[ VM ] Print a meaningful error message when a user attempts to run an AOT snapshot with a JIT VM.

Fixes #42482

Change-Id: I284a5673e30f59b127e69c712df93552cdfcde41
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/154834
Commit-Queue: Ben Konyi <bkonyi@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>

Author: bkonyi

runtime/bin/main.cc

@@ -1221,9 +1221,16 @@ void main(int argc, char** argv) {
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)
 
   if (should_run_user_program) {
-    // Run the main isolate until we aren't told to restart.
-    while (RunMainIsolate(script_name, &dart_options)) {
-      Syslog::PrintErr("Restarting VM\n");
+    if (!Dart_IsPrecompiledRuntime() && Snapshot::IsAOTSnapshot(script_name)) {
+      Syslog::PrintErr(
+          "%s is an AOT snapshot and should be run with 'dartaotruntime'\n",
+          script_name);
+      Platform::Exit(kErrorExitCode);
+    } else {
+      // Run the main isolate until we aren't told to restart.
+      while (RunMainIsolate(script_name, &dart_options)) {
+        Syslog::PrintErr("Restarting VM\n");
+      }
     }
   }
 

runtime/bin/snapshot_utils.cc

@@ -537,5 +537,24 @@ void Snapshot::GenerateAppAOTAsAssembly(const char* snapshot_filename) {
   }
 }
 
+bool Snapshot::IsAOTSnapshot(const char* snapshot_filename) {
+  // Header is simply "ELF" prefixed with the DEL character.
+  const char elf_header[] = {0x7F, 0x45, 0x4C, 0x46};
+  const int64_t elf_header_len = strlen(elf_header);
+  File* file = File::Open(NULL, snapshot_filename, File::kRead);
+  if (file == nullptr) {
+    return false;
+  }
+  if (file->Length() < elf_header_len) {
+    file->Release();
+    return false;
+  }
+  auto buf = std::unique_ptr<char[]>(new char[elf_header_len]);
+  bool success = file->ReadFully(buf.get(), elf_header_len);
+  file->Release();
+  ASSERT(success);
+  return (strncmp(elf_header, buf.get(), elf_header_len) == 0);
+}
+
 }  // namespace bin
 }  // namespace dart

runtime/bin/snapshot_utils.h

@@ -34,6 +34,10 @@ class Snapshot {
   static void GenerateAppJIT(const char* snapshot_filename);
   static void GenerateAppAOTAsAssembly(const char* snapshot_filename);
 
+  // Returns true if snapshot_filename points to an AOT snapshot (aka,
+  // an ELF binary). May report false negatives.
+  static bool IsAOTSnapshot(const char* snapshot_filename);
+
   static AppSnapshot* TryReadAppendedAppSnapshotElf(const char* container_path);
   static AppSnapshot* TryReadAppSnapshot(
       const char* script_uri,

tests/standalone/check_for_aot_snapshot_jit_test.dart

@@ -0,0 +1,59 @@
+// Copyright (c) 2020, 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';
+
+import 'package:expect/expect.dart';
+import 'package:path/path.dart' as path;
+
+main() {
+  final buildDir = path.dirname(Platform.executable);
+  final sdkDir = path.dirname(path.dirname(buildDir));
+  final platformDill = path.join(buildDir, 'vm_platform_strong.dill');
+  final genSnapshot = path.join(buildDir, 'gen_snapshot');
+
+  final exePath = Platform.resolvedExecutable;
+  final genSnapshotPath =
+      Uri.parse(Platform.executable).resolve('gen_snapshot').path;
+  final powTest = Platform.script.resolve('pow_test.dart').path;
+  final d = Directory.systemTemp.createTempSync('aot_tmp');
+  final kernelOutput = d.uri.resolve('pow_test.dill').path;
+  final aotOutput = d.uri.resolve('pow_test.aot').path;
+
+  final genKernelResult = Process.runSync(
+    'pkg/vm/tool/gen_kernel',
+    [
+      '--aot',
+      '--platform=$platformDill',
+      '-o',
+      kernelOutput,
+      powTest,
+    ],
+  );
+  Expect.equals(genKernelResult.exitCode, 0);
+
+  final genAotResult = Process.runSync(
+    genSnapshot,
+    [
+      '--snapshot_kind=app-aot-elf',
+      '--elf=$aotOutput',
+      kernelOutput,
+    ],
+  );
+  Expect.equals(genAotResult.exitCode, 0);
+
+  final runAotResult = Process.runSync(
+    exePath,
+    [
+      'run',
+      aotOutput,
+    ],
+  );
+  Expect.equals(runAotResult.exitCode, 255);
+  Expect.stringContainsInOrder(
+    runAotResult.stderr,
+    [
+      "pow_test.aot is an AOT snapshot and should be run with 'dartaotruntime'",
+    ],
+  );
+}

tests/standalone/standalone_precompiled.status

@@ -6,6 +6,7 @@
 dwarf_stack_trace_test: Pass, RuntimeError # Issue 35563
 
 [ $runtime == dart_precompiled ]
+check_for_aot_snapshot_jit_test: SkipByDesign
 http_launch_test: Skip
 io/addlatexhash_test: Skip
 io/dart_std_io_pipe_test: Skip

tests/standalone_2/check_for_aot_snapshot_jit_test.dart

@@ -0,0 +1,59 @@
+// Copyright (c) 2020, 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';
+
+import 'package:expect/expect.dart';
+import 'package:path/path.dart' as path;
+
+main() {
+  final buildDir = path.dirname(Platform.executable);
+  final sdkDir = path.dirname(path.dirname(buildDir));
+  final platformDill = path.join(buildDir, 'vm_platform_strong.dill');
+  final genSnapshot = path.join(buildDir, 'gen_snapshot');
+
+  final exePath = Platform.resolvedExecutable;
+  final genSnapshotPath =
+      Uri.parse(Platform.executable).resolve('gen_snapshot').path;
+  final powTest = Platform.script.resolve('pow_test.dart').path;
+  final d = Directory.systemTemp.createTempSync('aot_tmp');
+  final kernelOutput = d.uri.resolve('pow_test.dill').path;
+  final aotOutput = d.uri.resolve('pow_test.aot').path;
+
+  final genKernelResult = Process.runSync(
+    'pkg/vm/tool/gen_kernel',
+    [
+      '--aot',
+      '--platform=$platformDill',
+      '-o',
+      kernelOutput,
+      powTest,
+    ],
+  );
+  Expect.equals(genKernelResult.exitCode, 0);
+
+  final genAotResult = Process.runSync(
+    genSnapshot,
+    [
+      '--snapshot_kind=app-aot-elf',
+      '--elf=$aotOutput',
+      kernelOutput,
+    ],
+  );
+  Expect.equals(genAotResult.exitCode, 0);
+
+  final runAotResult = Process.runSync(
+    exePath,
+    [
+      'run',
+      aotOutput,
+    ],
+  );
+  Expect.equals(runAotResult.exitCode, 255);
+  Expect.stringContainsInOrder(
+    runAotResult.stderr,
+    [
+      "pow_test.aot is an AOT snapshot and should be run with 'dartaotruntime'",
+    ],
+  );
+}

tests/standalone_2/standalone_2_precompiled.status

@@ -3,6 +3,7 @@
 # BSD-style license that can be found in the LICENSE file.
 
 [ $runtime == dart_precompiled ]
+check_for_aot_snapshot_jit_test: SkipByDesign
 http_launch_test: Skip
 io/addlatexhash_test: Skip
 io/dart_std_io_pipe_test: Skip