Re: [PATCH/RFA] Distinguish between EOF and character with value 0xff

[Jeff Johnston <jjohnstn at redhat dot com>]

Eric Blake wrote:
> Eric Blake <ebb9 <at> byu.net> writes:
>
>   
> > > Should any attempt be made to make it cleaner for those who don't?
> > >       
> > One way might be to write it in such a way that, for decent compilers, we 
> > trigger warnings.  Gcc is already smart enough to warn the user about the use 
> > of a char array index:
> >
> >
> > Maybe the trick is to rewrite the macros such that we force the original 
> >     
> input 
>   
> > to be treated as an array index; it is too late after the addition (at which 
> > point things have been promoted to int if they weren't already).  Untested:
> >
> > #define isalpha(c) ((*((&__ctype_ptr__[c])+1))&(_U|_L))
> >     
>
> I spent some time and actually tested my proposal.  I've verified that with the 
> patch below, the assembly produced by isalpha(i) is identical both before and 
> after the patch under gcc 4.3.2.  Meanwhile, 'gcc -Wall' is now able to 
> complain about isalpha((char)i) while staying silent for isalpha((unsigned char)
> i).
>
> OK to apply?  (And pardon the fact that gmane botched the long lines.)
>
>   
Yes, please resend as an attachment, otherwise I can't apply it, and 
include Mike's suggestion as well.

-- Jeff J.
> 2009-04-22  Eric Blake  <ebb9@byu.net>
>
> 	Trigger gcc warning if isFoo macros are called with plain char.
> 	* libc/include/ctype.h (isalpha, isupper, islower, isdigit)
> 	(isxdigit, isspace, ispunct, isalnum, isprint, isgraph)
> 	(iscntrl, isblank): Rewrite to let 'gcc -Wall' warn when user
> 	calls macro with a char argument.
>
> --- ctype.h.orig	2009-04-22 13:39:01.702341400 -0600
> +++ ctype.h	2009-04-22 15:19:08.381510200 -0600
> @@ -45,22 +45,22 @@
>  extern	__IMPORT char	*__ctype_ptr__;
>  
>  #ifndef __cplusplus
> -#define	isalpha(c)	((__ctype_ptr__)[(unsigned)((c)+1)]&(_U|_L))
> -#define	isupper(c)	(((__ctype_ptr__)[(unsigned)((c)+1)]&(_U|_L))
> ==_U)
> -#define	islower(c)	(((__ctype_ptr__)[(unsigned)((c)+1)]&(_U|_L))
> ==_L)
> -#define	isdigit(c)	((__ctype_ptr__)[(unsigned)((c)+1)]&_N)
> -#define	isxdigit(c)	((__ctype_ptr__)[(unsigned)((c)+1)]&(_X|_N))
> -#define	isspace(c)	((__ctype_ptr__)[(unsigned)((c)+1)]&_S)
> -#define ispunct(c)	((__ctype_ptr__)[(unsigned)((c)+1)]&_P)
> -#define isalnum(c)	((__ctype_ptr__)[(unsigned)((c)+1)]&(_U|_L|_N))
> -#define isprint(c)	((__ctype_ptr__)[(unsigned)((c)+1)]&(_P|_U|_L|_N|_B))
> -#define	isgraph(c)	((__ctype_ptr__)[(unsigned)((c)+1)]&
> (_P|_U|_L|_N))
> -#define iscntrl(c)	((__ctype_ptr__)[(unsigned)((c)+1)]&_C)
> +#define	isalpha(c)	((__ctype_ptr__+1)[c]&(_U|_L))
> +#define	isupper(c)	(((__ctype_ptr__+1)[c]&(_U|_L))==_U)
> +#define	islower(c)	(((__ctype_ptr__+1)[c]&(_U|_L))==_L)
> +#define	isdigit(c)	((__ctype_ptr__+1)[c]&_N)
> +#define	isxdigit(c)	((__ctype_ptr__+1)[c]&(_X|_N))
> +#define	isspace(c)	((__ctype_ptr__+1)[c]&_S)
> +#define ispunct(c)	((__ctype_ptr__+1)[c]&_P)
> +#define isalnum(c)	((__ctype_ptr__+1)[c]&(_U|_L|_N))
> +#define isprint(c)	((__ctype_ptr__+1)[c]&(_P|_U|_L|_N|_B))
> +#define	isgraph(c)	((__ctype_ptr__+1)[c]&(_P|_U|_L|_N))
> +#define iscntrl(c)	((__ctype_ptr__+1)[c]&_C)
>  
>  #if defined(__GNUC__) && \
>      (!defined(__STRICT_ANSI__) || __STDC_VERSION__ >= 199901L)
>  #define isblank(c) \
> -	__extension__ ({ int __c = (c); ((__ctype_ptr__)[(unsigned)((__c)+1)]
> &_B) || (__c) == '\t';})
> +	__extension__ ({ int __c = (c); ((__ctype_ptr__+1)[__c]&_B) || (__c) 
> == '\t';})
>  #endif
>  
>  
>
>
>
>