C和C++中寄存器变量的地址-C/C++问题

address of register variable in C and C++(C和C++中寄存器变量的地址)

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问题描述

我知道寄存器变量的概念及其用例，但根据我的尝试，我的脑海中几乎没有问题.

I know the concept of register variable and it's use cases but there are few questions in my mind based on what I have tried.

虽然我可以在 C++ 中访问，但我无法访问 C 中的寄存器变量的地址！为什么?访问寄存器变量的地址有什么问题吗?

I cannot access the address of a register variable in C though I can do it C++! Why? Is there any issue in accessing the addressing of a register variable?

假设如果我在 C++ 中将一个字符串变量声明为寄存器，那么该变量将存储在哪里?将C++中的'string'等非数字数据类型的存储类声明为register有什么意义?

Suppose if I declare a string variable in C++ as register, then where will that variable be stored? What is the point in declaring the storage class of non-numeric data types such as 'string' in C++ to be register??

更新:我认为 C++ 允许我们获取寄存器变量的地址，因为我的程序中没有出现任何错误，如下所示:

UPDATE: I thought that C++ allows us to fetch the address of a register variable, as I was not getting any error in my program which is as follows:

#include<iostream>
#include<time.h>

using namespace std;

clock_t beg, en;

int main(){

    int j, k=0;

    beg=clock();
    for(register int i=0;i<10000000;i++){
        /*if(k==0){
            cout<<&i<<endl;    // if this code is uncommented, then C++ rejects the recommendation to make 'i' as register
            k++;
        }*/
    }
    en=clock();

    cout<<en-beg<<endl;

    cout<<&j<<endl<<&k;

    return 0;
}

我观察到的是，如果我将变量i"作为寄存器并且不尝试使用&i"打印地址，那么 C++ 接受建议并将i"存储在寄存器中，这可以是从 for 循环的运行时间推断，如果i"在寄存器中，它将始终在 4-12 毫秒左右.但是，如果我尝试打印变量i"的地址，那么虽然我没有收到任何错误，但 C++ 拒绝了建议，这可以从执行循环的时间推断出来，如果 i 没有注册，则该时间总是超过 25！！

What I have observed is, if I make the variable 'i' as register and don't try to print the address using '&i' then C++ accepts the recommendation and stores 'i' in register, this can be infered from running time of for loop which will always be around 4-12 ms if 'i' is in register. But if I try to print address of variable 'i' then though I don't get any error but C++ rejects the recommendation and this can be infered from the time of execution of loop which is always more than 25 if i is not register!!

所以，基本上我无法获取具有存储类的变量的地址作为 C 和 C++ 中的寄存器！为什么?

So, basically I cannot fetch address of a variable with storage class as register in both C as well as C++!! WHY?