Enter and Exit scope when calling into the native library tag handler

runtime/vm/parser.cc

 // Copyright (c) 2012, 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.
 
 #include "vm/parser.h"
 
 #include "lib/invocation_mirror.h"
 #include "platform/utils.h"
 #include "vm/bootstrap.h"
 #include "vm/class_finalizer.h"
@@ skipping 4837 matching lines @@
     library_.AddObject(func, accessor_name);
   } else {
     library_.ReplaceObject(func, accessor_name);
   }
   if (metadata_pos >= 0) {
     library_.AddFunctionMetadata(func, metadata_pos);
   }
 }
 
 
+class DartApiScope : public StackResource {
+ public:
+  explicit DartApiScope(Isolate* isolate) : StackResource(isolate) {
+    Dart_EnterScope();
+  }
+  ~DartApiScope() {
+    Dart_ExitScope();
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DartApiScope);
+};
+
 
 RawObject* Parser::CallLibraryTagHandler(Dart_LibraryTag tag,
                                          intptr_t token_pos,
                                          const String& url) {
   Dart_LibraryTagHandler handler = isolate()->library_tag_handler();
   if (handler == NULL) {
     if (url.StartsWith(Symbols::DartScheme())) {
       if (tag == Dart_kCanonicalizeUrl) {
         return url.raw();
       }
       return Object::null();
     }
     ErrorMsg(token_pos, "no library handler registered");
   }
   // Block class finalization attempts when calling into the library
   // tag handler.
   isolate()->BlockClassFinalization();
+  DartApiScope api_scope(isolate());

[hausner, 2014/02/05 22:22:56]

If this is the only place you anticipate calls to enter/exit scope, it might be
a bit of overkill to introduce the class above.

[siva, 2014/02/05 23:10:55]

The reason I made it a class is because we have some calls to ErrorMessage which
do a long jump and out and we want this to be a stack resorce that gets cleaned
out.

On 2014/02/05 22:22:56, hausner wrote:

   Dart_Handle result = handler(tag,
                                Api::NewHandle(isolate(), library_.raw()),
                                Api::NewHandle(isolate(), url.raw()));
   isolate()->UnblockClassFinalization();
   if (Dart_IsError(result)) {
     // In case of an error we append an explanatory error message to the
     // error obtained from the library tag handler.
     Error& prev_error = Error::Handle();
     prev_error ^= Api::UnwrapHandle(result);
     AppendErrorMsg(prev_error, token_pos, "library handler failed");
@@ skipping 5915 matching lines @@
 void Parser::SkipQualIdent() {
   ASSERT(IsIdentifier());
   ConsumeToken();
   if (CurrentToken() == Token::kPERIOD) {
     ConsumeToken();  // Consume the kPERIOD token.
     ExpectIdentifier("identifier expected after '.'");
   }
 }
 
 }  // namespace dart