I'm using FunctionTemplate to create a function that has callback data, and
I want to get a callback when the function is no longer reachable from
Javascript so I can do some cleanup associated with the callback data. I'm
trying to do this with a weak reference callback, but I'm having some
trouble getting the weak callback to actually get called.
MVCE:
#include <stdlib.h>
#include <stdio.h>
#include <v8.h>
#include <libplatform/libplatform.h>
using namespace v8;
class MallocAllocator : public ArrayBuffer::Allocator {
public:
virtual void *Allocate(size_t size) {
void *data = AllocateUninitialized(size);
if (data != NULL)
memset(data, 0, size);
return data;
}
virtual void *AllocateUninitialized(size_t size) {
return malloc(size);
}
virtual void Free(void *data, size_t size) {
free(data);
}
};
void func_callback(const FunctionCallbackInfo<Value> &info) {}
void weak_callback(const WeakCallbackInfo<Persistent<String>> &info) {
Persistent<String> *handle = info.GetParameter();
printf("weak callback called with %p\n", handle);
delete handle;
}
int main() {
V8::InitializeICU();
Platform *current_platform = platform::CreateDefaultPlatform();
V8::InitializePlatform(current_platform);
V8::Initialize();
V8::SetFlagsFromString("--expose_gc", strlen("--expose_gc"));
Isolate::CreateParams params;
params.array_buffer_allocator = new MallocAllocator();
Isolate *isolate = Isolate::New(params);
HandleScope hs(isolate);
Local<Context> context = Context::New(isolate);
Local<String> key = String::NewFromUtf8(isolate, "test", NewStringType::
kNormal).ToLocalChecked();
Persistent<String> *weak_str = new Persistent<String>();
{
HandleScope hs(isolate);
Local<String> str = String::NewFromUtf8(isolate, "hi there",
NewStringType::kNormal).ToLocalChecked();
Local<FunctionTemplate> templ = FunctionTemplate::New(isolate,
func_callback, str);
weak_str->Reset(isolate, str);
weak_str->SetWeak(weak_str, weak_callback, WeakCallbackType::
kParameter);
context->Global()->Set(context,
key, templ->GetFunction(context).ToLocalChecked())
.FromJust();
}
context->Global()->Delete(context, key).FromJust();
isolate->RequestGarbageCollectionForTesting(Isolate::
GarbageCollectionType::kFullGarbageCollection);
return 0;
}
In this program, weak_callback never gets called. Anyone know why?
Thanks,
~Theodore
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