[ CLI ] Add support for passing VM options to Dart runtimes via DART_VM_OPTIONS

The DART_VM_OPTIONS environment variable allows for users to specify a
set of VM options to be processed by the Dart runtime in a
self-contained executable created by `dart compile exe`.

DART_VM_OPTIONS should be a comma separated list of options and flags
with no whitespace. Options that accept multiple values as a list of
comma separated values are not supported and will result in argument
parsing failing.

Fixes https://github.com/dart-lang/sdk/issues/54281

TEST=compile_test.dart

Change-Id: I1d94ab1b992753a7dd69da722c051c9464d6d1cf
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/353820
Reviewed-by: Siva Annamalai <asiva@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>

CHANGELOG.md

@@ -81,6 +81,20 @@
 [#53218]: https://github.com/dart-lang/sdk/issues/53218
 [#53785]: https://github.com/dart-lang/sdk/issues/53785
 
+### Dart Runtime
+- Dart VM flags and options can now be provided to any executable
+  generated using `dart compile exe` via the `DART_VM_OPTIONS` environment
+  variable. `DART_VM_OPTIONS` should be set to a list of comma-separated flags
+  and options with no whitespace. Options that allow for multiple values to be
+  provided as comma-separated values are not supported
+  (e.g., `--timeline-streams=Dart,GC,Compiler`).
+
+  Example of a valid `DART_VM_OPTIONS` environment variable:
+
+  ```bash
+  DART_VM_OPTIONS=--random_seed=42,--verbose_gc
+  ```
+
 ## 3.3.0
 
 ### Language

pkg/dartdev/test/commands/compile_test.dart

@@ -738,6 +738,42 @@ void main() {}
     expect(result.stdout, contains('sound'));
   }, skip: isRunningOnIA32);
 
+  test('Compile and run exe with DART_VM_OPTIONS', () async {
+    final p = project(mainSrc: '''void main() {
+      // Empty
+    }''');
+    final inFile = path.canonicalize(path.join(p.dirPath, p.relativeFilePath));
+    final outFile = path.canonicalize(path.join(p.dirPath, 'myexe'));
+
+    var result = await p.run(
+      [
+        'compile',
+        'exe',
+        '-o',
+        outFile,
+        inFile,
+      ],
+    );
+
+    expect(result.stdout, isNot(contains(soundNullSafetyMessage)));
+    expect(result.stderr, isEmpty);
+    expect(result.exitCode, 0);
+    expect(File(outFile).existsSync(), true,
+        reason: 'File not found: $outFile');
+
+    result = Process.runSync(
+      outFile,
+      [],
+      environment: <String, String>{
+        'DART_VM_OPTIONS': '--help,--verbose',
+      },
+    );
+
+    expect(result.stderr, isEmpty);
+    expect(result.stdout, contains('vm_name'));
+    expect(result.exitCode, 255);
+  }, skip: isRunningOnIA32);
+
   test('Compile exe without info', () async {
     final p = project(mainSrc: '''void main() {}''');
     final inFile = path.canonicalize(path.join(p.dirPath, p.relativeFilePath));

runtime/bin/main_impl.cc

@@ -1192,6 +1192,39 @@ void main(int argc, char** argv) {
   }
   vm_options.AddArgument("--new_gen_growth_factor=4");
 
+  auto parse_arguments = [&](int argc, char** argv,
+                             CommandLineOptions* vm_options,
+                             CommandLineOptions* dart_options) {
+    bool success = Options::ParseArguments(
+        argc, argv, vm_run_app_snapshot, vm_options, &script_name, dart_options,
+        &print_flags_seen, &verbose_debug_seen);
+    if (!success) {
+      if (Options::help_option()) {
+        Options::PrintUsage();
+        Platform::Exit(0);
+      } else if (Options::version_option()) {
+        Options::PrintVersion();
+        Platform::Exit(0);
+      } else if (print_flags_seen) {
+        // Will set the VM flags, print them out and then we exit as no
+        // script was specified on the command line.
+        char* error =
+            Dart_SetVMFlags(vm_options->count(), vm_options->arguments());
+        if (error != nullptr) {
+          Syslog::PrintErr("Setting VM flags failed: %s\n", error);
+          free(error);
+          Platform::Exit(kErrorExitCode);
+        }
+        Platform::Exit(0);
+      } else {
+        // This usage error case will only be invoked when
+        // Options::disable_dart_dev() is false.
+        Options::PrintUsage();
+        Platform::Exit(kErrorExitCode);
+      }
+    }
+  };
+
   AppSnapshot* app_snapshot = nullptr;
 #if defined(DART_PRECOMPILED_RUNTIME)
   // If the executable binary contains the runtime together with an appended
@@ -1213,40 +1246,23 @@ void main(int argc, char** argv) {
       for (int i = 1; i < argc; i++) {
         dart_options.AddArgument(argv[i]);
       }
+
+      // Parse DART_VM_OPTIONS options.
+      int env_argc = 0;
+      char** env_argv = Options::GetEnvArguments(&env_argc);
+      if (env_argv != nullptr) {
+        // Any Dart options that are generated based on parsing DART_VM_OPTIONS
+        // are useless, so we'll throw them away rather than passing them along.
+        CommandLineOptions tmp_options(env_argc + EXTRA_VM_ARGUMENTS);
+        parse_arguments(env_argc, env_argv, &vm_options, &tmp_options);
+      }
     }
   }
 #endif
 
