Is there any way to get the callback of the AssemblyScipt object being destructor?

[LukiYLS]

My requirement is this, AssemblyScirpt compiled by Wasm will bridge to the new C++ objects, so I need to notify C++ to release the objects created by C++ when the AssemblyScirpt object is released.

[LukiYLS]

As mentioned by #383

[dcodeIO]

There is a rough mechanism in place that is meant as the internal stepping stone to eventually implement FinalizationRegistry. While unsafe and not yet convenient, a global __finalize function can be provided that is called with an object's pointer when it is collected. Here's the respective test case to get an idea how implementing it manually for now could look:

assemblyscript/tests/compiler/rt/finalize.ts

Lines 1 to 13 in 454529d

	var expect: usize = 0;
	var ran = false;
	// @ts-ignore
	@global function __finalize(ptr: usize): void {
	assert(ptr == expect);
	ran = true;
	}
	class Ref {}
	expect = changetype<usize>(new Ref());
	__collect();
	assert(ran);

[LukiYLS]

There is a rough mechanism in place that is meant as the internal stepping stone to eventually implement FinalizationRegistry. While unsafe and not yet convenient, a global __finalize function can be provided that is called with an object's pointer when it is collected. Here's the respective test case to get an idea how implementing it manually for now could look:

assemblyscript/tests/compiler/rt/finalize.ts

Lines 1 to 13 in 454529d

	var expect: usize = 0;
	var ran = false;
	// @ts-ignore
	@global function __finalize(ptr: usize): void {
	assert(ptr == expect);
	ran = true;
	}
	class Ref {}
	expect = changetype<usize>(new Ref());
	__collect();
	assert(ran);

I found a problem, the ptr changes every time after resize

how to solve this problem?

[dcodeIO]

From the mention of "resize" I assume that these are the backing buffers of the respective arrays. When resized, a new backing buffer is allocated and the old one is left for the GC. The array object itself remains if it is still referenced, it's just the buffers.

[LukiYLS]

After memory.grow, I can find the object through changetype in the __finalize function, and then call the object's destructor function

// @ts-ignore 
 @global function __finalize(ptr: usize): void { 
   let object = changetype<Object>(ptr)
   object.finalize()
 } 

In this way, I find that sometimes an exception is thrown

[dcodeIO]

Not every ptr free'd is an Object. Looking at the class id might help:

import { OBJECT, TOTAL_OVERHEAD } from "rt/common";

@global function __finalize(ptr: usize): void { 
  var obj = changetype<OBJECT>(ptr - TOTAL_OVERHEAD)
  if (obj.rtId == idof<Object>()) {
    ...
  }
}

[github-actions]

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