Hi Naresh,
On Mon, Mar 18, 2024 at 02:55:54PM +0530, Naresh Kamboju wrote:
The following build warnings / errors noticed on x86 kselftests build with clang nightly / clang-17 on Linux next tag next-20240318.
This build config is generated from kselftest merge configs [1].
Reported-by: Linux Kernel Functional Testing lkft@linaro.org
Build log:
In file included from net/sunrpc/sched.c:31: In file included from include/trace/events/sunrpc.h:2524: In file included from include/trace/define_trace.h:102: In file included from include/trace/trace_events.h:419: include/trace/events/sunrpc.h:707:4: error: result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Werror,-Wstring-compare] 667 | __assign_str(progname, | ~~~~~~~~~~~~~~~~~~~~~~ 668 | task->tk_client->cl_program->name); | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 669 | __entry->version = task->tk_client->cl_vers; | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 670 | __assign_str(procedure, task->tk_msg.rpc_proc->p_name); |
Thanks for the report. This is caused by commit 433e1d88a3be ("tracing: Add warning if string in __assign_str() does not match __string()") from the tracing tree, not a change on the netdev side (although I have left them on CC for this reply so they are aware of that).
To resolve it, [1] needs to be applied then the following diff can be applied on top of that to fully clear it up (as __builtin_constant_p() does not influence diagnostics in the front end, so the warning still triggers on the else branch when it will really use strcmp(), as Steve tested at [2]).
[1]: https://lore.kernel.org/20240312113002.00031668@gandalf.local.home/ [2]: https://lore.kernel.org/20240313161420.3b668558@gandalf.local.home/
diff --git a/include/trace/stages/stage6_event_callback.h b/include/trace/stages/stage6_event_callback.h index 83da83a0c14f..dbd27adb1b83 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, 13, "-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'; \