On Fri, Jul 12, 2019 at 10:58:48AM +0200, Arnd Bergmann wrote:
> clang-9 does not like the way that the is_signed_type() compares
> function pointers deep inside of the trace even macros:
>
> In file included from arch/x86/xen/trace.c:21:
> In file included from include/trace/events/xen.h:475:
> In file included from include/trace/define_trace.h:102:
> In file included from include/trace/trace_events.h:467:
> include/trace/events/xen.h:69:7: error: ordered comparison of function
> pointers ('xen_mc_callback_fn_t' (aka 'void (*)(void *)') and
> 'xen_mc_callback_fn_t') [-Werror,-Wordered-compare-function-pointers]
> __field(xen_mc_callback_fn_t, fn)
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> include/trace/trace_events.h:415:29: note: expanded from macro '__field'
> #define __field(type, item) __field_ext(type, item, FILTER_OTHER)
> ^
> include/trace/trace_events.h:401:6: note: expanded from macro '__field_ext'
> is_signed_type(type), filter_type); \
> ^
> include/linux/trace_events.h:540:44: note: expanded from macro
> 'is_signed_type'
> #define is_signed_type(type) (((type)(-1)) < (type)1)
> ^
> note: (skipping 1 expansions in backtrace; use -fmacro-backtrace-limit=0 to
> see all)
> include/trace/trace_events.h:77:16: note: expanded from macro 'TRACE_EVENT'
> PARAMS(tstruct), \
> ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> include/linux/tracepoint.h:95:25: note: expanded from macro 'PARAMS'
> #define PARAMS(args...) args
> ^
> include/trace/trace_events.h:455:2: note: expanded from macro
> 'DECLARE_EVENT_CLASS'
> tstruct; \
> ^~~~~~~
>
> I guess the warning is reasonable in principle, though this seems to
> be the only instance we get in the entire kernel today.
> Shut up the warning by making it a void pointer in the exported
> structure.
>
> Fixes: c796f213a693 ("xen/trace: add multicall tracing")
> Signed-off-by: Arnd Bergmann <a...@arndb.de>
Nick suggested this as well, I think it's reasonable to work around it
in this one location since this is indeed the only instance of this
warning that I see in the kernel tree across all of my builds.
Reviewed-by: Nathan Chancellor <natechancel...@gmail.com>
