diff -r 000000000000 -r 6474c204b198 js/public/Value.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/public/Value.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,2014 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* JS::Value implementation. */
+
+#ifndef js_Value_h
+#define js_Value_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/FloatingPoint.h"
+#include "mozilla/Likely.h"
+
+#include <limits> /* for std::numeric_limits */
+
+#include "jstypes.h"
+
+#include "js/Anchor.h"
+#include "js/RootingAPI.h"
+#include "js/Utility.h"
+
+namespace JS { class Value; }
+
+/* JS::Value can store a full int32_t. */
+#define JSVAL_INT_BITS          32
+#define JSVAL_INT_MIN           ((int32_t)0x80000000)
+#define JSVAL_INT_MAX           ((int32_t)0x7fffffff)
+
+/*
+ * Try to get jsvals 64-bit aligned. We could almost assert that all values are
+ * aligned, but MSVC and GCC occasionally break alignment.
+ */
+#if defined(__GNUC__) || defined(__xlc__) || defined(__xlC__)
+# define JSVAL_ALIGNMENT        __attribute__((aligned (8)))
+#elif defined(_MSC_VER)
+  /*
+   * Structs can be aligned with MSVC, but not if they are used as parameters,
+   * so we just don't try to align.
+   */
+# define JSVAL_ALIGNMENT
+#elif defined(__SUNPRO_C) || defined(__SUNPRO_CC)
+# define JSVAL_ALIGNMENT
+#elif defined(__HP_cc) || defined(__HP_aCC)
+# define JSVAL_ALIGNMENT
+#endif
+
+#if JS_BITS_PER_WORD == 64
+# define JSVAL_TAG_SHIFT 47
+#endif
+
+/*
+ * We try to use enums so that printing a jsval_layout in the debugger shows
+ * nice symbolic type tags, however we can only do this when we can force the
+ * underlying type of the enum to be the desired size.
+ */
+#if !defined(__SUNPRO_CC) && !defined(__xlC__)
+
+#if defined(_MSC_VER)
+# define JS_ENUM_HEADER(id, type)              enum id : type
+# define JS_ENUM_FOOTER(id)
+#else
+# define JS_ENUM_HEADER(id, type)              enum id
+# define JS_ENUM_FOOTER(id)                    __attribute__((packed))
+#endif
+
+/* Remember to propagate changes to the C defines below. */
+JS_ENUM_HEADER(JSValueType, uint8_t)
+{
+    JSVAL_TYPE_DOUBLE              = 0x00,
+    JSVAL_TYPE_INT32               = 0x01,
+    JSVAL_TYPE_UNDEFINED           = 0x02,
+    JSVAL_TYPE_BOOLEAN             = 0x03,
+    JSVAL_TYPE_MAGIC               = 0x04,
+    JSVAL_TYPE_STRING              = 0x05,
+    JSVAL_TYPE_NULL                = 0x06,
+    JSVAL_TYPE_OBJECT              = 0x07,
+
+    /* These never appear in a jsval; they are only provided as an out-of-band value. */
+    JSVAL_TYPE_UNKNOWN             = 0x20,
+    JSVAL_TYPE_MISSING             = 0x21
+} JS_ENUM_FOOTER(JSValueType);
+
+JS_STATIC_ASSERT(sizeof(JSValueType) == 1);
+
+#if JS_BITS_PER_WORD == 32
+
+/* Remember to propagate changes to the C defines below. */
+JS_ENUM_HEADER(JSValueTag, uint32_t)
+{
+    JSVAL_TAG_CLEAR                = 0xFFFFFF80,
+    JSVAL_TAG_INT32                = JSVAL_TAG_CLEAR | JSVAL_TYPE_INT32,
+    JSVAL_TAG_UNDEFINED            = JSVAL_TAG_CLEAR | JSVAL_TYPE_UNDEFINED,
+    JSVAL_TAG_STRING               = JSVAL_TAG_CLEAR | JSVAL_TYPE_STRING,
+    JSVAL_TAG_BOOLEAN              = JSVAL_TAG_CLEAR | JSVAL_TYPE_BOOLEAN,
+    JSVAL_TAG_MAGIC                = JSVAL_TAG_CLEAR | JSVAL_TYPE_MAGIC,
+    JSVAL_TAG_NULL                 = JSVAL_TAG_CLEAR | JSVAL_TYPE_NULL,
+    JSVAL_TAG_OBJECT               = JSVAL_TAG_CLEAR | JSVAL_TYPE_OBJECT
+} JS_ENUM_FOOTER(JSValueTag);
+
+JS_STATIC_ASSERT(sizeof(JSValueTag) == 4);
+
+#elif JS_BITS_PER_WORD == 64
+
+/* Remember to propagate changes to the C defines below. */
+JS_ENUM_HEADER(JSValueTag, uint32_t)
+{
+    JSVAL_TAG_MAX_DOUBLE           = 0x1FFF0,
+    JSVAL_TAG_INT32                = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_INT32,
+    JSVAL_TAG_UNDEFINED            = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_UNDEFINED,
+    JSVAL_TAG_STRING               = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_STRING,
+    JSVAL_TAG_BOOLEAN              = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_BOOLEAN,
+    JSVAL_TAG_MAGIC                = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_MAGIC,
+    JSVAL_TAG_NULL                 = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_NULL,
+    JSVAL_TAG_OBJECT               = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_OBJECT
+} JS_ENUM_FOOTER(JSValueTag);
+
+JS_STATIC_ASSERT(sizeof(JSValueTag) == sizeof(uint32_t));
+
+JS_ENUM_HEADER(JSValueShiftedTag, uint64_t)
+{
+    JSVAL_SHIFTED_TAG_MAX_DOUBLE   = ((((uint64_t)JSVAL_TAG_MAX_DOUBLE) << JSVAL_TAG_SHIFT) | 0xFFFFFFFF),
+    JSVAL_SHIFTED_TAG_INT32        = (((uint64_t)JSVAL_TAG_INT32)      << JSVAL_TAG_SHIFT),
+    JSVAL_SHIFTED_TAG_UNDEFINED    = (((uint64_t)JSVAL_TAG_UNDEFINED)  << JSVAL_TAG_SHIFT),
+    JSVAL_SHIFTED_TAG_STRING       = (((uint64_t)JSVAL_TAG_STRING)     << JSVAL_TAG_SHIFT),
+    JSVAL_SHIFTED_TAG_BOOLEAN      = (((uint64_t)JSVAL_TAG_BOOLEAN)    << JSVAL_TAG_SHIFT),
+    JSVAL_SHIFTED_TAG_MAGIC        = (((uint64_t)JSVAL_TAG_MAGIC)      << JSVAL_TAG_SHIFT),
+    JSVAL_SHIFTED_TAG_NULL         = (((uint64_t)JSVAL_TAG_NULL)       << JSVAL_TAG_SHIFT),
+    JSVAL_SHIFTED_TAG_OBJECT       = (((uint64_t)JSVAL_TAG_OBJECT)     << JSVAL_TAG_SHIFT)
+} JS_ENUM_FOOTER(JSValueShiftedTag);
+
+JS_STATIC_ASSERT(sizeof(JSValueShiftedTag) == sizeof(uint64_t));
+
+#endif
+
+#else  /* !defined(__SUNPRO_CC) && !defined(__xlC__) */
+
+typedef uint8_t JSValueType;
+#define JSVAL_TYPE_DOUBLE            ((uint8_t)0x00)
+#define JSVAL_TYPE_INT32             ((uint8_t)0x01)
+#define JSVAL_TYPE_UNDEFINED         ((uint8_t)0x02)
+#define JSVAL_TYPE_BOOLEAN           ((uint8_t)0x03)
+#define JSVAL_TYPE_MAGIC             ((uint8_t)0x04)
+#define JSVAL_TYPE_STRING            ((uint8_t)0x05)
+#define JSVAL_TYPE_NULL              ((uint8_t)0x06)
+#define JSVAL_TYPE_OBJECT            ((uint8_t)0x07)
+#define JSVAL_TYPE_UNKNOWN           ((uint8_t)0x20)
+
+#if JS_BITS_PER_WORD == 32
+
+typedef uint32_t JSValueTag;
+#define JSVAL_TAG_CLEAR              ((uint32_t)(0xFFFFFF80))
+#define JSVAL_TAG_INT32              ((uint32_t)(JSVAL_TAG_CLEAR | JSVAL_TYPE_INT32))
+#define JSVAL_TAG_UNDEFINED          ((uint32_t)(JSVAL_TAG_CLEAR | JSVAL_TYPE_UNDEFINED))
+#define JSVAL_TAG_STRING             ((uint32_t)(JSVAL_TAG_CLEAR | JSVAL_TYPE_STRING))
+#define JSVAL_TAG_BOOLEAN            ((uint32_t)(JSVAL_TAG_CLEAR | JSVAL_TYPE_BOOLEAN))
+#define JSVAL_TAG_MAGIC              ((uint32_t)(JSVAL_TAG_CLEAR | JSVAL_TYPE_MAGIC))
+#define JSVAL_TAG_NULL               ((uint32_t)(JSVAL_TAG_CLEAR | JSVAL_TYPE_NULL))
+#define JSVAL_TAG_OBJECT             ((uint32_t)(JSVAL_TAG_CLEAR | JSVAL_TYPE_OBJECT))
+
+#elif JS_BITS_PER_WORD == 64
+
+typedef uint32_t JSValueTag;
+#define JSVAL_TAG_MAX_DOUBLE         ((uint32_t)(0x1FFF0))
+#define JSVAL_TAG_INT32              (uint32_t)(JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_INT32)
+#define JSVAL_TAG_UNDEFINED          (uint32_t)(JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_UNDEFINED)
+#define JSVAL_TAG_STRING             (uint32_t)(JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_STRING)
+#define JSVAL_TAG_BOOLEAN            (uint32_t)(JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_BOOLEAN)
+#define JSVAL_TAG_MAGIC              (uint32_t)(JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_MAGIC)
+#define JSVAL_TAG_NULL               (uint32_t)(JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_NULL)
