Reland "[test][d8] Add d8.log.getAndStop helper"

This is a reland of 95aa697b

Original change's description:
> [test][d8] Add d8.log.getAndStop helper
>
> The new helper function allows us to write tests for log parsing
> without the need to first generating a log file. This makes it easier
> to spot errors when the log format changes.
>
> - Add d8 global variable
> - Add file_name accessor to Logger and Log classes
> - Change OS::LogFileOpenMode to w+ / wb+
> - Use separate Log::WriteLogHeader method
> - Remove unused logger_ instance variable from Log
>
> Bug: v8:10644
> Change-Id: Ifc7e35aa4e91b3f01f0847843263946e085944c3
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2387563
> Commit-Queue: Camillo Bruni <cbruni@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Reviewed-by: Sathya Gunasekaran  <gsathya@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#69715}

Bug: v8:10644

TBR=verwaest@chromium.org

Change-Id: I54741344834d88a376b74e2e3a2047e880a94624
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2396081
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Sathya Gunasekaran  <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69769}

src/base/platform/platform-posix.cc

@@ -679,9 +679,7 @@ FILE* OS::OpenTemporaryFile() {
   return tmpfile();
 }
 
-
-const char* const OS::LogFileOpenMode = "w";
-
+const char* const OS::LogFileOpenMode = "w+";
 
 void OS::Print(const char* format, ...) {
   va_list args;

src/base/platform/platform-win32.cc

@@ -603,8 +603,7 @@ FILE* OS::OpenTemporaryFile() {
 
 
 // Open log file in binary mode to avoid /n -> /r/n conversion.
-const char* const OS::LogFileOpenMode = "wb";
-
+const char* const OS::LogFileOpenMode = "wb+";
 
 // Print (debug) message to console.
 void OS::Print(const char* format, ...) {

src/d8/d8.cc

@@ -43,6 +43,7 @@
 #include "src/init/v8.h"
 #include "src/interpreter/interpreter.h"
 #include "src/logging/counters.h"
+#include "src/logging/log-utils.h"
 #include "src/objects/managed.h"
 #include "src/objects/objects-inl.h"
 #include "src/objects/objects.h"
@@ -1503,6 +1504,41 @@ void Shell::RealmSharedSet(Local<String> property, Local<Value> value,
   data->realm_shared_.Reset(isolate, value);
 }
 
+void Shell::LogGetAndStop(const v8::FunctionCallbackInfo<v8::Value>& args) {
+  Isolate* isolate = args.GetIsolate();
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  HandleScope handle_scope(isolate);
+
+  std::string file_name = i_isolate->logger()->file_name();
+  if (i::Log::IsLoggingToConsole(file_name)) {
+    Throw(isolate, "Logging to console instead of file.");
+    return;
+  }
+  if (!i_isolate->logger()->is_logging()) {
+    Throw(isolate, "Logging not enabled.");
+    return;
+  }
+
+  std::string raw_log;
+  FILE* log_file = i_isolate->logger()->TearDownAndGetLogFile();
+  CHECK_NOT_NULL(log_file);
+
+  bool exists = false;
+  raw_log = i::ReadFile(log_file, &exists, true);
+  fclose(log_file);
+
+  if (!exists) {
+    Throw(isolate, "Unable to read log file.");
+    return;
+  }
+  Local<String> result =
+      String::NewFromUtf8(isolate, raw_log.c_str(), NewStringType::kNormal,
+                          static_cast<int>(raw_log.size()))
+          .ToLocalChecked();
+
+  args.GetReturnValue().Set(result);
+}
+
 // async_hooks.createHook() registers functions to be called for different
 // lifetime events of each async operation.
 void Shell::AsyncHooksCreateHook(
@@ -2071,6 +2107,11 @@ Local<String> Shell::Stringify(Isolate* isolate, Local<Value> value) {
 
