I tried to ship WebAssembly feature in v8 7.2 for my Android Project. I
have successfully imported v8 as a static library. But I came across an
issue that WebAssembly didn't call either then nor catch callback. Here is
my code below:
std::unique_ptr<v8::Platform> platform;
v8::Isolate *isolate;
v8::Persistent<v8::Context> persistentContext;
void runMain();
void runScript();
void _log(const v8::FunctionCallbackInfo<v8::Value>& info) {
v8::String::Utf8Value utf(isolate, info[0].As<v8::String>());
__android_log_print(ANDROID_LOG_DEBUG, "V8Native", "%s",*utf);
}
void JNICALL
Java_com_hustunique_v8demoapplication_MainActivity_initV8(JNIEnv *env,
jobject /* this */) {
// Initialize V8.
v8::V8::InitializeICU();
platform = v8::platform::NewDefaultPlatform();
v8::V8::InitializePlatform(&(*platform.get()));
v8::V8::Initialize();
runMain();
}
void runMain() {
// Create a new Isolate and make it the current one.
v8::Isolate::CreateParams create_params;
create_params.array_buffer_allocator =
v8::ArrayBuffer::Allocator::NewDefaultAllocator();
isolate = v8::Isolate::New(create_params);
// isolate->Enter();
v8::Isolate::Scope isolate_scope(isolate);
v8::HandleScope scope(isolate);
auto global_template = v8::ObjectTemplate::New(isolate);
global_template->Set(v8::String::NewFromUtf8(isolate, "log"),
v8::FunctionTemplate::New(isolate, _log)); // set log function here, as
it is used in my sample javascript code
// Enter the context for compiling and running the sample script.
v8::Local<v8::Context> context = v8::Context::New(isolate, nullptr,
global_template);
persistentContext.Reset(isolate, context);
// Run the script to get the result.
runScript();
}
void runScript() {
// sample wasm javascript code here.
const char *csource = R"(
WebAssembly.instantiate(new
Uint8Array([0,97,115,109,1,0,0,0,1,8,2,96,1,127,0,96,0,0,2,8,1,2,106,
115,1,95,0,0,3,2,1,1,8,1,1,10,9,1,7,0,65,185,10,16,0,11]),
{js:{_:console.log('Called from WebAssembly Hello
world')}}).then(function(obj) {
log('Called with instance ' + obj);
}).catch(function(err) {
log('Called with error ' + err);
});
)"; // should call my Hello World log and trigger the error or return the
instance successfully
v8::HandleScope handle_scope(isolate);
auto ctx = persistentContext.Get(isolate);
v8::Context::Scope context_scope(ctx);
v8::TryCatch try_catch(isolate);
v8::Local<v8::String> source = v8::String::NewFromUtf8(isolate, csource,
v8::NewStringType::kNormal).ToLocalChecked();
v8::Local<v8::Script> script =
v8::Script::Compile(ctx, source).ToLocalChecked();
v8::Local<v8::Value> result;
if (!script->Run(ctx).ToLocal(&result)) {
ReportException(isolate, &try_catch); // report exception, ignore the
implementation here
return;
}
// Convert the result to an UTF8 string and print it.
v8::String::Utf8Value utf8(isolate, result);
__android_log_print(ANDROID_LOG_INFO, "V8Native", "%s\n", *utf8);
}
In the demo above, I got the output with Called from WebAssembly Hello world as
excepted, but I couldn't get the error message nor the instance info.
I made a simple example on the website
<https://webassembly.studio/?f=kwaxhg1bkbs> compared with my demo above,
here is the output in the website, which can be reproduced easily I think:
Called from WebAssembly Hello world
>
> Called with error LinkError: WebAssembly.instantiate(): Import #0
> module="js" function="_" error: function import requires a callable
>
It seems that in my demo, neither resolve nor reject was called from
WebAssembly's returning promise. After checking the type of
v8::Local<v8::Value>
result in runScript method, v8 runtime confirms that it is a promise object.
I have tried several things here but none of them works:
1. 1. call v8::Isolate::RunMicroTasks(). Nothing happened
2. 2. cast result to v8::Local<v8::Promise> at the end of runScript method,
then run with:
3.
4. auto resolver = v8::Resolver::New(context)->toLocalChecked();
while (promise->State() == v8::PromiseState::kPending) {
isolate->RunMicroTasks();
}
if (promise->State() == v8::PromiseState::kFullfilled) {
resolver->Resolve(context, promise->Result());
}
if (promise->State() == v8::PromiseState::kRejected) {
resolver->Reject(context, promise->Result());
}
This snippet didn't work either, besides, it stuck at the kPending status.
I searched for something like flush the promise queue, but didn't get any
solutions. What am I missing here?
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