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From: "carlosgalvezp at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/109663] New: False positive? Converting from initializer
 list would use explicit constructor
Date: Fri, 28 Apr 2023 09:56:13 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109663

            Bug ID: 109663
           Summary: False positive? Converting from initializer list would
                    use explicit constructor
           Product: gcc
           Version: 13.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: carlosgalvezp at gmail dot com
  Target Milestone: ---

Created attachment 54950
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D54950&action=3Dedit
Preprocessed source

Hi!

We are bumping our GCC installation from
6910cad55ffc330dc9767d2c8e0b66ccfa4134af to
cc035c5d8672f87dc8c2756d9f8367903aa72d93 (GCC 13.1 release), and are now
getting a handful of errors in this type of code compiling in C++14 mode:

#include <Eigen/Dense>

int main()
{
    constexpr std::size_t kColumns{4};
    constexpr std::size_t kRows{4};
    using MyVector =3D Eigen::Matrix<float, kColumns, 1>;
    using MyMatrix =3D Eigen::Matrix<float, kColumns, kRows>;

    MyMatrix matrix{MyMatrix::Zero()};
    MyVector const& my_col{matrix.col(0)};
}

Godbolt: https://godbolt.org/z/rx6EY4qbY

Preprocessed source attached.

I am wondering if this is a False Positive or a real error that should be
fixed?=