Re: src/kwset.c (kwsincr): Replace arbitrary array size by proper value

[Julian Foad]

Charles Levert wrote:
> Proposed patch; I'll write a ChangeLog entry if
> it's accepted.
>
> I have checked that this will hold for CHAR_BIT
> up to 1023.  Custom tools used for checking
> this available upon request (part analytical,
> part experimental).
>
>
>
> --- src/kwset.c 2005-07-04 01:14:37 -0400
> +++ src/kwset.c 2005-07-04 11:45:33 -0400
> @@ -121,6 +121,14 @@ kwsalloc (char const *trans)
>    return (kwset_t) kwset;
>  }
>  
> +/* This upper bound is valid for CHAR_BIT >= 4 and
> +   exact for CHAR_BIT in { 4..11, 13, 15, 17, 19 }. */
> +#if CHAR_BIT < 4
> +#error "CHAR_BIT is smaller than 4; yeah, right!"

I don't much like that "#error".  For one thing, I think we can just assume 
that CHAR_BIT is not less than 4.  For another thing, we have no precedent for 
using "#error" elsewhere; I don't know what our conditions for supporting 
pre-ANSI-C compilers are but I think there is still a conscious attempt to 
support them where possible, by avoiding pre-ANSI-C features unless they are 
really useful or really easy to work around.

> +#else
> +#define DEPTH_SIZE (CHAR_BIT + CHAR_BIT/2)
> +#endif
> +
>  /* Add the given string to the contents of the keyword set.  Return NULL
>     for success, an error message otherwise. */
>  const char *
> @@ -131,8 +139,8 @@ kwsincr (kwset_t kws, char const *text, 
>    register unsigned char label;
>    register struct tree *link;
>    register int depth;
> -  struct tree *links[12];
> -  enum { L, R } dirs[12];
> +  struct tree *links[DEPTH_SIZE];
> +  enum { L, R } dirs[DEPTH_SIZE];

I guess you could make this change now without the "#if ... #error" part.

- Julian