C Unsigned int提供负值？ [英] C Unsigned int providing a negative value?

问题描述

我有一个无符号整数，但当我用％d打印出来时，有时会出现负值吗？

I have an unsigned integer but when i print it out using %d there is sometimes a negative value there?

推荐答案

打印％d 将读取整数作为带符号的十进制数，无论其定义的类型如何。

Printing %d will read the integer as a signed decimal number, regardless of its defined type.

打印无符号数字，使用％u 。

To print unsigned numbers, use %u.

这是因为C处理变量参数的方式。编译器只是从堆栈中提取值（键入 void * 并指向调用堆栈）并且 printf 必须从你给它的格式字符串中找出数据包含的内容。

This happens because of C's way to handle variable arguments. The compiler just pulls values from the stack (typed as void* and pointing to the call stack) and printf has to figure out what the data contains from the format string you give it to.

这就是你需要提供格式字符串的原因 - C无法 RTTI 或基类（对象 in例如，Java从中获取通用或预定义的 toString 。

This is why you need to supply the format string - C has no way of RTTI or a 'base class' (Object in Java, for example) to get a generic or predefined toString from.

这篇关于C Unsigned int提供负值？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！