Re: git: 96acaa960023 - main - compat32: provide a type and a macro for (u)int64_t handling on non-x86 arches

On Tue, Jan 20, 2026 at 04:05:19PM +0000, Jessica Clarke wrote:
> On 20 Jan 2026, at 14:42, Konstantin Belousov <kib@FreeBSD.org> wrote:
> > 
> > The branch main has been updated by kib:
> > 
> > URL: https://cgit.FreeBSD.org/src/commit/?id=96acaa960023c20e852e04e7cc5c6a5faca36c67
> > 
> > commit 96acaa960023c20e852e04e7cc5c6a5faca36c67
> > Author:     Konstantin Belousov <kib@FreeBSD.org>
> > AuthorDate: 2026-01-12 04:45:36 +0000
> > Commit:     Konstantin Belousov <kib@FreeBSD.org>
> > CommitDate: 2026-01-20 14:42:35 +0000
> > 
> >    compat32: provide a type and a macro for (u)int64_t handling on non-x86 arches
> > 
> >    uint64_t is 4-byte aligned on i386, but is 8-bytes aligned on all other
> >    32bit arches FreeBSD supports.  Provide the freebsd32_uint64_t type and
> >    the FU64_CP() macro, which are intended to be used where 32bit ABI uses
> >    (u)int64_t type, and do proper layout and copying for the aggregate type.
> > 
> >    Reviewed by:    des, emaste
> >    Sponsored by:   The FreeBSD Foundation
> >    MFC after:      1 week
> >    Differential revision:  https://reviews.freebsd.org/D54663
> > ---
> > sys/compat/freebsd32/freebsd32.h | 11 ++++++++++-
> > sys/sys/abi_compat.h             |  8 ++++++++
> > 2 files changed, 18 insertions(+), 1 deletion(-)
> > 
> > diff --git a/sys/compat/freebsd32/freebsd32.h b/sys/compat/freebsd32/freebsd32.h
> > index 9d724c93fee7..7324f9adf70c 100644
> > --- a/sys/compat/freebsd32/freebsd32.h
> > +++ b/sys/compat/freebsd32/freebsd32.h
> > @@ -36,8 +36,17 @@
> > #include <sys/_ffcounter.h>
> > 
> > /*
> > - * i386 is the only arch with a 32-bit time_t
> > + * i386 is the only arch with a 32-bit time_t.
> > + * Also it is the only arch with (u)int64_t having 4-bytes alignment.
> >  */
> > +typedef struct {
> > +#ifdef __amd64__
> > + uint32_t val[2];
> > +#else
> > + uint64_t val;
> > +#endif
> > +} freebsd32_uint64_t;
> 
> Any reason not to use:
> 
>   typedef uint64_t freebsd32_uint64_t __aligned(4);
> 
> on amd64 (and normal typedef elsewhere)? Then you can just use the
> normal CP. See for example https://godbolt.org/z/svseWv7xo.
Yes, this way it uses only std C instead of the GNU extension, and not
depend on compiler properly handle unaligned types.

IMO it is better that way, and all machinery is hidden under the typedef+
the macro.