c++ - 为什么相同的类型不同？

Question

为什么这样(字符在我的实现中签名):

cout << std::is_same< char,signed char>::value;

输出错误？

Answer 1

这三种类型是在不同的时间引入的。

来自 C99 Rational:

Three types of char are specified:
signed, plain, and unsigned. A plain char may be represented as either signed or unsigned depending upon the implementation, as in prior practice. The type signed char was introduced in C89 to make available a one-byte signed integer type on those systems which implement plain char as unsigned char.

它们必须在 C++ 中保持独立的类型，以允许对 char 的重载是可移植的。