[vm] Pass --enable-ffi value to compiler for better error message

Done to mirror how `--enable-mirrors` is implemented.

For this file:

```
$ cat tffi.dart
import "dart:ffi";

void main() {}
```

Before:

```
$ out/ReleaseX64/dart --enable-ffi=false tffi.dart
error: import of dart:ffi is not supported in the current Dart runtime
```

Now:

```
$ out/ReleaseX64/dart --enable-ffi=false tffi.dart
tffi.dart:1:8: Error: Dart library 'dart:ffi' is not available on this platform.
import "dart:ffi";
       ^
```

and for

```
$ cat tffi2.dart
const x = bool.fromEnvironment("dart.library.ffi");
final y = bool.fromEnvironment("dart.library.ffi");

void main() {
  print("$x vs $y");
}
```

Before:

```
$ out/ReleaseX64/dart --enable-ffi=false tffi2.dart
true vs false
```

Now:

```
$ out/ReleaseX64/dart --enable-ffi=false tffi2.dart
false vs false
```

Tested: Updated tests/ffi/vmspecific_enable_ffi_test.dart
Change-Id: I8194fcf8ad227baec66e05f2b3d235315e2a9f80
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/545840
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Jens Johansen <jensj@google.com>

Author: jensjoha

pkg/kernel/lib/target/targets.dart

@@ -14,6 +14,7 @@ import 'changed_structure_notifier.dart';
 class TargetFlags {
   final bool trackCreationLocations;
   final bool supportMirrors;
+  final bool supportFfi;
 
   /// Whether the backend expects closure contexts to be present in the AST.
   ///
@@ -34,6 +35,7 @@ class TargetFlags {
   const new({
     this.trackCreationLocations = false,
     this.supportMirrors = true,
+    this.supportFfi = true,
     this.isClosureContextLoweringEnabled = false,
     this.constKeepLocalsIndicator,
     this.includeUnsupportedPlatformLibraryStubs = false,
@@ -45,6 +47,7 @@ class TargetFlags {
     return other is TargetFlags &&
         trackCreationLocations == other.trackCreationLocations &&
         supportMirrors == other.supportMirrors &&
+        supportFfi == other.supportFfi &&
         includeUnsupportedPlatformLibraryStubs ==
             other.includeUnsupportedPlatformLibraryStubs &&
         constKeepLocalsIndicator == other.constKeepLocalsIndicator;
@@ -55,6 +58,7 @@ class TargetFlags {
     int hash = 485786;
     hash = 0x3fffffff & (hash * 31 + (hash ^ trackCreationLocations.hashCode));
     hash = 0x3fffffff & (hash * 31 + (hash ^ supportMirrors.hashCode));
+    hash = 0x3fffffff & (hash * 31 + (hash ^ supportFfi.hashCode));
     hash =
         0x3fffffff &
         (hash * 31 + (hash ^ includeUnsupportedPlatformLibraryStubs.hashCode));

pkg/vm/bin/kernel_service.dart

@@ -97,6 +97,7 @@ CompilerOptions setupCompilerOptions(
   String invocationModes,
   String verbosityLevel,
   bool enableMirrors,
+  bool enableFfi,
 ) {
   final expFlags = <String>[];
   if (experimentalFlags != null) {
@@ -106,7 +107,9 @@ CompilerOptions setupCompilerOptions(
   }
 
   Verbosity verbosity = Verbosity.parseArgument(verbosityLevel);
-  Target target = new VmTarget(new TargetFlags(supportMirrors: enableMirrors));
+  Target target = new VmTarget(
+    new TargetFlags(supportMirrors: enableMirrors, supportFfi: enableFfi),
+  );
   return new CompilerOptions()
     ..fileSystem = fileSystem
     ..target = target
@@ -172,6 +175,7 @@ abstract class Compiler {
   final String invocationModes;
   final String verbosityLevel;
   final bool enableMirrors;
+  final bool enableFfi;
   final bool generateBytecode;
 
   final List<String> errorsPlain = <String>[];
@@ -189,6 +193,7 @@ abstract class Compiler {
     this.invocationModes = '',
     this.verbosityLevel = Verbosity.defaultValue,
     required this.enableMirrors,
+    required this.enableFfi,
     required this.generateBytecode,
   }) {
     Uri? packagesUri = null;
@@ -215,6 +220,7 @@ abstract class Compiler {
       invocationModes,
       verbosityLevel,
       enableMirrors,
+      enableFfi,
     );
   }
 
