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()")
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
