Hi Immanuel,
Seems the messages that come from V8 instance are cut off, maybe because of
sockpp. They are also not complete, there should be a response for each
request but in your case there are only 3 responses.
The logic to wait the V8 instance should be done in `runMessageLoopOnPause`
method.
In my example, I'm calling a Boost method to get a new message from CDT.
So, until there is a new message the V8 instance would wait.
On Friday, August 21, 2020 at 10:10:15 AM UTC+2, Immanuel Haffner wrote:
>
> Here is what the network messages in CDT look like:
>
> [image: cdt_network.png]
>
> I guess the execution doesn't wait for CDT. My WebAssembly function is
> executed right away and the connection is closed.
> How do I make my `v8::Isolate` instance wait for commands from CDT?
>
> Am Donnerstag, 20. August 2020 22:04:15 UTC+2 schrieb Elmi Ahmadov:
>>
>> Seems you've managed to make a communication between CDT and your server.
>> I also checked `sockpp` which does not support websocket protocol out of
>> box. Probably, you should implement all required parts yourself.
>>
>> I'm using Google Groups old UI which allows me to add image to the post,
>> it's next to the `Link`:
>>
>> [image: Screenshot from 2020-08-20 21-58-22.png]
>>
>>
>> But I also couldn't find it in the new UI, if you're using the new UI you
>> can switch back to the old UI, click settings (gear icon) at the top of the
>> page and click "Return to classic Google Groups", then you can attach an
>> image.
>>
>> On Thursday, August 20, 2020 at 1:54:43 PM UTC+2, Immanuel Haffner wrote:
>>>
>>> Hi Elmi,
>>>
>>> thank you for checking. My biggest mistage was to write directly to a
>>> socket rather than use the WebSocket protocol. After doing so, i now see
>>> some messages in CDT. However, there are only 8 green and one last red
>>> message. I suppose the last message wasn't sent in full. The second last
>>> message was "Runtime.runIfWaitingForDebugger". There is no
>>> `Debugger.scriptExecuted` message, though.
>>>
>>> Checking V8 code I couldn't find `schedulePauseOnNextStatement`, who is
>>> invoking that?
>>>
>>> How do I attach an image to a Google Groups post?
>>>
>>> Elmi Ahmadov schrieb am Donnerstag, 20. August 2020 um 11:59:17 UTC+2:
>>>
>>>> I checked your code and you're missing
>>>> `runMessageLoopOnMessage`/`quitMessageLoopOnPause` and
>>>> `schedulePauseOnNextStatement` (this could be redundant), but in general,
>>>> these methods are necessary. in `runMessageLoopOnPause` method, you should
>>>> block the thread until there is a new message from CDT, in case there is a
>>>> breakpoint and CDT requires user action.
>>>> Maybe your code does not wait for a user action and execution is done
>>>> very quickly.
>>>>
>>>> Could you please post WS messages from CDT Network monitor tab? There
>>>> should be such response messages: *`Debugger.scriptExecuted`* and
>>>> *`Debugger.paused`*.
>>>> And one important thing is you have to execute your code after you got
>>>> a *`**Runtime.runIfWaitingForDebugger` *message from CDT.
>>>>
>>>>
>>>> On Thursday, August 20, 2020 at 10:36:30 AM UTC+2 haffner....@gmail.com
>>>> wrote:
>>>>
>>>>> Ok, I figured the cause for the segmentation violation. I must dispose
>>>>> of the inspector and the session and channel before disposing of the
>>>>> isolate. I am still left with "WebSocket disconnected". The CDT Network
>>>>> monitor says "Connection closed before receiving a handshake response".
>>>>> Maybe I did something wrong establishing a TCP connection?
>>>>>
>>>>> Immanuel Haffner schrieb am Donnerstag, 20. August 2020 um 10:07:27
>>>>> UTC+2:
>>>>>
>>>>>>
>>>>>> Hi again,
>>>>>>
>>>>>> I figured that the `chome-devtools://` part doesn't work in
>>>>>> Chromium. Using `devtools://` instead works. However, I get a
>>>>>> segmentation
>>>>>> violation.
