Webasm: null pointer passed to rust

#1

I am migrating a legacy JS code to Rust+WebAssembly, replace one part at a time and running the original tests (that use QUnit). The code is rather large, so I cannot post it, and I was not able to make a

I am getting a strange bug with some structs. Briefly, everything works in the browser until I get an error out of the blue "null pointer passed to rust". (All methods use &self, the struct only contains some f64 inside)

It seems that it happens when a container holding a "Rust object" is deleted, as if something is not being deallocated in the right order. I am having a hard time chasing this bug. Any idea how to approach this bug or what the source might be?

#2

A quick follow up. There is an instance of a Rust object inside a JS object. A function that is periodically called using a timer calls a method of the JS object which in turn tries to access a property of the rust object. Everything works until that part of the program finishes, objects gets destroyed, ptr becomes 0 for the rust object and I get a null pointer passed to rust. Importantly, this does not happen when the original pure JS object is used.

It seems that things are getting GC in the wrong order.

#3

If you haven't tried it already, logging via console.log in several places (the timer, a Drop implementation for the Rust struct, etc.) might help determine exactly when the struct is being destroyed.