No memory management in JLVal?

[ShuhuaGao]

For example, the following constructor allocates a boxed Float64 on the Julia side, but we need to keep it alive:
https://github.com/HyperSphereStudio/JULIA.Net/blob/3bd7bf222bea19d7e82b899888a4237ef16e1c75/src/csharp/JLVal.cs#L23

In the memory management documentation, there is

Typically, Julia objects are freed by a garbage collector (GC), but the GC does not automatically know that we are holding a reference to a Julia value from C. This means the GC can free objects out from under you, rendering pointers invalid.

My understanding is that, even if you are still using the object in C#, Julia is unaware of it. Consequently, Julia may deallocate it without your control and the IntPtr stored inside the JLVal instance becomes invalid.

Of course, all other data objects like a Julia array need such proper memory management.

[HyperSphereStudio]

Julia provides a built in solution to this problem that can be acessed via Julia.GCPUSH & Julia.GCPOP.

When you push the object using this method, it will preserve its references until it is popped. However this requires the following structure of code:

Julia.GCPUSH(obj);
//Code
Julia.GCPOP();

It is kind of bulky to use which is why I provided an easier interface:

Say we have have a C# int we want to box. You would do

var i = new JLVAL(5);

The GC has no idea we want to keep it alive.

In order to keep it alive, do the following:

var handle = i.Pin();

The handle has a destructor that will auto free itself when it goes out of scope or you can free it earlier.

I can also make an object stay pinned even if the handle goes out of the scope but that is unsafe and I dont have an interface for that at the moment. It is just a possibility.

My next update reworks this feature to be more efficient

[ShuhuaGao]

Sorry, I did not notice the Pin method. I tried automatic memory management previously (but unfortunately lost the code now). Is it better to do something like Pin the object in its constructor? The user is not required to do it manually. That is, the Dispose pattern in C#.

[HyperSphereStudio]

The problem is that the JLVAL is a structure and cannot have a destructor

I could make a class version of the JLVAL but that would cause a massive perfomance hit