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

From: John Maddock (john_at_[hidden])
Date: 2006-07-24 10:38:27

Johan Råde wrote:
>>> 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 };
>>
>
> Are you sure? An aggregate can not have user defined constructors,
> but I believe user defined assignment operators ar OK.
>
> I tested with VC++ 7.1, and there my fix can be combined with
> aggregate initialization.
> (If I add a constructor though, then aggregate initialization does not
> work with VC++ 7.1.)
>
> So I think my fix works.
>
>> 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 no idea. The error only seems to pop up in fairly complex
> situations with templates and pointer-to-members.

I've checked with VC8 and GCC-3.4 and both accept the code.  However, I 
actually think VC7.1 is correct in rejecting it (although possibly for the 
wrong reasons!).

Boost.Array is not intended to be either copy-constructable or assignable, 
so instantiating a function returning an array-by-value *should* fail to 
compile.  Or at the very least we're in a very grey area: it all depends on 
whether the body of the function is instantiated when you take it's 
address - or just it's signature - that's the sort of thing that's entirely 
at the whim of the compiler :-)

John.