c++ - 未初始化变量的值是如何确定的？

Question

给定一个程序:

int main()
{

    short myVariableName1;  // stores from -32768 to +32767
    short int myVariableName2;  // stores from -32768 to +32767
    signed short myVariableName3;  // stores from -32768 to +32767
    signed short int myVariableName4;  // stores from -32768 to +32767
    unsigned short myVariableName5;  // stores from 0 to +65535
    unsigned short int myVariableName6;  // stores from 0 to +65535

    int myVariableName7;  // stores from -32768 to +32767
    signed int myVariableName8;  // stores from -32768 to +32767
    unsigned int myVariableName9;  // stores from 0 to +65535

    long     myVariableName10;  // stores from -2147483648 to +2147483647
    long     int myVariableName11;  // stores from -2147483648 to +2147483647
    signed   long myVariableName12;  // stores from -2147483648 to +2147483647
    signed   long int myVariableName13;  // stores from -2147483648 to +2147483647
    unsigned long myVariableName14;  // stores from 0 to +4294967295
    unsigned long int myVariableName15;  // stores from 0 to +4294967295
    cout << "Hello World!" << endl;
    cout << myVariableName1 << endl;
    cout << myVariableName2 << endl;
    cout << myVariableName3 << endl;
    cout << myVariableName4 << endl;
    cout << myVariableName5 << endl;
    cout << myVariableName6 << endl;
    cout << myVariableName7 << endl;
    cout << myVariableName8 << endl;
    cout << myVariableName9 << endl;
    cout << myVariableName10 << endl;
    cout << myVariableName11 << endl;
    cout << myVariableName12 << endl;
    cout << myVariableName13 << endl;
    cout << myVariableName14 << endl;
    cout << myVariableName15 << endl;
    cin.get();

    return 0;
}

打印出未分配的变量将打印之前存储在该内存位置的任何内容。我注意到，在多次连续执行中，打印的值没有改变 - 这告诉我每次执行时内存中的位置都是相同的。

我只是好奇这是怎么确定的，为什么会这样。

Answer 1

这些变量存在于堆栈中。程序的执行看起来是确定性的，所以每次运行它时都会发生同样的事情。它不一定选择相同的地址(如今许多运行时都使用地址空间随机化技术来确保堆栈地址在运行之间不相同)，但堆栈上的相对地址包含相同的地址每次都有数据。