Fix an off-by-one error in the stack frame iteration.

runtime/vm/object.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/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
@@ skipping 6612 matching lines @@
   }
 #endif  // DEBUG
 }
 
 
 void Stackmap::SetCode(const Code& code) const {
   StorePointer(&raw_ptr()->code_, code.raw());
 }
 
 
-bool Stackmap::GetBit(intptr_t bit_offset) const {
-  ASSERT(InRange(bit_offset));
-  int byte_offset = bit_offset >> kBitsPerByteLog2;
-  int bit_remainder = bit_offset & (kBitsPerByte - 1);
+bool Stackmap::GetBit(intptr_t bit_index) const {
+  ASSERT(InRange(bit_index));
+  int byte_index = bit_index >> kBitsPerByteLog2;
+  int bit_remainder = bit_index & (kBitsPerByte - 1);
   uint8_t byte_mask = 1U << bit_remainder;
-  uint8_t byte = raw_ptr()->data_[byte_offset];
+  uint8_t byte = raw_ptr()->data_[byte_index];
   return (byte & byte_mask);
 }
 
 
-void Stackmap::SetBit(intptr_t bit_offset, bool value) const {
-  ASSERT(InRange(bit_offset));
-  int byte_offset = bit_offset >> kBitsPerByteLog2;
-  int bit_remainder = bit_offset & (kBitsPerByte - 1);
+void Stackmap::SetBit(intptr_t bit_index, bool value) const {
+  ASSERT(InRange(bit_index));
+  int byte_index = bit_index >> kBitsPerByteLog2;
+  int bit_remainder = bit_index & (kBitsPerByte - 1);
   uint8_t byte_mask = 1U << bit_remainder;
-  uint8_t* byte_addr = &(raw_ptr()->data_[byte_offset]);
+  uint8_t* byte_addr = &(raw_ptr()->data_[byte_index]);
   if (value) {
     *byte_addr |= byte_mask;
   } else {
     *byte_addr &= ~byte_mask;
   }
 }
 
 
 RawStackmap* Stackmap::New(uword pc_offset, BitmapBuilder* bmap) {
   ASSERT(Object::stackmap_class() != Class::null());
   ASSERT(bmap != NULL);
   Stackmap& result = Stackmap::Handle();
   intptr_t size = bmap->SizeInBytes();
   {
     // Stackmap data objects are associated with a code object, allocate them
     // in old generation.
     RawObject* raw = Object::Allocate(Stackmap::kInstanceKind,
                                       Stackmap::InstanceSize(size),
                                       Heap::kOld);
     NoGCScope no_gc;
     result ^= raw;
     result.set_bitmap_size_in_bytes(size);
   }
   result.SetPC(pc_offset);
   intptr_t bound = bmap->SizeInBits();
   for (intptr_t i = 0; i < bound; i++) {
     result.SetBit(i, bmap->Get(i));
   }
-  result.SetMinBitOffset(bmap->Minimum());
-  result.SetMaxBitOffset(bmap->Maximum());
+  result.SetMinBitIndex(bmap->Minimum());
+  result.SetMaxBitIndex(bmap->Maximum());
   return result.raw();
 }
 
 
 void Stackmap::set_bitmap_size_in_bytes(intptr_t value) const {
   // This is only safe because we create a new Smi, which does not cause
   // heap allocation.
   raw_ptr()->bitmap_size_in_bytes_ = Smi::New(value);
 }
 
 
 const char* Stackmap::ToCString() const {
   if (IsNull()) {
     return "{null}";
   } else {
     intptr_t index = OS::SNPrint(NULL, 0, "0x%lx { ", PC());
     intptr_t alloc_size =
-        index + ((MaximumBitOffset() + 1) * 2) + 2;  // "{ 1 0 .... }".
+        index + ((MaximumBitIndex() + 1) * 2) + 2;  // "{ 1 0 .... }".
     Isolate* isolate = Isolate::Current();
     char* chars = reinterpret_cast<char*>(
         isolate->current_zone()->Allocate(alloc_size));
     index = OS::SNPrint(chars, alloc_size, "0x%lx { ", PC());
-    for (intptr_t i = 0; i <= MaximumBitOffset(); i++) {
+    for (intptr_t i = 0; i <= MaximumBitIndex(); i++) {
       index += OS::SNPrint((chars + index),
                            (alloc_size - index),
                            "%d ",
                            IsObject(i) ? 1 : 0);
     }
     OS::SNPrint((chars + index), (alloc_size - index), "}");
     return chars;
   }
 }
 
@@ skipping 394 matching lines @@
       node_ids->Add(node_id);
       ic_data_obj = CodePatcher::GetInstanceCallIcDataAt(descriptors.PC(i));
       ic_data_objs.Add(ic_data_obj);
     }
   }
   return max_id;
 }
 
 
 RawStackmap* Code::GetStackmap(uword pc, Array* maps, Stackmap* map) const {
-  // This code is used only during iterating frames during a GC and hence
-  // it should not in turn start a GC.
+  // This code is used during iterating frames during a GC and hence it
+  // should not in turn start a GC.
   NoGCScope no_gc;
   if (stackmaps() == Array::null()) {
     // No stack maps are present in the code object which means this
     // frame relies on tagged pointers.
     return Stackmap::null();
   }
   // A stack map is present in the code object, use the stack map to visit
   // frame slots which are marked as having objects.
   *maps = stackmaps();
   *map = Stackmap::null();
@@ skipping 3723 matching lines @@
   const String& str = String::Handle(pattern());
   const char* format = "JSRegExp: pattern=%s flags=%s";
   intptr_t len = OS::SNPrint(NULL, 0, format, str.ToCString(), Flags());
   char* chars = reinterpret_cast<char*>(
       Isolate::Current()->current_zone()->Allocate(len + 1));
   OS::SNPrint(chars, (len + 1), format, str.ToCString(), Flags());
   return chars;
 }
 
 }  // namespace dart