Re: Casting ctype lookups

[David Laight <david%l8s.co.uk@localhost>]

On Wed, Nov 14, 2012 at 10:36:42AM -0500, D'Arcy J.M. Cain wrote:
> 
> Functions yes but the macros don't work the same.
> 
> $ cat t.c
> #include <stdio.h>
> #include <ctype.h>
> void func(char *s)
> {
>   while (*s++) *s = toupper(*s);
> }
> int main(void)
> {
>   char s[] = "Test string";
> 
>   func(s);
>   printf("%s\n", s);
>   return 0;
> }
> $ gcc -Wall -Werror -o t t.c && ./t
> cc1: warnings being treated as errors
> t.c: In function 'func':
> t.c:5:3: error: array subscript has type 'char'
> $ gcc -Wall -Werror -D_CTYPE_NOINLINE -o t t.c && ./t
> TEST STRING
> 
> With my proposed change the function and the macro both act the same.

and your program dumps core because it is invalid.

If your code is in EBCDIC (not ASCII) then "Test string" is (I think):
{ 0xe3, 0x85, 0xa2, 0xa3, 0x40, 0xa2, 0xa3, 0x99, 0x89, 0x95, 0x87, 0 }
and you keep passing invalid values to toupper() - with undefined
results (which is allowed to include 'format the hard drive').

FWIW toupper() used to only be defined on values where islower()
returned 'non-zero', SYSV used to use the same array for toupper()
and tolower().

        David

-- 
David Laight: david%l8s.co.uk@localhost