x =!x是什么意思？

Question

虽然readinf MuPDF遇到了源代码行

x = !x;

想知道上面的代码是做什么的？

编译时也会出错

assuming signed overflow does not occur when simplifying 
condition to constant [-Werror=strict-overflow ]

Answer 1

!x将评估为0或1,取决于的价值x.

• 如果x是0,则评估为1.
• 否则,它评估为0.