src: port coverage serialization to C++

This patch moves the serialization of coverage profiles into
C++. With this we no longer need to patch `process.reallyExit`
and hook into the exit events, but instead hook into relevant
places in C++ which are safe from user manipulation. This also
makes the code easier to reuse for other types of profiles.

lib/internal/bootstrap/pre_execution.js

@@ -110,20 +110,10 @@ function setupWarningHandler() {
 // Setup User-facing NODE_V8_COVERAGE environment variable that writes
 // ScriptCoverage to a specified file.
 function setupCoverageHooks(dir) {
-  const originalReallyExit = process.reallyExit;
   const cwd = require('internal/process/execution').tryGetCwd();
   const { resolve } = require('path');
   const coverageDirectory = resolve(cwd, dir);
-  const {
-    writeCoverage,
-    setCoverageDirectory
-  } = require('internal/profiler');
-  setCoverageDirectory(coverageDirectory);
-  process.on('exit', writeCoverage);
-  process.reallyExit = (code) => {
-    writeCoverage();
-    originalReallyExit(code);
-  };
+  internalBinding('profiler').setCoverageDirectory(coverageDirectory);
   return coverageDirectory;
 }
 

lib/internal/process/per_thread.js

@@ -157,10 +157,6 @@ function wrapProcessMethods(binding) {
 
   function kill(pid, sig) {
     var err;
-    if (process.env.NODE_V8_COVERAGE) {
-      const { writeCoverage } = require('internal/profiler');
-      writeCoverage();
-    }
 
     // eslint-disable-next-line eqeqeq
     if (pid != (pid | 0)) {

node.gyp

@@ -169,7 +169,6 @@
       'lib/internal/process/worker_thread_only.js',
       'lib/internal/process/report.js',
       'lib/internal/process/task_queues.js',
-      'lib/internal/profiler.js',
       'lib/internal/querystring.js',
       'lib/internal/readline.js',
       'lib/internal/repl.js',

src/env-inl.h

@@ -638,6 +638,26 @@ inline const std::vector<std::string>& Environment::exec_argv() {
   return exec_argv_;
 }
 
+#if HAVE_INSPECTOR
+inline void Environment::set_coverage_directory(const char* dir) {
+  coverage_directory_ = std::string(dir);
+}
+
+inline void Environment::set_coverage_connection(
+    std::unique_ptr<profiler::V8CoverageConnection> connection) {
+  CHECK_NULL(coverage_connection_);
+  std::swap(coverage_connection_, connection);
+}
+
+inline profiler::V8CoverageConnection* Environment::coverage_connection() {
+  return coverage_connection_.get();
+}
+
+inline const std::string& Environment::coverage_directory() const {
+  return coverage_directory_;
+}
+#endif  // HAVE_INSPECTOR
+
 inline std::shared_ptr<HostPort> Environment::inspector_host_port() {
   return inspector_host_port_;
 }

src/env.cc

@@ -715,7 +715,6 @@ Local<Value> Environment::GetNow() {
     return Number::New(isolate(), static_cast<double>(now));
 }
 
-
 void Environment::set_debug_categories(const std::string& cats, bool enabled) {
   std::string debug_categories = cats;
   while (!debug_categories.empty()) {

src/env.h

@@ -27,6 +27,7 @@
 #include "aliased_buffer.h"
 #if HAVE_INSPECTOR
 #include "inspector_agent.h"
+#include "inspector_profiler.h"
 #endif
 #include "handle_wrap.h"
 #include "node.h"
@@ -67,6 +68,12 @@ namespace tracing {
 class AgentWriterHandle;
 }
 
+#if HAVE_INSPECTOR
+namespace profiler {
+class V8CoverageConnection;
+}  // namespace profiler
+#endif  // HAVE_INSPECTOR
+
 namespace worker {
 class Worker;
 }
@@ -366,7 +373,6 @@ constexpr size_t kFsStatsBufferLength = kFsStatsFieldsNumber * 2;
   V(async_hooks_init_function, v8::Function)                                   \
   V(async_hooks_promise_resolve_function, v8::Function)                        \
   V(buffer_prototype_object, v8::Object)                                       \
-  V(coverage_connection, v8::Object)                                           \
   V(crypto_key_object_constructor, v8::Function)                               \
   V(domain_callback, v8::Function)                                             \
   V(domexception_function, v8::Function)                                       \
@@ -390,7 +396,6 @@ constexpr size_t kFsStatsBufferLength = kFsStatsFieldsNumber * 2;
   V(inspector_console_extension_installer, v8::Function)                       \
   V(message_port, v8::Object)                                                  \
   V(native_module_require, v8::Function)                                       \
-  V(on_coverage_message_function, v8::Function)                                \
   V(performance_entry_callback, v8::Function)                                  \
   V(performance_entry_template, v8::Function)                                  \
   V(process_object, v8::Object)                                                \
@@ -1116,6 +1121,15 @@ class Environment : public MemoryRetainer {
 
   inline AsyncRequest* thread_stopper() { return &thread_stopper_; }
 
+#if HAVE_INSPECTOR
+  void set_coverage_connection(
+      std::unique_ptr<profiler::V8CoverageConnection> connection);
+  profiler::V8CoverageConnection* coverage_connection();
+
+  inline void set_coverage_directory(const char* directory);
+  inline const std::string& coverage_directory() const;
+#endif  // HAVE_INSPECTOR
+
  private:
   inline void CreateImmediate(native_immediate_callback cb,
                               void* data,
@@ -1146,6 +1160,11 @@ class Environment : public MemoryRetainer {
   size_t async_callback_scope_depth_ = 0;
   std::vector<double> destroy_async_id_list_;
 
+#if HAVE_INSPECTOR
+  std::unique_ptr<profiler::V8CoverageConnection> coverage_connection_;
+  std::string coverage_directory_;
+#endif  // HAVE_INSPECTOR
+
   std::shared_ptr<EnvironmentOptions> options_;
   // options_ contains debug options parsed from CLI arguments,
   // while inspector_host_port_ stores the actual inspector host

src/inspector/node_inspector.gypi

@@ -45,6 +45,7 @@
     '../../src/inspector_io.cc',
     '../../src/inspector_agent.h',
     '../../src/inspector_io.h',
+    '../../src/inspector_profiler.h',
     '../../src/inspector_profiler.cc',
     '../../src/inspector_js_api.cc',
     '../../src/inspector_socket.cc',