Make the internal parts of our external API a bit more const-correct.

include/v8.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /** \mainpage V8 API Reference Guide
  *
  * V8 is Google's open source JavaScript engine.
  *
  * This set of documents provides reference material generated from the
  * V8 header file, include/v8.h.
@@ skipping 5441 matching lines @@
   int smi_shift_bits = kSmiTagSize + kSmiShiftSize;
   intptr_t tagged_value =
       (static_cast<intptr_t>(value) << smi_shift_bits) | kSmiTag;
   return reinterpret_cast<internal::Object*>(tagged_value);
 }
 
 // Smi constants for 32-bit systems.
 template <> struct SmiTagging<4> {
   static const int kSmiShiftSize = 0;
   static const int kSmiValueSize = 31;
-  V8_INLINE static int SmiToInt(internal::Object* value) {
+  V8_INLINE static int SmiToInt(const internal::Object* value) {
     int shift_bits = kSmiTagSize + kSmiShiftSize;
     // Throw away top 32 bits and shift down (requires >> to be sign extending).
     return static_cast<int>(reinterpret_cast<intptr_t>(value)) >> shift_bits;
   }
   V8_INLINE static internal::Object* IntToSmi(int value) {
     return internal::IntToSmi<kSmiShiftSize>(value);
   }
   V8_INLINE static bool IsValidSmi(intptr_t value) {
     // To be representable as an tagged small integer, the two
     // most-significant bits of 'value' must be either 00 or 11 due to
     // sign-extension. To check this we add 01 to the two
     // most-significant bits, and check if the most-significant bit is 0
     //
     // CAUTION: The original code below:
     // bool result = ((value + 0x40000000) & 0x80000000) == 0;
     // may lead to incorrect results according to the C language spec, and
     // in fact doesn't work correctly with gcc4.1.1 in some cases: The
     // compiler may produce undefined results in case of signed integer
     // overflow. The computation must be done w/ unsigned ints.
     return static_cast<uintptr_t>(value + 0x40000000U) < 0x80000000U;
   }
 };
 
 // Smi constants for 64-bit systems.
 template <> struct SmiTagging<8> {
   static const int kSmiShiftSize = 31;
   static const int kSmiValueSize = 32;
-  V8_INLINE static int SmiToInt(internal::Object* value) {
+  V8_INLINE static int SmiToInt(const internal::Object* value) {
     int shift_bits = kSmiTagSize + kSmiShiftSize;
     // Shift down and throw away top 32 bits.
     return static_cast<int>(reinterpret_cast<intptr_t>(value) >> shift_bits);
   }
   V8_INLINE static internal::Object* IntToSmi(int value) {
     return internal::IntToSmi<kSmiShiftSize>(value);
   }
   V8_INLINE static bool IsValidSmi(intptr_t value) {
     // To be representable as a long smi, the value must be a 32-bit integer.
     return (value == static_cast<int32_t>(value));
@@ skipping 67 matching lines @@
 
   static const uint32_t kNumIsolateDataSlots = 4;
 
   V8_EXPORT static void CheckInitializedImpl(v8::Isolate* isolate);
   V8_INLINE static void CheckInitialized(v8::Isolate* isolate) {
 #ifdef V8_ENABLE_CHECKS
     CheckInitializedImpl(isolate);
 #endif
   }
 
-  V8_INLINE static bool HasHeapObjectTag(internal::Object* value) {
+  V8_INLINE static bool HasHeapObjectTag(const internal::Object* value) {
     return ((reinterpret_cast<intptr_t>(value) & kHeapObjectTagMask) ==
             kHeapObjectTag);
   }
 
-  V8_INLINE static int SmiValue(internal::Object* value) {
+  V8_INLINE static int SmiValue(const internal::Object* value) {
     return PlatformSmiTagging::SmiToInt(value);
   }
 
   V8_INLINE static internal::Object* IntToSmi(int value) {
     return PlatformSmiTagging::IntToSmi(value);
   }
 
   V8_INLINE static bool IsValidSmi(intptr_t value) {
     return PlatformSmiTagging::IsValidSmi(value);
   }
 
