Verify/document assumption about stack resource addresses.

runtime/vm/exceptions.cc

 // Copyright (c) 2011, 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/exceptions.h"
 
 #include "platform/address_sanitizer.h"
 
 #include "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
@@ skipping 263 matching lines @@
 
   // Continue simulating at the given pc in the given frame after setting up the
   // exception object in the kExceptionObjectReg register and the stacktrace
   // object (may be raw null) in the kStackTraceObjectReg register.
 
   Simulator::Current()->Longjmp(program_counter, stack_pointer, frame_pointer,
                                 raw_exception, raw_stacktrace, isolate);
 #else
   // Prepare for unwinding frames by destroying all the stack resources
   // in the previous frames.
-
-  while (isolate->top_resource() != NULL &&
-         (reinterpret_cast<uword>(isolate->top_resource()) < stack_pointer)) {
-    isolate->top_resource()->~StackResource();
-  }
+  StackResource::Unwind(isolate, stack_pointer);
+  // There should be some stack resources left, since we never cross the
+  // bottommost C++ frame with its handlescope, etc.
+  ASSERT(isolate->top_resource() != NULL);
 
   // Call a stub to set up the exception object in kExceptionObjectReg,
   // to set up the stacktrace object in kStackTraceObjectReg, and to
   // continue execution at the given pc in the given frame.
   typedef void (*ExcpHandler)(uword, uword, uword, RawObject*, RawObject*,
                               Isolate*);
   ExcpHandler func = reinterpret_cast<ExcpHandler>(
       StubCode::JumpToExceptionHandlerEntryPoint());
 
   // Unpoison the stack before we tear it down in the generated stub code.
@@ skipping 455 matching lines @@
 
 // Throw JavascriptCompatibilityError exception.
 void Exceptions::ThrowJavascriptCompatibilityError(const char* msg) {
   const Array& exc_args = Array::Handle(Array::New(1));
   const String& msg_str = String::Handle(String::New(msg));
   exc_args.SetAt(0, msg_str);
   Exceptions::ThrowByType(Exceptions::kJavascriptCompatibilityError, exc_args);
 }
 
 }  // namespace dart