[Bug c++/71774] New: Bogus "is protected" error when list-initializing a base class with a defaulted protected constructor and a virtual function

[rs2740 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71774

            Bug ID: 71774
           Summary: Bogus "is protected" error when list-initializing a
                    base class with a defaulted protected constructor and
                    a virtual function
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rs2740 at gmail dot com
  Target Milestone: ---

Reduced from http://stackoverflow.com/q/38213809/2756719. Repro:

class Meow
{
  protected:
    Meow() =default;        
    virtual void f() {}
};

class Purr : public Meow
{
  public:
    Purr()
      : Meow{}
    {}  
};

prog.cc: In constructor 'Purr::Purr()':
prog.cc:12:14: error: 'constexpr Meow::Meow()' is protected within this context
       : Meow{}
              ^
prog.cc:4:5: note: declared protected here
     Meow() =default;
     ^~~~

Possibly related to PR63151, however this example reproduces in GCC 4.7.3 and
4.8.5 (on Wandbox), while that PR is known to work in 4.8.2.