Re: [RFC PATCH 1/8] compiler/gcc: Emit build-time warning for GCC prior to version 4.8

[Arnd Bergmann]

On Fri, Jan 10, 2020 at 5:56 PM Will Deacon <will@xxxxxxxxxx> wrote:
>
> Prior to version 4.8, GCC may miscompile READ_ONCE() by erroneously
> discarding the 'volatile' qualifier:
>
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145
>
> We've been working around this using some nasty hacks which make
> READ_ONCE() both horribly complicated and also prevent us from enforcing
> that it is only used on scalar types. Since GCC 4.8 is pretty old for
> kernel builds now, emit a warning if we detect it during the build.

No objection to recommending gcc-4.8, but I think this should either
just warn once during the kernel build instead of for every file, or
it should become a hard requirement.

       Arnd