Comma operator and parentheses - C Language

Example 1

int x;
int a=(x=2),12;// 赋值优先级高于逗号，相当于a=x=2，12是多余的
printf("a=%d",a);

Results: a = 2

Example 2

int x;
int a=((x=2),12);// 括号里从左到右执行，只会返回最后一个，即12
printf("a=%d",a);

Results: a = 12