"ubyte[size] store = void" in std.variant

[Steven Schveighoffer]

On Tue, 15 Jun 2010 09:04:23 -0400, Graham Fawcett <fawcett at uwindsor.ca>  
wrote:

> Hi folks,
>
> The following statement appears in std.variant:
>
> 190    union
> 191    {
> 192        ubyte[size] store = void;
> 193        // conservatively mark the region as pointers
> 194        static if (size >= (void*).sizeof)
> 195            void* p[size / (void*).sizeof];
> 196    }
>
> The '= void' on line 192 sometimes leads to 'Error: void initializer
> has no value' errors in application code. For example, this fails to
> compile on DMD 2.047:
>
>   foreach (int v; map! "a.get!int" (variantArray(1,2,3)))
>     writeln(v);
>
> Changing line 192 to 'ubyte[size] store;' resolves the issue.
>
> My question is: what is the point of the '= void' initializer here?
> Would std.variant be broken if '= void' were removed?

= void means don't initialize the data.  Otherwise, the compiler/runtime  
will fill in the data will all 0s.  However, I'm not sure how that works  
with a union, since you may have conflicting requirements for  
initialization.

Is there a place in the spec that covers this?

-Steve