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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