Re: [PATCH] bpf: avoid warning for wrong pointer cast

From: Alexei Starovoitov
Date: Tue Apr 19 2016 - 12:29:09 EST

On 4/19/16 3:09 AM, Philip Li wrote:
On Tue, Apr 19, 2016 at 10:33:34AM +0800, Fengguang Wu wrote:
Fengguang, any idea why build-bot sometimes silent?

Sorry I went off for some time.. Philip, would you help have a check?
Hi Alexei, i have done some investigation for this. Fengguang, pls correct me if my understanding is wrong.

0day has caught the warning for f1ff54 commit around 2016-3-22, which considers the same warning in future is not new one, thus neglect it.

rli9@inn /kbuild-tests/build-error$ cat kernel-trace-bpf_trace.c:warning:cast-to-pointer-from-integer-of-different-size
kernel/trace/bpf_trace.c:345:13: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]

2016-03-22 17:12:38 xian bpf:master:321e70e79c94e5e6394a882d567baac949b74000 i386-randconfig-x009-201612 f1ff543dbdd3eff53c8328cfb582f18e6c3d56ec

And for f1ff54's warning, 0day actually bisects to it, but then it checks the head of bpf/master at that time which is 321e70e, find the error is not existed, so
it ignores the interim warning to not send email report.

2016-03-22_17:15:49 O: R: /kbuild/src/consumer/kernel/trace/bpf_trace.c:345:13: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
2016-03-22_17:15:49 O: grep -h -r . /tmp/kernel/i386-randconfig-x009-201612/gcc-5/f1ff543dbdd3eff53c8328cfb582f18e6c3d56ec/build-error # 0 errors
2016-03-22_17:15:49 O: grep -h -r . /tmp/kernel/i386-randconfig-x009-201612/gcc-5/f1ff543dbdd3eff53c8328cfb582f18e6c3d56ec/build-error/ # 0 errors
2016-03-22_17:15:49 O: /c/kernel-tests/list-head bpf:master:321e70e79c94e5e6394a882d567baac949b74000 i386-randconfig-x009-201612
2016-03-22_17:16:03 O: .
2016-03-22_17:16:03 O: ..
2016-03-22_17:16:03 O: kernel-trace-bpf_trace.c:warning:cast-to-pointer-from-integer-of-different-size
2016-03-22_17:16:03 O: 2016-03-22 17:16:03 don't email interim warnings
2016-03-22_17:16:03 O: 2016-03-22 17:16:03 error no longer exist in head bpf/master 321e70e79c94e5e6394a882d567baac949b74000, check
/tmp/kernel/i386-randconfig-x009-201612/gcc-5/321e70e79c94e5e6394a882d567baac949b74000, errno 14
2016-03-22_17:16:03 O: 2016-03-22 17:16:03 Don't email interim warnings!

what really happens to 321e70e is it has build error (i rerun it to confirm), which is reported. So this is
a possible change to be done in 0day to report the first bad commit when HEAD is build error.

excellent sleuthing! Sounds like the adjustment to 0day is forthcoming.
Thank you for great tool!