Index: lib/sanitizer_common/CMakeLists.txt
===================================================================
--- lib/sanitizer_common/CMakeLists.txt
+++ lib/sanitizer_common/CMakeLists.txt
@@ -144,6 +144,7 @@
   sanitizer_libignore.h
   sanitizer_linux.h
   sanitizer_list.h
+  sanitizer_local_object_view.h
   sanitizer_mac.h
   sanitizer_malloc_mac.inc
   sanitizer_mutex.h
Index: lib/sanitizer_common/sanitizer_allocator.h
===================================================================
--- lib/sanitizer_common/sanitizer_allocator.h
+++ lib/sanitizer_common/sanitizer_allocator.h
@@ -14,12 +14,13 @@
 #ifndef SANITIZER_ALLOCATOR_H
 #define SANITIZER_ALLOCATOR_H
 
-#include "sanitizer_internal_defs.h"
 #include "sanitizer_common.h"
+#include "sanitizer_internal_defs.h"
+#include "sanitizer_lfstack.h"
 #include "sanitizer_libc.h"
 #include "sanitizer_list.h"
+#include "sanitizer_local_object_view.h"
 #include "sanitizer_mutex.h"
-#include "sanitizer_lfstack.h"
 #include "sanitizer_procmaps.h"
 
 namespace __sanitizer {
Index: lib/sanitizer_common/sanitizer_allocator_secondary.h
===================================================================
--- lib/sanitizer_common/sanitizer_allocator_secondary.h
+++ lib/sanitizer_common/sanitizer_allocator_secondary.h
@@ -68,7 +68,8 @@
 // The main purpose of this allocator is to cover large and rare allocation
 // sizes not covered by more efficient allocators (e.g. SizeClassAllocator64).
 template <class MapUnmapCallback = NoOpMapUnmapCallback,
-          class PtrArrayT = DefaultLargeMmapAllocatorPtrArray>
+          class PtrArrayT = DefaultLargeMmapAllocatorPtrArray,
+          template <typename> class ObjectViewT = LocalObjectView>
 class LargeMmapAllocator {
  public:
   void InitLinkerInitialized() {
@@ -271,17 +272,32 @@
   // Iterate over all existing chunks.
   // The allocator must be locked when calling this function.
   void ForEachChunk(ForEachChunkCallback callback, void *arg) {
-    EnsureSortedChunks();  // Avoid doing the sort while iterating.
+    if (ObjectView::IsLocal()) {
+      // Avoid doing the sort while iterating. We don't do
+      // this for out-of-process enumeration because we can't
+      // perform writes.
+      EnsureSortedChunks();
+    }
     for (uptr i = 0; i < n_chunks_; i++) {
-      auto t = chunks_[i];
+      // Compute address of header pointer
+      Header **header_ptr_addr = &(chunks_[i]);
+      // Copy header pointer into this process
+      auto t = ObjectView::MakeView(header_ptr_addr);
+
       callback(reinterpret_cast<uptr>(GetUser(t)), arg);
+
       // Consistency check: verify that the array did not change.
-      CHECK_EQ(chunks_[i], t);
-      CHECK_EQ(chunks_[i]->chunk_idx, i);
+      auto t2 = ObjectView::MakeView(&chunks_[i]);
+      CHECK_EQ(static_cast<Header *>(t), static_cast<Header *>(t2));
+      auto header_view = ObjectView::MakeView(static_cast<Header *>(t2));
+      CHECK_EQ(static_cast<Header>(header_view).chunk_idx, i);
     }
   }
 
  private:
+  typedef LargeMmapAllocator<MapUnmapCallback, PtrArrayT, ObjectViewT> ThisT;
+  using ObjectView = ObjectViewT<ThisT>;
+
   struct Header {
     uptr map_beg;
     uptr map_size;
@@ -316,4 +332,3 @@
   } stats;
   StaticSpinMutex mutex_;
 };
-
Index: lib/sanitizer_common/sanitizer_local_object_view.h
===================================================================
--- /dev/null
+++ lib/sanitizer_common/sanitizer_local_object_view.h
@@ -0,0 +1,85 @@
+//===-- sanitizer_local_object_view.h ---------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// The "local" (i.e. in-process) implementation of the `ObjectView` abstraction.
+//
+//===----------------------------------------------------------------------===//
+#ifndef SANITIZER_LOCAL_OBJECT_VIEW_H
+#define SANITIZER_LOCAL_OBJECT_VIEW_H
+#include "sanitizer_internal_defs.h"
+
+namespace __sanitizer {
+
+template <typename T>
+struct ObjectViewBase {
+  static uptr GetSize() { return sizeof(T); }
+};
+
+// Provides the implementation of the `ObjectView` abstraction for efficient
+// views on in-process objects of type `ObjectTy`. This implementation does not
+// make copies of objects and thus does not allocate any storage for these
+// copies.
+//
+// Generic in/out-of-process code should only use the subset of the interface
+// shared between `LocalObjectView` and `RemoteObjectView`.
+template <typename ObjectTy>
+struct LocalObjectView : ObjectViewBase<ObjectTy> {
+ private:
+  uptr target_address;
+
+ public:
+  using ObjectType = ObjectTy;
+  ALWAYS_INLINE LocalObjectView(uptr target_address)
+      : target_address(target_address) {}
+  ALWAYS_INLINE LocalObjectView(ObjectTy* target_address)
+      : LocalObjectView(reinterpret_cast<uptr>(target_address)) {}
+  ~LocalObjectView() {}
+
+  // Allow moving
+  LocalObjectView(LocalObjectView&& other) = default;
+
+  // Forbid assignment
+  LocalObjectView& operator=(const LocalObjectView&) = delete;
+  LocalObjectView& operator=(LocalObjectView&&) = delete;
+  LocalObjectView(const LocalObjectView&) = delete;
+
+  // Returns true iff the target address is memory
+  // local to this process.
+  ALWAYS_INLINE static bool IsLocal() { return true; }
+
+  // Returns true iff it is safe to dereference the pointer returned by
+  // `GetLocalAddress()`.
+  ALWAYS_INLINE bool IsValid() const { return true; }
+
+  // Return the address of an object of type `ObjectTy` in the current process.
+  ALWAYS_INLINE ObjectTy* GetLocalAddress() const {
+    return reinterpret_cast<ObjectTy*>(target_address);
+  }
+
+  // Return the address of an object of type `ObjectTy` in the target process.
+  ALWAYS_INLINE uptr GetTargetAddress() { return target_address; }
+
+  // Convenience functions for constructing views into other objects.
+  template <typename OtherObjectTy>
+  static LocalObjectView<OtherObjectTy> MakeView(
+      OtherObjectTy* target_address) {
+    return LocalObjectView<OtherObjectTy>(target_address);
+  }
+  template <typename OtherObjectTy>
+  static LocalObjectView<OtherObjectTy> MakeView(uptr target_address) {
+    return LocalObjectView<OtherObjectTy>(target_address);
+  }
+
+  // Implicit conversion operator so RemoteObjectView<ObjectTy>
+  // can be treated like a `ObjectTy&`.
+  operator ObjectTy&() const { return *(GetLocalAddress()); }
+};
+
+};  // namespace __sanitizer
+#endif