boolean - Is sizeof(bool) defined in the C++ language standard?

Question

I can't find an answer in the standard documentation. Does the C++ language standard require sizeof(bool) to always be 1 (for 1 byte), or is this size implementation-defined?

Answer 1

sizeof(bool) is implementation defined, and the standard puts notable emphasis on this fact.

§5.3.3/1, abridged:

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⁾]

Footnote 69):

sizeof(bool) is not required to be 1.