Bugzilla

For the wasm->js calls (exits), I think that GC doesn't pose a specific problem, because the wasm caller is responsible for rooting the values.  I think I can manage to implement interpreter exits with no issue.

For js->wasm calls (entries), I had a thought: perhaps we should generate webassembly stubs -- like, stubs written in WebAssembly.  If you have:

```
(module
  (function $f (export "f") (result i32 anyref f64)
    ...))
```

Then you would generate the equivalent of:

```
(module
  (import "env" "void-to-i32-anyref-f64" $target
    (func $target (result i32 anyref f64)))
  (import "env" "make-array"
    (func $make-array (param i32) (result anyref)))
  (import "env" "array-set-i32"
    (func $array-set-i32 (param i32 anyref i32)))
  (import "env" "array-set-f64"
    (func $array-set-f64 (param f64 anyref i32)))
  (import "env" "array-set-anyref"
    (func $array-set-anyref (param anyref anyref i32)))
  (function export "void-to-i32-anyref-f64-stub" (result anyref)
    (local $array anyref)
    (call $target)
    (i32.const 3)
    (call $make-array)
    (local.tee $array)
    (i32.const 0)
    (call $array-init-i32)
    (local.get $array)
    (i32.const 1)
    (call $array-init-anyref)
    (local.get $array)
    (i32.const 2)
    (call $array-init-f64)
    (local.get $array)))
```

and instantiate the stub module with the target function, as well as with the helpers.

For the wasm->js calls (exits), I think that GC doesn't pose a specific problem, because the wasm caller is responsible for rooting the values.  I think I can manage to implement interpreter exits with no issue.

For js->wasm calls (entries), I had a thought: perhaps we should generate webassembly stubs -- like, stubs written in WebAssembly.  If you have:

```
(module
  (function $f (export "f") (result i32 anyref f64)
    ...))
```

Then you would generate the equivalent of:

```
(module
  (import "env" "void-to-i32-anyref-f64" $target
    (func $target (result i32 anyref f64)))
  (import "env" "make-array"
    (func $make-array (param i32) (result anyref)))
  (import "env" "array-set-i32"
    (func $array-set-i32 (param i32 anyref i32)))
  (import "env" "array-set-f64"
    (func $array-set-f64 (param f64 anyref i32)))
  (import "env" "array-set-anyref"
    (func $array-set-anyref (param anyref anyref i32)))
  (function export "void-to-i32-anyref-f64-stub" (result anyref)
    (local $array anyref)
    (call $target)
    (i32.const 3)
    (call $make-array)
    (local.tee $array)
    (i32.const 0)
    (call $array-set-i32)
    (local.get $array)
    (i32.const 1)
    (call $array-set-anyref)
    (local.get $array)
    (i32.const 2)
    (call $array-set-f64)
    (local.get $array)))
```

and instantiate the stub module with the target function, as well as with the helpers.

For the wasm->js calls (exits), I think that GC doesn't pose a specific problem, because the wasm caller is responsible for rooting the values.  I think I can manage to implement interpreter exits with no issue.

For js->wasm calls (entries), I had a thought: perhaps we should generate webassembly stubs -- like, stubs written in WebAssembly.  If you have:

```
(module
  (function $f (export "f") (result i32 anyref f64)
    ...))
```

Then you would generate the equivalent of:

```
(module
  (import "env" "void-to-i32-anyref-f64" $target
    (func $target (result i32 anyref f64)))
  (import "env" "make-array"
    (func $make-array (param i32) (result anyref)))
  (import "env" "array-set-i32"
    (func $array-set-i32 (param i32 anyref i32)))
  (import "env" "array-set-f64"
    (func $array-set-f64 (param f64 anyref i32)))
  (import "env" "array-set-anyref"
    (func $array-set-anyref (param anyref anyref i32)))
  (function export "void-to-i32-anyref-f64-stub" (result anyref)
    (local $array anyref)
    (call $target)
    (i32.const 3)
    (call $make-array)
    (local.get $array)
    (i32.const 2)
    (call $array-set-f64)
    (local.get $array)
    (i32.const 1)
    (call $array-set-anyref)
    (local.tee $array)
    (i32.const 0)
    (call $array-set-i32)
    (local.get $array)))
```

and instantiate the stub module with the target function, as well as with the helpers.  *edit: updated order of results*