Don't use the size-zero array hack to access variable data in Snapshot.

runtime/vm/snapshot.h

 // 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.
 
 #ifndef VM_SNAPSHOT_H_
 #define VM_SNAPSHOT_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
@@ skipping 127 matching lines @@
     kMessage,   // A partial snapshot used only for isolate messaging.
   };
 
   static const int kHeaderSize = 2 * sizeof(int64_t);
   static const int kLengthIndex = 0;
   static const int kSnapshotFlagIndex = 1;
 
   static const Snapshot* SetupFromBuffer(const void* raw_memory);
 
   // Getters.
-  const uint8_t* content() const { return content_; }
   intptr_t length() const {
     return static_cast<intptr_t>(ReadUnaligned(&unaligned_length_));
   }
   Kind kind() const {
     return static_cast<Kind>(ReadUnaligned(&unaligned_kind_));
   }
 
   bool IsMessageSnapshot() const { return kind() == kMessage; }
   bool IsScriptSnapshot() const { return kind() == kScript; }
   bool IsFullSnapshot() const { return kind() == kFull; }
   uint8_t* Addr() { return reinterpret_cast<uint8_t*>(this); }
 
   static intptr_t length_offset() {
     return OFFSET_OF(Snapshot, unaligned_length_);
   }
   static intptr_t kind_offset() {
     return OFFSET_OF(Snapshot, unaligned_kind_);
   }
 
  private:
   // Prevent Snapshot from ever being allocated directly.
   Snapshot();
 
   // The following fields are potentially unaligned.
   int64_t unaligned_length_;  // Stream length.
   int64_t unaligned_kind_;  // Kind of snapshot.
-  uint8_t content_[];  // Stream content.
 
+ public:
+  // Variable length data follows here.
+  const uint8_t* content() const { OPEN_ARRAY_START(uint8_t, uint8_t); }

[siva, 2014/09/24 22:02:53]

Why not move this block to the top above the 'private:' stuff?

[rmacnak, 2014/09/24 22:38:08]

The intention was for content() to appear in the position the data occupies on
the object, a la raw_object.h. Leaving content() private and marking users as
friends as discussed offline doesn't work because one of the users in an API
function and friend doesn't play well with DART_EXPORT. Moving content() back to
the public block.

+
+ private:
   DISALLOW_COPY_AND_ASSIGN(Snapshot);
 };
 
 
 class BaseReader {
  public:
   BaseReader(const uint8_t* buffer, intptr_t size) : stream_(buffer, size) {}
   // Reads raw data (for basic types).
   // sizeof(T) must be in {1,2,4,8}.
   template <typename T>
@@ skipping 539 matching lines @@
  private:
   SnapshotWriter* writer_;
   bool as_references_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapshotWriterVisitor);
 };
 
 }  // namespace dart
 
 #endif  // VM_SNAPSHOT_H_