Re: gcc needs copy consturctor for inplace constructed object passed to func as reference, others not

Hi all,

I have the following problem ( explanation below code ):

// main.cpp

class noncopyable
{
 protected:
        noncopyable() {}
        ~noncopyable() {}
 private: // emphasize the following members are private
        noncopyable( const noncopyable& );
        const noncopyable& operator=( const noncopyable& );
};

class MyClass: noncopyable
{
public:
    MyClass( ) { }
};

class IFormatter
{
public:
    void func( const MyClass& ) { }
    virtual ~IFormatter( ){}
};
int main()
{
    MyClass mc;
    IFormatter f;
    f.func( MyClass( ) ); // doesn't work
        f.func( mc ); // works
    return 0;
}

This code is accepted by comeau in strict mode and by all MSVC that I
had used 7.0 up to 8.0
.

gcc 4.0.2 complains that the copy constructor of MyClass is private.

Now I wannted to further simplify by removing the noncopyable base and
instead making the copy and assignment private in MyClass.

class MyClass
{
public:
    MyClass( ) { }
private:
    MyClass( MyClass const& );
    MyClass const& operator=( MyClass const& );
};

class IFormatter
{
public:
    void func( MyClass const& ) { }
    virtual ~IFormatter( ){}
};
int main()
{
    MyClass mc;
    IFormatter f;
    f.func( MyClass( ) );
    return 0;
}

surprisingly, now even comeau complains:

Comeau C/C++ 4.3.3 (Aug 6 2003 15:13:37) for ONLINE_EVALUATION_BETA1
Copyright 1988-2003 Comeau Computing. All rights reserved.
MODE:strict errors C++

"ComeauTest.c", line 35: error: "MyClass::MyClass(const MyClass &)",
required for
          copy that was eliminated, is inaccessible
   f.func( MyClass( ) );
   ^

Could it be possible that comeau is wrong for one or the other example?
Or did I change something significantly in my simplification?

Could someone try this with a gcc 4.1.x or 3.x.x ?