Re: [PATCH v5 11/14] software node: move small properties inline when copying

Andy Shevchenko
2019-10-16T16:23:12Z

On Wed, Oct 16, 2019 at 07:18:45PM +0300, Andy Shevchenko wrote:
> On Wed, Oct 16, 2019 at 09:01:26AM -0700, Dmitry Torokhov wrote:
> > On Wed, Oct 16, 2019 at 10:48:57AM +0300, Andy Shevchenko wrote:
> > > On Tue, Oct 15, 2019 at 11:25:53AM -0700, Dmitry Torokhov wrote:
>
> > > You store a value as union, but going to read as a member of union?
> > > I'm pretty sure it breaks standard rules.
> >
> > No, I move the values _in place_ of the union, and the data is always
> > fetched via void pointers. And copying data via char * or memcpy() is
> > allowed even in C99 and C11.
> >
> > But I am wondering why are we actually worrying about all of this? The
> > kernel is gnu89 and I think is going to stay this way because we use
> > initializers with a cast in a lot of places:
> >
> > #define __RAW_SPIN_LOCK_UNLOCKED(lockname) \
> > (raw_spinlock_t) __RAW_SPIN_LOCK_INITIALIZER(lockname)
> >
> > and C99 and gnu99 do not allow this. See
> > https://lore.kernel.org/lkml/20141019231031.GB9319@node.dhcp.inet.fi/
>
> This is simple not a cast.

4.62 Compound literals in C99
ISO C99 supports compound literals. A compound literal looks like a cast
followed by an initializer. Its value is an object of the type specified in the
cast, containing the elements specified in the initializer. It is an lvalue.

--
With Best Regards,
Andy Shevchenko