Take an example that already exists in d8.cc [0], the v8 js global function, `read( fn )` [1], which reads file named in `fn`, converts the buffer to a v8/js string [2] and returns that to the caller [3][4]. So the "magic" is in the `args.GetReturnValue().Set(source);` [4] line. The `const v8::FunctionCallbackInfo<v8::Value>& args` stack variable (and the return from the C++ function) is the interface between your code and the v8 runtime.
If `source` in [4] was some other JS type, say, `v8::Integer`, `v8::Number`, or `v8::Value`, then setting the return value is how you "dynamically set the type" (JS is dynamic typed language) from C++ (a statically typed language). It is not necessary to statically declare what your intention is for the return value, nor are you required to return only one type for any given input. [0] https://github.com/v8/v8/blob/master/src/d8.cc [1] https://github.com/v8/v8/blob/master/src/d8.cc#L545 [2] https://github.com/v8/v8/blob/master/src/d8.cc#L1189 [3] https://github.com/v8/v8/blob/master/src/d8.cc#L551 [4] https://github.com/v8/v8/blob/master/src/d8.cc#L556 On Fri, Sep 25, 2015 at 5:37 AM, Abhinav Jangda <[email protected]> wrote: > Hello Everyone, > > I am doing some changes in d8.cc as needed by my project. For this I need to > add and register a C++ function which will be called in Javascript source. > This C++ function must return an integer. Here is my function (in v8 > namespace) > > Local<Value> test (const FunctionCallbackInfo<Value>& args) > { > return args[0]; > } > > > And Here is how I am registering it in CreateGlobalTemplate function of > Shell. > Local<ObjectTemplate> Shell::CreateGlobalTemplate(Isolate* isolate) { > Local<ObjectTemplate> global_template = ObjectTemplate::New(isolate); > global_template->Set(String::NewFromUtf8 (isolate, "test", > NewStringType::kNormal).ToLocalChecked(), > FunctionTemplate::New (isolate, test)); > > > When I am making d8 I get the following errors > > CXX(target) /home/abhi/ssl/v/v8/out/ia32.release/obj.target/d8/src/d8.o > ../src/d8.cc: In static member function ‘static > v8::Local<v8::ObjectTemplate> > v8::Shell::CreateGlobalTemplate(v8::Isolate*)’: > ../src/d8.cc:1059:39: error: no matching function for call to > ‘v8::FunctionTemplate::New(v8::Isolate*&, v8::Local<v8::Value> (&)(const > v8::FunctionCallbackInfo<v8::Value>&))’ > FunctionTemplate::New (isolate, test)); > ^ > ../src/d8.cc:1059:39: note: candidate is: > In file included from .././src/v8.h:29:0, > from .././src/gdb-jit.h:8, > from ../src/d8.cc:30: > .././include/v8.h:4350:34: note: static v8::Local<v8::FunctionTemplate> > v8::FunctionTemplate::New(v8::Isolate*, v8::FunctionCallback, > v8::Local<v8::Value>, v8::Local<v8::Signature>, int) <near match> > static Local<FunctionTemplate> New( > ^ > .././include/v8.h:4350:34: note: no known conversion for argument 2 from > ‘v8::Local<v8::Value>(const v8::FunctionCallbackInfo<v8::Value>&)’ to > ‘v8::FunctionCallback {aka void (*)(const > v8::FunctionCallbackInfo<v8::Value>&)}’ > > > Can anyone please tell me what should be the function declaration if I need > to return a value. Any help will be highly appreciated. > > Thank You, > Abhinav > > > -- > -- > v8-users mailing list > [email protected] > http://groups.google.com/group/v8-users > --- > You received this message because you are subscribed to the Google Groups > "v8-users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. -- -- v8-users mailing list [email protected] http://groups.google.com/group/v8-users --- You received this message because you are subscribed to the Google Groups "v8-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
