How to use memory in version 3.0

[poria-cat]

Summary

I am trying to use wasmer to run as AssemblyScript in rust, import functions is the main way to do this, but I'm stuck with memory and ptr at the moment 😭

We can use memory in version 1 and version 2 by set with LazyInit, but in new version, LazyInit was deleted. So I'm confused about how to use it in import functions.

How should I use it in the new version?

[syrusakbary]

Hi! Thanks for opening the issue.

Seeing how other projects have upgraded Wasmer might help you a bit: swc-project/swc#5456

You can also post here your code and we can help you on migrating to 3.0.

Meanwhile, here are the migration docs: https://github.com/wasmerio/wasmer/blob/master/docs/migration_to_3.0.0.md

[syrusakbary]

Basically,

You will need to move from

#[derive(wasmer::WasmerEnv, Clone)]
pub struct MyEnv {
    #[wasmer(export)]
    pub memory: wasmer::LazyInit<Memory>,
    #[wasmer(export(name = "__alloc"))]
    pub alloc_guest_memory: LazyInit<NativeFunc<u32, i32>>,
}

let my_env = MyEnv {
  memory: Default::default(),
  alloc_guest_memory: Default::default(),
};

let instance = Instance::new(&module, &imports);

To:

pub struct MyEnv {
    pub memory: Option<Memory>,
    pub alloc_guest_memory: Option<TypedFunction<i32, i32>>,
}

let mut my_env = MyEnv {
  memory: None,
  alloc_guest_memory: None,
};

let instance = Instance::new(&module, &imports);
my_env.memory = instance.exports.get_memory("memory");
my_env.alloc_guest_memory = instance.exports.get_typed_function("__alloc");

[poria-cat]

This is so great, just what I was looking for. Many thanks @syrusakbary !

[poria-cat]

Basically,

You will need to move from

#[derive(wasmer::WasmerEnv, Clone)]
pub struct MyEnv {
    #[wasmer(export)]
    pub memory: wasmer::LazyInit<Memory>,
    #[wasmer(export(name = "__alloc"))]
    pub alloc_guest_memory: LazyInit<NativeFunc<u32, i32>>,
}

let my_env = MyEnv {
  memory: Default::default(),
  alloc_guest_memory: Default::default(),
};

let instance = Instance::new(&module, &imports);

To:

pub struct MyEnv {
    pub memory: Option<Memory>,
    pub alloc_guest_memory: Option<TypedFunction<i32, i32>>,
}

let mut my_env = MyEnv {
  memory: None,
  alloc_guest_memory: None,
};

let instance = Instance::new(&module, &imports);
my_env.memory = instance.exports.get_memory("memory");
my_env.alloc_guest_memory = instance.exports.get_typed_function("__alloc");

WoW get it , this is even clearer. Thanks again 🙏🏻

I think this issue can be closed in a few days, so if anyone has a similar problem it will be easy to find a way @syrusakbary .

[syrusakbary]

I'll add my suggested code on the migration guide so it's easier to find!