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    SubjectRe: union: was: Re: [PATCH printk v1 05/18] printk: Add non-BKL console basic infrastructure
    On Tue 2023-03-28 11:48:06, John Ogness wrote:
    > On 2023-03-28, Petr Mladek <pmladek@suse.com> wrote:
    > >> A compilation check would be nice. Is that possible?
    > >
    > > I think the following might do the trick:
    > >
    > > static_assert(sizeof(struct cons_state) == sizeof(atomic_long_t));
    >
    > I never realized the kernel code was allowed to have that. But it is
    > everywhere! :-) Thanks. I've added and tested the following:
    >
    > /*
    > * The nbcon_state struct is used to easily create and interpret values that
    > * are stored in the console.nbcon_state variable. Make sure this struct stays
    > * within the size boundaries of that atomic variable's underlying type in
    > * order to avoid any accidental truncation.
    > */
    > static_assert(sizeof(struct nbcon_state) <= sizeof(long));
    >
    > Note that I am checking against sizeof(long), the underlying variable
    > type. We probably shouldn't assume sizeof(atomic_long_t) is always
    > sizeof(long).

    Makes sense and looks good to me.

    Best Regards,
    Petr

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