+#define JSVAL_TAG_OBJECT             (uint32_t)(JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_OBJECT)
+
+typedef uint64_t JSValueShiftedTag;
+#define JSVAL_SHIFTED_TAG_MAX_DOUBLE ((((uint64_t)JSVAL_TAG_MAX_DOUBLE) << JSVAL_TAG_SHIFT) | 0xFFFFFFFF)
+#define JSVAL_SHIFTED_TAG_INT32      (((uint64_t)JSVAL_TAG_INT32)      << JSVAL_TAG_SHIFT)
+#define JSVAL_SHIFTED_TAG_UNDEFINED  (((uint64_t)JSVAL_TAG_UNDEFINED)  << JSVAL_TAG_SHIFT)
+#define JSVAL_SHIFTED_TAG_STRING     (((uint64_t)JSVAL_TAG_STRING)     << JSVAL_TAG_SHIFT)
+#define JSVAL_SHIFTED_TAG_BOOLEAN    (((uint64_t)JSVAL_TAG_BOOLEAN)    << JSVAL_TAG_SHIFT)
+#define JSVAL_SHIFTED_TAG_MAGIC      (((uint64_t)JSVAL_TAG_MAGIC)      << JSVAL_TAG_SHIFT)
+#define JSVAL_SHIFTED_TAG_NULL       (((uint64_t)JSVAL_TAG_NULL)       << JSVAL_TAG_SHIFT)
+#define JSVAL_SHIFTED_TAG_OBJECT     (((uint64_t)JSVAL_TAG_OBJECT)     << JSVAL_TAG_SHIFT)
+
+#endif  /* JS_BITS_PER_WORD */
+#endif  /* !defined(__SUNPRO_CC) && !defined(__xlC__) */
+
+#define JSVAL_LOWER_INCL_TYPE_OF_OBJ_OR_NULL_SET        JSVAL_TYPE_NULL
+#define JSVAL_UPPER_EXCL_TYPE_OF_PRIMITIVE_SET          JSVAL_TYPE_OBJECT
+#define JSVAL_UPPER_INCL_TYPE_OF_NUMBER_SET             JSVAL_TYPE_INT32
+#define JSVAL_LOWER_INCL_TYPE_OF_PTR_PAYLOAD_SET        JSVAL_TYPE_MAGIC
+
+#if JS_BITS_PER_WORD == 32
+
+#define JSVAL_TYPE_TO_TAG(type)      ((JSValueTag)(JSVAL_TAG_CLEAR | (type)))
+
+#define JSVAL_LOWER_INCL_TAG_OF_OBJ_OR_NULL_SET         JSVAL_TAG_NULL
+#define JSVAL_UPPER_EXCL_TAG_OF_PRIMITIVE_SET           JSVAL_TAG_OBJECT
+#define JSVAL_UPPER_INCL_TAG_OF_NUMBER_SET              JSVAL_TAG_INT32
+#define JSVAL_LOWER_INCL_TAG_OF_GCTHING_SET             JSVAL_TAG_STRING
+
+#elif JS_BITS_PER_WORD == 64
+
+#define JSVAL_PAYLOAD_MASK           0x00007FFFFFFFFFFFLL
+#define JSVAL_TAG_MASK               0xFFFF800000000000LL
+#define JSVAL_TYPE_TO_TAG(type)      ((JSValueTag)(JSVAL_TAG_MAX_DOUBLE | (type)))
+#define JSVAL_TYPE_TO_SHIFTED_TAG(type) (((uint64_t)JSVAL_TYPE_TO_TAG(type)) << JSVAL_TAG_SHIFT)
+
+#define JSVAL_LOWER_INCL_TAG_OF_OBJ_OR_NULL_SET         JSVAL_TAG_NULL
+#define JSVAL_UPPER_EXCL_TAG_OF_PRIMITIVE_SET           JSVAL_TAG_OBJECT
+#define JSVAL_UPPER_INCL_TAG_OF_NUMBER_SET              JSVAL_TAG_INT32
+#define JSVAL_LOWER_INCL_TAG_OF_GCTHING_SET             JSVAL_TAG_STRING
+
+#define JSVAL_LOWER_INCL_SHIFTED_TAG_OF_OBJ_OR_NULL_SET  JSVAL_SHIFTED_TAG_NULL
+#define JSVAL_UPPER_EXCL_SHIFTED_TAG_OF_PRIMITIVE_SET    JSVAL_SHIFTED_TAG_OBJECT
+#define JSVAL_UPPER_EXCL_SHIFTED_TAG_OF_NUMBER_SET       JSVAL_SHIFTED_TAG_UNDEFINED
+#define JSVAL_LOWER_INCL_SHIFTED_TAG_OF_GCTHING_SET      JSVAL_SHIFTED_TAG_STRING
+
+#endif /* JS_BITS_PER_WORD */
+
+typedef enum JSWhyMagic
+{
+    JS_ELEMENTS_HOLE,            /* a hole in a native object's elements */
+    JS_NATIVE_ENUMERATE,         /* indicates that a custom enumerate hook forwarded
+                                  * to JS_EnumerateState, which really means the object can be
+                                  * enumerated like a native object. */
+    JS_NO_ITER_VALUE,            /* there is not a pending iterator value */
+    JS_GENERATOR_CLOSING,        /* exception value thrown when closing a generator */
+    JS_NO_CONSTANT,              /* compiler sentinel value */
+    JS_THIS_POISON,              /* used in debug builds to catch tracing errors */
+    JS_ARG_POISON,               /* used in debug builds to catch tracing errors */
+    JS_SERIALIZE_NO_NODE,        /* an empty subnode in the AST serializer */
+    JS_LAZY_ARGUMENTS,           /* lazy arguments value on the stack */
+    JS_OPTIMIZED_ARGUMENTS,      /* optimized-away 'arguments' value */
+    JS_IS_CONSTRUCTING,          /* magic value passed to natives to indicate construction */
+    JS_OVERWRITTEN_CALLEE,       /* arguments.callee has been overwritten */
+    JS_BLOCK_NEEDS_CLONE,        /* value of static block object slot */
+    JS_HASH_KEY_EMPTY,           /* see class js::HashableValue */
+    JS_ION_ERROR,                /* error while running Ion code */
+    JS_ION_BAILOUT,              /* status code to signal EnterIon will OSR into Interpret */
+    JS_OPTIMIZED_OUT,            /* optimized out slot */
+    JS_GENERIC_MAGIC             /* for local use */
+} JSWhyMagic;
+
+#if defined(IS_LITTLE_ENDIAN)
+# if JS_BITS_PER_WORD == 32
+typedef union jsval_layout
+{
+    uint64_t asBits;
+    struct {
+        union {
+            int32_t        i32;
+            uint32_t       u32;
+            uint32_t       boo;     // Don't use |bool| -- it must be four bytes.
+            JSString       *str;
+            JSObject       *obj;
+            void           *ptr;
+            JSWhyMagic     why;
+            size_t         word;
+            uintptr_t      uintptr;
+        } payload;
+        JSValueTag tag;
+    } s;
+    double asDouble;
+    void *asPtr;
+} JSVAL_ALIGNMENT jsval_layout;
+# elif JS_BITS_PER_WORD == 64
+typedef union jsval_layout
+{
+    uint64_t asBits;
+#if !defined(_WIN64)
+    /* MSVC does not pack these correctly :-( */
+    struct {
+        uint64_t           payload47 : 47;
+        JSValueTag         tag : 17;
+    } debugView;
+#endif
+    struct {
+        union {
+            int32_t        i32;
+            uint32_t       u32;
+            JSWhyMagic     why;
+        } payload;
+    } s;
+    double asDouble;
+    void *asPtr;
+    size_t asWord;
+    uintptr_t asUIntPtr;
+} JSVAL_ALIGNMENT jsval_layout;
+# endif  /* JS_BITS_PER_WORD */
+#else   /* defined(IS_LITTLE_ENDIAN) */
+# if JS_BITS_PER_WORD == 32
+typedef union jsval_layout
+{
+    uint64_t asBits;
+    struct {
+        JSValueTag tag;
+        union {
+            int32_t        i32;
+            uint32_t       u32;
+            uint32_t       boo;     // Don't use |bool| -- it must be four bytes.
+            JSString       *str;
+            JSObject       *obj;
+            void           *ptr;
+            JSWhyMagic     why;
+            size_t         word;
+            uintptr_t      uintptr;
+        } payload;
+    } s;
+    double asDouble;
+    void *asPtr;
+} JSVAL_ALIGNMENT jsval_layout;
+# elif JS_BITS_PER_WORD == 64
+typedef union jsval_layout
+{
+    uint64_t asBits;
+    struct {
+        JSValueTag         tag : 17;
+        uint64_t           payload47 : 47;
+    } debugView;
+    struct {
+        uint32_t           padding;
+        union {
+            int32_t        i32;
+            uint32_t       u32;
+            JSWhyMagic     why;
+        } payload;
+    } s;
+    double asDouble;
+    void *asPtr;
+    size_t asWord;
+    uintptr_t asUIntPtr;
+} JSVAL_ALIGNMENT jsval_layout;
+# endif /* JS_BITS_PER_WORD */
+#endif  /* defined(IS_LITTLE_ENDIAN) */
+
+JS_STATIC_ASSERT(sizeof(jsval_layout) == 8);
+
+/*
+ * For codesize purposes on some platforms, it's important that the
+ * compiler know that JS::Values constructed from constant values can be
+ * folded to constant bit patterns at compile time, rather than
+ * constructed at runtime.  Doing this requires a fair amount of C++11
+ * features, which are not supported on all of our compilers.  Set up
+ * some defines and helper macros in an attempt to confine the ugliness
+ * here, rather than scattering it all about the file.  The important
+ * features are:
+ *
+ * - constexpr;
+ * - defaulted functions;
+ * - C99-style designated initializers.
