Inheriting from a typedef that is inside another class

[itaj sherman]

The following does not compile on my VC6. Is it standard?


#include <iostream>

class Base
{
public:
explicit Base()
{
std::cout << "Base:ctor()" << "\n";
}

};


class Scope
{
public:
typedef Base BaseInScope;
};



class Derived:
public Scope::BaseInScope
{
public:
explicit Derived()
:
Scope::BaseInScope()
{
std::cout << "Derived:ctor()" << "\n";
}
};


D:\code\Test\Test\Test.cpp(39) : error C2614: 'Derived' : illegal
member initialization: 'BaseInScope' is not a base or member



The following fixes the problem:


class Derived:
public Scope::BaseInScope
{
public:
typedef Scope::BaseInScope MyBase

explicit Derived()
:
MyBase()
{
std::cout << "Derived:ctor()" << "\n";
}
};


and also:


class Derived:
public Scope::BaseInScope
{
public:
explicit Derived()
:
Base()
{
std::cout << "Derived:ctor()" << "\n";
}
};

 

[Frank Birbacher]

Hi!

<quote>
Comeau C/C++ 4.3.10.1 (May 7 2008 20:26:48) for ONLINE_EVALUATION_BETA1
Copyright 1988-2008 Comeau Computing. All rights reserved.
MODE:strict errors C++ noC++0x_extensions


In strict mode, with -tused, Compile succeeded (but remember, the Comeau
online compiler does not link).
</quote>

In short this means "it is standard".

Well, I wonder what would do the "explicit" specification to the default
ctor? There isn't even a warning about it which makes me wonder if there
is any effect. Is there?

Frank

 

[David Côme]

The following does not compile on my VC6. Is it standard?

Change it for VS C++ 2008.

#include <iostream>

class Base
{
public:
explicit Base()
{
std::cout << "Base:ctor()" << "\n";
}

};


class Scope
{
public:
typedef Base BaseInScope;
};



class Derived:
public Scope::BaseInScope
{
public:
explicit Derived()
:
Scope::BaseInScope()
{
std::cout << "Derived:ctor()" << "\n";
}
};

compile perfectly with g++

 

[itaj sherman]

* Frank Birbacher:









The standard states that an "explicit" default constructor will be used to
perform to default initialization, so presumably "explicit" on a default
constructor has no effect whatsoever.

"explicit" on a copy constructor is more subtle.

Since I'm right back from my fav café having a beer in the sun, and is a bit
tired, I simply don't want to think about those subtleties... ;-)

Cheers, & hth.,

- Alf

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Thanks to you all.
Yes, the 'explicit' has no effect. It's just my custom to declare all
ctors explicit, and change that only if needed.
But it makes no difference for my problem.