[Bug libstdc++/95561] New: std::is_signed_v<__int128> is false

[Bug libstdc++/95561] New: std::is_signed_v<__int128> is false

[janezz55 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95561

            Bug ID: 95561
           Summary: std::is_signed_v<__int128> is false
           Product: gcc
           Version: 10.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: janezz55 at gmail dot com
  Target Milestone: ---

As the comment says, std::is_signed_v<__int128> should evaluate to true.

[Bug libstdc++/95561] std::is_signed_v<__int128> is false

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95561

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> ---
Are you using -std=gnu++17 or -std=c++17 ?

[Bug libstdc++/95561] std::is_signed_v<__int128> is false

[janezz55 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95561

--- Comment #2 from Janez Zemva <janezz55 at gmail dot com> ---
(In reply to Marc Glisse from comment #1)
> Are you using -std=gnu++17 or -std=c++17 ?

yes, of course.

[Bug libstdc++/95561] std::is_signed_v<__int128> is false

[janezz55 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95561

--- Comment #3 from Janez Zemva <janezz55 at gmail dot com> ---
BTW: std::is_integral_v<__int128> is also false. I'm not certain, whether this
is a bug, but reporting nonetheless.

[Bug libstdc++/95561] std::is_signed_v<__int128> is false

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95561

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Not a bug.

Marc was asking *which* option you're using, -std=gnu++17 or -std=c++17.

__int128 is not an integral type, so in strict -std=c++17 mode the standard
requires that is_integral_v<__int128> is false and therefore
is_signed_v<__int128> has to be false too.

With -std=gnu++17 both are true.

This is by design, not a bug. If you want to use non-standard extensions like
__int128 and have them treated as integral types, don't ask for strict standard
conformance with -std=c++17.

[Bug libstdc++/95561] std::is_signed_v<__int128> is false

[janezz55 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95561

--- Comment #5 from Janez Zemva <janezz55 at gmail dot com> ---
Thank you for the "fix", I am writing my own 128-bit integral type, but in the
mean time, I'm using __int128.