+ */
+#if defined(__clang__)
+#  if __has_feature(cxx_constexpr) && __has_feature(cxx_defaulted_functions)
+#    define JS_VALUE_IS_CONSTEXPR
+#  endif
+#elif defined(__GNUC__)
+/*
+ * We need 4.5 for defaulted functions, 4.6 for constexpr, 4.7 because 4.6
+ * doesn't understand |(X) { .field = ... }| syntax, and 4.7.3 because
+ * versions prior to that have bugs in the C++ front-end that cause crashes.
+ */
+#  if MOZ_GCC_VERSION_AT_LEAST(4, 7, 3)
+#    define JS_VALUE_IS_CONSTEXPR
+#  endif
+#endif
+
+#if defined(JS_VALUE_IS_CONSTEXPR)
+#  define JS_RETURN_LAYOUT_FROM_BITS(BITS) \
+    return (jsval_layout) { .asBits = (BITS) }
+#  define JS_VALUE_CONSTEXPR MOZ_CONSTEXPR
+#  define JS_VALUE_CONSTEXPR_VAR MOZ_CONSTEXPR_VAR
+#else
+#  define JS_RETURN_LAYOUT_FROM_BITS(BITS) \
+    jsval_layout l;                        \
+    l.asBits = (BITS);                     \
+    return l;
+#  define JS_VALUE_CONSTEXPR
+#  define JS_VALUE_CONSTEXPR_VAR const
+#endif
+
+#if JS_BITS_PER_WORD == 32
+
+/*
+ * N.B. GCC, in some but not all cases, chooses to emit signed comparison of
+ * JSValueTag even though its underlying type has been forced to be uint32_t.
+ * Thus, all comparisons should explicitly cast operands to uint32_t.
+ */
+
+static inline JS_VALUE_CONSTEXPR jsval_layout
+BUILD_JSVAL(JSValueTag tag, uint32_t payload)
+{
+    JS_RETURN_LAYOUT_FROM_BITS((((uint64_t)(uint32_t)tag) << 32) | payload);
+}
+
+static inline bool
+JSVAL_IS_DOUBLE_IMPL(jsval_layout l)
+{
+    return (uint32_t)l.s.tag <= (uint32_t)JSVAL_TAG_CLEAR;
+}
+
+static inline jsval_layout
+DOUBLE_TO_JSVAL_IMPL(double d)
+{
+    jsval_layout l;
+    l.asDouble = d;
+    MOZ_ASSERT(JSVAL_IS_DOUBLE_IMPL(l));
+    return l;
+}
+
+static inline bool
+JSVAL_IS_INT32_IMPL(jsval_layout l)
+{
+    return l.s.tag == JSVAL_TAG_INT32;
+}
+
+static inline int32_t
+JSVAL_TO_INT32_IMPL(jsval_layout l)
+{
+    return l.s.payload.i32;
+}
+
+static inline JS_VALUE_CONSTEXPR jsval_layout
+INT32_TO_JSVAL_IMPL(int32_t i)
+{
+#if defined(JS_VALUE_IS_CONSTEXPR)
+    return BUILD_JSVAL(JSVAL_TAG_INT32, i);
+#else
+    jsval_layout l;
+    l.s.tag = JSVAL_TAG_INT32;
+    l.s.payload.i32 = i;
+    return l;
+#endif
+}
+
+static inline bool
+JSVAL_IS_NUMBER_IMPL(jsval_layout l)
+{
+    JSValueTag tag = l.s.tag;
+    MOZ_ASSERT(tag != JSVAL_TAG_CLEAR);
+    return (uint32_t)tag <= (uint32_t)JSVAL_UPPER_INCL_TAG_OF_NUMBER_SET;
+}
+
+static inline bool
+JSVAL_IS_UNDEFINED_IMPL(jsval_layout l)
+{
+    return l.s.tag == JSVAL_TAG_UNDEFINED;
+}
+
+static inline bool
+JSVAL_IS_STRING_IMPL(jsval_layout l)
+{
+    return l.s.tag == JSVAL_TAG_STRING;
+}
+
+static inline jsval_layout
+STRING_TO_JSVAL_IMPL(JSString *str)
+{
+    jsval_layout l;
+    MOZ_ASSERT(uintptr_t(str) > 0x1000);
+    l.s.tag = JSVAL_TAG_STRING;
+    l.s.payload.str = str;
+    return l;
+}
+
+static inline JSString *
+JSVAL_TO_STRING_IMPL(jsval_layout l)
+{
+    return l.s.payload.str;
+}
+
+static inline bool
+JSVAL_IS_BOOLEAN_IMPL(jsval_layout l)
+{
+    return l.s.tag == JSVAL_TAG_BOOLEAN;
+}
+
+static inline bool
+JSVAL_TO_BOOLEAN_IMPL(jsval_layout l)
+{
+    return l.s.payload.boo;
+}
+
+static inline jsval_layout
+BOOLEAN_TO_JSVAL_IMPL(bool b)
+{
+    jsval_layout l;
+    l.s.tag = JSVAL_TAG_BOOLEAN;
+    l.s.payload.boo = b;
+    return l;
+}
+
+static inline bool
+JSVAL_IS_MAGIC_IMPL(jsval_layout l)
+{
+    return l.s.tag == JSVAL_TAG_MAGIC;
+}
+
+static inline bool
+JSVAL_IS_OBJECT_IMPL(jsval_layout l)
+{
+    return l.s.tag == JSVAL_TAG_OBJECT;
+}
+
+static inline bool
+JSVAL_IS_PRIMITIVE_IMPL(jsval_layout l)
+{
+    return (uint32_t)l.s.tag < (uint32_t)JSVAL_UPPER_EXCL_TAG_OF_PRIMITIVE_SET;
+}
+
+static inline bool
+JSVAL_IS_OBJECT_OR_NULL_IMPL(jsval_layout l)
+{
+    MOZ_ASSERT((uint32_t)l.s.tag <= (uint32_t)JSVAL_TAG_OBJECT);
+    return (uint32_t)l.s.tag >= (uint32_t)JSVAL_LOWER_INCL_TAG_OF_OBJ_OR_NULL_SET;
+}
+
+static inline JSObject *
+JSVAL_TO_OBJECT_IMPL(jsval_layout l)
+{
+    return l.s.payload.obj;
+}
+
+static inline jsval_layout
+OBJECT_TO_JSVAL_IMPL(JSObject *obj)
+{
+    jsval_layout l;
+    MOZ_ASSERT(uintptr_t(obj) > 0x1000 || uintptr_t(obj) == 0x42);
+    l.s.tag = JSVAL_TAG_OBJECT;
+    l.s.payload.obj = obj;
+    return l;
+}
+
+static inline bool
+JSVAL_IS_NULL_IMPL(jsval_layout l)
+{
+    return l.s.tag == JSVAL_TAG_NULL;
+}
+
+static inline jsval_layout
+PRIVATE_PTR_TO_JSVAL_IMPL(void *ptr)
+{
+    jsval_layout l;
+    MOZ_ASSERT(((uint32_t)ptr & 1) == 0);
+    l.s.tag = (JSValueTag)0;
+    l.s.payload.ptr = ptr;
+    MOZ_ASSERT(JSVAL_IS_DOUBLE_IMPL(l));
+    return l;
+}
+
+static inline void *
+JSVAL_TO_PRIVATE_PTR_IMPL(jsval_layout l)
+{
+    return l.s.payload.ptr;
+}
+
+static inline bool
+JSVAL_IS_GCTHING_IMPL(jsval_layout l)
+{
+    /* gcc sometimes generates signed < without explicit casts. */
+    return (uint32_t)l.s.tag >= (uint32_t)JSVAL_LOWER_INCL_TAG_OF_GCTHING_SET;
+}
+
+static inline void *
+JSVAL_TO_GCTHING_IMPL(jsval_layout l)
+{
+    return l.s.payload.ptr;
+}
+
+static inline bool
+JSVAL_IS_TRACEABLE_IMPL(jsval_layout l)
+{
+    return l.s.tag == JSVAL_TAG_STRING || l.s.tag == JSVAL_TAG_OBJECT;
+}
+
+static inline uint32_t
+JSVAL_TRACE_KIND_IMPL(jsval_layout l)
+{
+    return (uint32_t)(bool)JSVAL_IS_STRING_IMPL(l);
+}
+
+static inline bool
+JSVAL_IS_SPECIFIC_INT32_IMPL(jsval_layout l, int32_t i32)
+{
+    return l.s.tag == JSVAL_TAG_INT32 && l.s.payload.i32 == i32;
+}
+
+static inline bool
+JSVAL_IS_SPECIFIC_BOOLEAN(jsval_layout l, bool b)
+{
+    return (l.s.tag == JSVAL_TAG_BOOLEAN) && (l.s.payload.boo == uint32_t(b));
+}
+
+static inline jsval_layout
+MAGIC_TO_JSVAL_IMPL(JSWhyMagic why)
+{
+    jsval_layout l;
+    l.s.tag = JSVAL_TAG_MAGIC;
+    l.s.payload.why = why;
+    return l;
+}
+
+static inline jsval_layout
+MAGIC_UINT32_TO_JSVAL_IMPL(uint32_t payload)
+{
+    jsval_layout l;
+    l.s.tag = JSVAL_TAG_MAGIC;
+    l.s.payload.u32 = payload;
+    return l;
+}
+
+static inline bool
+JSVAL_SAME_TYPE_IMPL(jsval_layout lhs, jsval_layout rhs)
+{
+    JSValueTag ltag = lhs.s.tag, rtag = rhs.s.tag;
+    return ltag == rtag || (ltag < JSVAL_TAG_CLEAR && rtag < JSVAL_TAG_CLEAR);
+}
+
+static inline JSValueType
