isalpha(0), etc

[Alex]

Is the result of the various isxxx() functions declared in <ctype.h> when
given an argument of 0 defined? And if so, how? Does locale make a
difference?

TIA,
Alex

 

[Régis Troadec]

"Alex" <[email protected]> a écrit dans le message de

Hi,

Is the result of the various isxxx() functions declared in <ctype.h> when
given an argument of 0 defined? And if so, how? Does locale make a
difference?

Yes, the chars classification functions provided by <ctype.h> can take 0 in
argument. The parameter of an isxxx() function shall be an int
representable as an unsigned char (0 is) or EOF, otherwise the behavior is
undefined. The behavior of all these functions may differ according to the
locale, but concerning isxxx(0), I don't think it should change something.

Regis

 

[Alex]

Yes, the chars classification functions provided by <ctype.h> can take 0
in argument. The parameter of an isxxx() function shall be an int
representable as an unsigned char (0 is) or EOF, otherwise the behavior is
undefined.

Sorry if I was not clear. Allow me to rephrase:

Are the return values of the isxxx() functions specified when called with an
argument of 0? If so, what are they? (eg they all return 0 except
iscntrl().)

Alex

 

[Régis Troadec]

Sorry if I was not clear. Allow me to rephrase:

Are the return values of the isxxx() functions specified when called with an
argument of 0? If so, what are they? (eg they all return 0 except
iscntrl().)

I beg your pardon, I'm sorry to have misunderstood you.
By reading the J.4 annex concerning locale specific behavior, I would say
that it's implementation defined (e.g all chars classification functions may
not return 0 if 0 is passed in argument as well as iscntrl() may not always
return true). The sets of control characters, printing characters and those
tested by the isxxx() may differ according to the implementation.
But I think that in most cases (and most of charsets), 0 stands for a
control character (NUL in ASCII) and that the isxxx() functions return 0
except iscntrl().

Regis