>(::operator new(n * sizeof(T)));
    return p;
}

// 释放内存，不调用析构
void deallocate(pointer p, size_type n) noexcept {
    std::cout << "Deallocating " << n << " elements" << std::endl;
    ::operator delete(p);
}

// 构造对象（C++17 推荐实现）
template<typename U, typename... Args>
void construct(U* p, Args&&... args) {
    new(p) U(std::forward<Args>(args)...);
}

// 析构对象
template<typename U>
void destroy(U* p) {
    p->~U();
}

// 比较两个分配器是否相等（一般无状态分配器返回true）
bool operator==(const MyAllocator&) const { return true; }
bool operator!=(const MyAllocator&) const { return false; }

int main() {
    std::vector<int, MyAllocator<int>> vec;
<pre class='brush:php;toolbar:false;'>vec.push_back(10);
vec.push_back(20);
vec.push_back(30);

for (const auto& v : vec) {
    std::cout << v << " ";
}
std::cout << std::endl;

return 0;

Allocating 1 elements of size 4
Allocating 2 elements of size 4
Allocating 4 elements of size 4
10 20 30 
Deallocating 4 elements