re: lib/50009: strptime small enhancement

[matthew green <mrg%eterna.com.au@localhost>]

The following reply was made to PR lib/50009; it has been noted by GNATS.

From: matthew green <mrg%eterna.com.au@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: lib-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
    netbsd-bugs%netbsd.org@localhost, devnexen%gmail.com@localhost
Subject: re: lib/50009: strptime small enhancement
Date: Mon, 29 Jun 2015 14:42:18 +1000

 >  On Sun, Jun 28, 2015 at 07:50:00PM +0000, devnexen%gmail.com@localhost wrote:
 >   > +#ifndef ISLEAPYEAR
 >   > +#define ISLEAPYEAR(y) ((y % 400) == 0 && (y % 4) == 0 && (y % 100) != 0)
 >   > +#endif
 >  
 >  ...this is wrong...
 
 indeed, sys/clock.h has this:
 
 63 /*
 64  * This inline avoids some unnecessary modulo operations
 65  * as compared with the usual macro:
 66  *   ( ((year % 4) == 0 &&
 67  *      (year % 100) != 0) ||
 68  *     ((year % 400) == 0) )
 69  * It is otherwise equivalent.
 70  */
 71 static inline int
 72 is_leap_year(uint64_t year)
 73 {
 74         if ((year & 3) != 0)
 75                 return 0;
 76
 77         if (__predict_false((year % 100) != 0))
 78                 return 1;
 79
 80         return __predict_false((year % 400) == 0);
 81 }
 
 which should probably be used instead, for netbsd, or at
 least the same expression in the comment.
 
 (the macro above also doesn't work properly for various
 inputs, like a good macro should.)
 
 
 .mrg.