@@ -309,6 +315,7 @@ class CompilerWrapper extends Compiler {
     String invocationModes = '',
     String verbosityLevel = Verbosity.defaultValue,
     required bool enableMirrors,
+    required bool enableFfi,
     required super.generateBytecode,
   }) : super(
          isolateGroupId,
@@ -320,6 +327,7 @@ class CompilerWrapper extends Compiler {
          invocationModes: invocationModes,
          verbosityLevel: verbosityLevel,
          enableMirrors: enableMirrors,
+         enableFfi: enableFfi,
        );
 
   factory CompilerWrapper.forExpressionCompilationOnly(
@@ -332,6 +340,7 @@ class CompilerWrapper extends Compiler {
     String? packageConfig,
     String invocationModes = '',
     required bool enableMirrors,
+    required bool enableFfi,
     required bool generateBytecode,
   }) {
     CompilerWrapper result = CompilerWrapper(
@@ -343,6 +352,7 @@ class CompilerWrapper extends Compiler {
       packageConfig: packageConfig,
       invocationModes: invocationModes,
       enableMirrors: enableMirrors,
+      enableFfi: enableFfi,
       generateBytecode: generateBytecode,
     );
     result.generator = new IncrementalCompiler.forExpressionCompilationOnly(
@@ -381,6 +391,7 @@ class CompilerWrapper extends Compiler {
       packageConfig: packageConfig,
       invocationModes: invocationModes,
       enableMirrors: enableMirrors,
+      enableFfi: enableFfi,
       generateBytecode: generateBytecode,
     );
     final generator = this.generator!;
@@ -431,6 +442,7 @@ Future<CompilerWrapper> lookupOrBuildNewIncrementalCompiler(
   String invocationModes = '',
   String verbosityLevel = Verbosity.defaultValue,
   required bool enableMirrors,
+  required bool enableFfi,
   required bool generateBytecode,
 }) async {
   CompilerWrapper? compiler = lookupIncrementalCompiler(isolateGroupId);
@@ -470,6 +482,7 @@ Future<CompilerWrapper> lookupOrBuildNewIncrementalCompiler(
         invocationModes: invocationModes,
         verbosityLevel: verbosityLevel,
         enableMirrors: enableMirrors,
+        enableFfi: enableFfi,
         generateBytecode: generateBytecode,
       );
     }
@@ -530,7 +543,8 @@ Future _processExpressionCompilationRequest(request) async {
       ? request[19].cast<String>()
       : null;
   final bool enableMirrors = request[20];
-  final bool generateBytecode = request[21];
+  final bool enableFfi = request[21];
+  final bool generateBytecode = request[22];
 
   CompilerWrapper? compiler = isolateCompilers[isolateGroupId];
 
@@ -629,6 +643,7 @@ Future _processExpressionCompilationRequest(request) async {
           experimentalFlags: experimentalFlags,
           packageConfig: packageConfigFile,
           enableMirrors: enableMirrors,
+          enableFfi: enableFfi,
           generateBytecode: generateBytecode,
         );
         isolateCompilers[isolateGroupId] = compiler;
@@ -841,7 +856,8 @@ Future _processLoadRequest(request) async {
   final String? multirootScheme = request[13];
   final String verbosityLevel = request[14];
   final bool enableMirrors = request[15];
-  final bool generateBytecode = request[16];
+  final bool enableFfi = request[16];
+  final bool generateBytecode = request[17];
   Uri platformKernelPath;
   List<int>? platformKernel = null;
   if (request[3] is String) {
@@ -922,6 +938,7 @@ Future _processLoadRequest(request) async {
       invocationModes: invocationModes,
       verbosityLevel: verbosityLevel,
       enableMirrors: enableMirrors,
+      enableFfi: enableFfi,
       generateBytecode: generateBytecode,
     );
     FileSystem fileSystem = compiler.fileSystem;
@@ -1202,6 +1219,7 @@ Future trainInternal(String scriptUri, String? platformKernelPath) async {
     null /* multirootScheme */,
     'all' /* CFE logging mode */,
     true /* enableMirrors */,
+    true /* enableFfi */,
     false /* generateBytecode */,
   ];
   await _processLoadRequest(request);

pkg/vm/lib/modular/target/vm.dart

@@ -50,6 +50,8 @@ class VmTarget extends Target {
   Class? _closure;
   Class? _syncStarIterable;
 