+JSVAL_EXTRACT_NON_DOUBLE_TYPE_IMPL(jsval_layout l)
+{
+    uint32_t type = l.s.tag & 0xF;
+    MOZ_ASSERT(type > JSVAL_TYPE_DOUBLE);
+    return (JSValueType)type;
+}
+
+#elif JS_BITS_PER_WORD == 64
+
+static inline JS_VALUE_CONSTEXPR jsval_layout
+BUILD_JSVAL(JSValueTag tag, uint64_t payload)
+{
+    JS_RETURN_LAYOUT_FROM_BITS((((uint64_t)(uint32_t)tag) << JSVAL_TAG_SHIFT) | payload);
+}
+
+static inline bool
+JSVAL_IS_DOUBLE_IMPL(jsval_layout l)
+{
+    return l.asBits <= JSVAL_SHIFTED_TAG_MAX_DOUBLE;
+}
+
+static inline jsval_layout
+DOUBLE_TO_JSVAL_IMPL(double d)
+{
+    jsval_layout l;
+    l.asDouble = d;
+    MOZ_ASSERT(l.asBits <= JSVAL_SHIFTED_TAG_MAX_DOUBLE);
+    return l;
+}
+
+static inline bool
+JSVAL_IS_INT32_IMPL(jsval_layout l)
+{
+    return (uint32_t)(l.asBits >> JSVAL_TAG_SHIFT) == JSVAL_TAG_INT32;
+}
+
+static inline int32_t
+JSVAL_TO_INT32_IMPL(jsval_layout l)
+{
+    return (int32_t)l.asBits;
+}
+
+static inline JS_VALUE_CONSTEXPR jsval_layout
+INT32_TO_JSVAL_IMPL(int32_t i32)
+{
+    JS_RETURN_LAYOUT_FROM_BITS(((uint64_t)(uint32_t)i32) | JSVAL_SHIFTED_TAG_INT32);
+}
+
+static inline bool
+JSVAL_IS_NUMBER_IMPL(jsval_layout l)
+{
+    return l.asBits < JSVAL_UPPER_EXCL_SHIFTED_TAG_OF_NUMBER_SET;
+}
+
+static inline bool
+JSVAL_IS_UNDEFINED_IMPL(jsval_layout l)
+{
+    return l.asBits == JSVAL_SHIFTED_TAG_UNDEFINED;
+}
+
+static inline bool
+JSVAL_IS_STRING_IMPL(jsval_layout l)
+{
+    return (uint32_t)(l.asBits >> JSVAL_TAG_SHIFT) == JSVAL_TAG_STRING;
+}
+
+static inline jsval_layout
+STRING_TO_JSVAL_IMPL(JSString *str)
+{
+    jsval_layout l;
+    uint64_t strBits = (uint64_t)str;
+    MOZ_ASSERT(uintptr_t(str) > 0x1000);
+    MOZ_ASSERT((strBits >> JSVAL_TAG_SHIFT) == 0);
+    l.asBits = strBits | JSVAL_SHIFTED_TAG_STRING;
+    return l;
+}
+
+static inline JSString *
+JSVAL_TO_STRING_IMPL(jsval_layout l)
+{
+    return (JSString *)(l.asBits & JSVAL_PAYLOAD_MASK);
+}
+
+static inline bool
+JSVAL_IS_BOOLEAN_IMPL(jsval_layout l)
+{
+    return (uint32_t)(l.asBits >> JSVAL_TAG_SHIFT) == JSVAL_TAG_BOOLEAN;
+}
+
+static inline bool
+JSVAL_TO_BOOLEAN_IMPL(jsval_layout l)
+{
+    return (bool)(l.asBits & JSVAL_PAYLOAD_MASK);
+}
+
+static inline jsval_layout
+BOOLEAN_TO_JSVAL_IMPL(bool b)
+{
+    jsval_layout l;
+    l.asBits = ((uint64_t)(uint32_t)b) | JSVAL_SHIFTED_TAG_BOOLEAN;
+    return l;
+}
+
+static inline bool
+JSVAL_IS_MAGIC_IMPL(jsval_layout l)
+{
+    return (l.asBits >> JSVAL_TAG_SHIFT) == JSVAL_TAG_MAGIC;
+}
+
+static inline bool
+JSVAL_IS_PRIMITIVE_IMPL(jsval_layout l)
+{
+    return l.asBits < JSVAL_UPPER_EXCL_SHIFTED_TAG_OF_PRIMITIVE_SET;
+}
+
+static inline bool
+JSVAL_IS_OBJECT_IMPL(jsval_layout l)
+{
+    MOZ_ASSERT((l.asBits >> JSVAL_TAG_SHIFT) <= JSVAL_TAG_OBJECT);
+    return l.asBits >= JSVAL_SHIFTED_TAG_OBJECT;
+}
+
+static inline bool
+JSVAL_IS_OBJECT_OR_NULL_IMPL(jsval_layout l)
+{
+    MOZ_ASSERT((l.asBits >> JSVAL_TAG_SHIFT) <= JSVAL_TAG_OBJECT);
+    return l.asBits >= JSVAL_LOWER_INCL_SHIFTED_TAG_OF_OBJ_OR_NULL_SET;
+}
+
+static inline JSObject *
+JSVAL_TO_OBJECT_IMPL(jsval_layout l)
+{
+    uint64_t ptrBits = l.asBits & JSVAL_PAYLOAD_MASK;
+    MOZ_ASSERT((ptrBits & 0x7) == 0);
+    return (JSObject *)ptrBits;
+}
+
+static inline jsval_layout
+OBJECT_TO_JSVAL_IMPL(JSObject *obj)
+{
+    jsval_layout l;
+    uint64_t objBits = (uint64_t)obj;
+    MOZ_ASSERT(uintptr_t(obj) > 0x1000 || uintptr_t(obj) == 0x42);
+    MOZ_ASSERT((objBits >> JSVAL_TAG_SHIFT) == 0);
+    l.asBits = objBits | JSVAL_SHIFTED_TAG_OBJECT;
+    return l;
+}
+
+static inline bool
+JSVAL_IS_NULL_IMPL(jsval_layout l)
+{
+    return l.asBits == JSVAL_SHIFTED_TAG_NULL;
+}
+
+static inline bool
+JSVAL_IS_GCTHING_IMPL(jsval_layout l)
+{
+    return l.asBits >= JSVAL_LOWER_INCL_SHIFTED_TAG_OF_GCTHING_SET;
+}
+
+static inline void *
+JSVAL_TO_GCTHING_IMPL(jsval_layout l)
+{
+    uint64_t ptrBits = l.asBits & JSVAL_PAYLOAD_MASK;
+    MOZ_ASSERT((ptrBits & 0x7) == 0);
+    return (void *)ptrBits;
+}
+
+static inline bool
+JSVAL_IS_TRACEABLE_IMPL(jsval_layout l)
+{
+    return JSVAL_IS_GCTHING_IMPL(l) && !JSVAL_IS_NULL_IMPL(l);
+}
+
+static inline uint32_t
+JSVAL_TRACE_KIND_IMPL(jsval_layout l)
+{
+    return (uint32_t)(bool)!(JSVAL_IS_OBJECT_IMPL(l));
+}
+
+static inline jsval_layout
+PRIVATE_PTR_TO_JSVAL_IMPL(void *ptr)
+{
+    jsval_layout l;
+    uint64_t ptrBits = (uint64_t)ptr;
+    MOZ_ASSERT((ptrBits & 1) == 0);
+    l.asBits = ptrBits >> 1;
+    MOZ_ASSERT(JSVAL_IS_DOUBLE_IMPL(l));
+    return l;
+}
+
+static inline void *
+JSVAL_TO_PRIVATE_PTR_IMPL(jsval_layout l)
+{
+    MOZ_ASSERT((l.asBits & 0x8000000000000000LL) == 0);
+    return (void *)(l.asBits << 1);
+}
+
+static inline bool
+JSVAL_IS_SPECIFIC_INT32_IMPL(jsval_layout l, int32_t i32)
+{
+    return l.asBits == (((uint64_t)(uint32_t)i32) | JSVAL_SHIFTED_TAG_INT32);
+}
+
+static inline bool
+JSVAL_IS_SPECIFIC_BOOLEAN(jsval_layout l, bool b)
+{
+    return l.asBits == (((uint64_t)(uint32_t)b) | JSVAL_SHIFTED_TAG_BOOLEAN);
+}
+
+static inline jsval_layout
+MAGIC_TO_JSVAL_IMPL(JSWhyMagic why)
+{
+    jsval_layout l;
+    l.asBits = ((uint64_t)(uint32_t)why) | JSVAL_SHIFTED_TAG_MAGIC;
+    return l;
+}
+
+static inline jsval_layout
+MAGIC_UINT32_TO_JSVAL_IMPL(uint32_t payload)
+{
+    jsval_layout l;
+    l.asBits = ((uint64_t)payload) | JSVAL_SHIFTED_TAG_MAGIC;
+    return l;
+}
+
+static inline bool
+JSVAL_SAME_TYPE_IMPL(jsval_layout lhs, jsval_layout rhs)
+{
+    uint64_t lbits = lhs.asBits, rbits = rhs.asBits;
+    return (lbits <= JSVAL_SHIFTED_TAG_MAX_DOUBLE && rbits <= JSVAL_SHIFTED_TAG_MAX_DOUBLE) ||
+           (((lbits ^ rbits) & 0xFFFF800000000000LL) == 0);
+}
+
+static inline JSValueType
+JSVAL_EXTRACT_NON_DOUBLE_TYPE_IMPL(jsval_layout l)
+{
+   uint64_t type = (l.asBits >> JSVAL_TAG_SHIFT) & 0xF;
+   MOZ_ASSERT(type > JSVAL_TYPE_DOUBLE);
+   return (JSValueType)type;
+}
+
+#endif  /* JS_BITS_PER_WORD */
+
+static inline jsval_layout JSVAL_TO_IMPL(JS::Value v);
+static inline JS_VALUE_CONSTEXPR JS::Value IMPL_TO_JSVAL(jsval_layout l);
+
+namespace JS {
+
+static inline JS_VALUE_CONSTEXPR JS::Value UndefinedValue();
+
+/**
+ * Returns a generic quiet NaN value, with all payload bits set to zero.
