Union copy

["Luís]

On Wednesday, 23 October 2013 at 18:07:37 UTC, Ali Çehreli wrote:
> If D's unions are like C's and C++'s, then it is not defined 
> what happens when accessing members of the union that are not 
> active.
>
> Either the anonymous struct or 'd' above is active, so only 
> that member can be accessed.

Is it not valid to initialize a double with a bit pattern that 
you read from somewhere (e.g. disk)? (reinterpret cast, I 
guess?). Something like this(?):

     void main()
     {
         long srcL = 0x7ff7a50200000000;
         double* srcD = cast(double*) &srcL;
         double dst = *srcD;

         writef("src: %x\n", srcL);
         writef("dst: %x\n", *cast(long*) cast(void*) &dst);
     }

If this is valid, the question seems to be why the 
quiet/signaling flag is changed.