[vm/ffi] DynamicLibrary.process() and DynamicLibrary.executable()

Change-Id: I6be84f24f0ac245ba176748e4a3ec1ba782798ce
Cq-Include-Trybots: luci.dart.try:vm-kernel-win-debug-x64-try,vm-kernel-mac-debug-x64-try,vm-ffi-android-debug-arm-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/113687
Commit-Queue: Samir Jindel <sjindel@google.com>
Reviewed-by: Daco Harkes <dacoharkes@google.com>

runtime/lib/ffi_dynamic_library.cc

@@ -36,14 +36,20 @@ static void* LoadExtensionLibrary(const char* library_file) {
 #elif defined(HOST_OS_WINDOWS)
   SetLastError(0);  // Clear any errors.
 
-  // Convert to wchar_t string.
-  const int name_len =
-      MultiByteToWideChar(CP_UTF8, 0, library_file, -1, NULL, 0);
-  wchar_t* name = new wchar_t[name_len];
-  MultiByteToWideChar(CP_UTF8, 0, library_file, -1, name, name_len);
+  void* ext;
 
-  void* ext = LoadLibraryW(name);
-  delete[] name;
+  if (library_file == nullptr) {
+    ext = GetModuleHandle(nullptr);
+  } else {
+    // Convert to wchar_t string.
+    const int name_len =
+        MultiByteToWideChar(CP_UTF8, 0, library_file, -1, NULL, 0);
+    wchar_t* name = new wchar_t[name_len];
+    MultiByteToWideChar(CP_UTF8, 0, library_file, -1, name, name_len);
+
+    ext = LoadLibraryW(name);
+    delete[] name;
+  }
 
   if (ext == nullptr) {
     const int error = GetLastError();
@@ -70,6 +76,22 @@ DEFINE_NATIVE_ENTRY(Ffi_dl_open, 0, 1) {
   return DynamicLibrary::New(handle);
 }
 
+DEFINE_NATIVE_ENTRY(Ffi_dl_processLibrary, 0, 0) {
+#if defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS) || defined(HOST_OS_ANDROID)
+  return DynamicLibrary::New(RTLD_DEFAULT);
+#else
+  const Array& args = Array::Handle(Array::New(1));
+  args.SetAt(0,
+             String::Handle(String::New(
+                 "DynamicLibrary.process is not available on this platform.")));
+  Exceptions::ThrowByType(Exceptions::kUnsupported, args);
+#endif
+}
+
+DEFINE_NATIVE_ENTRY(Ffi_dl_executableLibrary, 0, 0) {
+  return DynamicLibrary::New(LoadExtensionLibrary(nullptr));
+}
+
 static void* ResolveSymbol(void* handle, const char* symbol) {
 #if defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS) || defined(HOST_OS_ANDROID)
   dlerror();  // Clear any errors.

runtime/lib/ffi_dynamic_library_patch.dart

@@ -8,6 +8,8 @@ import "dart:_internal" show patch;
 import 'dart:typed_data' show TypedData;
 
 DynamicLibrary _open(String name) native "Ffi_dl_open";
+DynamicLibrary _processLibrary() native "Ffi_dl_processLibrary";
+DynamicLibrary _executableLibrary() native "Ffi_dl_executableLibrary";
 
 @patch
 @pragma("vm:entry-point")
@@ -17,6 +19,12 @@ class DynamicLibrary {
     return _open(name);
   }
 
+  @patch
+  factory DynamicLibrary.process() => _processLibrary();
+
+  @patch
+  factory DynamicLibrary.executable() => _executableLibrary();
+
   @patch
   Pointer<T> lookup<T extends NativeType>(String symbolName)
       native "Ffi_dl_lookup";

runtime/vm/bootstrap_natives.h

@@ -389,6 +389,8 @@ namespace dart {
   V(Ffi_dl_lookup, 2)                                                          \
   V(Ffi_dl_getHandle, 1)                                                       \
   V(Ffi_asExternalTypedData, 2)                                                \
+  V(Ffi_dl_processLibrary, 0)                                                  \
+  V(Ffi_dl_executableLibrary, 0)                                               \
   V(TransferableTypedData_factory, 2)                                          \
   V(TransferableTypedData_materialize, 1)
 

sdk/lib/ffi/dynamic_library.dart

@@ -6,11 +6,20 @@ part of dart.ffi;
 
 /// Represents a dynamically loaded C library.
 class DynamicLibrary {
-  /// Loads a dynamic library file. This is the equivalent of dlopen.
+  /// Creates a dynamic library holding all global symbols.
+  ///
+  /// Any symbol in a library currently loaded with global visibility (including
+  /// the executable itself) may be resolved in this library.
+  ///
+  /// This feature is not available on Windows, instead an exception is thrown.
+  external factory DynamicLibrary.process();
+
+  /// Creates a dynamic library representing the running executable.
+  external factory DynamicLibrary.executable();
+
+  /// Loads a dynamic library file with local visibility.
   ///
   /// Throws an [ArgumentError] if loading the dynamic library fails.
-  ///
-  /// Note that it loads the functions in the library lazily (RTLD_LAZY).
   external factory DynamicLibrary.open(String name);
 
   /// Looks up a symbol in the [DynamicLibrary] and returns its address in

tests/ffi/dynamic_library_test.dart

@@ -8,12 +8,13 @@
 
 library FfiTest;
 
+import 'dart:io';
 import 'dart:ffi';
 
-import 'dylib_utils.dart';
-
 import 'package:expect/expect.dart';
 
+import 'dylib_utils.dart';
+
 void main() {
   testOpen();
   testOpenError();
@@ -42,6 +43,20 @@ void testLookup() {
   DynamicLibrary l = dlopenPlatformSpecific("ffi_test_dynamic_library");
   var timesFour = l.lookupFunction<NativeDoubleUnOp, DoubleUnOp>("timesFour");
   Expect.approxEquals(12.0, timesFour(3));
+
+  if (Platform.isMacOS ||
+      Platform.isIOS ||
+      Platform.isAndroid ||
+      Platform.isLinux) {
+    // Lookup a symbol from 'libc' since it's loaded with global visibility.
+    DynamicLibrary p = DynamicLibrary.process();
+    Expect.isTrue(p.lookup<Void>("strcmp") != nullptr);
+  } else {
+    Expect.throws<UnsupportedError>(() => DynamicLibrary.process());
+  }
+
+  DynamicLibrary e = DynamicLibrary.executable();
+  Expect.isTrue(e.lookup("Dart_Invoke") != nullptr);
 }
 
 void testLookupError() {