+ *
+ * Among other properties, this NaN's bit pattern conforms to JS::Value's
+ * bit pattern restrictions.
+ */
+static MOZ_ALWAYS_INLINE double
+GenericNaN()
+{
+  return mozilla::SpecificNaN<double>(0, 0x8000000000000ULL);
+}
+
+/* MSVC with PGO miscompiles this function. */
+#if defined(_MSC_VER)
+# pragma optimize("g", off)
+#endif
+static inline double
+CanonicalizeNaN(double d)
+{
+    if (MOZ_UNLIKELY(mozilla::IsNaN(d)))
+        return GenericNaN();
+    return d;
+}
+#if defined(_MSC_VER)
+# pragma optimize("", on)
+#endif
+
+/*
+ * JS::Value is the interface for a single JavaScript Engine value.  A few
+ * general notes on JS::Value:
+ *
+ * - JS::Value has setX() and isX() members for X in
+ *
+ *     { Int32, Double, String, Boolean, Undefined, Null, Object, Magic }
+ *
+ *   JS::Value also contains toX() for each of the non-singleton types.
+ *
+ * - Magic is a singleton type whose payload contains either a JSWhyMagic "reason" for
+ *   the magic value or a uint32_t value. By providing JSWhyMagic values when
+ *   creating and checking for magic values, it is possible to assert, at
+ *   runtime, that only magic values with the expected reason flow through a
+ *   particular value. For example, if cx->exception has a magic value, the
+ *   reason must be JS_GENERATOR_CLOSING.
+ *
+ * - The JS::Value operations are preferred.  The JSVAL_* operations remain for
+ *   compatibility; they may be removed at some point.  These operations mostly
+ *   provide similar functionality.  But there are a few key differences.  One
+ *   is that JS::Value gives null a separate type. Thus
+ *
+ *           JSVAL_IS_OBJECT(v) === v.isObjectOrNull()
+ *       !JSVAL_IS_PRIMITIVE(v) === v.isObject()
+ *
+ *   Also, to help prevent mistakenly boxing a nullable JSObject* as an object,
+ *   Value::setObject takes a JSObject&. (Conversely, Value::toObject returns a
+ *   JSObject&.)  A convenience member Value::setObjectOrNull is provided.
+ *
+ * - JSVAL_VOID is the same as the singleton value of the Undefined type.
+ *
+ * - Note that JS::Value is 8 bytes on 32 and 64-bit architectures. Thus, on
+ *   32-bit user code should avoid copying jsval/JS::Value as much as possible,
+ *   preferring to pass by const Value &.
+ */
+class Value
+{
+  public:
+    /*
+     * N.B. the default constructor leaves Value unitialized. Adding a default
+     * constructor prevents Value from being stored in a union.
+     */
+#if defined(JS_VALUE_IS_CONSTEXPR)
+    Value() = default;
+    Value(const Value& v) = default;
+#endif
+
+    /*** Mutators ***/
+
+    void setNull() {
+        data.asBits = BUILD_JSVAL(JSVAL_TAG_NULL, 0).asBits;
+    }
+
+    void setUndefined() {
+        data.asBits = BUILD_JSVAL(JSVAL_TAG_UNDEFINED, 0).asBits;
+    }
+
+    void setInt32(int32_t i) {
+        data = INT32_TO_JSVAL_IMPL(i);
+    }
+
+    int32_t &getInt32Ref() {
+        MOZ_ASSERT(isInt32());
+        return data.s.payload.i32;
+    }
+
+    void setDouble(double d) {
+        data = DOUBLE_TO_JSVAL_IMPL(d);
+    }
+
+    void setNaN() {
+        setDouble(GenericNaN());
+    }
+
+    double &getDoubleRef() {
+        MOZ_ASSERT(isDouble());
+        return data.asDouble;
+    }
+
+    void setString(JSString *str) {
+        MOZ_ASSERT(!IsPoisonedPtr(str));
+        data = STRING_TO_JSVAL_IMPL(str);
+    }
+
+    void setObject(JSObject &obj) {
+        MOZ_ASSERT(!IsPoisonedPtr(&obj));
+        data = OBJECT_TO_JSVAL_IMPL(&obj);
+    }
+
+    void setBoolean(bool b) {
+        data = BOOLEAN_TO_JSVAL_IMPL(b);
+    }
+
+    void setMagic(JSWhyMagic why) {
+        data = MAGIC_TO_JSVAL_IMPL(why);
+    }
+
+    void setMagicUint32(uint32_t payload) {
+        data = MAGIC_UINT32_TO_JSVAL_IMPL(payload);
+    }
+
+    bool setNumber(uint32_t ui) {
+        if (ui > JSVAL_INT_MAX) {
+            setDouble((double)ui);
+            return false;
+        } else {
+            setInt32((int32_t)ui);
+            return true;
+        }
+    }
+
+    bool setNumber(double d) {
+        int32_t i;
+        if (mozilla::NumberIsInt32(d, &i)) {
+            setInt32(i);
+            return true;
+        }
+
+        setDouble(d);
+        return false;
+    }
+
+    void setObjectOrNull(JSObject *arg) {
+        if (arg)
+            setObject(*arg);
+        else
+            setNull();
+    }
+
+    void swap(Value &rhs) {
+        uint64_t tmp = rhs.data.asBits;
+        rhs.data.asBits = data.asBits;
+        data.asBits = tmp;
+    }
+
+    /*** Value type queries ***/
+
+    bool isUndefined() const {
+        return JSVAL_IS_UNDEFINED_IMPL(data);
+    }
+
+    bool isNull() const {
+        return JSVAL_IS_NULL_IMPL(data);
+    }
+
+    bool isNullOrUndefined() const {
+        return isNull() || isUndefined();
+    }
+
+    bool isInt32() const {
+        return JSVAL_IS_INT32_IMPL(data);
+    }
+
+    bool isInt32(int32_t i32) const {
+        return JSVAL_IS_SPECIFIC_INT32_IMPL(data, i32);
+    }
+
+    bool isDouble() const {
+        return JSVAL_IS_DOUBLE_IMPL(data);
+    }
+
+    bool isNumber() const {
+        return JSVAL_IS_NUMBER_IMPL(data);
+    }
+
+    bool isString() const {
+        return JSVAL_IS_STRING_IMPL(data);
+    }
+
+    bool isObject() const {
+        return JSVAL_IS_OBJECT_IMPL(data);
+    }
+
+    bool isPrimitive() const {
+        return JSVAL_IS_PRIMITIVE_IMPL(data);
+    }
+
+    bool isObjectOrNull() const {
+        return JSVAL_IS_OBJECT_OR_NULL_IMPL(data);
+    }
+
+    bool isGCThing() const {
+        return JSVAL_IS_GCTHING_IMPL(data);
+    }
+
+    bool isBoolean() const {
+        return JSVAL_IS_BOOLEAN_IMPL(data);
+    }
+
+    bool isTrue() const {
+        return JSVAL_IS_SPECIFIC_BOOLEAN(data, true);
+    }
+
+    bool isFalse() const {
+        return JSVAL_IS_SPECIFIC_BOOLEAN(data, false);
+    }
+
+    bool isMagic() const {
+        return JSVAL_IS_MAGIC_IMPL(data);
+    }
+
+    bool isMagic(JSWhyMagic why) const {
+        MOZ_ASSERT_IF(isMagic(), data.s.payload.why == why);
+        return JSVAL_IS_MAGIC_IMPL(data);
+    }
+
+    bool isMarkable() const {
+        return JSVAL_IS_TRACEABLE_IMPL(data);
+    }
+
+    JSGCTraceKind gcKind() const {
+        MOZ_ASSERT(isMarkable());
+        return JSGCTraceKind(JSVAL_TRACE_KIND_IMPL(data));
+    }
+
+    JSWhyMagic whyMagic() const {
+        MOZ_ASSERT(isMagic());
+        return data.s.payload.why;
+    }
+
+    uint32_t magicUint32() const {
+        MOZ_ASSERT(isMagic());
+        return data.s.payload.u32;
+    }
+
+    /*** Comparison ***/
+
+    bool operator==(const Value &rhs) const {
+        return data.asBits == rhs.data.asBits;
+    }
+
+    bool operator!=(const Value &rhs) const {
+        return data.asBits != rhs.data.asBits;
+    }
+
+    friend inline bool SameType(const Value &lhs, const Value &rhs);
+
+    /*** Extract the value's typed payload ***/
+
+    int32_t toInt32() const {
+        MOZ_ASSERT(isInt32());
+        return JSVAL_TO_INT32_IMPL(data);
+    }
+
+    double toDouble() const {
+        MOZ_ASSERT(isDouble());
+        return data.asDouble;
+    }
+
+    double toNumber() const {
+        MOZ_ASSERT(isNumber());
+        return isDouble() ? toDouble() : double(toInt32());
+    }
+
+    JSString *toString() const {
+        MOZ_ASSERT(isString());
+        return JSVAL_TO_STRING_IMPL(data);
+    }
+
+    JSObject &toObject() const {
+        MOZ_ASSERT(isObject());
+        return *JSVAL_TO_OBJECT_IMPL(data);
+    }
+
+    JSObject *toObjectOrNull() const {
+        MOZ_ASSERT(isObjectOrNull());
+        return JSVAL_TO_OBJECT_IMPL(data);
+    }
+
+    void *toGCThing() const {
+        MOZ_ASSERT(isGCThing());
+        return JSVAL_TO_GCTHING_IMPL(data);
+    }
+
+    bool toBoolean() const {
+        MOZ_ASSERT(isBoolean());
+        return JSVAL_TO_BOOLEAN_IMPL(data);
+    }
+
+    uint32_t payloadAsRawUint32() const {
+        MOZ_ASSERT(!isDouble());
+        return data.s.payload.u32;
+    }
+
+    uint64_t asRawBits() const {
+        return data.asBits;
+    }
+
+    JSValueType extractNonDoubleType() const {
+        return JSVAL_EXTRACT_NON_DOUBLE_TYPE_IMPL(data);
+    }
+
+    /*
+     * Private API
+     *
+     * Private setters/getters allow the caller to read/write arbitrary types
+     * that fit in the 64-bit payload. It is the caller's responsibility, after
+     * storing to a value with setPrivateX to read only using getPrivateX.
