Re: [Boost-users] [array] VC++ 7.1 bug and a proposed fix

From: AlisdairM (alisdair.meredith_at_[hidden])
Date: 2006-07-13 02:55:03

Johan Råde wrote:

> If I modify the array class by adding a non-templatized
> assignment operator, as follows,
> then the code does compile.
> 
> ---------------------------------------------------------
> 
> namespace boost {
>      template<class T, std::size_t N>
>      class array {
>          ...
>          array<T,N>& operator=(const array<T,N>& rhs) {
>              std::copy(rhs.begin(), rhs.end(), begin());
>              return *this;
>          }
>          ...
>      };
> }
> 
> ----------------------------------------------------------
> 
> So I propose that this assignment operator is added,
> as a VC++ 7.1 bug workaround, to the array class.

The problem with that workaround is that the array template would no
longer produce aggregate types, and we would lose the ability to use
brace initialization:

std::tr1::array< int, 4 > x = { 0, 1, 2, 3 };

That is an important motivating example for this library, and results
in other compromises such as no user-declared constructors.

Note that it has been accepted into standard library TR1 in this
version, and the working draught for the next Standard Library.

Hpwever, there may be language changes coming that will allow us to use
brace-initialization with non-aggregate types.  In that case we will
definitely take another look at the class and see if we want to support
this kind of code.

I am also concerned that the patch involves overloading an operator
that does not seem to be called anywhere in the example.  It is an
interesting test case though.

i/ does it fail on other compilers?
ii/ Is it a very specific failure with pointer-to-member, or the first
hint of a more general issue that should be solved?

> I have contacted Nicolai Josuttis concerning this,
> and he told me he is not maintaining the array library
> anymore.

Yes, I have taken on the maintenance now.
Thanks for the report, although I don't have an instant solution :¬(

-- 
AlisdairM