selftests/bpf: fix a clang compilation error for send_signal.c #2694
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Master branch: 357b3cc |
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Building selftests/bpf with latest clang compiler (clang15 built
from source), I hit the following compilation error:
/.../prog_tests/send_signal.c:43:16: error: variable 'j' set but not used [-Werror,-Wunused-but-set-variable]
volatile int j = 0;
^
1 error generated.
The problem also exists with clang13 and clang14. clang12 is okay.
In send_signal.c, we have the following code
volatile int j = 0;
...
for (int i = 0; i < 100000000 && !sigusr1_received; i++)
j /= i + 1;
to burn cpu cycles so bpf_send_signal() helper can be tested
in nmi mode.
Slightly changing 'j /= i + 1' to 'j /= i + j + 1' or 'j++' can
fix the problem. Further investigation indicated this should be
a clang bug ([1]). The upstream fix will be proposed later. But it is
a good idea to workaround the issue to unblock people who build
kernel/selftests with clang.
[1] https://discourse.llvm.org/t/strange-clang-unused-but-set-variable-error-with-volatile-variables/60841
Signed-off-by: Yonghong Song <yhs@fb.com>
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=622440 irrelevant now. Closing PR. |
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Pull request for series with
subject: selftests/bpf: fix a clang compilation error for send_signal.c
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=622430