[d8] Fix --enable-tracing

This CL fixes an issue with --enable-tracing which was introduced
recently where the tracing file was closed too early. In addition it
adds a test for --enable-tracing to avoid such an issue in the future.

R=machenbach@chromium.org, rmcilroy@chromium.org

Change-Id: I1b3699a4dfbe27230ac1d21d5f6bc7b2ee9ed435
Reviewed-on: https://chromium-review.googlesource.com/796214Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49742}

.gitignore

@@ -90,6 +90,7 @@ TAGS
 bsuite
 compile_commands.json
 d8
+!/test/mjsunit/d8
 d8_g
 gccauses
 gcsuspects

src/d8.cc

@@ -2876,6 +2876,9 @@ bool Shell::SetOptions(int argc, char* argv[]) {
     } else if (strcmp(argv[i], "--enable-tracing") == 0) {
       options.trace_enabled = true;
       argv[i] = nullptr;
+    } else if (strncmp(argv[i], "--trace-path=", 13) == 0) {
+      options.trace_path = argv[i] + 13;
+      argv[i] = nullptr;
     } else if (strncmp(argv[i], "--trace-config=", 15) == 0) {
       options.trace_config = argv[i] + 15;
       argv[i] = nullptr;
@@ -3306,7 +3309,8 @@ int Shell::Main(int argc, char* argv[]) {
   std::unique_ptr<platform::tracing::TracingController> tracing;
   if (options.trace_enabled && !i::FLAG_verify_predictable) {
     tracing = base::make_unique<platform::tracing::TracingController>();
-    trace_file.open("v8_trace.json");
+
+    trace_file.open(options.trace_path ? options.trace_path : "v8_trace.json");
     platform::tracing::TraceBuffer* trace_buffer =
         platform::tracing::TraceBuffer::CreateTraceBufferRingBuffer(
             platform::tracing::TraceBuffer::kRingBufferChunks,
@@ -3438,6 +3442,9 @@ int Shell::Main(int argc, char* argv[]) {
   V8::Dispose();
   V8::ShutdownPlatform();
 
+  // Delete the platform explicitly here to write the tracing output to the
+  // tracing file.
+  g_platform.reset();
   return result;
 }
 

src/d8.h

@@ -301,6 +301,7 @@ class ShellOptions {
         natives_blob(nullptr),
         snapshot_blob(nullptr),
         trace_enabled(false),
+        trace_path(nullptr),
         trace_config(nullptr),
         lcov_file(nullptr),
         disable_in_process_stack_traces(false),
@@ -334,6 +335,7 @@ class ShellOptions {
   const char* natives_blob;
   const char* snapshot_blob;
   bool trace_enabled;
+  const char* trace_path;
   const char* trace_config;
   const char* lcov_file;
   bool disable_in_process_stack_traces;

test/mjsunit/d8/.gitignore

+v8_trace.json

test/mjsunit/d8/enable-tracing.js

+// Copyright 2017 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: --enable-tracing --trace-path=test/mjsunit/d8/v8_trace.json
+
+// Just test that running d8 with --enable-tracing does not crash in a normal
+// execution without exceptions or calls to natives.

test/mjsunit/mjsunit.status

@@ -113,6 +113,12 @@
   'tools/tickprocessor': [PASS, NO_VARIANTS, ['arch == android_arm or arch == android_arm64 or arch == android_ia32', SKIP]],
   'tools/dumpcpp': [PASS, NO_VARIANTS, ['arch == android_arm or arch == android_arm64 or arch == android_ia32', SKIP]],
 
+  ##############################################################################
+  # This test generates a file in the test directory, so we cannot run several
+  # variants of the test simultaneously. Additionally the test should not be
+  # affected by variants.
+  'd8/enable-tracing': [PASS, NO_VARIANTS],
+
   ##############################################################################
   # Long running test that reproduces memory leak and should be run manually.
   'regress/regress-2073': [SKIP],