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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