Return a dynamic array: real bug!

[Gilles G.]

Replying to myself...
I just realised that dmd issues an error on the previous code (Error: escaping reference to local a) while gdc based on dmd 1.007 does not!
However, I really ran into trouble yesterday returning a static array using dmd. Here is how I do it:
   import std.stdio;
    int[] testGood()
    {
        int a[]; a.length=2;
        a[]=1;
        return a;
    }

    int[] testBad()
    in { /*nothing*/ }
    out{ /*nothing too*/}
    body
    {
        int a[2];
        a[]=1;
        return a;
    }

    int main()
    {
        int b[];
        b = testGood();
        writef("Good test:\n");
        writef("  b[0]=%d,  b[1]=%d\n",b[0],b[1]);
        writef("  b[0]=%d,  b[1]=%d\n",b[0],b[1]);
        b = testBad();
        writef("Bad test:\n");
        writef("  b[0]=%d,  b[1]=%d\n",b[0],b[1]);
        writef("  b[0]=%d,  b[1]=%d\n",b[0],b[1]);
        return 0;
    }

Then the DMD will just compile fine and the ouput is
>Good test:
>  b[0]=1,  b[1]=1
>  b[0]=1,  b[1]=1
>Bad test:
>  b[0]=4280528,  b[1]=4298584
>  b[0]=4280472,  b[1]=4280528

So it seems that using the in out and body statement changes the behavior of DMD...
Maybe I should file a bug report now.

--
Gilles




Gilles G. Wrote:

> Hello,
> I went into trouble returning a dynamic array from a function. For example:
>     import std.stdio;
>     int[] testGood()
>     {
>         int a[]; a.length=2;
>         a[]=1;
>         return a;
>     }
>     
>     int[] testBad()
>     {
>         int a[2];
>         a[]=1;
>         return a;
>     }
>     
>     int main()
>     {
>         int b[];
>         b = testGood();
>         writef("Good test:\n");
>         writef("  b[0]=%d,  b[1]=%d\n",b[0],b[1]);
>         writef("  b[0]=%d,  b[1]=%d\n",b[0],b[1]);
>         b = testBad();
>         writef("Bad test:\n");
>         writef("  b[0]=%d,  b[1]=%d\n",b[0],b[1]);
>         writef("  b[0]=%d,  b[1]=%d\n",b[0],b[1]);
>         return 0;
>     }
> This code outputs:
> >Good test:
> >  b[0]=1,  b[1]=1
> >  b[0]=1,  b[1]=1
> >Bad test:
> >  b[0]=0,  b[1]=1
> >  b[0]=0,  b[1]=1
> 
> I guess this is the good behavior since I should not return a static array from a function, but the compiler _should_ issue a warning here... or not?
> 
> --
> Gilles
>