filling arrays, avoid default init

[Stewart Gordon]

Thomas Kuehne wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Lionello Lunesu schrieb am 2007-01-09:
>> Lionello Lunesu wrote:
>>> Frank Benoit (keinfarbton) wrote:
>>>> TypeA[] ta = .... ; // big array with something
>>>> TypeB[] tb;
>>>> tb.length = ta.length; // (1)
>>>> foreach( uint i, TypeA a; ta ){
>>>>   tb[i] = ta[i].getB();
>>>> }
>>>>
>>>> (1) how can I avoid the default initialization?
>>>>
>>>> -- Frank
>>> type[] t = void;
>> Uhm, sorry. That doesn't seem to prevent the initialization at all...

Actually, it's unpredictable, even dangerous.

> Can you provide a code sampel?

----------
import std.stdio;

void main() {
     int[] data = void;

     writefln("%08x %08x", data.ptr, data.length);
     data.length = 16;
     writefln("%08x %08x", data.ptr, data.length);
     writefln(data);
}
----------

You'll be lucky if the last statement doesn't throw an AV.  The danger 
arises if you try to write to the memory at the uninitialised pointer.

> Tested on Linux:
> # import std.stdio;
> # 
> # typedef int X = 12_34_56_78;
> # 
> # void main(){
> #    X[4] a;
> #    X[4] b = void;
<snip>

Of course that works.  That's a static array.

Stewart.