c++ - sizeof(bool) 是否在 C++ 语言标准中定义？

Question

我在标准文档中找不到答案。 C++ 语言标准是否要求 sizeof(bool) 始终为 1(对于 1 个字节)，还是这个大小是实现定义的？

Answer 1

sizeof(bool) 是实现定义的，标准特别强调了这一事实。

§5.3.3/1，删节:

sizeof(char), sizeof(signed char) and sizeof(unsigned char) are 1; the result of sizeof applied to any other fundamental type is implementation-defined. [Note: in particular, sizeof(bool) and sizeof(wchar_t) are implementation-defined.⁶⁹⁾]

脚注 69):

sizeof(bool) is not required to be 1.