QEMU has a funny new build error message when I use the upstream kernel headers:

CC block/file-posix.o In file included from /home/cborntra/REPOS/qemu/include/qemu/timer.h:4, from /home/cborntra/REPOS/qemu/include/qemu/timed-average.h:29, from /home/cborntra/REPOS/qemu/include/block/accounting.h:28, from /home/cborntra/REPOS/qemu/include/block/block_int.h:27, from /home/cborntra/REPOS/qemu/block/file-posix.c:30: /usr/include/linux/swab.h: In function ‘__swab’: /home/cborntra/REPOS/qemu/include/qemu/bitops.h:20:34: error: "sizeof" is not defined, evaluates to 0 [-Werror=undef] 20 | #define BITS_PER_LONG (sizeof (unsigned long) * BITS_PER_BYTE) | ^~~~~~ /home/cborntra/REPOS/qemu/include/qemu/bitops.h:20:41: error: missing binary operator before token "(" 20 | #define BITS_PER_LONG (sizeof (unsigned long) * BITS_PER_BYTE) | ^ cc1: all warnings being treated as errors make: *** [/home/cborntra/REPOS/qemu/rules.mak:69: block/file-posix.o] Error 1 rm tests/qemu-iotests/socket_scm_helper.o

This was triggered by commit d5767057c9a ("uapi: rename ext2_swab() to swab() and share globally in swab.h") This patch is doing +#include <asm/bitsperlong.h> but it uses BITS_PER_LONG.

The kernel file asm/bitsperlong.h provide only __BITS_PER_LONG.

Let us use the __ variant in swap.h Fixes: d5767057c9a ("uapi: rename ext2_swab() to swab() and share globally in swab.h") Cc: Yury Norov yury.norov@gmail.com Cc: Allison Randal allison@lohutok.net Cc: Joe Perches joe@perches.com Cc: Thomas Gleixner tglx@linutronix.de Cc: William Breathitt Gray vilhelm.gray@gmail.com Signed-off-by: Christian Borntraeger borntraeger@de.ibm.com

---

include/uapi/linux/swab.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/swab.h b/include/uapi/linux/swab.h index fa7f97da5b76..7272f85d6d6a 100644 --- a/include/uapi/linux/swab.h +++ b/include/uapi/linux/swab.h @@ -135,9 +135,9 @@ static inline __attribute_const__ __u32 __fswahb32(__u32 val)

static __always_inline unsigned long __swab(const unsigned long y) { -#if BITS_PER_LONG == 64 +#if __BITS_PER_LONG == 64 return __swab64(y); -#else /* BITS_PER_LONG == 32 */ +#else /* __BITS_PER_LONG == 32 */ return __swab32(y); #endif }

Cc: stable@vger.kernel.org # 4.19.x: 467d12f5: include/uapi/linux/swab.h: fix userspace breakage