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From: "barry.revzin at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/95567] New: Defaulted virtual <=> has the wrong behavior
Date: Sun, 07 Jun 2020 23:34:02 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95567

            Bug ID: 95567
           Summary: Defaulted virtual <=3D> has the wrong behavior
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: barry.revzin at gmail dot com
  Target Milestone: ---

Reduced from Twitter user @feder_and_ink:

#include <compare>

struct B {
  B(int i) : i(i) {}

  VIRTUAL std::strong_ordering operator<=3D>(B const& other) const =3D defa=
ult;
  int i;
};

struct D : B {
  D(int i, int j) : B(i), j(j) {}
  int j;
};

bool check() {
    return B(2) =3D=3D D(2, 3);
}

With -DVIRTUAL=3D, check() returns true.
With -DVIRTUAL=3Dvirtual, check() erroneously returns false.
On compiler explorer: https://godbolt.org/z/hc3U5f=