dart2wasm imports strings as globals for which JavaScript engines would
provide the respective values. The standalone target needs to support
all WebAssembly runtimes, so it can't rely on this mechanism.
Instead, this imports functions to convert a WebAssembly arrays of char
codes or ASCII bytes into a string. For now, these functions have to
return JS strings since the rest of the SDK relies on that. In the
future, embedders would be able to return any string implementation as
an externref.
Because calling host functions is invalid in constant contexts, string
constants can't be regular globals. For now, this uses the default
non-eager constant implementation with one initialization function per
string constant. Eventually, we should probably initialize these
strings in a WASM start function instead.
TEST=pkg/dart2wasm/test/standalone_test.dart
Change-Id: I93b7c3846fbe99daa8ffa31e452f62672b61ce4b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/495020
Reviewed-by: Nate Biggs <natebiggs@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
Commit-Queue: Nate Biggs <natebiggs@google.com>
Simon Binder
03fd5927a4