 Local<ObjectTemplate> Shell::CreateGlobalTemplate(Isolate* isolate) {
   Local<ObjectTemplate> global_template = ObjectTemplate::New(isolate);
+  global_template->Set(Symbol::GetToStringTag(isolate),
+                       String::NewFromUtf8Literal(isolate, "global"));
+  global_template->Set(isolate, "version",
+                       FunctionTemplate::New(isolate, Version));
+
   global_template->Set(isolate, "print", FunctionTemplate::New(isolate, Print));
   global_template->Set(isolate, "printErr",
                        FunctionTemplate::New(isolate, PrintErr));
@@ -2089,57 +2130,37 @@ Local<ObjectTemplate> Shell::CreateGlobalTemplate(Isolate* isolate) {
   if (!options.omit_quit) {
     global_template->Set(isolate, "quit", FunctionTemplate::New(isolate, Quit));
   }
-  Local<ObjectTemplate> test_template = ObjectTemplate::New(isolate);
-  global_template->Set(isolate, "testRunner", test_template);
-  test_template->Set(isolate, "notifyDone",
-                     FunctionTemplate::New(isolate, NotifyDone));
-  test_template->Set(isolate, "waitUntilDone",
-                     FunctionTemplate::New(isolate, WaitUntilDone));
-  // Reliable access to quit functionality. The "quit" method function
-  // installed on the global object can be hidden with the --omit-quit flag
-  // (e.g. on asan bots).
-  test_template->Set(isolate, "quit", FunctionTemplate::New(isolate, Quit));
+  global_template->Set(isolate, "testRunner",
+                       Shell::CreateTestRunnerTemplate(isolate));
+  global_template->Set(isolate, "Realm", Shell::CreateRealmTemplate(isolate));
+  global_template->Set(isolate, "performance",
+                       Shell::CreatePerformanceTemplate(isolate));
+  global_template->Set(isolate, "Worker", Shell::CreateWorkerTemplate(isolate));
+  global_template->Set(isolate, "os", Shell::CreateOSTemplate(isolate));
+  global_template->Set(isolate, "d8", Shell::CreateD8Template(isolate));
 
-  global_template->Set(isolate, "version",
-                       FunctionTemplate::New(isolate, Version));
-  global_template->Set(Symbol::GetToStringTag(isolate),
-                       String::NewFromUtf8Literal(isolate, "global"));
+#ifdef V8_FUZZILLI
+  global_template->Set(
+      String::NewFromUtf8(isolate, "fuzzilli", NewStringType::kNormal)
+          .ToLocalChecked(),
+      FunctionTemplate::New(isolate, Fuzzilli), PropertyAttribute::DontEnum);
+#endif  // V8_FUZZILLI
 
-  // Bind the Realm object.
-  Local<ObjectTemplate> realm_template = ObjectTemplate::New(isolate);
-  realm_template->Set(isolate, "current",
-                      FunctionTemplate::New(isolate, RealmCurrent));
-  realm_template->Set(isolate, "owner",
-                      FunctionTemplate::New(isolate, RealmOwner));
-  realm_template->Set(isolate, "global",
-                      FunctionTemplate::New(isolate, RealmGlobal));
-  realm_template->Set(isolate, "create",
-                      FunctionTemplate::New(isolate, RealmCreate));
-  realm_template->Set(
-      isolate, "createAllowCrossRealmAccess",
-      FunctionTemplate::New(isolate, RealmCreateAllowCrossRealmAccess));
-  realm_template->Set(isolate, "navigate",
-                      FunctionTemplate::New(isolate, RealmNavigate));
-  realm_template->Set(isolate, "detachGlobal",
-                      FunctionTemplate::New(isolate, RealmDetachGlobal));
-  realm_template->Set(isolate, "dispose",
-                      FunctionTemplate::New(isolate, RealmDispose));
-  realm_template->Set(isolate, "switch",
-                      FunctionTemplate::New(isolate, RealmSwitch));
-  realm_template->Set(isolate, "eval",
-                      FunctionTemplate::New(isolate, RealmEval));
-  realm_template->SetAccessor(String::NewFromUtf8Literal(isolate, "shared"),
-                              RealmSharedGet, RealmSharedSet);
-  global_template->Set(isolate, "Realm", realm_template);
+  if (i::FLAG_expose_async_hooks) {
+    global_template->Set(isolate, "async_hooks",
+                         Shell::CreateAsyncHookTemplate(isolate));
+  }
 
