这个带括号和不带括号的 C++ 代码有什么区别？

Question

What is the purpose of the parentheses in the following piece of code? What would be happening if the parentheses were not there? Sorry, I am new to C++.

void foo(int * xPtr) {
  (*xPtr)++;
}

Answer 1

使用括号，您增加指针引用的对象，没有它们，您增加指向下一个内存地址的指针，然后取消引用它（在这种情况下什么都不做）。

Answer 2

If parentheses are not there then you are basically modifying the memory address stored inside xPtr and then dereferencing the pointer. So clearly this is not what is desired.

Say we want the value stored at memory location 1000 to be incremented, but

*xPtr++;

results in incrementing the memory location by 4 and then,value at memory location 1004 is accessed, assuming size of integer on the machine is 4 bytes .

Answer 3

(*xPtr)++ will increment the thing xPtr points to.

Postfix ++ has higher precedence than unary * ; without parentheses, the code would be parsed as *(xPtr++) - you're incrementing xPtr , not the thing xPtr points to.