On Mon, Aug 03, 2020 at 11:29:03PM +0900, Stafford Horne wrote: > Hello, Hi, > I am the maintainer of the OpenRISC architecture linux port, and recently have > started to look at the kbuild sparse errors. > > The Linux kernel kbuild process is reporting sparse error: > > net/dccp/proto.c: note: in included file (through include/asm-generic/atomic.h, arch/openrisc/include/asm/atomic.h, include/linux/atomic.h, ...): > arch/openrisc/include/asm/cmpxchg.h:101:29: sparse: sparse: shift too big (32) for type int > > Example: https://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg2256733.html > > I have traced this down to the case like the below. > > It reports an unexpected warning: > > simple_test.c:7:18: warning: shift too big (32) for type int > > This is not pssible because size = 4 should never call shift_small. > > I have debugged sparse when this is running and it seems that when checking the switch > cases it evaluates all cases, and thinks size = 4 is possible. I am not sure if this > is a problem with the sparse front end of the check logic. > > Can you help? Sure. The problem is sparse sees the expression '1 << (4 * 8)' and warns about it before it can know it will never be evaluated. The exact same problem happens with an even simpler example: int foo(void) { return 0; return 1 << 32; } I have an old series for this problem, I would just need to dust off. It shouldn't take much time, probably just a few days, maximum 10 (but I vaguely remember there was a nasty complication, which is why it's still pending). Best regards, -- Luc