-  Local<ObjectTemplate> performance_template = ObjectTemplate::New(isolate);
-  performance_template->Set(isolate, "now",
-                            FunctionTemplate::New(isolate, PerformanceNow));
-  performance_template->Set(
-      isolate, "measureMemory",
-      FunctionTemplate::New(isolate, PerformanceMeasureMemory));
-  global_template->Set(isolate, "performance", performance_template);
+  return global_template;
+}
+
+Local<ObjectTemplate> Shell::CreateOSTemplate(Isolate* isolate) {
+  Local<ObjectTemplate> os_template = ObjectTemplate::New(isolate);
+  AddOSMethods(isolate, os_template);
+  return os_template;
+}
 
+Local<FunctionTemplate> Shell::CreateWorkerTemplate(Isolate* isolate) {
   Local<FunctionTemplate> worker_fun_template =
       FunctionTemplate::New(isolate, WorkerNew);
   Local<Signature> worker_signature =
@@ -2164,23 +2185,12 @@ Local<ObjectTemplate> Shell::CreateGlobalTemplate(Isolate* isolate) {
       FunctionTemplate::New(isolate, WorkerGetMessage, Local<Value>(),
                             worker_signature));
   worker_fun_template->InstanceTemplate()->SetInternalFieldCount(1);
-  global_template->Set(isolate, "Worker", worker_fun_template);
-
-  Local<ObjectTemplate> os_templ = ObjectTemplate::New(isolate);
-  AddOSMethods(isolate, os_templ);
-  global_template->Set(isolate, "os", os_templ);
-
-#ifdef V8_FUZZILLI
-  global_template->Set(
-      String::NewFromUtf8(isolate, "fuzzilli", NewStringType::kNormal)
-          .ToLocalChecked(),
-      FunctionTemplate::New(isolate, Fuzzilli), PropertyAttribute::DontEnum);
-#endif  // V8_FUZZILLI
+  return worker_fun_template;
+}
 
-  if (i::FLAG_expose_async_hooks) {
+Local<ObjectTemplate> Shell::CreateAsyncHookTemplate(Isolate* isolate) {
   Local<ObjectTemplate> async_hooks_templ = ObjectTemplate::New(isolate);
-    async_hooks_templ->Set(
-        isolate, "createHook",
+  async_hooks_templ->Set(isolate, "createHook",
                          FunctionTemplate::New(isolate, AsyncHooksCreateHook));
   async_hooks_templ->Set(
       isolate, "executionAsyncId",
@@ -2188,10 +2198,70 @@ Local<ObjectTemplate> Shell::CreateGlobalTemplate(Isolate* isolate) {
   async_hooks_templ->Set(
       isolate, "triggerAsyncId",
       FunctionTemplate::New(isolate, AsyncHooksTriggerAsyncId));
-    global_template->Set(isolate, "async_hooks", async_hooks_templ);
-  }
+  return async_hooks_templ;
+}
 
