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From: "nir.livne at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/107070] New: GCC thinks !!b is an lvalue (bool b;)
Date: Wed, 28 Sep 2022 15:33:43 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 13.0
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107070

            Bug ID: 107070
           Summary: GCC thinks !!b is an lvalue (bool b;)
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nir.livne at gmail dot com
  Target Milestone: ---

#include <iostream>

// gcc   result: 0 1=20
// clang result: 1 1
// msvc  result: 1 1

int main() {
    bool b =3D true;

    // #1 GCC result with 0 while it should be 1
    std::cout << std::is_same<decltype(!(!b)), bool>::value << "\n";

    auto bb =3D (!(!b));
    std::cout << std::is_same<decltype(bb), bool>::value << "\n";

    // #2 this should not compile
    // !!b =3D true;
}=