c - 为什么 sizeof(x++) 不增加 x？

Question

这是在 dev c++ windows 中编译的代码:

#include <stdio.h>

int main() {
    int x = 5;
    printf("%d and ", sizeof(x++)); // note 1
    printf("%d\n", x); // note 2
    return 0;
}

我希望 x 在执行 note 1 后为 6。但是，输出是:

4 and 5

谁能解释为什么 x 在 note 1 之后不递增？

Answer 1

来自C99 Standard (重点是我的)

6.5.3.4/2

The sizeof operator yields the size (in bytes) of its operand, which may be an expression or the parenthesized name of a type. The size is determined from the type of the operand. The result is an integer. If the type of the operand is a variable length array type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an integer constant.