+     * Privates values are given a type which ensures they are not marked.
+     */
+
+    void setPrivate(void *ptr) {
+        data = PRIVATE_PTR_TO_JSVAL_IMPL(ptr);
+    }
+
+    void *toPrivate() const {
+        MOZ_ASSERT(JSVAL_IS_DOUBLE_IMPL(data));
+        return JSVAL_TO_PRIVATE_PTR_IMPL(data);
+    }
+
+    void setPrivateUint32(uint32_t ui) {
+        MOZ_ASSERT(uint32_t(int32_t(ui)) == ui);
+        setInt32(int32_t(ui));
+    }
+
+    uint32_t toPrivateUint32() const {
+        return uint32_t(toInt32());
+    }
+
+    /*
+     * An unmarked value is just a void* cast as a Value. Thus, the Value is
+     * not safe for GC and must not be marked. This API avoids raw casts
+     * and the ensuing strict-aliasing warnings.
+     */
+
+    void setUnmarkedPtr(void *ptr) {
+        data.asPtr = ptr;
+    }
+
+    void *toUnmarkedPtr() const {
+        return data.asPtr;
+    }
+
+    const size_t *payloadWord() const {
+#if JS_BITS_PER_WORD == 32
+        return &data.s.payload.word;
+#elif JS_BITS_PER_WORD == 64
+        return &data.asWord;
+#endif
+    }
+
+    const uintptr_t *payloadUIntPtr() const {
+#if JS_BITS_PER_WORD == 32
+        return &data.s.payload.uintptr;
+#elif JS_BITS_PER_WORD == 64
+        return &data.asUIntPtr;
+#endif
+    }
+
+#if !defined(_MSC_VER) && !defined(__sparc)
+  // Value must be POD so that MSVC will pass it by value and not in memory
+  // (bug 689101); the same is true for SPARC as well (bug 737344).  More
+  // precisely, we don't want Value return values compiled as out params.
+  private:
+#endif
+
+    jsval_layout data;
+
+  private:
+#if defined(JS_VALUE_IS_CONSTEXPR)
+    JS_VALUE_CONSTEXPR Value(jsval_layout layout) : data(layout) {}
+#endif
+
+    void staticAssertions() {
+        JS_STATIC_ASSERT(sizeof(JSValueType) == 1);
+        JS_STATIC_ASSERT(sizeof(JSValueTag) == 4);
+        JS_STATIC_ASSERT(sizeof(JSWhyMagic) <= 4);
+        JS_STATIC_ASSERT(sizeof(Value) == 8);
+    }
+
+    friend jsval_layout (::JSVAL_TO_IMPL)(Value);
+    friend Value JS_VALUE_CONSTEXPR (::IMPL_TO_JSVAL)(jsval_layout l);
+    friend Value JS_VALUE_CONSTEXPR (JS::UndefinedValue)();
+};
+
+inline bool
+IsPoisonedValue(const Value &v)
+{
+    if (v.isString())
+        return IsPoisonedPtr(v.toString());
+    if (v.isObject())
+        return IsPoisonedPtr(&v.toObject());
+    return false;
+}
+
+inline bool
+IsOptimizedPlaceholderMagicValue(const Value &v)
+{
+    if (v.isMagic()) {
+        MOZ_ASSERT(v.whyMagic() == JS_OPTIMIZED_ARGUMENTS || v.whyMagic() == JS_OPTIMIZED_OUT);
+        return true;
+    }
+    return false;
+}
+
+/************************************************************************/
+
+static inline Value
+NullValue()
+{
+    Value v;
+    v.setNull();
+    return v;
+}
+
+static inline JS_VALUE_CONSTEXPR Value
+UndefinedValue()
+{
+#if defined(JS_VALUE_IS_CONSTEXPR)
+    return Value(BUILD_JSVAL(JSVAL_TAG_UNDEFINED, 0));
+#else
+    JS::Value v;
+    v.setUndefined();
+    return v;
+#endif
+}
+
+static inline Value
+Int32Value(int32_t i32)
+{
+    Value v;
+    v.setInt32(i32);
+    return v;
+}
+
+static inline Value
+DoubleValue(double dbl)
+{
+    Value v;
+    v.setDouble(dbl);
+    return v;
+}
+
+static inline Value
+DoubleNaNValue()
+{
+    Value v;
+    v.setNaN();
+    return v;
+}
+
+static inline Value
+Float32Value(float f)
+{
+    Value v;
+    v.setDouble(f);
+    return v;
+}
+
+static inline Value
+StringValue(JSString *str)
+{
+    Value v;
+    v.setString(str);
+    return v;
+}
+
+static inline Value
+BooleanValue(bool boo)
+{
+    Value v;
+    v.setBoolean(boo);
+    return v;
+}
+
+static inline Value
+TrueValue()
+{
+    Value v;
+    v.setBoolean(true);
+    return v;
+}
+
+static inline Value
+FalseValue()
+{
+    Value v;
+    v.setBoolean(false);
+    return v;
+}
+
+static inline Value
+ObjectValue(JSObject &obj)
+{
+    Value v;
+    v.setObject(obj);
+    return v;
+}
+
+static inline Value
+ObjectValueCrashOnTouch()
+{
+    Value v;
+    v.setObject(*reinterpret_cast<JSObject *>(0x42));
+    return v;
+}
+
+static inline Value
+MagicValue(JSWhyMagic why)
+{
+    Value v;
+    v.setMagic(why);
+    return v;
+}
+
+static inline Value
+MagicValueUint32(uint32_t payload)
+{
+    Value v;
+    v.setMagicUint32(payload);
+    return v;
+}
+
+static inline Value
+NumberValue(float f)
+{
+    Value v;
+    v.setNumber(f);
+    return v;
+}
+
+static inline Value
+NumberValue(double dbl)
+{
+    Value v;
+    v.setNumber(dbl);
+    return v;
+}
+
+static inline Value
+NumberValue(int8_t i)
+{
+    return Int32Value(i);
+}
+
+static inline Value
+NumberValue(uint8_t i)
+{
+    return Int32Value(i);
+}
+
+static inline Value
+NumberValue(int16_t i)
+{
+    return Int32Value(i);
+}
+
+static inline Value
+NumberValue(uint16_t i)
+{
+    return Int32Value(i);
+}
+
+static inline Value
+NumberValue(int32_t i)
+{
+    return Int32Value(i);
+}
+
+static inline Value
+NumberValue(uint32_t i)
+{
+    Value v;
+    v.setNumber(i);
+    return v;
+}
+
+namespace detail {
+
+template <bool Signed>
+class MakeNumberValue
+{
+  public:
+    template<typename T>
+    static inline Value create(const T t)
+    {
+        Value v;
+        if (JSVAL_INT_MIN <= t && t <= JSVAL_INT_MAX)
+            v.setInt32(int32_t(t));
+        else
+            v.setDouble(double(t));
+        return v;
+    }
+};
+
+template <>
+class MakeNumberValue<false>
+{
+  public:
+    template<typename T>
+    static inline Value create(const T t)
+    {
+        Value v;
+        if (t <= JSVAL_INT_MAX)
+            v.setInt32(int32_t(t));
+        else
+            v.setDouble(double(t));
+        return v;
+    }
+};
+
+} // namespace detail
+
+template <typename T>
+static inline Value
+NumberValue(const T t)
+{
+    MOZ_ASSERT(T(double(t)) == t, "value creation would be lossy");
+    return detail::MakeNumberValue<std::numeric_limits<T>::is_signed>::create(t);
+}
+
+static inline Value
+ObjectOrNullValue(JSObject *obj)
+{
+    Value v;
+    v.setObjectOrNull(obj);
+    return v;
+}
+
+static inline Value
+PrivateValue(void *ptr)
+{
+    Value v;
+    v.setPrivate(ptr);
+    return v;
+}
+
+static inline Value
+PrivateUint32Value(uint32_t ui)
+{
+    Value v;
+    v.setPrivateUint32(ui);
+    return v;
+}
+
+inline bool
+SameType(const Value &lhs, const Value &rhs)
+{
+    return JSVAL_SAME_TYPE_IMPL(lhs.data, rhs.data);
+}
+
+} // namespace JS
+
+/************************************************************************/
+
+#ifdef JSGC_GENERATIONAL
+namespace JS {
+JS_PUBLIC_API(void) HeapValuePostBarrier(Value *valuep);
+JS_PUBLIC_API(void) HeapValueRelocate(Value *valuep);
+}
+#endif
+
+namespace js {
+
+template <> struct GCMethods<const JS::Value>
+{
+    static JS::Value initial() { return JS::UndefinedValue(); }
+    static ThingRootKind kind() { return THING_ROOT_VALUE; }
+    static bool poisoned(const JS::Value &v) { return JS::IsPoisonedValue(v); }
+};
+
+template <> struct GCMethods<JS::Value>
+{
+    static JS::Value initial() { return JS::UndefinedValue(); }
+    static ThingRootKind kind() { return THING_ROOT_VALUE; }
+    static bool poisoned(const JS::Value &v) { return JS::IsPoisonedValue(v); }
+    static bool needsPostBarrier(const JS::Value &v) { return v.isMarkable(); }
+#ifdef JSGC_GENERATIONAL
+    static void postBarrier(JS::Value *v) { JS::HeapValuePostBarrier(v); }
+    static void relocate(JS::Value *v) { JS::HeapValueRelocate(v); }
+#endif
+};
+
+template <class Outer> class MutableValueOperations;
+
+/*
+ * A class designed for CRTP use in implementing the non-mutating parts of the
+ * Value interface in Value-like classes.  Outer must be a class inheriting
+ * ValueOperations<Outer> with a visible extract() method returning the
+ * const Value* abstracted by Outer.
