我是否应该禁用C编译器符号/无符号不匹配的警告？ [英] Should I disable the C compiler signed/unsigned mismatch warning?

问题描述

微软C编译器警告，当您尝试比较两个变量，一个是签名，另一个是无符号的。例如：

The Microsoft C compiler warns when you try to compare two variables, and one is signed, and the other is unsigned. For example:

int a;    
unsigned b;

if ( a < b ) { // warning C4018: '&lt;' : signed/unsigned mismatch

}

有此警告，在世界的历史上，从未患过一个真正的错误？为什么是在那里啊？

Has this warning, in the history of the world, ever caught a real bug? Why's it there, anyway?

推荐答案

哦，是这样。但周围的其他方法。的忽略的这一警告引起了巨大的头痛我一天。我正在写该曲线的图表的函数，并混合符号和无符号的变量。在一个地方，我比较了负数无符号之一：

Oh it has. But the other way around. Ignoring that warning caused a huge headache to me one day. I was writing a function that plotted a graph, and mixed signed and unsigned variables. In one place, i compared a negative number to a unsigned one:

int32_t t; ...
uint32_t ut; ...

if(t < ut) { 
    ...
}

猜猜发生了什么？已签署的数字被提升到无符号的类型，因此是的大于的结尾，即使它是低于0最初。我花了几个小时，直到我发现的bug。

Guess what happened? The signed number got promoted to the unsigned type, and thus was greater at the end, even though it was below 0 originally. It took me a couple of hours until i found the bug.

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