>>>>>>
>>>>>> Here is the code I wrote to connect the V8 inspector:
>>>>>>
>>>>>> struct ServerChannel : v8_inspector::V8Inspector::Channel
>>>>>> {
>>>>>> private:
>>>>>> sockpp::tcp_socket *socket_;
>>>>>>
>>>>>> public:
>>>>>> ServerChannel() { }
>>>>>>
>>>>>> void set_socket(sockpp::tcp_socket *socket) { socket_ =
>>>>>> socket; }
>>>>>>
>>>>>> private:
>>>>>> void sendResponse(int,
>>>>>> std::unique_ptr<v8_inspector::StringBuffer> message) override {
>>>>>> auto v8_sv = message->string();
>>>>>> socket_->write_n(v8_sv.characters8(), v8_sv.length());
>>>>>> }
>>>>>>
>>>>>> void
>>>>>> sendNotification(std::unique_ptr<v8_inspector::StringBuffer> message)
>>>>>> override {
>>>>>> auto v8_sv = message->string();
>>>>>> socket_->write_n(v8_sv.characters8(), v8_sv.length());
>>>>>> }
>>>>>>
>>>>>> void flushProtocolNotifications() override { }
>>>>>> };
>>>>>>
>>>>>> struct MyV8InspectorClient : v8_inspector::V8InspectorClient
>>>>>> {
>>>>>> private:
>>>>>> sockpp::tcp_acceptor acceptor_;
>>>>>> std::unique_ptr<ServerChannel> channel_;
>>>>>> std::unique_ptr<v8_inspector::V8Inspector> inspector_;
>>>>>> std::unique_ptr<v8_inspector::V8InspectorSession> session_;
>>>>>> int16_t port_;
>>>>>>
>>>>>> public:
>>>>>> MyV8InspectorClient(int16_t port, v8::Isolate *isolate)
>>>>>> : acceptor_(port)
>>>>>> , port_(port)
>>>>>> {
>>>>>> if (not acceptor_)
>>>>>> throw std::runtime_error("failed to initalize TCP
>>>>>> server");
>>>>>>
>>>>>> channel_ = std::make_unique<ServerChannel>();
>>>>>> inspector_ = v8_inspector::V8Inspector::create(isolate,
>>>>>> this);
>>>>>>
>>>>>> std::string state("mutable");
>>>>>> v8_inspector::StringView sv(reinterpret_cast<const
>>>>>> uint8_t*>(state.c_str()), state.length());
>>>>>> session_ = inspector_->connect(
>>>>>> /* contextGroupId= */ 1,
>>>>>> /* channel= */ channel_.get(),
>>>>>> /* state= */ sv
>>>>>> );
>>>>>> }
>>>>>>
>>>>>> MyV8InspectorClient(const MyV8InspectorClient&) = delete;
>>>>>> MyV8InspectorClient(MyV8InspectorClient&&) = default;
>>>>>>
>>>>>> ~MyV8InspectorClient() {
>>>>>> session_.reset();
>>>>>> inspector_.reset();
>>>>>> channel_.reset();
>>>>>> }
>>>>>>
>>>>>> void onMessage(std::string_view sv) {
>>>>>> v8_inspector::StringView msg(reinterpret_cast<const
>>>>>> uint8_t*>(sv.data()), sv.length());
>>>>>> session_->dispatchProtocolMessage(msg);
>>>>>> }
>>>>>>
>>>>>> void launch() {
>>>>>> std::cout << "WebSocket based Inspector Agent started.\n"
>>>>>> << "Open the following link in your
>>>>>> Chrome/Chromium browser:\n\n\t"
>>>>>> <<
>>>>>> "devtools://devtools/bundled/inspector.html?experiments=true&v8only=true&ws=
>>>>>> 127.0.0.1:" << port_
>>>>>> << '\n' << std::endl;
>>>>>>
>>>>>> auto socket =
>>>>>> std::make_unique<sockpp::tcp_socket>(acceptor_.accept());
>>>>>> if (not *socket)
>>>>>> throw std::runtime_error("failed to establish
>>>>>> connection to TCP client");
