Allow dynamic resolution of Dart isolate and instructions snapshot

sky/engine/bindings/BUILD.gn

@@ -116,11 +116,11 @@ action("generate_snapshot_file") {
   ]
   inputs = [
     "//dart/runtime/tools/create_snapshot_file.py",
-    "snapshot.cc.tmpl",
+    "snapshot.c.tmpl",
     "$target_gen_dir/vm_isolate_snapshot.bin",
     "$target_gen_dir/isolate_snapshot.bin",
   ]
-  output = "$target_gen_dir/snapshot.cc"
+  output = "$target_gen_dir/snapshot.c"
   outputs = [
     output,
   ]
@@ -132,7 +132,7 @@ action("generate_snapshot_file") {
     "--input_bin",
     rebase_path("$target_gen_dir/isolate_snapshot.bin"),
     "--input_cc",
-    rebase_path("snapshot.cc.tmpl"),
+    rebase_path("snapshot.c.tmpl"),
     "--output",
     rebase_path(output),
   ]
@@ -171,7 +171,7 @@ action("generate_updater_snapshot_file") {
 
 source_set("snapshot_cc") {
   sources = [
-    "$target_gen_dir/snapshot.cc",
+    "$target_gen_dir/snapshot.c",
   ]
 
   deps = [

sky/engine/bindings/bindings.gni

@@ -137,14 +137,14 @@ template("dart_precompile") {
     ]
   }
 
-  snapshot_cc = "$target_gen_dir/" + target_name + "_precompiled_snapshot.cc"
-  snapshot_cc_gen_target_name = target_name + "_snapshot_cc"
-  action(snapshot_cc_gen_target_name) {
+  snapshot_c = "$target_gen_dir/" + target_name + "_precompiled_snapshot.c"
+  snapshot_c_gen_target_name = target_name + "_snapshot_c"
+  action(snapshot_c_gen_target_name) {
     deps = [
       ":$instructions_gen_target_name",
     ]
 
-    template_file = "//sky/engine/bindings/snapshot.cc.tmpl"
+    template_file = "//sky/engine/bindings/snapshot.c.tmpl"
 
     inputs = [
       template_file,
@@ -153,7 +153,7 @@ template("dart_precompile") {
     ]
 
     outputs = [
-      snapshot_cc,
+      snapshot_c,
     ]
 
     script = "//dart/runtime/tools/create_snapshot_file.py"
@@ -165,19 +165,19 @@ template("dart_precompile") {
       "--input_cc",
       rebase_path(template_file, root_build_dir),
       "--output",
-      rebase_path(snapshot_cc),
+      rebase_path(snapshot_c),
     ]
   }
 
   source_set(target_name) {
     sources = [
       assembly_path,
-      snapshot_cc,
+      snapshot_c,
     ]
 
     deps = [
       ":$instructions_gen_target_name",
-      ":$snapshot_cc_gen_target_name",
+      ":$snapshot_c_gen_target_name",
     ]
   }
 }

sky/engine/bindings/snapshot.cc.tmpl → sky/engine/bindings/snapshot.c.tmpl

@@ -6,22 +6,16 @@
 #include <stdint.h>
 #include <stddef.h>
 
-namespace blink {
-
 // The string on the next line will be filled in with the contents of the
 // generated snapshot binary file for the vm isolate.
 // This string forms the content of the dart vm isolate snapshot which
 // is loaded into the vm isolate.
-static const uint8_t vm_isolate_snapshot_buffer_[]
-    __attribute__((aligned(8))) = { % s};
-const uint8_t* kDartVmIsolateSnapshotBuffer = vm_isolate_snapshot_buffer_;
+const uint8_t kDartVmIsolateSnapshotBuffer[]
+    __attribute__((visibility("default"), aligned(8), used)) = { %s };
 
 // The string on the next line will be filled in with the contents of the
 // generated snapshot binary file for a regular dart isolate.
 // This string forms the content of a regular dart isolate snapshot which
 // is loaded into an isolate when it is created.
-static const uint8_t isolate_snapshot_buffer_[]
-    __attribute__((aligned(8))) = { % s};
-const uint8_t* kDartIsolateSnapshotBuffer = isolate_snapshot_buffer_;
-
-}  // namespace blink
+const uint8_t kDartIsolateSnapshotBuffer[]
+    __attribute__((visibility("default"), aligned(8), used)) = { %s };

sky/engine/core/script/dart_controller.cc

@@ -137,11 +137,12 @@ void DartController::RunFromLibrary(const String& name,
 }
 
 void DartController::CreateIsolateFor(std::unique_ptr<DOMDartState> state) {
-  CHECK(kDartIsolateSnapshotBuffer);
   char* error = nullptr;
   dom_dart_state_ = std::move(state);
   Dart_Isolate isolate = Dart_CreateIsolate(
-      dom_dart_state_->url().utf8().data(), "main", kDartIsolateSnapshotBuffer,
+      dom_dart_state_->url().utf8().data(), "main",
+      reinterpret_cast<uint8_t*>(
+          DartSymbolLookup(kDartIsolateSnapshotBufferName)),
       nullptr, static_cast<DartState*>(dom_dart_state_.get()), &error);
   Dart_SetMessageNotifyCallback(MessageNotifyCallback);
   CHECK(isolate) << error;

