On Mon, Mar 4, 2024 at 8:07 AM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > > On Mon, Mar 04 2024 at 06:42, Uros Bizjak wrote: > > > On Mon, Mar 4, 2024 at 12:49 AM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > >> > >> On Sun, Mar 03 2024 at 21:24, Uros Bizjak wrote: > >> > On Sun, Mar 3, 2024 at 9:21 PM Uros Bizjak <ubizjak@xxxxxxxxx> wrote: > >> >> On Sun, Mar 3, 2024 at 9:10 PM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > >> >> > That's so sad because it would provide us compiler based __percpu > >> >> > validation. > >> >> > >> >> Unfortunately, the c compiler can't strip qualifiers, so typeof() is > >> >> of limited use also when const and volatile qualifiers are used. > >> >> Perhaps some extension could be introduced to c standard to provide an > >> >> unqualified type, e.g. typeof_unqual(). > >> > > >> > Oh, there is one in C23 [1]. > >> > >> Yes. I found it right after ranting. > >> > >> gcc >= 14 and clang >= 16 have support for it of course only when adding > >> -std=c2x to the command line. > >> > >> Sigh. The name space qualifiers are non standard and then the thing > >> which makes them more useful is hidden behind a standard. > > > > With GCC, you can use __typeof_unqual__ (please note underscores) > > without -std=c2x [1]: > > > > "... Alternate spelling __typeof_unqual__ is available in all C modes > > and provides non-atomic unqualified version of what __typeof__ > > operator returns..." > > > > Please also see the example in my last post. It can be compiled without -std=... > > With gcc >= 14. Not so with clang... Please note that clang-17.0.6 currently fails to compile kernel with named address spaces [1]. So perhaps kernel can use __typeof_unqual__ (available without -std=c2x) in the hope that clang implements __typeof_unqual__ in one of its next releases, following the examples of GCC [2] and MSVC[3]. [1] https://lore.kernel.org/lkml/20240320173758.GA3017166@dev-arch.thelio-3990X/ [2] https://gcc.gnu.org/onlinedocs/gcc/Typeof.html [3] https://learn.microsoft.com/en-us/cpp/c-language/typeof-unqual-c?view=msvc-170 Uros.
