bug#54124: fmt inserts garbage in certain cases?

[Paul Eggert]

On 2/23/22 17:29, Pádraig Brady wrote:
> Given isspace('\n') returns true, then it makes some sense that 
> isspace("Next Line")
> would return true,

POSIX says that the application must insure that argument to isspace is 
either EOF or "a character representable as an unsigned char", and 
arguably since 0x85 not either one of those things the behavior of 
isspace(0x85) is undefined.

However, the C standard does not have this wording, and since POSIX is 
supposed to defer to the C standard here, this appears to be a bug in 
POSIX (as well as a bug in macOS). It's understandable if the Apple C 
library's developers got confused by the POSIX wording.