-  return global_template;
+Local<ObjectTemplate> Shell::CreateTestRunnerTemplate(Isolate* isolate) {
+  Local<ObjectTemplate> test_template = ObjectTemplate::New(isolate);
+  test_template->Set(isolate, "notifyDone",
+                     FunctionTemplate::New(isolate, NotifyDone));
+  test_template->Set(isolate, "waitUntilDone",
+                     FunctionTemplate::New(isolate, WaitUntilDone));
+  // Reliable access to quit functionality. The "quit" method function
+  // installed on the global object can be hidden with the --omit-quit flag
+  // (e.g. on asan bots).
+  test_template->Set(isolate, "quit", FunctionTemplate::New(isolate, Quit));
+  return test_template;
+}
+
+Local<ObjectTemplate> Shell::CreatePerformanceTemplate(Isolate* isolate) {
+  Local<ObjectTemplate> performance_template = ObjectTemplate::New(isolate);
+  performance_template->Set(isolate, "now",
+                            FunctionTemplate::New(isolate, PerformanceNow));
+  performance_template->Set(
+      isolate, "measureMemory",
+      FunctionTemplate::New(isolate, PerformanceMeasureMemory));
+  return performance_template;
+}
+
+Local<ObjectTemplate> Shell::CreateRealmTemplate(Isolate* isolate) {
+  Local<ObjectTemplate> realm_template = ObjectTemplate::New(isolate);
+  realm_template->Set(isolate, "current",
+                      FunctionTemplate::New(isolate, RealmCurrent));
+  realm_template->Set(isolate, "owner",
+                      FunctionTemplate::New(isolate, RealmOwner));
+  realm_template->Set(isolate, "global",
+                      FunctionTemplate::New(isolate, RealmGlobal));
+  realm_template->Set(isolate, "create",
+                      FunctionTemplate::New(isolate, RealmCreate));
+  realm_template->Set(
+      isolate, "createAllowCrossRealmAccess",
+      FunctionTemplate::New(isolate, RealmCreateAllowCrossRealmAccess));
+  realm_template->Set(isolate, "navigate",
+                      FunctionTemplate::New(isolate, RealmNavigate));
+  realm_template->Set(isolate, "detachGlobal",
+                      FunctionTemplate::New(isolate, RealmDetachGlobal));
+  realm_template->Set(isolate, "dispose",
+                      FunctionTemplate::New(isolate, RealmDispose));
+  realm_template->Set(isolate, "switch",
+                      FunctionTemplate::New(isolate, RealmSwitch));
+  realm_template->Set(isolate, "eval",
+                      FunctionTemplate::New(isolate, RealmEval));
+  realm_template->SetAccessor(String::NewFromUtf8Literal(isolate, "shared"),
+                              RealmSharedGet, RealmSharedSet);
+  return realm_template;
+}
+
+Local<ObjectTemplate> Shell::CreateD8Template(Isolate* isolate) {
+  Local<ObjectTemplate> d8_template = ObjectTemplate::New(isolate);
+  {
+    Local<ObjectTemplate> log_template = ObjectTemplate::New(isolate);
+    log_template->Set(isolate, "getAndStop",
+                      FunctionTemplate::New(isolate, LogGetAndStop));
+
+    d8_template->Set(isolate, "log", log_template);
+  }
+  return d8_template;
 }
 
 static void PrintMessageCallback(Local<Message> message, Local<Value> error) {

src/d8/d8.h

@@ -401,6 +401,8 @@ class Shell : public i::AllStatic {
   static void RealmSharedSet(Local<String> property, Local<Value> value,
                              const PropertyCallbackInfo<void>& info);
 
+  static void LogGetAndStop(const v8::FunctionCallbackInfo<v8::Value>& args);
+
   static void AsyncHooksCreateHook(
       const v8::FunctionCallbackInfo<v8::Value>& args);
   static void AsyncHooksExecutionAsyncId(
@@ -539,7 +541,16 @@ class Shell : public i::AllStatic {
   static Local<String> Stringify(Isolate* isolate, Local<Value> value);
   static void RunShell(Isolate* isolate);
   static bool SetOptions(int argc, char* argv[]);
+
   static Local<ObjectTemplate> CreateGlobalTemplate(Isolate* isolate);
+  static Local<ObjectTemplate> CreateOSTemplate(Isolate* isolate);
+  static Local<FunctionTemplate> CreateWorkerTemplate(Isolate* isolate);
+  static Local<ObjectTemplate> CreateAsyncHookTemplate(Isolate* isolate);
+  static Local<ObjectTemplate> CreateTestRunnerTemplate(Isolate* isolate);
+  static Local<ObjectTemplate> CreatePerformanceTemplate(Isolate* isolate);
+  static Local<ObjectTemplate> CreateRealmTemplate(Isolate* isolate);
+  static Local<ObjectTemplate> CreateD8Template(Isolate* isolate);
+
   static MaybeLocal<Context> CreateRealm(
       const v8::FunctionCallbackInfo<v8::Value>& args, int index,
       v8::MaybeLocal<Value> global_object);

src/execution/isolate.cc

@@ -3077,7 +3077,8 @@ void Isolate::Deinit() {
   cancelable_task_manager()->CancelAndWait();
 
   heap_.TearDown();
-  logger_->TearDown();
+  FILE* logfile = logger_->TearDownAndGetLogFile();
+  if (logfile != nullptr) fclose(logfile);
 
   if (wasm_engine_) {
     wasm_engine_->RemoveIsolate(this);

src/logging/log-utils.cc

@@ -23,28 +23,43 @@ const char* const Log::kLogToTemporaryFile = "&";
 const char* const Log::kLogToConsole = "-";
 