>>>>>> channel_->set_socket(socket.get());
>>>>>>
>>>>>> auto thread =
>>>>>> std::thread([this](std::unique_ptr<sockpp::tcp_socket> socket) {
>>>>>> uint8_t buf[512];
>>>>>> std::vector<uint8_t> msg;
>>>>>> msg.reserve(512);
>>>>>> std::size_t n;
>>>>>>
>>>>>> for (;;) {
>>>>>> std::cerr << "receiving bytes..." << std::endl;
>>>>>> while ((n = socket->read_n(buf, ARR_SIZE(buf))) >
>>>>>> 0)
>>>>>> msg.insert(msg.end(), buf, buf + n); //
>>>>>> append recently read bytes to msg
>>>>>> if (not msg.empty()) {
>>>>>> std::cerr << "the received message is " <<
>>>>>> msg.size() << " bytes" << std::endl;
>>>>>> std::string_view
>>>>>> sv(reinterpret_cast<char*>(&msg[0]), msg.size());
>>>>>> this->onMessage(sv);
>>>>>> msg.clear();
>>>>>> }
>>>>>> std::this_thread::yield();
>>>>>> }
>>>>>> },
>>>>>> std::move(socket));
>>>>>> thread.detach();
>>>>>> }
>>>>>> };
>>>>>>
>>>>>> It's mostly taken from your example and condensed into a single
>>>>>> class. Instead of boost, I use sockpp for socket programming.i
>>>>>>
>>>>>> After creating a `v8::Isolate`, I do the following:
>>>>>>
>>>>>> inspector_ = std::make_unique<MyV8InspectorClient>(cdt_port,
>>>>>> isolate_);
>>>>>> inspector_->launch();
>>>>>>
>>>>>> However, when connecting to the inspector it says "WebSocket
>>>>>> disconnected" and the application crashes with a segmentation violation:
>>>>>>
>>>>>> AddressSanitizer:DEADLYSIGNAL
>>>>>> =================================================================
>>>>>> ==13072==ERROR: AddressSanitizer: SEGV on unknown address
>>>>>> 0x1d580000a838 (pc 0x561c8173e6b4 bp 0x7fff75fa6430 sp 0x7fff75fa6430 T0)
>>>>>> ==13072==The signal is caused by a READ memory access.
>>>>>> #0 0x561c8173e6b4 in v8::Isolate::GetHeapProfiler()
>>>>>> ../../../../../third-party/v8/v8/src/execution/isolate.h:1059:48
>>>>>> #1 0x561c82d3fd77 in
>>>>>> v8_inspector::V8HeapProfilerAgentImpl::stopTrackingHeapObjectsInternal()
>>>>>> ../../../../../third-party/v8/v8/src/inspector/v8-heap-profiler-agent-impl.cc:316:14
>>>>>> #2 0x561c82d3feb9 in
>>>>>> v8_inspector::V8HeapProfilerAgentImpl::disable()
>>>>>> ../../../../../third-party/v8/v8/src/inspector/v8-heap-profiler-agent-impl.cc:204:3
>>>>>> #3 0x561c8208f095 in
>>>>>> v8_inspector::V8InspectorSessionImpl::~V8InspectorSessionImpl()
>>>>>> ../../../../../third-party/v8/v8/src/inspector/v8-inspector-session-impl.cc:151:24
>>>>>> #4 0x561c8208f33d in
>>>>>> v8_inspector::V8InspectorSessionImpl::~V8InspectorSessionImpl()
>>>>>> ../../../../../third-party/v8/v8/src/inspector/v8-inspector-session-impl.cc:147:51
>>>>>> #5 0x561c80ec9eff in
>>>>>> std::default_delete<v8_inspector::V8InspectorSession>::operator()(v8_inspector::V8InspectorSession*)
>>>>>>
>>>>>> const
>>>>>> /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../include/c++/10.1.0/bits/unique_ptr.h:84:2
>>>>>> #6 0x561c80ec9d3e in
