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Handles as return values

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Started by bozho April 27, 2005 04:21 AM

1 comment, last by WitchLord 19 years, 2 months ago

bozho

122

Author

April 27, 2005 04:21 AM

Hi! I have a question about script functions allocating objects and returning handles. I'd like to do something like this:


Test1@ foo() {
   Test1 t;
   return @t;
}

However, it seems that Test1's constructor is not called when creating the object, and it is deallocated when exiting the function (when I retreive the return value, it's not a valid pointer) Shouldn't 'return @t' cause AddRef to be called? I have also tried:


Test1@ foo() {
   Test1 t;
   Test1@ t2;
   @t2 = @t;
   return @t2;
}

But, the same thing happens: AddRef is called twice, then Release is called twice and return value is not a valid pointer. Am I doing something wrong, or is this a bug/not implemented? On a side note: Wouldn't it be more natural to work with handles the same way pointers are handled in C/C++? The last script would then look like this:


Test1@ foo() {
   Test1 t;
   Test1@ t2;
   t2 = @t; // since t2 is a handle (pointer)
   return t2;
}

Of course, we'd need a dereference operator: *t2 = t;

bozho

122

Author

April 27, 2005 04:54 AM

Ok, I should've read the overview a bit more carefully :)

I forgot to register constructor/destructor behaviour...

WitchLord

4,838

April 27, 2005 09:12 AM

I assume that everything works ok now.

I chose to do the syntax for the handles as I did since I think it is more consistent. It was a consious choice to go against the syntax of pointers in C++. Basically an object handle behaves the exact same way as the real object until you explicitly tell the compiler you wish to do a handle operation. This means that:

obj o;obj@ h;h = @o;

Would try to assign the handle of o to the object that h refers to.

Also, with this way of working with the handles, there is no need for a dereferencing operator (*), not the indirect member access operator (->).

Still, I'm currently making the compiler do implicit conversion to handles where it doesn't lead to ambiguities. For example:

@h = @o;h = @o;@h = o;

All these three statements will work, and will have the exact same effect.

Passing parameters by handle will be equally easy. No longer will there be a need to add the @ before the argument to pass it's handle, the compiler will implicitly do it for you.

I will have this completed for 2.2.0 WIP 2.

Regards,
Andreas

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Handles as return values

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🎉 Celebrating 25 Years of GameDev.net! 🎉

Handles as return values

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