Hello,

I have the following code that works. I'd like to change the t tsData to ts
tsData, but this does segfault. I do not understand how I dereferece the ts
struct correctly. Perhaps someone could give me a hint. Thanks.
Oliver

-----------------

alias rs *r;
alias ts *t;

struct ts {
    int d;
    union {
        int[] intData;
        double[] doubleData;
    }
}

struct rs {
    int i;
    union {
        int intData;
        //ts tsData;
        t tsData;
    };

    this( int i, int d, ref int[] data) {
        this.i = i;
        this.tsData.d = d;
        this.tsData.intData = data;
    }
}

r makeData(int i, int d, int[] data) {
    return new rs(i,d,data);
}

int main () {

    int i = 1;
    int[] data = [1,2];
    auto test = makeData(i,1,data);

    return 0;
}

Oliver:

> ...

struct Ts {
    int d;

    union {
        int[] intData;
        double[] doubleData;
    }
}

struct Rs {
    int i;

    union {
        int intData;
        Ts* tsData;
    }

    this(int i, int d, int[] data) {
        this.i = i;
        this.tsData = new typeof(*tsData);
        this.tsData.d = d;
        this.tsData.intData = data;
    }
}

Rs* makeData(int i, int d, int[] data) {
    return new Rs(i, d, data);
}

void main () {
    int i = 1;
    int[] data = [1, 2];
    auto test = makeData(i, 1, data);
}


- You have not created the pointed inner struct.
- Don't use aliases like those ones, they confuse the code.
- Struct names are better with a starting uppercase letter in D.

Bye,
bearophile

On 19/02/2011 13:18, Oliver wrote:
>
> Hello,
>
> I have the following code that works.

What?  The code you've posted doesn't work.

> I'd like to change the t tsData to ts tsData, but this does segfault.

The code you've posted throws an AV, and correctly so.  If you change tsData to a ts, it runs successfully.  At least in 2.051 Windows.  Is something different happening on your setup?

> I do not understand how I dereferece the ts struct correctly.

You don't dereference a struct, you dereference a pointer.

<snip>
> struct rs {
>      int i;
>      union {
>          int intData;
>          //ts tsData;
>          t tsData;
>      };
>
>      this( int i, int d, ref int[] data) {
>          this.i = i;
>          this.tsData.d = d;
>          this.tsData.intData = data;
>      }
> }
<snip>

You have not initialised tsData.  Consequently, you are trying to dereference a null pointer.  Hence the segfault.

For it to work with tsData being a pointer, you need to add something like this:

    this.tsData = new ts;

Stewart.

== Quote from bearophile (bearophileHUGS@lycos.com)'s article
> Oliver:
> > ...
> struct Ts {
>     int d;
>     union {
>         int[] intData;
>         double[] doubleData;
>     }
> }
> struct Rs {
>     int i;
>     union {
>         int intData;
>         Ts* tsData;
>     }
>     this(int i, int d, int[] data) {
>         this.i = i;
>         this.tsData = new typeof(*tsData);
>         this.tsData.d = d;
>         this.tsData.intData = data;
>     }
> }
> Rs* makeData(int i, int d, int[] data) {
>     return new Rs(i, d, data);
> }
> void main () {
>     int i = 1;
>     int[] data = [1, 2];
>     auto test = makeData(i, 1, data);
> }
> - You have not created the pointed inner struct.

Yes, thanks, I got it.

> - Don't use aliases like those ones, they confuse the code.
> - Struct names are better with a starting uppercase letter in D.
> Bye,
> bearophile

Thanks for the comments.
Olier

== Quote from Stewart Gordon (smjg_1998@yahoo.com)'s article
> On 19/02/2011 13:18, Oliver wrote:
> >
> > Hello,
> >
> > I have the following code that works.
> What?  The code you've posted doesn't work.

Sorry for that, in the post I got the // and the second one mixed up.

> > I'd like to change the t tsData to ts tsData, but this does segfault.
> The code you've posted throws an AV, and correctly so.  If you change tsData to
a ts, it
> runs successfully.  At least in 2.051 Windows.  Is something different happening
on your
> setup?

No, no that was a mixup on my side.

> > I do not understand how I dereferece the ts struct correctly.
> You don't dereference a struct, you dereference a pointer.

Yea, well that sould have read dereference the pointer to the struct.

> <snip>
> > struct rs {
> >      int i;
> >      union {
> >          int intData;
> >          //ts tsData;
> >          t tsData;
> >      };
> >
> >      this( int i, int d, ref int[] data) {
> >          this.i = i;
> >          this.tsData.d = d;
> >          this.tsData.intData = data;
> >      }
> > }
> <snip>
> You have not initialised tsData.  Consequently, you are trying to dereference a null
> pointer.  Hence the segfault.
> For it to work with tsData being a pointer, you need to add something like this:
>      this.tsData = new ts;

Thanks, that was what I did not get - for what ever reason - which seems obvious now.

Oliver

> Stewart.