[Bug libc/11435] <ctype.h> inhibits -Wchar-subscript warning on invalid use of character classification macros

["bart dot vanassche at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

------- Additional Comments From bart dot vanassche at gmail dot com  2010-03-26 12:00 -------
See also http://sourceware.org/git/?p=glibc.git;a=blob;f=ctype/ctype.h;hb=HEAD

Note: Cygwin's <ctype.h> header file contains the following comment:

/* These macros are intentionally written in a manner that will trigger
   a gcc -Wall warning if the user mistakenly passes a 'char' instead
   of an int containing an 'unsigned char'.  Note that the sizeof will
   always be 1, which is what we want for mapping EOF to __ctype_ptr__[0];
   the use of a raw index inside the sizeof triggers the gcc warning if
   __c was of type char, and sizeof masks side effects of the extra __c.
   Meanwhile, the real index to __ctype_ptr__+1 must be cast to int,
   since isalpha(0x100000001LL) must equal isalpha(1), rather than being
   an out-of-bounds reference on a 64-bit machine.  */
#define __ctype_lookup(__c) ((__ctype_ptr__+sizeof(""[__c]))[(int)(__c)])


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http://sourceware.org/bugzilla/show_bug.cgi?id=11435

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