On 27.09.2006 03:55, David Laight wrote:
> The following reply was made to PR lib/34632; it has been noted by GNATS.
> 
> From: David Laight <david@l8s.co.uk>
> To: gnats-bugs@netbsd.org
> Cc: 
> Subject: Re: lib/34632: isalpha() and possibly other ctype functions segfault
> Date: Wed, 27 Sep 2006 00:49:53 +0100
> 
>  On Tue, Sep 26, 2006 at 07:37:36PM -0400, Christos Zoulas wrote:
>  > | Other systems (AIX, MacOS, various Linuxes) have chosen a user-friendly way and return 0.
>  
>  Are you sure ?

Yes. I did check it out.
Btw, I forgot to add FreeBSD to the list of systems that do not segfault.

>  The isxxx() 'functions' are almost always implemented (and were designed to
>  be implemented) as an array lookup checking for several bits.
>  Since the domain of the functions is 'all the values of unsigned char + EOF'
>  it is typically -1..255, calling the function with an -ve value in a
>  signed char indexes off the front of the array.  If you are lucky this
>  doesn't have the relevent bit(s) set and is a zero, it might have a
>  bit set and return 1, it might not be mapped and so core dump.
>  The standards allow 'undefined' behaviour - this includes formatting
>  your hard disk or crushing your nuts.


-- 
Wbr, 
Antony Dovgal