sky/engine/core/script/dart_init.cc

@@ -48,17 +48,12 @@ void EnsureHandleWatcherStarted() {
   // during shutdown.
   Dart_Handle mojo_core_lib = Dart_LookupLibrary(ToDart("dart:mojo.internal"));
   CHECK(!LogIfError((mojo_core_lib)));
-  Dart_Handle handle_watcher_type = Dart_GetType(
-      mojo_core_lib,
-      Dart_NewStringFromCString("MojoHandleWatcher"),
-      0,
-      nullptr);
+  Dart_Handle handle_watcher_type =
+      Dart_GetType(mojo_core_lib,
+                   Dart_NewStringFromCString("MojoHandleWatcher"), 0, nullptr);
   CHECK(!LogIfError(handle_watcher_type));
   CHECK(!LogIfError(Dart_Invoke(
-      handle_watcher_type,
-      Dart_NewStringFromCString("_start"),
-      0,
-      nullptr)));
+      handle_watcher_type, Dart_NewStringFromCString("_start"), 0, nullptr)));
 
   // RunLoop until the handle watcher isolate is spun-up.
   CHECK(!LogIfError(Dart_RunLoop()));
@@ -87,15 +82,15 @@ static const char* kDartArgs[] = {
 #endif
 };
 
-static const char* kDartPrecompilationArgs[] {
-  "--precompilation",
+static const char* kDartPrecompilationArgs[]{
+    "--precompilation",
 };
 
 static const char* kDartCheckedModeArgs[] = {
-  "--enable_asserts",
-  "--enable_type_checks",
-  "--error_on_bad_type",
-  "--error_on_bad_override",
+    "--enable_asserts",
+    "--enable_type_checks",
+    "--error_on_bad_type",
+    "--error_on_bad_override",
 };
 
 void UnhandledExceptionCallback(Dart_Handle error) {
@@ -108,17 +103,12 @@ void IsolateShutdownCallback(void* callback_data) {
 
 bool IsServiceIsolateURL(const char* url_name) {
   return url_name != nullptr &&
-      String(url_name) == DART_VM_SERVICE_ISOLATE_NAME;
+         String(url_name) == DART_VM_SERVICE_ISOLATE_NAME;
 }
 
 static const uint8_t* PrecompiledInstructionsSymbolIfPresent() {
-  dlerror();  // clear previous errors on thread
-  void* sym = nullptr;
-#ifdef RTLD_SELF
-  static const char kInstructionsSnapshotSymbolName[] = "kInstructionsSnapshot";
-  sym = dlsym(RTLD_SELF, kInstructionsSnapshotSymbolName);
-#endif
-  return (dlerror() != nullptr) ? nullptr : reinterpret_cast<uint8_t * >(sym);
+  return reinterpret_cast<uint8_t*>(
+      DartSymbolLookup(kInstructionsSnapshotName));
 }
 
 static bool IsRunningPrecompiledCode() {
@@ -136,11 +126,11 @@ Dart_Isolate IsolateCreateCallback(const char* script_uri,
                                    void* callback_data,
                                    char** error) {
   if (IsServiceIsolateURL(script_uri)) {
-    CHECK(kDartIsolateSnapshotBuffer);
     DartState* dart_state = new DartState();
-    Dart_Isolate isolate =
-        Dart_CreateIsolate(script_uri, "main", kDartIsolateSnapshotBuffer,
-                           nullptr, nullptr, error);
+    Dart_Isolate isolate = Dart_CreateIsolate(
+        script_uri, "main", reinterpret_cast<const uint8_t*>(DartSymbolLookup(
+                                kDartIsolateSnapshotBufferName)),
+        nullptr, nullptr, error);
     CHECK(isolate) << error;
     dart_state->SetIsolate(isolate);
     CHECK(Dart_IsServiceIsolate(isolate));
@@ -157,9 +147,8 @@ Dart_Isolate IsolateCreateCallback(const char* script_uri,
       if (RuntimeEnabledFeatures::observatoryEnabled()) {
         std::string ip = "127.0.0.1";
         const intptr_t port = 8181;
-        const bool service_isolate_booted =
-            DartServiceIsolate::Startup(ip, port, DartLibraryTagHandler,
-                                        IsRunningPrecompiledCode(), error);
+        const bool service_isolate_booted = DartServiceIsolate::Startup(
+            ip, port, DartLibraryTagHandler, IsRunningPrecompiledCode(), error);
         CHECK(service_isolate_booted) << error;
       }
     }
@@ -168,12 +157,12 @@ Dart_Isolate IsolateCreateCallback(const char* script_uri,
   }
 
