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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/107939] [11/12/13 Regression] Rejects use of `extern const`
 variable in a template
Date: Wed, 30 Nov 2022 19:35:56 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: needs-bisection, rejects-valid
X-Bugzilla-Severity: normal
X-Bugzilla-Who: pinskia at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
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X-Bugzilla-Target-Milestone: 11.4
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 cf_reconfirmed_on everconfirmed
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107939

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |needs-bisection
   Target Milestone|---                         |11.4
            Summary|Rejects use of `extern      |[11/12/13 Regression]
                   |const` variable in a        |Rejects use of `extern
                   |template                    |const` variable in a
                   |                            |template
   Last reconfirmed|                            |2022-11-30
     Ever confirmed|0                           |1

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Replacing auto with int (and adding a message to static_assert), gets you a
valid C++14 testcase:
```

struct Q {
  struct P {
    const Q* p;
  };
  int n;
  constexpr P operator()(int) const { return {this}; }
};

extern const Q q;

#if 1
template<int> constexpr auto p =3D q(0);
static_assert(p<0>.p =3D=3D &q, "");
#else
constexpr auto p =3D q(0);
static_assert(p.p =3D=3D &q, "");
#endif

constexpr Q q =3D {};
```
This worked with GCC 10.4.0.=