 // static
-FILE* Log::CreateOutputHandle(const char* file_name) {
+FILE* Log::CreateOutputHandle(std::string file_name) {
   // If we're logging anything, we need to open the log file.
   if (!Log::InitLogAtStart()) {
     return nullptr;
-  } else if (strcmp(file_name, kLogToConsole) == 0) {
+  } else if (Log::IsLoggingToConsole(file_name)) {
     return stdout;
-  } else if (strcmp(file_name, kLogToTemporaryFile) == 0) {
+  } else if (Log::IsLoggingToTemporaryFile(file_name)) {
     return base::OS::OpenTemporaryFile();
   } else {
-    return base::OS::FOpen(file_name, base::OS::LogFileOpenMode);
+    return base::OS::FOpen(file_name.c_str(), base::OS::LogFileOpenMode);
   }
 }
 
-Log::Log(Logger* logger, const char* file_name)
-    : output_handle_(Log::CreateOutputHandle(file_name)),
+// static
+bool Log::IsLoggingToConsole(std::string file_name) {
+  return file_name.compare(Log::kLogToConsole) == 0;
+}
+
+// static
+bool Log::IsLoggingToTemporaryFile(std::string file_name) {
+  return file_name.compare(Log::kLogToTemporaryFile) == 0;
+}
+
+Log::Log(std::string file_name)
+    : file_name_(file_name),
+      output_handle_(Log::CreateOutputHandle(file_name)),
       os_(output_handle_ == nullptr ? stdout : output_handle_),
       is_enabled_(output_handle_ != nullptr),
-      format_buffer_(NewArray<char>(kMessageBufferSize)),
-      logger_(logger) {
-
+      format_buffer_(NewArray<char>(kMessageBufferSize)) {
   if (output_handle_ == nullptr) return;
-  Log::MessageBuilder msg(this);
+  WriteLogHeader();
+}
+
+void Log::WriteLogHeader() {
+  std::unique_ptr<Log::MessageBuilder> msg_ptr = NewMessageBuilder();
+  if (!msg_ptr) return;
+  Log::MessageBuilder& msg = *msg_ptr.get();
   LogSeparator kNext = LogSeparator::kSeparator;
   msg << "v8-version" << kNext << Version::GetMajor() << kNext
       << Version::GetMinor() << kNext << Version::GetBuild() << kNext
@@ -71,20 +86,17 @@ FILE* Log::Close() {
   base::MutexGuard guard(&mutex_);
   FILE* result = nullptr;
   if (output_handle_ != nullptr) {
-    if (strcmp(FLAG_logfile, kLogToTemporaryFile) != 0) {
-      fclose(output_handle_);
-    } else {
+    fflush(output_handle_);
     result = output_handle_;
   }
-  }
   output_handle_ = nullptr;
-
   format_buffer_.reset();
-
   is_enabled_.store(false, std::memory_order_relaxed);
   return result;
 }
 
+std::string Log::file_name() const { return file_name_; }
+
 Log::MessageBuilder::MessageBuilder(Log* log)
     : log_(log), lock_guard_(&log_->mutex_) {
   DCHECK_NOT_NULL(log_->format_buffer_.get());

src/logging/log-utils.h

@@ -30,22 +30,27 @@ enum class LogSeparator { kSeparator };
 // Functions and data for performing output of log messages.
 class Log {
  public:
-  Log(Logger* log, const char* log_file_name);
+  explicit Log(std::string log_file_name);
 
