[Freeciv-Dev] Re: Compiler-warnings

[Raimar Falke <hawk@xxxxxxxxxxxxxxxxxxxxxxx>]

On Wed, Jan 24, 2001 at 10:09:14PM +0100, Stepan Roh wrote:
> 
> 
> On Wed, 24 Jan 2001, Raimar Falke wrote:
> 
> > gcc -Wall gives:
> > a.c: In function `main':
> > a.c:10: warning: array subscript has type `char'
> >
> > So it looks like gcc will accept signed or unsigned char as array
> > subscripts. It can also be done using int. Both solution will silence
> > the warning but maybe there is also something else to consider.
> 
> There is a gcc option -Wchar-subscripts (citation from info docs
> follows), which is enabled with -Wall (and can be disabled with
> -Wno-char-subscripts).

I know. I looked at the code:
$ grep -n isal stdinhand.c
1957:  for(cptr_s=str; *cptr_s && !isalnum(*cptr_s); cptr_s++);
1960:  for(cptr_d=arg_level; *cptr_s && isalnum(*cptr_s); cptr_s++, cptr_d++) {
2000:  for(; *cptr_s && !isalnum(*cptr_s); cptr_s++);
2004:      *cptr_s && (*cptr_s == '-' || *cptr_s == ' ' || isalnum(*cptr_s));
2224:  for(cptr_s=str; *cptr_s && !isalnum(*cptr_s); cptr_s++);
2225:  for(cptr_d=command; *cptr_s && isalnum(*cptr_s); cptr_s++, cptr_d++)
2368:  for(cptr_s=str; *cptr_s && !isalnum(*cptr_s); cptr_s++);
2369:  for(cptr_d=command; *cptr_s && isalnum(*cptr_s); cptr_s++, cptr_d++)
2451:  return isalnum(c);
2459:  return (c == '-') || (c == '*') || (c == '+') || (c == '=') || 
isalnum(c);
2598:  for(cptr_s=str; *cptr_s && !isalnum(*cptr_s); cptr_s++);
2600:  for(cptr_d=command; *cptr_s && isalnum(*cptr_s) &&
3334:  while (str_itr < rl_line_buffer + start && !isalnum(*str_itr))
3341:  if (isalnum(*str_itr)) /* not a distinct word */
3346:      if (isalnum(*str_itr))
3366:    if (isalnum(*str_itr))
3395:    if (isalnum(*chptr)) {

So isalnum() is a macro which uses arrays and the compiler gives
warnings. Quoting from glibc's ctype.h:
   These point into arrays of 384, so they can be indexed by any `unsigned
   char' value [0,255]; by EOF (-1); or by any `signed char' value
   [-128,-1).  ISO C requires that the ctype functions work for `unsigned
   char' values and for EOF; we also support negative `signed char' values
   for broken old programs.  The case conversion arrays are of `int's
   rather than `unsigned char's because tolower (EOF) must be EOF, which

So isalnum() works only for unsigned char on all platforms.

        Raimar

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