>>>>>> std::__uniq_ptr_impl<v8_inspector::V8InspectorSession,
>>>>>> std::default_delete<v8_inspector::V8InspectorSession>
>>>>>> >::reset(v8_inspector::V8InspectorSession*)
>>>>>> /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../include/c++/10.1.0/bits/unique_ptr.h:181:4
>>>>>> #7 0x561c80eca183 in
>>>>>> std::unique_ptr<v8_inspector::V8InspectorSession,
>>>>>> std::default_delete<v8_inspector::V8InspectorSession>
>>>>>> >::reset(v8_inspector::V8InspectorSession*)
>>>>>> /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../include/c++/10.1.0/bits/unique_ptr.h:455:7
>>>>>> #8 0x561c80ec7193 in
>>>>>> db::v8_helper::MyV8InspectorClient::~MyV8InspectorClient()
>>>>>> /home/immanuel/Documents/Work/PhD/mutable/mutable/build/debug/../../src/backend/V8Platform.hpp:74:18
>>>>>> #9 0x561c80ec723b in
>>>>>> db::v8_helper::MyV8InspectorClient::~MyV8InspectorClient()
>>>>>> /home/immanuel/Documents/Work/PhD/mutable/mutable/build/debug/../../src/backend/V8Platform.hpp:73:28
>>>>>> #10 0x561c80eb361f in
>>>>>> std::default_delete<db::v8_helper::MyV8InspectorClient>::operator()(db::v8_helper::MyV8InspectorClient*)
>>>>>>
>>>>>> const
>>>>>> /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../include/c++/10.1.0/bits/unique_ptr.h:84:2
>>>>>> #11 0x561c80eaede6 in
>>>>>> std::unique_ptr<db::v8_helper::MyV8InspectorClient,
>>>>>> std::default_delete<db::v8_helper::MyV8InspectorClient> >::~unique_ptr()
>>>>>> /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../include/c++/10.1.0/bits/unique_ptr.h:360:4
>>>>>> #12 0x561c80ea6e97 in db::V8Platform::~V8Platform()
>>>>>> /home/immanuel/Documents/Work/PhD/mutable/mutable/build/debug/../../src/backend/V8Platform.cpp:221:1
>>>>>> #13 0x561c80ea6f2b in db::V8Platform::~V8Platform()
>>>>>> /home/immanuel/Documents/Work/PhD/mutable/mutable/build/debug/../../src/backend/V8Platform.cpp:218:1
>>>>>> #14 0x561c80e9ea3f in
>>>>>> std::default_delete<db::WasmPlatform>::operator()(db::WasmPlatform*)
>>>>>> const
>>>>>> /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../include/c++/10.1.0/bits/unique_ptr.h:84:2
>>>>>> #15 0x561c80e9e8f6 in std::unique_ptr<db::WasmPlatform,
>>>>>> std::default_delete<db::WasmPlatform> >::~unique_ptr()
>>>>>> /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../include/c++/10.1.0/bits/unique_ptr.h:360:4
>>>>>> #16 0x561c80e8efbd in db::WasmBackend::~WasmBackend()
>>>>>> /home/immanuel/Documents/Work/PhD/mutable/mutable/build/debug/../../src/backend/WebAssembly.hpp:110:8
>>>>>> #17 0x561c80e8efeb in db::WasmBackend::~WasmBackend()
>>>>>> /home/immanuel/Documents/Work/PhD/mutable/mutable/build/debug/../../src/backend/WebAssembly.hpp:110:8
>>>>>> #18 0x561c80ccf1ff in
>>>>>> std::default_delete<db::Backend>::operator()(db::Backend*) const
>>>>>> /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../include/c++/10.1.0/bits/unique_ptr.h:84:2