   // Parse command line arguments.
   if (app_snapshot == nullptr) {
-    bool success = Options::ParseArguments(
-        argc, argv, vm_run_app_snapshot, &vm_options, &script_name,
-        &dart_options, &print_flags_seen, &verbose_debug_seen);
-    if (!success) {
-      if (Options::help_option()) {
-        Options::PrintUsage();
-        Platform::Exit(0);
-      } else if (Options::version_option()) {
-        Options::PrintVersion();
-        Platform::Exit(0);
-      } else if (print_flags_seen) {
-        // Will set the VM flags, print them out and then we exit as no
-        // script was specified on the command line.
-        char* error =
-            Dart_SetVMFlags(vm_options.count(), vm_options.arguments());
-        if (error != nullptr) {
-          Syslog::PrintErr("Setting VM flags failed: %s\n", error);
-          free(error);
-          Platform::Exit(kErrorExitCode);
-        }
-        Platform::Exit(0);
-      } else {
-        // This usage error case will only be invoked when
-        // Options::disable_dart_dev() is false.
-        Options::PrintUsage();
-        Platform::Exit(kErrorExitCode);
-      }
-    }
+    parse_arguments(argc, argv, &vm_options, &dart_options);
   }
 
   DartUtils::SetEnvironment(Options::environment());
@@ -1452,7 +1468,7 @@ void main(int argc, char** argv) {
   }
 
   // Free environment if any.
-  Options::DestroyEnvironment();
+  Options::Cleanup();
 
   Platform::Exit(global_exit_code);
 }

runtime/bin/main_options.cc

@@ -261,6 +261,13 @@ bool Options::ProcessEnvironmentOption(const char* arg,
                                                    &Options::environment_);
 }
 
+void Options::Cleanup() {
+#if defined(DART_PRECOMPILED_RUNTIME)
+  DestroyEnvArgv();
+#endif
+  DestroyEnvironment();
+}
+
 void Options::DestroyEnvironment() {
   if (environment_ != nullptr) {
     for (SimpleHashMap::Entry* p = environment_->Start(); p != nullptr;
@@ -273,6 +280,71 @@ void Options::DestroyEnvironment() {
   }
 }
 
+#if defined(DART_PRECOMPILED_RUNTIME)
+// Retrieves the set of arguments stored in the DART_VM_OPTIONS environment
+// variable.
+//
+// DART_VM_OPTIONS should contain a list of comma-separated options and flags
+// with no spaces. Options that support providing multiple values as
+// comma-separated lists (e.g., --timeline-streams=Dart,GC,Compiler) are not
+// supported and will cause argument parsing to fail.
+char** Options::GetEnvArguments(int* argc) {
+  ASSERT(argc != nullptr);
+  const char* env_args_str = std::getenv("DART_VM_OPTIONS");
+  if (env_args_str == nullptr) {
+    *argc = 0;
+    return nullptr;
+  }
+
+  intptr_t n = strlen(env_args_str);
+  if (n == 0) {
+    return nullptr;
+  }
+
+  // Find the number of arguments based on the number of ','s.
+  //
+  // WARNING: this won't work for arguments that support CSVs. There's less
+  // than a handful of options that support multiple values. If we want to
+  // support this case, we need to determine a way to specify groupings of CSVs
+  // in environment variables.
+  int arg_count = 1;
+  for (int i = 0; i < n; ++i) {
+    // Ignore the last comma if it's the last character in the string.
+    if (env_args_str[i] == ',' && i + 1 != n) {
+      arg_count++;
+    }
+  }
+
+  env_argv_ = new char*[arg_count];
+  env_argc_ = arg_count;
+  *argc = arg_count;
+
+  int current_arg = 0;
+  char* token;
+  char* rest = const_cast<char*>(env_args_str);
+
+  // Split out the individual arguments.
+  while ((token = strtok_r(rest, ",", &rest)) != nullptr) {
+    // TODO(bkonyi): consider stripping leading/trailing whitespace from
+    // arguments.
+    env_argv_[current_arg++] = Utils::StrNDup(token, rest - token);
+  }
+
+  return env_argv_;
+}
+
+char** Options::env_argv_ = nullptr;
+int Options::env_argc_ = 0;
+
+void Options::DestroyEnvArgv() {
+  for (int i = 0; i < env_argc_; ++i) {
+    free(env_argv_[i]);
+  }
+  delete[] env_argv_;
+  env_argv_ = nullptr;
+}
+#endif  // defined(DART_PRECOMPILED_RUNTIME)
+
 bool Options::ExtractPortAndAddress(const char* option_value,
                                     int* out_port,
                                     const char** out_ip,

runtime/bin/main_options.h

@@ -157,9 +157,19 @@ class Options {
   static void PrintUsage();
   static void PrintVersion();
 
-  static void DestroyEnvironment();
+  static void Cleanup();
+
+#if defined(DART_PRECOMPILED_RUNTIME)
+  // Get the list of options in DART_VM_OPTIONS.
+  static char** GetEnvArguments(int* argc);
+#endif  // defined(DART_PRECOMPILED_RUNTIME)
 
  private:
+  static void DestroyEnvironment();
+#if defined(DART_PRECOMPILED_RUNTIME)
+  static void DestroyEnvArgv();
+#endif  // defined(DART_PRECOMPILED_RUNTIME)
+
 #define STRING_OPTION_DECL(flag, variable) static const char* variable##_;
   STRING_OPTIONS_LIST(STRING_OPTION_DECL)
 #undef STRING_OPTION_DECL
@@ -182,6 +192,11 @@ class Options {
 
   static dart::SimpleHashMap* environment_;
 
+#if defined(DART_PRECOMPILED_RUNTIME)
+  static char** env_argv_;
+  static int env_argc_;
+#endif  // defined(DART_PRECOMPILED_RUNTIME)
+
 // Frontend argument processing.
 #if !defined(DART_PRECOMPILED_RUNTIME)
   static DFE* dfe_;