c - 静态变量的声明和放置

Question

X是否只在函数第一次执行时被Y初始化一次？

int foo(int y) {

   static int x = y;
   x = x + 1;
   return x;
}

while(1) {
  y = y+1;
  foo(y);
}

Answer 1

不可以，用局部变量初始化静态变量是无效的。

例如，函数内部的static就是这样。

int foo(void)
{
   static int y = 0;
}

上面的语句等同于下面两件事:

 1) static int y = 0;
    int foo(void)
    {

    }

 2) And the variable y' should be used only in the function foo(). So you are 
    telling the compiler that I want a variable that is a global(with respect
    to memory and initialization at the compilation time), but the variable
    should be used only inside the function, if it is used outside this function
    let me know. 


 So, dynamic initialization of a static variable(that is actually initialized at
 the time of compilation) is invalid.