Re: [PATCH] x86: work around clang IAS bug referencing __force_order

[Thomas Gleixner]

Arnd Bergmann <arnd@xxxxxxxx> writes:
> When using the clang integrated assembler, we get a reference
> to __force_order that should normally get ignored in a few
> rare cases:
>
> ERROR: modpost: "__force_order" [drivers/cpufreq/powernow-k6.ko] undefined!
>
> Add a 'static' definition so any file in which this happens can
> have a local copy.

That's a horrible hack.

And the only reason why it does not trigger -Wunused-variable warnings
all over the place is because it's "referenced" in unused inline
functions and then optimized out along with the unused inlines.

>   * It is not referenced from the code, but GCC < 5 with -fPIE would fail
>   * due to an undefined symbol. Define it to make these ancient GCCs
>   work.

Bah, we really should have moved straight to GCC5 instead of upping it
just to 4.9

> + *
> + * Clang sometimes fails to kill the reference to the dummy variable, so
> + * provide an actual copy.

Can that compiler be fixed instead?

Aside of that is there a reason to make this 'static' thing wrapped in
#ifdeffery? A quick check with GCC8.3 just works. But maybe 4.9 gets
unhappy. Can't say due to: -ENOANCIENTCOMPILER :)

Thanks,

        tglx