>>>>>> #19 0x561c80ca8b16 in std::unique_ptr<db::Backend,
>>>>>> std::default_delete<db::Backend> >::~unique_ptr()
>>>>>> /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../include/c++/10.1.0/bits/unique_ptr.h:360:4
>>>>>> #20 0x561c80c86dd9 in process_stream(std::istream&, char
>>>>>> const*, db::Diagnostic)
>>>>>> /home/immanuel/Documents/Work/PhD/mutable/mutable/build/debug/../../src/shell.cpp:151:13
>>>>>> #21 0x561c80c9a265 in main
>>>>>> /home/immanuel/Documents/Work/PhD/mutable/mutable/build/debug/../../src/shell.cpp:675:13
>>>>>> #22 0x7f6259a37001 in __libc_start_main
>>>>>> (/usr/lib/libc.so.6+0x27001)
>>>>>> #23 0x561c80ba722d in _start
>>>>>> (/home/immanuel/Documents/Work/PhD/mutable/mutable/build/debug/bin/shell+0x117222d)
>>>>>>
>>>>>> AddressSanitizer can not provide additional info.
>>>>>> SUMMARY: AddressSanitizer: SEGV
>>>>>> ../../../../../third-party/v8/v8/src/execution/isolate.h:1059:48 in
>>>>>> v8::Isolate::GetHeapProfiler()
>>>>>>
>>>>>> Can you spot what's going wrong? I did not override
>>>>>> `V8InspectorClientImpl::runMessageLoopOnPause` like you did. Is this
>>>>>> necessary?
>>>>>>
>>>>>> Kind regards,
>>>>>> Immanuel
>>>>>> Elmi Ahmadov schrieb am Mittwoch, 19. August 2020 um 21:40:58 UTC+2:
>>>>>>
>>>>>>> Dear Immanuel,
>>>>>>>
>>>>>>> You've got the right idea from my example code. You need a websocket
>>>>>>> to create a communication channel between V8 Inspector and CDT.
>>>>>>> The URL to debug the code is usually as follows and it works for me.
>>>>>>>
>>>>>>> devtools:
>>>>>>> //devtools/bundled/inspector.html?experiments=true&v8only=true&ws=IP:WebSocketPort
>>>>>>>
>>>>>>> Without a minimal sample code it's difficult to say what you're
>>>>>>> missing.
>>>>>>> You can also use Chrome DevTools Network Activity tab (you need to
>>>>>>> open another Inspector console, see the screenshot), just filter
>>>>>>> *WS* to see what happens between your server and CDT, which helped
>>>>>>> me a lot.
>>>>>>>
>>>>>>>
>>>>>>> [image: Screenshot from 2020-08-19 21-37-48.png]
>>>>>>>
>>>>>>> There is another Chrome built-in feature that helped me is *Protocol
>>>>>>> Monitor*, you can here how to enable it:
>>>>>>> https://chromedevtools.github.io/devtools-protocol/
>>>>>>>
>>>>>>> On Wednesday, August 19, 2020 at 4:17:00 PM UTC+2, Immanuel Haffner
>>>>>>> wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> Dear Elmi,
>>>>>>>>
>>>>>>>> thank you for your reply. I had a long look at your example. To be
>>>>>>>> honest, I find it a bit bloatet.
>>>>>>>>
>>>>>>>> Let me phrase in my own words what I have learned from your code:
>>>>>>>>
>>>>>>>> 1) I need a socket to receive messages from CDT and send responses
>>>>>>>> back to CDT.
>>>>>>>> 2) I must implement `v8_inspector::V8Inspector::Channel` to have
>>>>>>>> `sendResponse()` and `sendNotification()` send the respective message
>>>>>>>> over
>>>>>>>> the socket to CDT.