   // Create & start the handle watcher isolate
-  CHECK(kDartIsolateSnapshotBuffer);
   // TODO(abarth): Who deletes this DartState instance?
   DartState* dart_state = new DartState();
-  Dart_Isolate isolate =
-      Dart_CreateIsolate("sky:handle_watcher", "", kDartIsolateSnapshotBuffer,
-                         nullptr, dart_state, error);
+  Dart_Isolate isolate = Dart_CreateIsolate(
+      "sky:handle_watcher", "", reinterpret_cast<uint8_t*>(DartSymbolLookup(
+                                    kDartIsolateSnapshotBufferName)),
+      nullptr, dart_state, error);
   CHECK(isolate) << error;
   dart_state->SetIsolate(isolate);
 
@@ -195,7 +184,47 @@ Dart_Isolate IsolateCreateCallback(const char* script_uri,
   return isolate;
 }
 
-} // namespace
+}  // namespace
+
+const char* kDartVmIsolateSnapshotBufferName = "kDartVmIsolateSnapshotBuffer";
+const char* kDartIsolateSnapshotBufferName = "kDartIsolateSnapshotBuffer";
+const char* kInstructionsSnapshotName = "kInstructionsSnapshot";
+
+const char* kDartApplicationLibraryPath =
+    "FlutterApplication.framework/FlutterApplication";
+
+static void* DartLookupSymbolInLibrary(const char* symbol_name,
+                                       const char* library) {
+  if (symbol_name == nullptr) {
+    return nullptr;
+  }
+  dlerror();  // clear previous errors on thread
+  void* library_handle = dlopen(library, RTLD_NOW);
+  if (dlerror() != nullptr) {
+    return nullptr;
+  }
+  void* sym = dlsym(library_handle, symbol_name);
+  return dlerror() != nullptr ? nullptr : sym;
+}
+
+void* DartSymbolLookup(const char* symbol_name) {
+  if (symbol_name == nullptr) {
+    return nullptr;
+  }
+
+  // First the application library is checked for the valid symbols. This
+  // library may not necessarily exist. If it does exist, it is loaded and the
+  // symbols resolved. Once the application library is loaded, there is
+  // currently no provision to unload the same.
+  void* symbol =
+      DartLookupSymbolInLibrary(symbol_name, kDartApplicationLibraryPath);
+  if (symbol != nullptr) {
+    return symbol;
+  }
+
+  // Check inside the default library
+  return DartLookupSymbolInLibrary(symbol_name, nullptr);
+}
 
 void InitDartVM() {
   dart::bin::BootstrapDartIo();
@@ -217,21 +246,21 @@ void InitDartVM() {
   CHECK(Dart_SetVMFlags(args.size(), args.data()));
   // This should be called before calling Dart_Initialize.
   DartDebugger::InitDebugger();
-  CHECK(Dart_Initialize(
-      kDartVmIsolateSnapshotBuffer,
-      PrecompiledInstructionsSymbolIfPresent(),
-      IsolateCreateCallback,
-      nullptr,  // Isolate interrupt callback.
-      UnhandledExceptionCallback, IsolateShutdownCallback,
-      // File IO callbacks.
-      nullptr, nullptr, nullptr, nullptr,
-      // Entroy source
-      nullptr,
-      // VM service assets archive
-      nullptr) == nullptr);
+  CHECK(Dart_Initialize(reinterpret_cast<uint8_t*>(
+                            DartSymbolLookup(kDartVmIsolateSnapshotBufferName)),
+                        PrecompiledInstructionsSymbolIfPresent(),
+                        IsolateCreateCallback,
+                        nullptr,  // Isolate interrupt callback.
+                        UnhandledExceptionCallback, IsolateShutdownCallback,
+                        // File IO callbacks.
+                        nullptr, nullptr, nullptr, nullptr,
+                        // Entroy source
+                        nullptr,
+                        // VM service assets archive
+                        nullptr) == nullptr);
   // Wait for load port- ensures handle watcher and service isolates are
   // running.
   Dart_ServiceWaitForLoadPort();
 }
 
-} // namespace blink
+}  // namespace blink

sky/engine/core/script/dart_init.h

@@ -9,8 +9,11 @@
 
 namespace blink {
 
-extern const uint8_t* kDartVmIsolateSnapshotBuffer;
-extern const uint8_t* kDartIsolateSnapshotBuffer;
+extern const char* kDartVmIsolateSnapshotBufferName;
+extern const char* kDartIsolateSnapshotBufferName;
+extern const char* kInstructionsSnapshotName;
+
+void* DartSymbolLookup(const char* symbol_name);
 
 void InitDartVM();
 Dart_Handle DartLibraryTagHandler(Dart_LibraryTag tag,