   static bool InitLogAtStart() {
-    return FLAG_log || FLAG_log_api || FLAG_log_code || FLAG_log_handles ||
-           FLAG_log_suspect || FLAG_ll_prof || FLAG_perf_basic_prof ||
-           FLAG_perf_prof || FLAG_log_source_code || FLAG_gdbjit ||
-           FLAG_log_internal_timer_events || FLAG_prof_cpp || FLAG_trace_ic ||
-           FLAG_log_function_events || FLAG_trace_zone_stats ||
+    return FLAG_log || FLAG_log_all || FLAG_log_api || FLAG_log_code ||
+           FLAG_log_handles || FLAG_log_suspect || FLAG_ll_prof ||
+           FLAG_perf_basic_prof || FLAG_perf_prof || FLAG_log_source_code ||
+           FLAG_gdbjit || FLAG_log_internal_timer_events || FLAG_prof_cpp ||
+           FLAG_trace_ic || FLAG_log_function_events || FLAG_trace_zone_stats ||
            FLAG_turbo_profiling_log_builtins;
   }
 
+  V8_EXPORT_PRIVATE static bool IsLoggingToConsole(std::string file_name);
+  V8_EXPORT_PRIVATE static bool IsLoggingToTemporaryFile(std::string file_name);
+
   // Frees all resources acquired in Initialize and Open... functions.
   // When a temporary file is used for the log, returns its stream descriptor,
   // leaving the file open.
   FILE* Close();
 
+  std::string file_name() const;
+
   // Returns whether logging is enabled.
   bool IsEnabled() { return is_enabled_.load(std::memory_order_relaxed); }
 
@@ -109,19 +114,15 @@ class Log {
   std::unique_ptr<Log::MessageBuilder> NewMessageBuilder();
 
  private:
-  static FILE* CreateOutputHandle(const char* file_name);
-
-  // Implementation of writing to a log file.
-  int WriteToFile(const char* msg, int length) {
-    DCHECK_NOT_NULL(output_handle_);
-    os_.write(msg, length);
-    DCHECK(!os_.bad());
-    return length;
-  }
+  static FILE* CreateOutputHandle(std::string file_name);
+
+  void WriteLogHeader();
 
+  std::string file_name_;
   // When logging is active output_handle_ is used to store a pointer to log
   // destination.  mutex_ should be acquired before using output_handle_.
   FILE* output_handle_;
+
   OFStream os_;
 
   // Stores whether logging is enabled.
@@ -134,10 +135,6 @@ class Log {
   // Buffer used for formatting log messages. This is a singleton buffer and
   // mutex_ should be acquired before using it.
   std::unique_ptr<char[]> format_buffer_;
-
-  Logger* logger_;
-
-  friend class Logger;
 };
 
 template <>

src/logging/log.cc

@@ -1974,16 +1974,13 @@ void Logger::LogAllMaps() {
   }
 }
 
-static void AddIsolateIdIfNeeded(std::ostream& os,  // NOLINT
-                                 Isolate* isolate) {
-  if (FLAG_logfile_per_isolate) {
-    os << "isolate-" << isolate << "-" << base::OS::GetCurrentProcessId()
-       << "-";
-  }
+static void AddIsolateIdIfNeeded(std::ostream& os, Isolate* isolate) {
+  if (!FLAG_logfile_per_isolate) return;
+  os << "isolate-" << isolate << "-" << base::OS::GetCurrentProcessId() << "-";
 }
 
-static void PrepareLogFileName(std::ostream& os,  // NOLINT
-                               Isolate* isolate, const char* file_name) {
+static void PrepareLogFileName(std::ostream& os, Isolate* isolate,
+                               const char* file_name) {
   int dir_separator_count = 0;
   for (const char* p = file_name; *p; p++) {
     if (base::OS::isDirectorySeparator(*p)) dir_separator_count++;
@@ -2032,9 +2029,8 @@ bool Logger::SetUp(Isolate* isolate) {
   is_initialized_ = true;
 
   std::ostringstream log_file_name;
-  std::ostringstream source_log_file_name;
   PrepareLogFileName(log_file_name, isolate, FLAG_logfile);
-  log_ = std::make_unique<Log>(this, log_file_name.str().c_str());
+  log_ = std::make_unique<Log>(log_file_name.str());
 
 #if V8_OS_LINUX
   if (FLAG_perf_basic_prof) {
@@ -2063,9 +2059,7 @@ bool Logger::SetUp(Isolate* isolate) {
 
   ticker_ = std::make_unique<Ticker>(isolate, FLAG_prof_sampling_interval);
 
