linux-kernel - Re: [rostedt-trace:for-next 58/100] samples/ftrace/ftrace-direct-multi.c:8:6: warning: no previous prototype for function 'my_direct

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Date:   Mon, 1 Nov 2021 15:42:57 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     kernel test robot <lkp@...el.com>, llvm@...ts.linux.dev,
        kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org
Subject: Re: [rostedt-trace:for-next 58/100]
 samples/ftrace/ftrace-direct-multi.c:8:6: warning: no previous prototype for
 function 'my_direct_func'

On Mon, Nov 01, 2021 at 10:24:34AM -0400, Steven Rostedt wrote:
> On Mon, 1 Nov 2021 14:37:08 +0100
> Jiri Olsa <jolsa@...hat.com> wrote:
> 
> > > If you fix the issue, kindly add following tag as appropriate
> > > Reported-by: kernel test robot <lkp@...el.com>
> > > 
> > > All warnings (new ones prefixed by >>):
> > >   
> > > >> samples/ftrace/ftrace-direct-multi.c:8:6: warning: no previous prototype for function 'my_direct_func' [-Wmissing-prototypes]  
> > >    void my_direct_func(unsigned long ip)
> > >         ^
> > >    samples/ftrace/ftrace-direct-multi.c:8:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
> > >    void my_direct_func(unsigned long ip)  
> > 
> > hum, that can actually be static.. I'll check
> > 
> 
> I'm not sure it can, because you call it from inline assembly, and the
> symbol may not be passed to the assembler.

yes, I just found that.. I actually could not add any input/output
arguments to asm, got a compilation error.. I think it's because
it's used outside any function

> 
> It may work with some options, but may not for all.
> 
> I think the best thing to do is just create a prototype to quiet the
> warning (with a comment).

ok, I'll send it.. should be on top of you for-next branch?

thanks,
jirka