+ */
+template <class Outer>
+class ValueOperations
+{
+    friend class MutableValueOperations<Outer>;
+
+    const JS::Value * value() const { return static_cast<const Outer*>(this)->extract(); }
+
+  public:
+    bool isUndefined() const { return value()->isUndefined(); }
+    bool isNull() const { return value()->isNull(); }
+    bool isBoolean() const { return value()->isBoolean(); }
+    bool isTrue() const { return value()->isTrue(); }
+    bool isFalse() const { return value()->isFalse(); }
+    bool isNumber() const { return value()->isNumber(); }
+    bool isInt32() const { return value()->isInt32(); }
+    bool isDouble() const { return value()->isDouble(); }
+    bool isString() const { return value()->isString(); }
+    bool isObject() const { return value()->isObject(); }
+    bool isMagic() const { return value()->isMagic(); }
+    bool isMagic(JSWhyMagic why) const { return value()->isMagic(why); }
+    bool isMarkable() const { return value()->isMarkable(); }
+    bool isPrimitive() const { return value()->isPrimitive(); }
+    bool isGCThing() const { return value()->isGCThing(); }
+
+    bool isNullOrUndefined() const { return value()->isNullOrUndefined(); }
+    bool isObjectOrNull() const { return value()->isObjectOrNull(); }
+
+    bool toBoolean() const { return value()->toBoolean(); }
+    double toNumber() const { return value()->toNumber(); }
+    int32_t toInt32() const { return value()->toInt32(); }
+    double toDouble() const { return value()->toDouble(); }
+    JSString *toString() const { return value()->toString(); }
+    JSObject &toObject() const { return value()->toObject(); }
+    JSObject *toObjectOrNull() const { return value()->toObjectOrNull(); }
+    void *toGCThing() const { return value()->toGCThing(); }
+
+    JSValueType extractNonDoubleType() const { return value()->extractNonDoubleType(); }
+    uint32_t toPrivateUint32() const { return value()->toPrivateUint32(); }
+
+    JSWhyMagic whyMagic() const { return value()->whyMagic(); }
+    uint32_t magicUint32() const { return value()->magicUint32(); }
+};
+
+/*
+ * A class designed for CRTP use in implementing all the mutating parts of the
+ * Value interface in Value-like classes.  Outer must be a class inheriting
+ * MutableValueOperations<Outer> with visible extractMutable() and extract()
+ * methods returning the const Value* and Value* abstracted by Outer.
+ */
+template <class Outer>
+class MutableValueOperations : public ValueOperations<Outer>
+{
+    JS::Value * value() { return static_cast<Outer*>(this)->extractMutable(); }
+
+  public:
+    void setNull() { value()->setNull(); }
+    void setUndefined() { value()->setUndefined(); }
+    void setInt32(int32_t i) { value()->setInt32(i); }
+    void setDouble(double d) { value()->setDouble(d); }
+    void setNaN() { setDouble(JS::GenericNaN()); }
+    void setBoolean(bool b) { value()->setBoolean(b); }
+    void setMagic(JSWhyMagic why) { value()->setMagic(why); }
+    bool setNumber(uint32_t ui) { return value()->setNumber(ui); }
+    bool setNumber(double d) { return value()->setNumber(d); }
+    void setString(JSString *str) { this->value()->setString(str); }
+    void setObject(JSObject &obj) { this->value()->setObject(obj); }
+    void setObjectOrNull(JSObject *arg) { this->value()->setObjectOrNull(arg); }
+};
+
+/*
+ * Augment the generic Heap<T> interface when T = Value with
+ * type-querying, value-extracting, and mutating operations.
+ */
+template <>
+class HeapBase<JS::Value> : public ValueOperations<JS::Heap<JS::Value> >
+{
+    typedef JS::Heap<JS::Value> Outer;
+
+    friend class ValueOperations<Outer>;
+
+    const JS::Value * extract() const { return static_cast<const Outer*>(this)->address(); }
+
+    void setBarriered(const JS::Value &v) {
+        static_cast<JS::Heap<JS::Value> *>(this)->set(v);
+    }
+
+  public:
+    void setNull() { setBarriered(JS::NullValue()); }
+    void setUndefined() { setBarriered(JS::UndefinedValue()); }
+    void setInt32(int32_t i) { setBarriered(JS::Int32Value(i)); }
+    void setDouble(double d) { setBarriered(JS::DoubleValue(d)); }
+    void setNaN() { setDouble(JS::GenericNaN()); }
+    void setBoolean(bool b) { setBarriered(JS::BooleanValue(b)); }
+    void setMagic(JSWhyMagic why) { setBarriered(JS::MagicValue(why)); }
+    void setString(JSString *str) { setBarriered(JS::StringValue(str)); }
+    void setObject(JSObject &obj) { setBarriered(JS::ObjectValue(obj)); }
+
+    bool setNumber(uint32_t ui) {
+        if (ui > JSVAL_INT_MAX) {
+            setDouble((double)ui);
+            return false;
+        } else {
+            setInt32((int32_t)ui);
+            return true;
+        }
+    }
+
+    bool setNumber(double d) {
+        int32_t i;
+        if (mozilla::NumberIsInt32(d, &i)) {
+            setInt32(i);
+            return true;
+        }
+
+        setDouble(d);
+        return false;
+    }
+
+    void setObjectOrNull(JSObject *arg) {
+        if (arg)
+            setObject(*arg);
+        else
+            setNull();
+    }
+};
+
+/*
+ * Augment the generic Handle<T> interface when T = Value with type-querying
+ * and value-extracting operations.
+ */
+template <>
+class HandleBase<JS::Value> : public ValueOperations<JS::Handle<JS::Value> >
+{
+    friend class ValueOperations<JS::Handle<JS::Value> >;
+    const JS::Value * extract() const {
+        return static_cast<const JS::Handle<JS::Value>*>(this)->address();
+    }
+};
+
+/*
+ * Augment the generic MutableHandle<T> interface when T = Value with
+ * type-querying, value-extracting, and mutating operations.
+ */
+template <>
+class MutableHandleBase<JS::Value> : public MutableValueOperations<JS::MutableHandle<JS::Value> >
+{
+    friend class ValueOperations<JS::MutableHandle<JS::Value> >;
+    const JS::Value * extract() const {
+        return static_cast<const JS::MutableHandle<JS::Value>*>(this)->address();
+    }
+
+    friend class MutableValueOperations<JS::MutableHandle<JS::Value> >;
+    JS::Value * extractMutable() {
+        return static_cast<JS::MutableHandle<JS::Value>*>(this)->address();
+    }
+};
+
+/*
+ * Augment the generic Rooted<T> interface when T = Value with type-querying,
+ * value-extracting, and mutating operations.
