Re: [boost] Re: type_traits: has_copy_constructor<>

From: Peter Dimov (pdimov_at_[hidden])
Date: 2003-10-01 05:57:10

Daniel Frey wrote:
> David Abrahams wrote:
>> All types have a copy_ctor.
> 
> I heard that several times, but I am still not sure if it's true. I
> think you are refering to the fact that the compiler generates a
> copy-ctor if the class doesn't provide one explicitly, right? But what
> happens if the compiler cannot create a copy-ctor? Consider:
> 
> class A
> {
>    A();
>    A(A&);
> public:
>    A(int) {}
> };
> 
> class B
> {
>    A a;
> public:
>    B(int i) : a(i) {}
> };
> 
> int main()
> {
>    B b( 42 );
> }

Add

    B b2( b );

and ask EDG:

Comeau C/C++ 4.3.0.1 (Aug 21 2002 15:45:32) for MS_WINDOWS_x86
Copyright 1988-2002 Comeau Computing.  All rights reserved.
MODE:strict errors C++

"testbed.cpp", line 11: error: "A::A(A &)" is inaccessible
     A a;
       ^
          detected during implicit generation of "B::B(B &)" at line 19

1 error detected in the compilation of "testbed.cpp".

Or you could read 12.8, I guess. ;-)