Re: [patch] compiler, clang: suppress warning for unused static inline functions

[Matthias Kaehlcke]

El Wed, May 24, 2017 at 02:01:15PM -0700 David Rientjes ha dit:

> GCC explicitly does not warn for unused static inline functions for
> -Wunused-function.  The manual states:
> 
> 	Warn whenever a static function is declared but not defined or
> 	a non-inline static function is unused.
> 
> Clang does warn for static inline functions that are unused.
> 
> It turns out that suppressing the warnings avoids potentially complex
> #ifdef directives, which also reduces LOC.
> 
> Supress the warning for clang.
> 
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
> ---

As expressed earlier in other threads, I don't think gcc's behavior is
preferable in this case. The warning on static inline functions (only
in .c files) allows to detect truly unused code. About 50% of the
warnings I have looked into so far fall into this category.

In my opinion it is more valuable to detect dead code than not having
a few more __maybe_unused attributes (there aren't really that many
instances, at least with x86 and arm64 defconfig). In most cases it is
not necessary to use #ifdef, it is an option which is preferred by
some maintainers. The reduced LOC is arguable, since dectecting dead
code allows to remove it.

I'm not a kernel maintainer, so it's not my decision whether this
warning should be silenced, my personal opinion is that it's benfits
outweigh the inconveniences of dealing with half-false positives,
generally caused by the heavy use of #ifdef by the kernel itself.