Re: [PATCH bpf] bpf: syscall_nrs: fix no previous prototype for "syscall_defines"

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On Tue, Oct 1, 2024 at 6:06 AM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Fri, Sep 27, 2024 at 10:22 PM Jason Xing <kerneljasonxing@xxxxxxxxx> wrote:
> >
> > Hello Andrii,
> >
> > On Sat, Sep 28, 2024 at 7:08 AM Andrii Nakryiko
> > <andrii.nakryiko@xxxxxxxxx> wrote:
> > >
> > > On Fri, Sep 20, 2024 at 12:37 PM Jason Xing <kerneljasonxing@xxxxxxxxx> wrote:
> > > >
> > > > On Thu, Sep 19, 2024 at 11:17 PM Alexei Starovoitov
> > > > <alexei.starovoitov@xxxxxxxxx> wrote:
> > > > >
> > > > > On Thu, Sep 19, 2024 at 9:55 PM Jason Xing <kerneljasonxing@xxxxxxxxx> wrote:
> > > > > >
> > > > > > From: Jason Xing <kernelxing@xxxxxxxxxxx>
> > > > > >
> > > > > > In some environments (gcc treated as error in W=1, which is default), if we
> > > > > > make -C samples/bpf/, it will be stopped because of
> > > > > > "no previous prototype" error like this:
> > > > > >
> > > > > >   ../samples/bpf/syscall_nrs.c:7:6:
> > > > > >   error: no previous prototype for ‘syscall_defines’ [-Werror=missing-prototypes]
> > > > > >    void syscall_defines(void)
> > > > > >         ^~~~~~~~~~~~~~~
> > > > >
> > > > > samples/bpf/ doesn't accept patches any more.
> > > > > If this samples/test is useful, refactor it to the test_progs framework.
> > > > > Otherwise delete it.
> > > > >
> > > > > pw-bot: cr
> > > >
> > > > After reconsidering what Alexei said, I still feel we could take this
> > > > patch? It is because:
> > > > 1) the patch itself  is more of a fix instead of optimization,
> > > > 2)as long as samples/bpf exists in the kernel, we cannot easily let
> > > > it(issues) go and ignore it.
> > > >
> > > > Applying such a patch won't cause any further confusion, right? As we
> > > > can see, it's like a fix which does not introduce anything new here.
> > > >
> > > > What do you bpf maintainers think?
> > >
> > > I think it's fine to minimally fix the issue in samples/bpf, but I
> > > don't think this weirdly-looking extra declaration is the best fix.
> >
> > Thanks for your reply.
> >
> > >
> > > Can you mark that function static? Will that work?
> >
> > Not really, it will print:
> > samples/bpf/syscall_nrs.c:7:13: error: ‘syscall_defines’ defined but
> > not used [-Werror=unused-function]
> >  static void syscall_defines(void)
> >              ^~~~~~~~~~~~~~~
> > cc1: all warnings being treated as errors
> >
> > > Or, as a plan B,
> > > use pragma to disable this warning, it's clearly "expected" in this
> > > case.
> >
> > Yes, I admit the use in this function is "expected" like you said
> > because this file will be converted into a .h file. Could you kindly
> > show me more hints on how to disable the warning when compiling? I
> > tried to remove something like "-Wmissing-prototypes", but the warning
> > still happens.
> >
>
> Grep for "#pragma GCC diagnostic ignored" uses in kernel sources.

Thanks a lot! It works. Let me re-post it to "fix" this issue.

Thanks,
Jason





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