-  if (Log::InitLogAtStart()) {
-    is_logging_ = true;
-  }
+  if (Log::InitLogAtStart()) is_logging_ = true;
 
   timer_.Start();
 
@@ -2075,9 +2069,7 @@ bool Logger::SetUp(Isolate* isolate) {
     profiler_->Engage();
   }
 
-  if (is_logging_) {
-    AddCodeEventListener(this);
-  }
+  if (is_logging_) AddCodeEventListener(this);
 
   return true;
 }
@@ -2104,6 +2096,7 @@ void Logger::SetCodeEventHandler(uint32_t options,
 }
 
 sampler::Sampler* Logger::sampler() { return ticker_.get(); }
+std::string Logger::file_name() const { return log_.get()->file_name(); }
 
 void Logger::StopProfilerThread() {
   if (profiler_ != nullptr) {
@@ -2112,14 +2105,16 @@ void Logger::StopProfilerThread() {
   }
 }
 
-FILE* Logger::TearDown() {
+FILE* Logger::TearDownAndGetLogFile() {
   if (!is_initialized_) return nullptr;
   is_initialized_ = false;
+  is_logging_ = false;
 
   // Stop the profiler thread before closing the file.
   StopProfilerThread();
 
   ticker_.reset();
+  timer_.Stop();
 
 #if V8_OS_LINUX
   if (perf_basic_logger_) {

src/logging/log.h

@@ -126,18 +126,19 @@ class Logger : public CodeEventListener {
   // Acquires resources for logging if the right flags are set.
   bool SetUp(Isolate* isolate);
 
+  // Frees resources acquired in SetUp.
+  // When a temporary file is used for the log, returns its stream descriptor,
+  // leaving the file open.
+  V8_EXPORT_PRIVATE FILE* TearDownAndGetLogFile();
+
   // Sets the current code event handler.
   void SetCodeEventHandler(uint32_t options, JitCodeEventHandler event_handler);
 
   sampler::Sampler* sampler();
+  V8_EXPORT_PRIVATE std::string file_name() const;
 
   V8_EXPORT_PRIVATE void StopProfilerThread();
 
-  // Frees resources acquired in SetUp.
-  // When a temporary file is used for the log, returns its stream descriptor,
-  // leaving the file open.
-  V8_EXPORT_PRIVATE FILE* TearDown();
-
   // Emits an event with a string value -> (name, value).
   V8_EXPORT_PRIVATE void StringEvent(const char* name, const char* value);
 

test/cctest/test-log.cc

@@ -83,8 +83,8 @@ class ScopedLoggerInitializer {
 
   ~ScopedLoggerInitializer() {
     env_->Exit();
-    logger_->TearDown();
-    if (temp_file_ != nullptr) fclose(temp_file_);
+    FILE* log_file = logger_->TearDownAndGetLogFile();
+    if (log_file != nullptr) fclose(log_file);
     i::FLAG_prof = saved_prof_;
     i::FLAG_log = saved_log_;
   }
@@ -203,9 +203,8 @@ class ScopedLoggerInitializer {
 
  private:
   FILE* StopLoggingGetTempFile() {
-    temp_file_ = logger_->TearDown();
+    temp_file_ = logger_->TearDownAndGetLogFile();
     CHECK(temp_file_);
-    fflush(temp_file_);
     rewind(temp_file_);
     return temp_file_;
   }

test/mjsunit/tools/log.js

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --log-all --log --no-stress-opt
+
+function testFunctionWithFunnyName(o) {
+  return o.a;
+}
+
+(function testLoopWithFunnyName() {
+  const o = {a:1};
+  let result = 0;
+  for (let i = 0; i < 1000; i++) {
+    result += testFunctionWithFunnyName(o);
+  }
+})();
+
+const log = d8.log.getAndStop();
+
+// Check that we have a minimally working log file.
+assertTrue(log.length > 0);
+assertTrue(log.indexOf('v8-version') == 0);
+assertTrue(log.indexOf('testFunctionWithFunnyName') >= 10);
+assertTrue(log.indexOf('testLoopWithFunnyName') >= 10);