Paul Eggert wrote:
> #define COUNT_ONE_BITS(BUILTIN, TYPE) \
> + verify ((TYPE) -1 >> 31 >> 31 <= 3); \
> int count = count_one_bits_32 (x); \
> - if (CHAR_BIT * sizeof (TYPE) > 32) \
> + if (1 < (TYPE) -1 >> 31) \
> count += count_one_bits_32 (x >> 31 >> 1); \
At this point, IMO, it would be useful to add comments:
--- lib/count-one-bits.h 25 Jul 2007 03:13:20 -0000 1.1
+++ lib/count-one-bits.h 14 Aug 2007 21:50:36 -0000
@@ -20,19 +20,21 @@
#ifndef COUNT_ONE_BITS_H
# define COUNT_ONE_BITS_H 1
-#include <limits.h>
#include <stdlib.h>
#include "verify.h"
+/* Expand the code which computes the number of 1-bits of the local
+ variable 'x' of type TYPE (an unsigned integer type) and returns it
+ from the current function. */
#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR >= 4)
#define COUNT_ONE_BITS(BUILTIN, TYPE) \
return BUILTIN (x);
#else
-#define COUNT_ONE_BITS(BUILTIN, TYPE) \
- int count = count_one_bits_32 (x); \
- if (CHAR_BIT * sizeof (TYPE) > 32) \
- count += count_one_bits_32 (x >> 31 >> 1); \
- (void) verify_true (CHAR_BIT * sizeof (TYPE) <= 64); \
+#define COUNT_ONE_BITS(BUILTIN, TYPE) \
+ verify ((TYPE) -1 >> 31 >> 31 <= 3); /* TYPE has at most 64 bits */ \
+ int count = count_one_bits_32 (x); \
+ if (1 < (TYPE) -1 >> 31) /* TYPE has more than 32 bits? */ \
+ count += count_one_bits_32 (x >> 31 >> 1); \
return count;
/* Compute and return the the number of 1-bits set in the least
