[Vala] Help needed with unowned objects

[Tambet <qtvali gmail com>]

Hello!

I'm new to Vala and I'm trying to figure out if it meets the following
requirements:
- Bindings to C or other mainstream language (to have some code base, like
hashset)
- Some trivial memory management and decent sytax
- Way to work with unmanaged objects, which is very important

I have looked into manual of it and can't find a clear answer to these
questions, can I have such object:
- Allocation and deallocation is fully manual - I can alloc arbitrary amount
of memory to that object and work with it in whichever way I choose.
- No additional data will be added to it ([Compact] struct?).
- Allocating this object will just request memory and not fill it with zeros
or do other operations (often this would be 1/3 of total time needed to
create an object, except what OS does).
- I can cast this object to something, what has some interface and methods
(which are then capable to work with this* pointer).

I did look at code compiled by Vala and saw the following at initialization:
public static unowned AltStruct a() {
    unowned AltStruct a = AltStruct();
    return a;
}

Compiles into:
void demo_hello_world_a (AltStruct* result) {
    AltStruct a = {0};
    memset (&a, 0, sizeof (AltStruct));
    *result = a;
    return;
}

This is:
    AltStruct a = {0};
    memset (&a, 0, sizeof (AltStruct));

As much as I understand, this would first initialize it with a zero-value
(it contains one int) and then fill it's memory area with zeroes?

Could I write code, which compiles into:
void demo_hello_world_a (AltStruct* result) {
    AltStruct a;
    *result = a;
    return;
}

And, moreover, could I write code, which compiles into:
void demo_hello_world_a (AltStruct* result) {
    int i = 7;
    AltStruct* a;
    a = calloc(1, sizeof(a));
    *result = a;
    return;
}

And, as a side-question, is this "AltStruct* result" compiled into exactly
the same code (as fast as) as if the function did return a result? Probably
is?

Tambet