[PATCH, libstdc++] GLIBCXX_HAVE_INT64_T
Fri Jan 8 18:37:03 GMT 2021
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,
>#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;
> typedef long long streamoff;
>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.
-------------- next part --------------
A non-text attachment was scrubbed...
Size: 4183 bytes
Desc: not available
More information about the Libstdc++