Re: [PATCH] sched: Work around undefined behavior in sched class checking

On Wed, May 05, 2021 at 07:34:42AM -0700, Andi Kleen wrote:

quoted

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Use RELOC_HIDE to make this work. This hides the symbols from gcc,
so the optimizer won't make these assumption. I also split
the BUG_ONs in multiple.

Urgh, that insanity again :/ Can't we pretty please get a GCC flag to
disable that?

Even if that was done (I could totally see the gcc people pushing back on this;
why should they add special flags just for Linux developers not understanding
ISO-C?)

I understand C fine, I just don't agree with it. I also want to
explicitly define as much UB as is possible, because UB is just utter
garbage.

So just like we do with -fwrapv and others, add more knobs that
explictly define away UB. Less UB is more better. This being C it's
unlikely we'll ever get to no UB, but we should damn well try :-)

you would still need the fix for already shipping compilers.

Yes, there is that.