std::addressof
Defined in header <memory> | ? | ? |
|---|---|---|
? | (1) | ? |
template< class T > T* addressof(T& arg); | (since C++11) (until C++17) | |
template< class T > constexpr T* addressof(T& arg); | (since C++17) | |
template <class T> const T* addressof(const T&&) = delete; | (2) | (since C++17) |
1%29获取对象或函数的实际地址。arg，即使在超载的情况下operator&
2%29 rvalue重载被删除，以防止使用const罗兹。
The expression std::addressof(E) is a constant subexpression, if E is an lvalue constant subexpression. | (since C++17) |
|---|
参数
arg | - | lvalue object or function |
|---|
返回值
指向arg...
例外
1%29
noexcept规格：
noexcept
可能的实施
模板<类T>T%2A地址%28 t&Arg%29{返回重解释[医]铸造<T%2A>%28及[医]CAST<char&>%28重新解释[医]铸造<Const挥发性焦炭&>%28 arg%29%29%29；}
*。
注：上述实施过于简化而不是constexpr%28，需要编译器支持%29。
例
运算符&可以重载指针包装类以获得指向指针的指针：
二次
#include <iostream>
#include <memory>
template<class T>
struct Ptr {
T* pad; // add pad to show difference between 'this' and 'data'
T* data;
Ptr(T* arg) : pad(nullptr), data(arg)
{
std::cout << "Ctor this = " << this << std::endl;
}
~Ptr() { delete data; }
T** operator&() { return &data; }
};
template<class T>
void f(Ptr<T>* p)
{
std::cout << "Ptr overload called with p = " << p << '\n';
}
void f(int** p)
{
std::cout << "int** overload called with p = " << p << '\n';
}
int main()
{
Ptr<int> p(new int(42));
f(&p); // calls int** overload
f(std::addressof(p)); // calls Ptr<int>* overload, (= this)
}二次
可能的产出：
二次
Ctor this = 0x7fff59ae6e88
int** overload called with p = 0x7fff59ae6e90
Ptr overload called with p = 0x7fff59ae6e88二次
另见
allocator | the default allocator (class template) |
|---|---|
pointer_to static | obtains a dereferenceable pointer to its argument (public static member function of std::pointer_traits) |
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