>>>>>>>> 3) I need an instance of `v8_inspector::V8InspectorClient`. I am
>>>>>>>> not sure whether I must overwrite anything from this class in a
>>>>>>>> subclass. I
>>>>>>>> think the base class is actually fine...
>>>>>>>> 4) I must use `v8_inspector::V8Inspector::create()` to create an
>>>>>>>> instance of `v8_inspector::V8Inspector`. I believe this is where all
>>>>>>>> the
>>>>>>>> inspector logic is implemented...
>>>>>>>> 5) Using the `V8Inspector` instance I create a
>>>>>>>> `v8_inspector::V8InspectorSession` by calling `connect()`. Here I must
>>>>>>>> pass
>>>>>>>> a reference to an instance of my `v8_inspector::V8Inspector::Channel`
>>>>>>>> subclass.
>>>>>>>> This was the basic setup. Now it's time to run the server loop.
>>>>>>>> 6) In a detached thread, read from the socket and pass the message
>>>>>>>> on by invoking `dispatchProtocolMessage()` on my instance
>>>>>>>> of `v8_inspector::V8InspectorSession`.
>>>>>>>>
>>>>>>>> When running my code, the TCP acceptor is set up and waiting for a
>>>>>>>> client. I visit `localhost:<PORT>` with Chromium (the
>>>>>>>> chrome-devtool://
>>>>>>>> links just won't work). Then my application executes the WebAssembly
>>>>>>>> and
>>>>>>>> the browser says the page isn't working (ERR_EMPTY_RESPONSE).
>>>>>>>>
>>>>>>>> What am I missing?
>>>>>>>> Elmi Ahmadov schrieb am Mittwoch, 19. August 2020 um 10:21:38 UTC+2:
>>>>>>>>
>>>>>>>>> Hi.
>>>>>>>>>
>>>>>>>>> I have an example project how to use V8 inspector API:
>>>>>>>>> https://github.com/ahmadov/v8_inspector_example. Hope this would
>>>>>>>>> help.
>>>>>>>>>
>>>>>>>>> Best regards
>>>>>>>>>
>>>>>>>>> On Wednesday, August 19, 2020 at 10:11:00 AM UTC+2, Immanuel
>>>>>>>>> Haffner wrote:
>>>>>>>>>>
>>>>>>>>>> Hi all,
>>>>>>>>>>
>>>>>>>>>> I followed this V8 documentation [1] to embed V8 into my
>>>>>>>>>> application. The application compiles inputs to WebAssembly modules
>>>>>>>>>> and
>>>>>>>>>> executes them in embedded V8. Now I would like to debug these
>>>>>>>>>> WebAssembly
>>>>>>>>>> modules. Searching online brought me to ChromeDevTools and the
>>>>>>>>>> v8-inspector API. I mostly followed this guide [2] to set up a
>>>>>>>>>> `V8InspectorSession` and implemented the `V8Inspector::Channel`
>>>>>>>>>> interface
>>>>>>>>>> by creating a TCP server, waiting for a connection, and then in
>>>>>>>>>> `sendResponse()` and `sendNotification()` I simply send the message
>>>>>>>>>> over
>>>>>>>>>> the TCP socket.
>>>>>>>>>>
>>>>>>>>>> To debug, I launch chromium and connect to localhost on the port
>>>>>>>>>> where the TCP server was created. Sadly, this doesn't work. The
>>>>>>>>>> `sendResponse()` and `sendNotification()` methods are never invoked.
>>>>>>>>>>
>>>>>>>>>> Can someone please point me to a tutorial or give me some
>>>>>>>>>> guidance?
>>>>>>>>>>
>>>>>>>>>> Thanks,
>>>>>>>>>> Immanuel
>>>>>>>>>>
>>>>>>>>>> [1] https://v8.dev/docs/embed
>>>>>>>>>> [2]
>>>>>>>>>> https://hyperandroid.com/2020/02/12/v8-inspector-from-an-embedder-standpoint/
>>>>>>>>>>
>>>>>>>>>
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