On Mon, Dec 14, 2015 at 12:16 PM, Jason Merrill <ja...@redhat.com> wrote: > On 12/12/2015 01:42 PM, Marc Glisse wrote: >> >> On Sat, 12 Dec 2015, Jakub Jelinek wrote: >> >>> On Sat, Dec 12, 2015 at 09:51:23AM -0500, Jason Merrill wrote: >>>> >>>> On 12/11/2015 06:52 PM, H.J. Lu wrote: >>>>> >>>>> On Thu, Dec 10, 2015 at 3:24 AM, Richard Biener >>>>> <richard.guent...@gmail.com> wrote: >>>>>> >>>>>> On Wed, Dec 9, 2015 at 10:31 PM, Markus Trippelsdorf >>>>>> <mar...@trippelsdorf.de> wrote: >>>>>>> >>>>>>> On 2015.12.09 at 10:53 -0800, H.J. Lu wrote: >>>>>>>> >>>>>>>> >>>>>>>> Empty C++ class is a corner case which isn't covered in psABI nor >>>>>>>> C++ ABI. >>>>>>>> There is no mention of "empty record" in GCC documentation. But >>>>>>>> there are >>>>>>>> plenty of "empty class" in gcc/cp. This change affects all >>>>>>>> targets. C++ ABI >>>>>>>> should specify how it should be passed. >> >> >> >> About this patch, aren't we supposed to enable new C++ ABIs with >> -fabi-version=42 (or whatever the next number is)? > > > Yes, the patch should definitely make this conditional on > abi_version_at_least. > >>>>>>> There is a C++ ABI mailinglist, where you could discuss this issue: >>>>>>> http://sourcerytools.com/cgi-bin/mailman/listinfo/cxx-abi-dev >>>>>> >>>>>> >>>>>> Yep. As long as the ABI doesn't state how to pass those I'd rather >>>>>> _not_ change GCCs way. >>>>> >>>>> >>>>> It is agreed that GCC is wrong on this: >>>>> >>>>> >>>>> http://sourcerytools.com/pipermail/cxx-abi-dev/2015-December/002876.html >>>>> >>>> >>>> Yes, I think this is just a (nasty) bug on some GCC targets. >>> >>> >>> Well, the argument in that thread is weird, because C and C++ empty >>> structs >>> are different, so it isn't surprising they are passed differently. >>> C++ makes those sizeof == 1, while C has them sizeof == 0. >> >> >> Maybe it isn't surprising, but it isn't particularly helpful either. It >> increases the number of places where the 2 are incompatible. >> (I personally don't care about empty C structs) > > > Yep. The C standard doesn't have empty structs; it's a GNU extension. But > in any case argument passing can be compatible between C and C++, so it > really should be. > >
Before I make any changes, I'd like to ask if we should make argument passing can be compatible between C and C++ for all targets GCC support or just x86. -- H.J.
