转换unsigned int类型以签署诠释三 [英] Convert unsigned int to signed int C

问题描述

我试图 65529 从 unsigned int类型转换为签署 INT 。我试着做这样的转换：

I am trying to convert 65529 from an unsigned int to a signed int. I tried doing a cast like this:

unsigned int x = 65529;
int y = (int) x;

但是仍返回65529时，它应该返回-7。这是为什么？

But y is still returning 65529 when it should return -7. Why is that?

推荐答案

好像你正期待 INT 和 unsigned int类型来是一个16位的整数。这显然​​不是这样。最有可能的，这是一个32位整数 - 这是足够大，以避免环绕，你期待

It seems like you are expecting int and unsigned int to be a 16-bit integer. That's apparently not the case. Most likely, it's a 32-bit integer - which is large enough to avoid the wrap-around that you're expecting.

请注意，有这样做，因为无/有符号间铸造的值超出范围是实现定义没有C兼容的完全的方式。但是，这仍然会在大多数情况下工作：

Note that there is no fully C-compliant way to do this because casting between signed/unsigned for values out of range is implementation-defined. But this will still work in most cases:

unsigned int x = 65529;
int y = (short) x;      //  If short is a 16-bit integer.

或者：

unsigned int x = 65529;
int y = (int16_t) x;    //  This is defined in <stdint.h>

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