[poc] buildkernel + clang + -Werror

[Alexander Best]

On Sun Nov  6 11, Dimitry Andric wrote:
> On 2011-11-06 21:33, Alexander Best wrote:
> ... 
> > the problem is, something like
> > 
> > uint x;
> > 
> > if (x < 0) ...
> > 
> > clang will warn about this, yet it is 100% valid code so my vote would be to
> > make such an error into a warning.
> 
> Sorry, but checking something unsigned to be smaller than zero is bogus,
> or at the least superfluous, and it's perfectly sane to warn about this,
> especially since the compiler is not going to emit code for it at all.

there was a discussion with the topic
"disable -Wtautological-compare for clang" on freebsd-toolchain@ and most of
the devs considered this code *not* to be bogus. ;)

> 
> The only time when this sort of check could be relevant, is when you are
> using a typedef'd type, and you have no way to be sure if the type is
> signed or unsigned.  But then you will be in for trouble anyway...
> 
> 
> ...
> > the same with 
> > 
> > int x;
> > 
> > x = x;
> > 
> > i believe in both cases clang is too picky.
> 
> This is a often-used idiom for attempting to 'shut up' a compiler when
> it (quite legitimately) complains about unused variables or arguments.
> 
> However, a better idiom is:
> 
>   (void) x;
> 
> but even this can lead some compilers or analysis tools to complain
> about "statements that don't do anything".  A better way is to provide
> UNUSED_VARIABLE and UNUSED_ARGUMENT macros, and handle shutting up the
> compiler in its specific way there.
> 
> Of course, the best solution is to just eliminate the unused variables
> or arguments.  If that is not possible, for example due to a function
> signature that cannot be changed because of API considerations, you can
> always use __unused attributes.

i see. does PR #162321 fall into this category, or can the assignment be removed?

cheers.
alex