On Tue, Mar 12, 2024 at 11:30:02AM -0400, Steven Rostedt wrote: > From: "Steven Rostedt (Google)" <rost...@goodmis.org> > > The WARN_ON() check in __assign_str() to catch where the source variable > to the macro doesn't match the source variable to __string() gives an > error in clang: > > >> include/trace/events/sunrpc.h:703:4: warning: result of comparison against > >> a string literal is unspecified (use an explicit string comparison > >> function instead) [-Wstring-compare] > 670 | __assign_str(progname, "unknown"); > > That's because the __assign_str() macro has: > > WARN_ON_ONCE((src) != __data_offsets.dst##_ptr_); > > Where "src" is a string literal. Clang warns when comparing a string > literal directly as it is undefined to what the value of the literal is. > > Since this is still to make sure the same string that goes to __string() > is the same as __assign_str(), for string literals do a test for that and > then use strcmp() in those cases > > Note that this depends on commit 51270d573a8d ("tracing/net_sched: Fix > tracepoints that save qdisc_dev() as a string") being applied, as this was > what found that bug. > > Reported-by: kernel test robot <l...@intel.com> > Closes: > https://lore.kernel.org/oe-kbuild-all/202402292111.kidexylu-...@intel.com/ > Fixes: 433e1d88a3be ("tracing: Add warning if string in __assign_str() does > not match __string()")
Is this change destined for 6.9 or 6.10? I applied it to current trace/core (eb1533d156d3) along with 51270d573a8d but the warning is still present. I even tried __builtin_choose_expr(__is_constexpr((src)), strcmp((src), __data_offsets.dst##_ptr_), (src) != __data_offsets.dst##_ptr_)); but not even that silenced the warning. I think we will still need a diag directive to fully silence this warning. > Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org> > --- > include/trace/stages/stage6_event_callback.h | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/include/trace/stages/stage6_event_callback.h > b/include/trace/stages/stage6_event_callback.h > index a0c15f67eabe..83da83a0c14f 100644 > --- a/include/trace/stages/stage6_event_callback.h > +++ b/include/trace/stages/stage6_event_callback.h > @@ -35,7 +35,9 @@ > do { \ > char *__str__ = __get_str(dst); \ > int __len__ = __get_dynamic_array_len(dst) - 1; \ > - WARN_ON_ONCE((src) != __data_offsets.dst##_ptr_); \ > + WARN_ON_ONCE(__builtin_constant_p(src) ? \ > + strcmp((src), __data_offsets.dst##_ptr_) : \ > + (src) != __data_offsets.dst##_ptr_); \ > memcpy(__str__, __data_offsets.dst##_ptr_ ? : \ > EVENT_NULL_STR, __len__); \ > __str__[__len__] = '\0'; \ > -- > 2.43.0 >