为什么比较一个无符号的Int> = 0 a“无意义的比较”？ [英] Why Is Comparing if an Unsigned Int >= 0 a "Pointless Comparison"?

问题描述

Pe186无符号无符号比较零

当我试图编译下面的代码时：

  for（clLoop = cpLoopStart ; clLoop> = 0; clLoop--）
 {
 //做某事
} 
  

我不明白为什么。我可以理解，如果我正在寻找小于零的值，因为 unsigned int 永远不能为负数。但是我在这里找的是如果等于为零，肯定可以是 unsigned int 。

我甚至可以看到这个错误，如果在这个循环中我试图预递减而不是后递减，但是情况并非如此。

> = ）零。这个表达式总是成立的，因为无符号整数永远不会小于零。

编译器试图提醒你，你正在编程一个无限循环。 p>

I got warning:

Pe186 "Pointless comparison of unsigned int with zero"

when I tried to compile the following code:

for(clLoop = cpLoopStart; clLoop >= 0; clLoop--)                                  
{
    //Do something
}

I don't understand why. I could understand, if I were looking for a value less than zero, since an unsigned int can never be negative. But all I am looking for here is if it is equal to zero, which an unsigned int certainly can be.

I could even see this error if in this loop I tried to pre-decrement instead of post-decrement, but again that is not the case.

解决方案

You check whether the unsigned int is greater than or equal (>=) zero. This expression will always be true, because unsigned integers will never be less than zero.

The compiler tries to warn you that you are about to program an infinite loop.

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