In order to avoid name clash on distributions which decide to include
kernel headers instead of UAPI ones. For example, on SLES 11SP4:
gcc -DHAVE_CONFIG_H -I./linux/x86_64 -I./linux -I. -Wall -O2 -c net.c
In file included from /usr/include/linux/sysctl.h:25:0,
from /usr/include/linux/netfilter.h:6,
from /usr/include/linux/netfilter_arp.h:8,
from /usr/include/linux/netfilter_arp/arp_tables.h:14,
from net.c:60:
net.c: In function 'print_packet_mreq':
gcc_compat.h:59:27: error: negative width in bit-field '<anonymous>'
# define MUST_BE_ARRAY(a) BUILD_BUG_ON_ZERO(!SAME_TYPE((a), &(a)[0]))
^
defs.h:76:53: note: in expansion of macro 'MUST_BE_ARRAY'
#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]) + MUST_BE_ARRAY(a))
^
net.c:747:22: note: in expansion of macro 'ARRAY_SIZE'
if (mreq.mr_alen > ARRAY_SIZE(mreq.mr_address))
^
due to the fact BUILD_BUG_ON_ZERO is already defined in <linux/kernel.h>.
* gcc_compat.h (BUILD_BUG_ON_ZERO): Rename to FAIL_BUILD_ON_ZERO.
(MUST_BE_ARRAY): Update usage.
#if GNUC_PREREQ(3, 0)
# define SAME_TYPE(x, y) __builtin_types_compatible_p(typeof(x), typeof(y))
-# define BUILD_BUG_ON_ZERO(expr) (sizeof(int[-1 + 2 * !!(expr)]) * 0)
+# define FAIL_BUILD_ON_ZERO(expr) (sizeof(int[-1 + 2 * !!(expr)]) * 0)
/* &(a)[0] is a pointer and not an array, shouldn't be treated as the same */
-# define MUST_BE_ARRAY(a) BUILD_BUG_ON_ZERO(!SAME_TYPE((a), &(a)[0]))
+# define MUST_BE_ARRAY(a) FAIL_BUILD_ON_ZERO(!SAME_TYPE((a), &(a)[0]))
#else
# define SAME_TYPE(x, y) 0
# define MUST_BE_ARRAY(a) 0