bug#18266: handling bytes not part of the charset, and other garbage

[Paul Eggert]

Vincent Lefevre wrote:
> the C locale corresponds to ANSI_X3.4-1968,

No it doesn't, at least not on any current platform I'm aware of.  And 
POSIX does not require that.  POSIX even allows the C locale to be 
multibyte, e.g., UTF-8.

> I would say that this should be the same for invalid
> byte sequences in a UTF-8 locale.

One *could* design an encoding with that property, but it wouldn't be 
UTF-8; it would be something else.  I don't know of any C library that 
does that to UTF-8.  There are good arguments against doing it, e.g., 
one loses the property that one can concatenate character strings by 
concatenating their byte representations.

Anyway I'm afraid we may be going off the deep end here.  After all, 
grep can't impose its coding system design onto the operating system; 
it's more the other way around.