You don't need to build the Dart SDK to run dart2wasm, as long as you have a Dart SDK installed and have the [Dart SDK repository checked out](https://github.com/dart-lang/sdk/wiki/Building#getting-the-source). NB: the SDK must be checked out using depot tools and not just cloned from this repo.
| `--shared-memory-max-pages`*pagecount* | | Max size of the imported memory buffer. If `--shared-import-memory` is specified, this must also be specified.
To import a function, declare it as a global, external function and mark it with a `wasm:import` pragma indicating the imported name (which must be two identifiers separated by a dot):
```dart
@pragma("wasm:import", "foo.bar")
external void fooBar(Object object);
```
which will call `foo.bar` on the host side:
```javascript
var foo = {
bar: function(object) { /* implementation here */ }
};
```
To export a function, mark it with a `wasm:export` pragma:
```dart
@pragma("wasm:export")
void foo(double x) { /* implementation here */ }
@pragma("wasm:export", "baz")
void bar(double x) { /* implementation here */ }
```
With the Wasm module instance in `inst`, these can be called as:
```javascript
inst.exports.foo(1);
inst.exports.baz(2);
```
### Types to use for interop
In the signatures of imported and exported functions, use the following types:
- For JS objects, use a JS interop type, e.g. `JSAny`, which translates to the Wasm `externref` type. These can be passed around and stored as opaque values on the Dart side.
- For Dart objects, use the corresponding Dart type. This will be emitted as `anyref` and automatically converted to and from the Dart type at the boundary.