+ */
+template <>
+class RootedBase<JS::Value> : public MutableValueOperations<JS::Rooted<JS::Value> >
+{
+    friend class ValueOperations<JS::Rooted<JS::Value> >;
+    const JS::Value * extract() const {
+        return static_cast<const JS::Rooted<JS::Value>*>(this)->address();
+    }
+
+    friend class MutableValueOperations<JS::Rooted<JS::Value> >;
+    JS::Value * extractMutable() {
+        return static_cast<JS::Rooted<JS::Value>*>(this)->address();
+    }
+};
+
+} // namespace js
+
+inline jsval_layout
+JSVAL_TO_IMPL(JS::Value v)
+{
+    return v.data;
+}
+
+inline JS_VALUE_CONSTEXPR JS::Value
+IMPL_TO_JSVAL(jsval_layout l)
+{
+#if defined(JS_VALUE_IS_CONSTEXPR)
+    return JS::Value(l);
+#else
+    JS::Value v;
+    v.data = l;
+    return v;
+#endif
+}
+
+namespace JS {
+
+#ifndef __GNUC__
+/*
+ * The default assignment operator for |struct C| has the signature:
+ *
+ *   C& C::operator=(const C&)
+ *
+ * And in particular requires implicit conversion of |this| to type |C| for the
+ * return value. But |volatile C| cannot thus be converted to |C|, so just
+ * doing |sink = hold| as in the non-specialized version would fail to compile.
+ * Do the assignment on asBits instead, since I don't think we want to give
+ * jsval_layout an assignment operator returning |volatile jsval_layout|.
+ */
+template<>
+inline Anchor<Value>::~Anchor()
+{
+    volatile uint64_t bits;
+    bits = JSVAL_TO_IMPL(hold).asBits;
+}
+#endif
+
+#ifdef JS_DEBUG
+namespace detail {
+
+struct ValueAlignmentTester { char c; JS::Value v; };
+static_assert(sizeof(ValueAlignmentTester) == 16,
+              "JS::Value must be 16-byte-aligned");
+
+struct LayoutAlignmentTester { char c; jsval_layout l; };
+static_assert(sizeof(LayoutAlignmentTester) == 16,
+              "jsval_layout must be 16-byte-aligned");
+
+} // namespace detail
+#endif /* JS_DEBUG */
+
+} // namespace JS
+
+/*
+ * JS::Value and jsval are the same type; jsval is the old name, kept around
+ * for backwards compatibility along with all the JSVAL_* operations below.
+ * jsval_layout is an implementation detail and should not be used externally.
+ */
+typedef JS::Value jsval;
+
+static_assert(sizeof(jsval_layout) == sizeof(JS::Value),
+              "jsval_layout and JS::Value must have identical layouts");
+
+/************************************************************************/
+
+static inline bool
+JSVAL_IS_NULL(jsval v)
+{
+    return JSVAL_IS_NULL_IMPL(JSVAL_TO_IMPL(v));
+}
+
+static inline bool
+JSVAL_IS_VOID(jsval v)
+{
+    return JSVAL_IS_UNDEFINED_IMPL(JSVAL_TO_IMPL(v));
+}
+
+static inline bool
+JSVAL_IS_INT(jsval v)
+{
+    return JSVAL_IS_INT32_IMPL(JSVAL_TO_IMPL(v));
+}
+
+static inline int32_t
+JSVAL_TO_INT(jsval v)
+{
+    MOZ_ASSERT(JSVAL_IS_INT(v));
+    return JSVAL_TO_INT32_IMPL(JSVAL_TO_IMPL(v));
+}
+
+static inline JS_VALUE_CONSTEXPR jsval
+INT_TO_JSVAL(int32_t i)
+{
+    return IMPL_TO_JSVAL(INT32_TO_JSVAL_IMPL(i));
+}
+
+static inline bool
+JSVAL_IS_DOUBLE(jsval v)
+{
+    return JSVAL_IS_DOUBLE_IMPL(JSVAL_TO_IMPL(v));
+}
+
+static inline double
+JSVAL_TO_DOUBLE(jsval v)
+{
+    jsval_layout l;
+    MOZ_ASSERT(JSVAL_IS_DOUBLE(v));
+    l = JSVAL_TO_IMPL(v);
+    return l.asDouble;
+}
+
+static inline JS_VALUE_CONSTEXPR jsval
+DOUBLE_TO_JSVAL(double d)
+{
+    /*
+     * This is a manually inlined version of:
+     *    d = JS_CANONICALIZE_NAN(d);
+     *    return IMPL_TO_JSVAL(DOUBLE_TO_JSVAL_IMPL(d));
+     * because GCC from XCode 3.1.4 miscompiles the above code.
+     */
+#if defined(JS_VALUE_IS_CONSTEXPR)
+    return IMPL_TO_JSVAL(MOZ_UNLIKELY(d != d)
+                         ? (jsval_layout) { .asBits = 0x7FF8000000000000LL }
+                         : (jsval_layout) { .asDouble = d });
+#else
+    jsval_layout l;
+    if (MOZ_UNLIKELY(d != d))
+        l.asBits = 0x7FF8000000000000LL;
+    else
+        l.asDouble = d;
+    return IMPL_TO_JSVAL(l);
+#endif
+}
+
+static inline JS_VALUE_CONSTEXPR jsval
+UINT_TO_JSVAL(uint32_t i)
+{
+    return (i <= JSVAL_INT_MAX
+            ? INT_TO_JSVAL((int32_t)i)
+            : DOUBLE_TO_JSVAL((double)i));
+}
+
+static inline bool
+JSVAL_IS_NUMBER(jsval v)
+{
+    return JSVAL_IS_NUMBER_IMPL(JSVAL_TO_IMPL(v));
+}
+
+static inline bool
+JSVAL_IS_STRING(jsval v)
+{
+    return JSVAL_IS_STRING_IMPL(JSVAL_TO_IMPL(v));
+}
+
+static inline JSString *
+JSVAL_TO_STRING(jsval v)
+{
+    MOZ_ASSERT(JSVAL_IS_STRING(v));
+    return JSVAL_TO_STRING_IMPL(JSVAL_TO_IMPL(v));
+}
+
+static inline jsval
+STRING_TO_JSVAL(JSString *str)
+{
+    return IMPL_TO_JSVAL(STRING_TO_JSVAL_IMPL(str));
+}
+
+static inline JSObject *
+JSVAL_TO_OBJECT(jsval v)
+{
+    MOZ_ASSERT(JSVAL_IS_OBJECT_OR_NULL_IMPL(JSVAL_TO_IMPL(v)));
+    return JSVAL_TO_OBJECT_IMPL(JSVAL_TO_IMPL(v));
+}
+
+static inline jsval
+OBJECT_TO_JSVAL(JSObject *obj)
+{
+    if (obj)
+        return IMPL_TO_JSVAL(OBJECT_TO_JSVAL_IMPL(obj));
+    return IMPL_TO_JSVAL(BUILD_JSVAL(JSVAL_TAG_NULL, 0));
+}
+
+static inline bool
+JSVAL_IS_BOOLEAN(jsval v)
+{
+    return JSVAL_IS_BOOLEAN_IMPL(JSVAL_TO_IMPL(v));
+}
+
+static inline bool
+JSVAL_TO_BOOLEAN(jsval v)
+{
+    MOZ_ASSERT(JSVAL_IS_BOOLEAN(v));
+    return JSVAL_TO_BOOLEAN_IMPL(JSVAL_TO_IMPL(v));
+}
+
+static inline jsval
+BOOLEAN_TO_JSVAL(bool b)
+{
+    return IMPL_TO_JSVAL(BOOLEAN_TO_JSVAL_IMPL(b));
+}
+
+static inline bool
+JSVAL_IS_PRIMITIVE(jsval v)
+{
+    return JSVAL_IS_PRIMITIVE_IMPL(JSVAL_TO_IMPL(v));
+}
+
+static inline bool
+JSVAL_IS_GCTHING(jsval v)
+{
+    return JSVAL_IS_GCTHING_IMPL(JSVAL_TO_IMPL(v));
+}
+
+static inline void *
+JSVAL_TO_GCTHING(jsval v)
+{
+    MOZ_ASSERT(JSVAL_IS_GCTHING(v));
+    return JSVAL_TO_GCTHING_IMPL(JSVAL_TO_IMPL(v));
+}
+
+/* To be GC-safe, privates are tagged as doubles. */
+
+static inline jsval
+PRIVATE_TO_JSVAL(void *ptr)
+{
+    return IMPL_TO_JSVAL(PRIVATE_PTR_TO_JSVAL_IMPL(ptr));
+}
+
+static inline void *
+JSVAL_TO_PRIVATE(jsval v)
+{
+    MOZ_ASSERT(JSVAL_IS_DOUBLE(v));
+    return JSVAL_TO_PRIVATE_PTR_IMPL(JSVAL_TO_IMPL(v));
+}
+
+// JS constants. For efficiency, prefer predicates (e.g. v.isNull()) and
+// constructing values from scratch (e.g. Int32Value(0)).  These constants are
+// stored in memory and initialized at startup, so testing against them and
+// using them requires memory loads and will be correspondingly slow.
+extern JS_PUBLIC_DATA(const jsval) JSVAL_NULL;
+extern JS_PUBLIC_DATA(const jsval) JSVAL_ZERO;
+extern JS_PUBLIC_DATA(const jsval) JSVAL_ONE;
+extern JS_PUBLIC_DATA(const jsval) JSVAL_FALSE;
+extern JS_PUBLIC_DATA(const jsval) JSVAL_TRUE;
+extern JS_PUBLIC_DATA(const jsval) JSVAL_VOID;
+
+namespace JS {
+
+extern JS_PUBLIC_DATA(const HandleValue) NullHandleValue;
+extern JS_PUBLIC_DATA(const HandleValue) UndefinedHandleValue;
+
+}
+
+#undef JS_VALUE_IS_CONSTEXPR
+#undef JS_RETURN_LAYOUT_FROM_BITS
+
+#endif /* js_Value_h */