Visual C++: Copy Constructor Bug for Base Class with Template Constructor

Visual C++: Copy Constructor Bug for Base Class with Template Constructor by Victor Scherba

Closed

as Fixed

Type:	Bug
ID:	651972
Opened:	3/17/2011 5:29:12 AM
Access Restriction:	Public

Workaround(s)

view

User(s) can reproduce this bug

struct base
{
    base() {}

    base(const base&) {}

    template <class Other>
    base(const Other&) {}
};

struct derived : base
{
};

derived der1, der2(der1); // invokes template constuctor instead of copy constructor, what is wrong.

I have checked it on GCC and Comeau compilers, and them works without this bug.
This bug, for example, does not it possible to inherit boost::function class template properly.

I seem, when compiler generates default copy constructor for derived class it pass into base constructor parameter of a derived type considering implicit upcasting. But I can be wrong.

Details (expand)

Visual Studio 2010

As shown in description and attachment.

English

Windows XP

English

Calling base template constructor with argument of derived type.

Calling base copy constructor.

File Name	Submitted By	Submitted On	File Size
base_constructor_bug.cpp	Victor Scherba	3/17/2011	437 bytes

Posted by Microsoft on 9/17/2011 at 10:58 AM

Hi: this issue has been fixed. The fix should show up in a future release of Visual C++.

Thank you for reporting the issue.

Jonathan Caves
Visual C++ Compiler Team

Posted by Noah Roberts on 4/21/2011 at 9:58 AM

Probably related to a bug I posted a while back: http://connect.microsoft.com/VisualStudio/feedback/details/587787/implicit-copy-constructor-calls-base-with-derived-type-under-specific-conditions#details

Posted by Microsoft on 3/17/2011 at 8:01 PM

Thank you for submitting feedback on Visual Studio 2010 and .NET Framework. Your issue has been routed to the appropriate VS development team for review. We will contact you if we require any additional information.

Posted by Microsoft on 3/17/2011 at 6:13 AM

Thank you for your feedback, we are currently reviewing the issue you have submitted. If this issue is urgent, please contact support directly(http://support.microsoft.com)

Posted by Cassio Neri on 11/23/2012 at 9:27 AM

Alternatively, you can SFINAE away the template constructor when Other derives from base:

#include <type_traits>

// ...

template <class Other>
base(const Other&, typename std::enable_if<!std::is_base_of<base, Other>::value>::type* = nullptr) {}

Posted by Noah Roberts on 4/21/2011 at 10:00 AM

Write a user-defined copy constructor and upcast 'other' to the base type before passing it on.