Re: [PATCH v3 1/2] tracing: Allow tracer to add more than 32 options

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Wed, 15 Oct 2025 17:20:20 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Tue, 30 Sep 2025 07:34:53 +0900
> "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:
> 
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -86,6 +86,11 @@ void __init disable_tracing_selftest(const char *reason)
> >  #define tracing_selftest_disabled	0
> >  #endif
> >  
> > +/* Define TRACE_ITER_* flags. */
> > +#undef C
> > +#define C(a, b) const u64 TRACE_ITER_##a = (1ULL << TRACE_ITER_##a##_BIT);
> > +TRACE_FLAGS
> > +
> 
> 
> 
> >  #undef C
> > -#define C(a, b) TRACE_ITER_##a = (1 << TRACE_ITER_##a##_BIT)
> > +#define C(a, b) extern const u64 TRACE_ITER_##a;
> >  
> > -enum trace_iterator_flags { TRACE_FLAGS };
> > +TRACE_FLAGS
> > +#undef C
> 
> Why all this work when this could have been simply fixed with a:
> 
> -enum trace_iterator_flags { TRACE_FLAGS };
> +enum64 trace_iterator_flags { TRACE_FLAGS };

With enum64, clang 18 caused this error.

In file included from /home/mhiramat/ksrc/linux/kernel/trace/ring_buffer.c:36:
/home/mhiramat/ksrc/linux/kernel/trace/trace.h:1427:1: error: unknown type name 'enum64'; did you mean 'enum'?
 1427 | enum64 trace_iterator_flags { TRACE_FLAGS };
      | ^~~~~~
      | enum

But below (C++11/C23 or clang/gcc extension) passed.

-enum trace_iterator_flags { TRACE_FLAGS };
+enum trace_iterator_flags : uint64_t { TRACE_FLAGS };


So let's use this.

Thanks,


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>