+  DartLibrarySupport? _dartLibrarySupport;
+
   VmTarget(this.flags);
 
   @override
@@ -612,9 +614,15 @@ class VmTarget extends Target {
   }
 
   @override
-  DartLibrarySupport get dartLibrarySupport => flags.supportMirrors
+  DartLibrarySupport get dartLibrarySupport =>
+      _dartLibrarySupport ??= flags.supportMirrors && flags.supportFfi
       ? const DefaultDartLibrarySupport()
-      : const CustomizedDartLibrarySupport(unsupported: {'mirrors'});
+      : CustomizedDartLibrarySupport(
+          unsupported: {
+            if (!flags.supportMirrors) 'mirrors',
+            if (!flags.supportFfi) 'ffi',
+          },
+        );
 
   @override
   bool isSupportedPragma(String pragmaName) =>

pkg/vm/test/kernel_service_test.dart

@@ -150,6 +150,7 @@ Future<kernel_service.Status> singleShotCompile(
     /* [13] = String? = multirootScheme = */ null,
     /* [14] = String = verbosityLevel = */ Verbosity.all.name,
     /* [15] = bool = enableMirrors = */ false,
+    /* [15] = bool = enableFfi = */ false,
     /* [16] = bool = generateBytecode = */ false,
   ]);
 

runtime/vm/kernel_isolate.cc

@@ -682,7 +682,11 @@ class KernelCompilationRequest : public ValueObject {
 
     Dart_CObject enable_mirrors;
     enable_mirrors.type = Dart_CObject_kBool;
-    enable_mirrors.value.as_bool = FLAG_enable_mirrors;
+    enable_mirrors.value.as_bool = FLAG_enable_mirrors && !FLAG_interpreter;
+
+    Dart_CObject enable_ffi;
+    enable_ffi.type = Dart_CObject_kBool;
+    enable_ffi.value.as_bool = Api::IsFfiEnabled();
 
     Dart_CObject generate_bytecode;
     generate_bytecode.type = Dart_CObject_kBool;
@@ -711,6 +715,7 @@ class KernelCompilationRequest : public ValueObject {
                                    &enable_asserts,
                                    &experimental_flags_object,
                                    &enable_mirrors,
+                                   &enable_ffi,
                                    &generate_bytecode};
     message.value.as_array.values = message_arr;
     message.value.as_array.length = ARRAY_SIZE(message_arr);
@@ -918,6 +923,10 @@ class KernelCompilationRequest : public ValueObject {
     enable_mirrors.type = Dart_CObject_kBool;
     enable_mirrors.value.as_bool = FLAG_enable_mirrors && !FLAG_interpreter;
 
+    Dart_CObject enable_ffi;
+    enable_ffi.type = Dart_CObject_kBool;
+    enable_ffi.value.as_bool = Api::IsFfiEnabled();
+
     Dart_CObject generate_bytecode;
     generate_bytecode.type = Dart_CObject_kBool;
     generate_bytecode.value.as_bool = FLAG_interpreter;
@@ -938,6 +947,7 @@ class KernelCompilationRequest : public ValueObject {
                                    &multiroot_scheme_object,
                                    &verbosity_str,
                                    &enable_mirrors,
+                                   &enable_ffi,
                                    &generate_bytecode};
     message.value.as_array.values = message_arr;
     message.value.as_array.length = ARRAY_SIZE(message_arr);

tests/ffi/vmspecific_enable_ffi_test.dart

@@ -32,7 +32,8 @@ void main() {
 
   Expect.equals(254, result.exitCode);
   Expect.contains(
-    'import of dart:ffi is not supported in the current Dart runtime',
+    "vmspecific_enable_ffi_test_helper.dart:8:8: "
+    "Error: Dart library 'dart:ffi' is not available on this platform.",
     result.stderr,
   );
 }