-  V8_INLINE static int GetInstanceType(internal::Object* obj) {
+  V8_INLINE static int GetInstanceType(const internal::Object* obj) {
     typedef internal::Object O;
     O* map = ReadField<O*>(obj, kHeapObjectMapOffset);
     return ReadField<uint8_t>(map, kMapInstanceTypeOffset);
   }
 
-  V8_INLINE static int GetOddballKind(internal::Object* obj) {
+  V8_INLINE static int GetOddballKind(const internal::Object* obj) {
     typedef internal::Object O;
     return SmiValue(ReadField<O*>(obj, kOddballKindOffset));
   }
 
   V8_INLINE static bool IsExternalTwoByteString(int instance_type) {
     int representation = (instance_type & kFullStringRepresentationMask);
     return representation == kExternalTwoByteRepresentationTag;
   }
 
   V8_INLINE static uint8_t GetNodeFlag(internal::Object** obj, int shift) {
@@ skipping 12 matching lines @@
     uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + kNodeFlagsOffset;
     return *addr & kNodeStateMask;
   }
 
   V8_INLINE static void UpdateNodeState(internal::Object** obj,
                                         uint8_t value) {
     uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + kNodeFlagsOffset;
     *addr = static_cast<uint8_t>((*addr & ~kNodeStateMask) | value);
   }
 
-  V8_INLINE static void SetEmbedderData(v8::Isolate *isolate,
+  V8_INLINE static void SetEmbedderData(v8::Isolate* isolate,
                                         uint32_t slot,
-                                        void *data) {
+                                        void* data) {
     uint8_t *addr = reinterpret_cast<uint8_t *>(isolate) +
                     kIsolateEmbedderDataOffset + slot * kApiPointerSize;

[Michael Starzinger, 2014/06/18 13:48:16]

nit: There are three different indentation styles going on here and in the two
hunks below. I am sooooo looking forward to clang-format. :)

     *reinterpret_cast<void**>(addr) = data;
   }
 
-  V8_INLINE static void* GetEmbedderData(v8::Isolate* isolate, uint32_t slot) {
-    uint8_t* addr = reinterpret_cast<uint8_t*>(isolate) +
+  V8_INLINE static void* GetEmbedderData(const v8::Isolate* isolate,
+                                         uint32_t slot) {
+    const uint8_t* addr = reinterpret_cast<const uint8_t*>(isolate) +
         kIsolateEmbedderDataOffset + slot * kApiPointerSize;
-    return *reinterpret_cast<void**>(addr);
+    return *reinterpret_cast<void* const*>(addr);
   }
 
   V8_INLINE static internal::Object** GetRoot(v8::Isolate* isolate,
                                               int index) {
     uint8_t* addr = reinterpret_cast<uint8_t*>(isolate) + kIsolateRootsOffset;
     return reinterpret_cast<internal::Object**>(addr + index * kApiPointerSize);
   }
 
   template <typename T>
-  V8_INLINE static T ReadField(internal::Object* ptr, int offset) {
-    uint8_t* addr = reinterpret_cast<uint8_t*>(ptr) + offset - kHeapObjectTag;
-    return *reinterpret_cast<T*>(addr);
+  V8_INLINE static T ReadField(const internal::Object* ptr, int offset) {
+    const uint8_t* addr =
+        reinterpret_cast<const uint8_t*>(ptr) + offset - kHeapObjectTag;
+    return *reinterpret_cast<const T*>(addr);
   }
 
   template <typename T>
-  V8_INLINE static T ReadEmbedderData(v8::Context* context, int index) {
+  V8_INLINE static T ReadEmbedderData(const v8::Context* context, int index) {
     typedef internal::Object O;
     typedef internal::Internals I;
-    O* ctx = *reinterpret_cast<O**>(context);
+    O* ctx = *reinterpret_cast<O* const*>(context);
     int embedder_data_offset = I::kContextHeaderSize +
         (internal::kApiPointerSize * I::kContextEmbedderDataIndex);
     O* embedder_data = I::ReadField<O*>(ctx, embedder_data_offset);
     int value_offset =
         I::kFixedArrayHeaderSize + (internal::kApiPointerSize * index);
     return I::ReadField<T>(embedder_data, value_offset);
   }
 };
 
 }  // namespace internal
@@ skipping 979 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_