From: Steven Rostedt <rostedt@goodmis.org>
To: Justin Stitt <justinstitt@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>,
mhiramat@kernel.org, mathieu.desnoyers@efficios.com,
ndesaulniers@google.com, morbo@google.com,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
llvm@lists.linux.dev, patches@lists.linux.dev,
Linux Kernel Functional Testing <lkft@linaro.org>
Subject: Re: [PATCH 2/2] tracing: Ignore -Wstring-compare with diagnostic macros
Date: Tue, 19 Mar 2024 20:37:16 -0400 [thread overview]
Message-ID: <20240319203716.208c9b29@gandalf.local.home> (raw)
In-Reply-To: <CAFhGd8q_4QfjPwGhtfOA40ZGNF7_wf3V43rAvcb_qXQnz1TFOw@mail.gmail.com>
On Tue, 19 Mar 2024 17:30:41 -0700
Justin Stitt <justinstitt@google.com> wrote:
> > 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_); \
>
> What exactly is the point of the literal string comparison? Why
> doesn't strcmp do the trick?
This is done in the hotpath, and is only for debugging. The string passed
into __string() should be the same as the string passed into __assign_str().
But this is moot as I ended up always using strcmp() even if it will slow
down the recording of the event.
Next merge window the src parameter (along with the strcmp() checks) are
going away.
-- Steve
>
> > + __diag_pop(); \
> > memcpy(__str__, __data_offsets.dst##_ptr_ ? : \
> > EVENT_NULL_STR, __len__); \
> > __str__[__len__] = '\0'; \
> >
> > --
> > 2.44.0
> >
next prev parent reply other threads:[~2024-03-20 0:34 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-19 16:07 [PATCH 0/2] tracing: Fully silence instance of -Wstring-compare Nathan Chancellor
2024-03-19 16:07 ` [PATCH 1/2] compiler_types: Ensure __diag_clang() is always available Nathan Chancellor
2024-03-20 0:35 ` Justin Stitt
2024-03-19 16:07 ` [PATCH 2/2] tracing: Ignore -Wstring-compare with diagnostic macros Nathan Chancellor
2024-03-20 0:30 ` Justin Stitt
2024-03-20 0:37 ` Steven Rostedt [this message]
2024-03-19 22:15 ` [PATCH 0/2] tracing: Fully silence instance of -Wstring-compare Steven Rostedt
2024-03-19 22:27 ` Nathan Chancellor
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