On Thu, 2017-10-05 at 14:05 +0200, Arnd Bergmann wrote: > gcc produces a harmless warning about a recently introduced > signed integer overflow: > > drivers/net/wireless/rsi/rsi_91x_hal.c: In function 'rsi_prepare_mgmt_desc': > include/uapi/linux/swab.h:13:15: error: integer overflow in expression [-Werror=overflow] > (((__u16)(x) & (__u16)0x00ffU) << 8) | \ > ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~ > include/uapi/linux/swab.h:104:2: note: in expansion of macro '___constant_swab16' > ___constant_swab16(x) : \ > ^~~~~~~~~~~~~~~~~~ > include/uapi/linux/byteorder/big_endian.h:34:43: note: in expansion of macro '__swab16' > #define __cpu_to_le16(x) ((__force __le16)__swab16((x))) [] > The problem is that the 'mask' value is a signed integer that gets > turned into a negative number when truncated to 16 bits. Making it > an unsigned constant avoids this. I would expect there are more of these. Perhaps this define in include/uapi/linux/swab.h: #define __swab16(x) \ (__builtin_constant_p((__u16)(x)) ? \ ___constant_swab16(x) : \ __fswab16(x)) should be #define __swab16(x) \ (__builtin_c onstant_p((__u16)(x)) ? \ ___constant_swab16((__u16)(x)) : \ __fswab16((__u16)(x)))
