From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Torokhov Subject: Re: [PATCH v5 11/14] software node: move small properties inline when copying Date: Wed, 16 Oct 2019 09:44:50 -0700 Message-ID: <20191016164450.GC35946@dtor-ws> References: <20191011230721.206646-1-dmitry.torokhov@gmail.com> <20191011230721.206646-12-dmitry.torokhov@gmail.com> <20191015122028.GI32742@smile.fi.intel.com> <20191015182553.GG105649@dtor-ws> <20191016074857.GN32742@smile.fi.intel.com> <20191016160126.GB35946@dtor-ws> <20191016161845.GX32742@smile.fi.intel.com> <20191016162308.GY32742@smile.fi.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20191016162308.GY32742@smile.fi.intel.com> Sender: linux-kernel-owner@vger.kernel.org To: Andy Shevchenko Cc: "Rafael J. Wysocki" , Heikki Krogerus , Mika Westerberg , Linus Walleij , Ard Biesheuvel , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, platform-driver-x86@vger.kernel.org List-Id: platform-driver-x86.vger.kernel.org On Wed, Oct 16, 2019 at 07:23:08PM +0300, Andy Shevchenko wrote: > 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. Yes, these are compound literals. And they can not be used as initializers: https://lore.kernel.org/lkml/CAHk-=wgXBV57mz46ZB5XivjiSBGkM0cjuvnU2OWyfRF=+41NPQ@mail.gmail.com/ Thanks. -- Dmitry