Commit b1afefa62ca9 ("tracing: Use strcmp() in __assign_str() WARN_ON()
check") addressed a clang warning, -Wstring-compare, with the use of
__builtin_constant_p() to dispatch to strcmp() if the source string is a
string literal and a direct comparison if not. Unfortunately, even with
this change, the warning is still present because __builtin_constant_p()
is not evaluated at this stage of the pipeline, so clang still thinks
the else branch could occur for this situation:
include/trace/events/sunrpc.h:705:4: error: result of comparison against a
string literal is unspecified (use an explicit string comparison function
instead) [-Werror,-Wstring-compare]
...
include/trace/stages/stage6_event_callback.h:40:15: note: expanded from macro
'__assign_str'
40 | (src) != __data_offsets.dst##_ptr_);
\
| ^
...
Use the compiler diagnostic macros to disable this warning around the
WARN_ON_ONCE() expression since a string comparison function, strcmp(),
will always be used for the comparison of string literals.
Fixes: b1afefa62ca9 ("tracing: Use strcmp() in __assign_str() WARN_ON() check")
Reported-by: Linux Kernel Functional Testing <l...@linaro.org>
Closes:
https://lore.kernel.org/all/CA+G9fYs=otkazs6g1p1ewadfr0qoe6lgovsohqkxmfxoteo...@mail.gmail.com/
Signed-off-by: Nathan Chancellor <nat...@kernel.org>
---
include/trace/stages/stage6_event_callback.h | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/include/trace/stages/stage6_event_callback.h
b/include/trace/stages/stage6_event_callback.h
index 83da83a0c14f..56a4eea5a48e 100644
--- a/include/trace/stages/stage6_event_callback.h
+++ b/include/trace/stages/stage6_event_callback.h
@@ -35,9 +35,14 @@
do { \
char *__str__ = __get_str(dst); \
int __len__ = __get_dynamic_array_len(dst) - 1; \
+ __diag_push(); \
+ __diag_ignore(clang, 11, "-Wstring-compare", \
+ "__builtin_constant_p() ensures strcmp()" \
+ "will be used for string literals"); \
WARN_ON_ONCE(__builtin_constant_p(src) ? \
strcmp((src), __data_offsets.dst##_ptr_) : \
(src) != __data_offsets.dst##_ptr_); \
+ __diag_pop(); \
memcpy(__str__, __data_offsets.dst##_ptr_ ? : \
EVENT_NULL_STR, __len__); \
__str__[__len__] = '\0'; \
--
2.44.0
