2:53 a.m.
Hi Steve,
On Mon, Feb 14, 2022 at 10:20:00AM -0500, Steven Rostedt wrote:
On Sun, 13 Feb 2022 21:03:29 +0800
kernel test robot <lkp(a)intel.com> wrote:
> All errors (new ones prefixed by >>):
>
> >> kernel/trace/ftrace.c:7157:20: error: unused function
'ftrace_startup_enable' [-Werror,-Wunused-function]
> static inline void ftrace_startup_enable(int command) { }
> ^
> 1 error generated.
Strange. I always thought that static inline functions do not cause
warnings when not used? Especially, since they are often in headers when
things are turned off. Or is it because this is in a C file?
With -Wunused-function, clang will warn about unused static inline
functions within a .c file (but not .h), whereas GCC will not warn for
either. The unused attribute was added to the definition of inline to
make clang's behavior match GCC's.
Is this a new warning caused by a commit, or is it a new warning
because
the compiler now complains about it?
However, in commit 6863f5643dd7 ("kbuild: allow Clang to find unused
static inline functions for W=1 build"), Masahiro made it so that the
unused attribute does not get added at W=1 so that instances of unused
static inline functions can be caught and eliminated (or put into use,
if the function should have been used), hence this report.
I will be honest, I don't know why the robot flagged 172f7ba9772c as the
commit that introduced this warning but it seems legitimate if
CONFIG_DYNAMIC_FTRACE is not enabled, since ftrace_startup_enable() is
only ever used within an '#ifdef CONFIG_DYNAMIC_FTRACE' block so I guess
the stub is unnecessary?
Cheers,
Nathan