[vm] Fix leak when generating snapshot depfile.

Use depfiles for the SDK's application snapshots.

Add check that we don't try to create a script snapshot after loading from an app snapshot.

Bug: TO-596
Change-Id: Ib4209c3062dbe0f3c37b8f65e5a50ca64544a39b
Reviewed-on: https://dart-review.googlesource.com/26043
Commit-Queue: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Zach Anderson <zra@google.com>

runtime/bin/loader.cc

@@ -301,20 +301,21 @@ void Loader::ResolveDependenciesAsFilePaths() {
   for (intptr_t i = 0; i < dependencies->length(); i++) {
     char* resolved_uri = (*dependencies)[i];
 
-    uint8_t* scoped_file_path = NULL;
-    intptr_t scoped_file_path_length = -1;
+    uint8_t* file_path = NULL;
+    intptr_t file_path_length = -1;
     Dart_Handle uri = Dart_NewStringFromCString(resolved_uri);
     ASSERT(!Dart_IsError(uri));
-    Dart_Handle result = Loader::ResolveAsFilePath(uri, &scoped_file_path,
-                                                   &scoped_file_path_length);
+    Dart_Handle result =
+        Loader::ResolveAsFilePath(uri, &file_path, &file_path_length);
     if (Dart_IsError(result)) {
       Log::Print("Error resolving dependency: %s\n", Dart_GetError(result));
       return;
     }
 
-    (*dependencies)[i] =
-        StringUtils::StrNDup(reinterpret_cast<const char*>(scoped_file_path),
-                             scoped_file_path_length);
+    // Convert buffer buffer to NUL-terminated string.
+    (*dependencies)[i] = StringUtils::StrNDup(
+        reinterpret_cast<const char*>(file_path), file_path_length);
+    free(file_path);
     free(resolved_uri);
   }
 }

runtime/bin/main.cc

@@ -756,6 +756,12 @@ bool RunMainIsolate(const char* script_name, CommandLineOptions* dart_options) {
   Dart_EnterScope();
 
   if (Options::gen_snapshot_kind() == kScript) {
+    if (vm_run_app_snapshot) {
+      Log::PrintErr("Cannot create a script snapshot from an app snapshot.\n");
+      // The snapshot would contain references to the app snapshot instead of
+      // the core snapshot.
+      Platform::Exit(kErrorExitCode);
+    }
     Snapshot::GenerateScript(Options::snapshot_filename());
   } else {
     // Lookup the library of the root script.

tests/standalone/script_snapshot_depfile_test.dart

@@ -0,0 +1,53 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import "dart:io";
+
+void main(List<String> args) {
+  if (args.contains("--child")) {
+    print("Hello, pre-scanned world!");
+  } else {
+    generateSnapshot();
+  }
+}
+
+void generateSnapshot() {
+  var tempDir = Directory.systemTemp.createTempSync("script-snapshot");
+  var snapshotPath = tempDir.uri.resolve("hello.snapshot").toFilePath();
+  var depfilePath = tempDir.uri.resolve("hello.snapshot.d").toFilePath();
+  var scriptPath = Platform.script.toFilePath();
+
+  var exec = Platform.resolvedExecutable;
+  var args = new List();
+  args.addAll(Platform.executableArguments);
+  args.add("--snapshot=$snapshotPath");
+  args.add("--snapshot-depfile=$depfilePath");
+  args.add(scriptPath);
+  args.add("--child");
+  var result = Process.runSync(exec, args);
+
+  print("Exit code: ${result.exitCode}");
+  print("stdout:");
+  print(result.stdout);
+  print("stderr:");
+  print(result.stderr);
+
+  if (result.exitCode != 0) {
+    throw "Bad exit code: ${result.exitCode}";
+  }
+
+  var depfileContents = new File(depfilePath).readAsStringSync();
+  print("depfile:");
+  print(depfileContents);
+  if (!depfileContents.contains(snapshotPath)) {
+    print("snapshotPath:");
+    print(snapshotPath);
+    throw "Missing snapshot path";
+  }
+  if (!depfileContents.contains(scriptPath)) {
+    print("scriptPath:");
+    print(scriptPath);
+    throw "Missing script path";
+  }
+}

tests/standalone/standalone.status

@@ -21,6 +21,7 @@ no_assert_test: Fail, OK # This is testing a vm flag.
 
 [ $runtime != vm || $compiler != none ]
 script_snapshot_not_executed_test: SkipByDesign # Only makes sense running from source.
+script_snapshot_depfile_test: SkipByDesign # Only makes sense running from source.
 
 [ (($hot_reload) || ($hot_reload_rollback)) ]
 script_snapshot_not_executed_test: RuntimeError

utils/application_snapshot.gni

@@ -39,25 +39,26 @@ template("application_snapshot") {
   }
   compiled_action(target_name) {
     tool = "$_dart_root/runtime/bin:dart"
-    deps = extra_deps + [ "$_dart_root/pkg:pkg_files_stamp" ]
+    deps = extra_deps
+    depfile = "$root_gen_dir/$name.dart.snapshot.d"
 
-    inputs = extra_inputs + [
-               "$_dart_root/sdk/lib/_internal/sdk_library_metadata/lib/libraries.dart",
-               "$root_gen_dir/pkg_files.stamp",
-             ]
+    main_file = rebase_path(main_dart)
+
+    inputs = extra_inputs + [ main_file ]
 
     output = "$root_gen_dir/$name.dart.snapshot"
     outputs = [
       output,
     ]
 
+    abs_depfile = rebase_path(depfile)
     abs_output = rebase_path(output)
-    main_file = rebase_path(main_dart)
 
     args = [
       "--deterministic",
       "--packages=$dot_packages",
       "--snapshot=$abs_output",
+      "--snapshot-depfile=$abs_depfile",
     ]
 
     if (dart_snapshot_kind == "script") {