[PATCH, libstdc++] GLIBCXX_HAVE_INT64_T

David Edelsohn dje.gcc@gmail.com
Fri Apr 30 20:18:20 GMT 2021


On Fri, Apr 30, 2021 at 3:31 PM Jonathan Wakely <jwakely@redhat.com> wrote:
>
> On 29/04/21 16:06 -0400, David Edelsohn wrote:
> >On Fri, Jan 8, 2021 at 1:37 PM Jonathan Wakely <jwakely@redhat.com> wrote:
> >>
> >> On 06/01/21 19:41 -0500, David Edelsohn wrote:
> >> >Thanks for clarifying the issue.
> >> >
> >> >As you implicitly point out, GCC knows the type of INT64 and defines
> >> >the macro __INT64_TYPE__ .  The revised code can use that directly,
> >> >such as:
> >> >
> >> >#if defined(_GLIBCXX_HAVE_INT64_T_LONG) \
> >> >    || defined(_GLIBCXX_HAVE_INT64_T_LONG_LONG)
> >> >   typedef __INT64_TYPE__   streamoff;
> >> > #elif defined(_GLIBCXX_HAVE_INT64_T)
> >> >   typedef int64_t                     streamoff;
> >> > #else
> >> >   typedef long long                 streamoff;
> >> > #endif
> >> >
> >> >Are there any additional issues not addressed by that approach, other
> >> >than possible further simplification?
> >>
> >> That avoids the ABI break that Jakub pointed out. But I think we can
> >> simplify it further, as in the attached patch.
> >>
> >> This uses __INT64_TYPE__ if that's defined, and long long otherwise. I
> >> think that should be equivalent in all practical cases (I can imagine
> >> some strange target where __INT64_TYPE__ is defined by the compiler,
> >> but int64_t isn't defined when the configure checks look for it, and
> >> so the current code would use long long and with my patch would use
> >> __INT64_TYPE__ which could be long ... but I think in practice that's
> >> unlikely. It was probably more likely in older releases where the
> >> configure test would have been done with -std=gnu++98 and so int64_t
> >> might not have been declared by libc's <stdint.h>, but if that was the
> >> case then any ABI break it caused happened years ago.
> >
> >Hi, Jonathan
> >
> >Polite ping.
> >
> >Now that GCC 11.1 has been released, can this patch be applied to
> >libstdc++?  As I replied at the time to Jakub's concerns, both Clang
> >(since 3.0.0) and ICC (since at least 16.0.0) have defined
> >__INT64_TYPE__ .
>
> Pushed to trunk after testing on x86_64-linux and powerpc-aix.

Hi, Jonathan

Thanks very much!  It's very helpful to remove the multilib differences.

I'll follow up about the int128 change in a separate email.

Thanks, David


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