c - x->a = x->b,++x++ ->b; 是什么意思？在给定的程序中做什么？

Question

这个问题已经有答案了:

Why are these constructs using pre and post-increment undefined behavior? (14 个回答)

已关闭 7 年前。

int main() 
{
    struct data{
        int a;
        int b;
    }y[4] = {1,10,3,30,2,20,4,40};

    struct data *x = y;
    int i;

    for(i = 0; i < 4; i++)
    {
         x->a = x->b, ++x++ ->b;
         printf("%d%d\t", y[i].a, y[i].b);
    }


    return 0;
}

这段代码是如何工作的？

Answer 1

声明

x->a = x->b, ++x++ ->b;  //note the comma operator after x->a = x->b

相当于

x->a = x->b;     // Assign member `a` to first member of element of array y 
++( (x++) ->b);  // Fetch the member b of element of array y and then increment 
                 // it by 1. Increment `x` by 1 after `b` is fetched.