Fix source position for stack traces with optimized top function.

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 "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
 #include "vm/flags.h"
@@ skipping 45 matching lines @@
         // For optimized frames, extract all the inlined functions if any
         // into the stack trace.
         InlinedFunctionsInDartFrameIterator optimized_frames(frame);
         while (true) {
           uword pc = 0;
           func = optimized_frames.GetNextFunction(&pc);
           if (func.IsNull()) {
             break;
           }
           ASSERT(pc != 0);
-          code = func.unoptimized_code();
-          offset = Smi::New(pc - code.EntryPoint());
           if (ShouldShowFunction(func)) {
+            code = func.unoptimized_code();
+            offset = Smi::New(pc - code.EntryPoint());
+            ASSERT(0 <= offset.Value() && offset.Value() < code.Size());
             func_list.Add(func);
             code_list.Add(code);
             pc_offset_list.Add(offset);
           }
         }
       } else {
         offset = Smi::New(frame->pc() - code.EntryPoint());
         func = code.function();
         if (ShouldShowFunction(func)) {
           func_list.Add(func);
@@ skipping 398 matching lines @@
     case kIsolateUnhandledException:
       library = Library::IsolateLibrary();
       class_name = &Symbols::IsolateUnhandledException();
       break;
   }
 
   return DartLibraryCalls::ExceptionCreate(library, *class_name, arguments);
 }
 
 }  // namespace dart