要在C中签名int的字节 [英] Byte to signed int in C

问题描述

我在C中的一个char中存储了一个二进制值，我想将此字节转换为C中的有符号int. 目前我有这样的东西:

I have a binary value stored in a char in C, I want transform this byte into signed int in C. Currently I have something like this:

char a = 0xff;
int b = a; 
printf("value of b: %d\n", b);

标准输出的结果将为"255"，所需的输出为"-1".

The result in standard output will be "255", the desired output is "-1".

推荐答案

替换:

char a = 0xff

通过

signed char a = 0xff;  // or more explicit: = -1

让printf打印-1.

如果您不想更改a的类型，请在注释中添加@veer，只需将a强制转换为(signed char)，然后将其值分配给b.

If you don't want to change the type of a, as @veer added in the comments you can simply cast a to (signed char) before assigning its value to b.

请注意，在这两种情况下，此整数转换都是实现定义的，但这是常见的实现定义的行为.

Note that in both cases, this integer conversion is implementation-defined but this is the commonly seen implementation-defined behavior.

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