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* [Bug c++/98216] New: [C++20] std::array<double, N> template parameter error with negative values
@ 2020-12-09 15:43 emmanuel.le-trong@cnrs-orleans.fr
  2020-12-09 16:04 ` [Bug c++/98216] " redi at gcc dot gnu.org
                   ` (13 more replies)
  0 siblings, 14 replies; 15+ messages in thread
From: emmanuel.le-trong@cnrs-orleans.fr @ 2020-12-09 15:43 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98216

            Bug ID: 98216
           Summary: [C++20] std::array<double, N> template parameter error
                    with negative values
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: emmanuel.le-trong@cnrs-orleans.fr
  Target Milestone: ---

Sorry for the bad title, I can't figure out how to summarize this:

    #include <array>
    #include <cassert>

        using
    an_array = std::array <double, 1>;

        constexpr auto
    add_array (an_array a, an_array const& b)
    {
        a[0] += b[0];
        return a;
    }

        template <an_array A>
        struct
    wrapper
    {
            static constexpr auto
        arr = A;
    };


        template <an_array A1 ,an_array A2 >
        auto
    add (wrapper <A1> const&, wrapper <A2> const&)
    {
        return wrapper <add_array (A1, A2)> {};
    }

    constexpr auto ONE       = an_array {{  1. }};
    constexpr auto MINUS_ONE = an_array {{ -1. }}; 
    constexpr auto MINUS_TWO = an_array {{ -2. }}; 

        int
    main ()
    {
        auto a = wrapper <MINUS_TWO> {};
        auto b = wrapper <ONE> {};
        auto c = add (a, b);
        assert (c.arr == MINUS_TWO); // <- should fail
        assert (c.arr == MINUS_ONE); // <- should pass
    }

Compiled with version 11.0.0 20201209, the first assertion passes and the
second fails. It should be the opposite.

FWIW, if you replace double by float, it works as intended.

^ permalink raw reply	[flat|nested] 15+ messages in thread
end of thread, other threads:[~2021-10-14 21:39 UTC | newest]

Thread overview: 15+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-12-09 15:43 [Bug c++/98216] New: [C++20] std::array<double, N> template parameter error with negative values emmanuel.le-trong@cnrs-orleans.fr
2020-12-09 16:04 ` [Bug c++/98216] " redi at gcc dot gnu.org
2020-12-10  7:33 ` rguenth at gcc dot gnu.org
2020-12-10 17:05 ` redi at gcc dot gnu.org
2020-12-10 17:16 ` redi at gcc dot gnu.org
2020-12-10 17:56 ` emmanuel.le-trong@cnrs-orleans.fr
2020-12-14 20:56 ` ppalka at gcc dot gnu.org
2021-07-27  8:08 ` [Bug c++/98216] [C++20] template mangling for double template argument is wrong pinskia at gcc dot gnu.org
2021-09-23 18:57 ` ppalka at gcc dot gnu.org
2021-09-23 19:01 ` ppalka at gcc dot gnu.org
2021-09-24 16:36 ` cvs-commit at gcc dot gnu.org
2021-09-24 19:36 ` emmanuel.le-trong@cnrs-orleans.fr
2021-10-06 14:15 ` cvs-commit at gcc dot gnu.org
2021-10-14 19:06 ` hq.ks at web dot de
2021-10-14 21:39 ` pinskia at gcc dot gnu.org

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