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diff --git a/js/public/GCAnnotations.h b/js/public/GCAnnotations.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * 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/. */
+
+#ifndef js_GCAnnotations_h
+#define js_GCAnnotations_h
+
+// Set of annotations for the rooting hazard analysis, used to categorize types
+// and functions.
+#ifdef XGILL_PLUGIN
+
+#  define JS_EXPECT_HAZARDS __attribute__((annotate("Expect Hazards")))
+
+// Mark a type as being a GC thing (eg js::gc::Cell has this annotation).
+#  define JS_HAZ_GC_THING __attribute__((annotate("GC Thing")))
+
+// Mark a type as holding a pointer to a GC thing (eg JS::Value has this
+// annotation.) "Inherited" by templatized types with
+// MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS.
+#  define JS_HAZ_GC_POINTER __attribute__((annotate("GC Pointer")))
+
+// Same as JS_HAZ_GC_POINTER, except additionally treat pointers to these
+// as GC pointers themselves in order to check references to them, since
+// the analysis cannot distinguish between pointers and references.
+#  define JS_HAZ_GC_REF __attribute__((annotate("GC Pointer or Reference")))
+
+// Mark a type as a rooted pointer, suitable for use on the stack (eg all
+// Rooted<T> instantiations should have this.) "Inherited" by templatized types
+// with MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS.
+#  define JS_HAZ_ROOTED __attribute__((annotate("Rooted Pointer")))
+
+// Mark a type as something that should not be held live across a GC, but which
+// is not itself a GC pointer. Note that this property is *not* inherited by
+// templatized types with MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS.
+#  define JS_HAZ_GC_INVALIDATED __attribute__((annotate("Invalidated by GC")))
+
+// Mark a class as a base class of rooted types, eg CustomAutoRooter. All
+// descendants of this class will be considered rooted, though classes that
+// merely contain these as a field member will not be. "Inherited" by
+// templatized types with MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS
+#  define JS_HAZ_ROOTED_BASE __attribute__((annotate("Rooted Base")))
+
+// Mark a type that would otherwise be considered a GC Pointer (eg because it
+// contains a JS::Value field) as a non-GC pointer. It is handled almost the
+// same in the analysis as a rooted pointer, except it will not be reported as
+// an unnecessary root if used across a GC call. This should rarely be used,
+// but makes sense for something like ErrorResult, which only contains a GC
+// pointer when it holds an exception (and it does its own rooting,
+// conditionally.)
+#  define JS_HAZ_NON_GC_POINTER \
+    __attribute__((annotate("Suppressed GC Pointer")))
+
+// Mark a function as something that runs a garbage collection, potentially
+// invalidating GC pointers.
+#  define JS_HAZ_GC_CALL __attribute__((annotate("GC Call")))
+
+// Mark an RAII class as suppressing GC within its scope.
+#  define JS_HAZ_GC_SUPPRESSED __attribute__((annotate("Suppress GC")))
+
+// Mark a function as one that can run script if called.  This obviously
+// subsumes JS_HAZ_GC_CALL, since anything that can run script can GC.`
+#  define JS_HAZ_CAN_RUN_SCRIPT __attribute__((annotate("Can run script")))
+
+// Mark a function as able to call JSNatives. Otherwise, JSNatives don't show
+// up in the callgraph. This doesn't matter for the can-GC analysis, but it is
+// very nice for other uses of the callgraph.
+#  define JS_HAZ_JSNATIVE_CALLER __attribute__((annotate("Calls JSNatives")))
+
+// Mark a variable as being "GC safe", i.e., it does not contain any
+// invalidatable pointers at the current point in the code. A typical
+// example might be a collection containing GC pointers, which at the
+// present time is empty. This property is only temporary; the next use
+// of the variable will invalidate it (on the assumption that a GC pointer
+// might be added to it.) Try to use this as early as possible, probably
+// immediately after construction, so that if future mutations through
+// the variable are added, they won't be covered by the annotation.
+#  define JS_HAZ_VALUE_IS_GC_SAFE(var) JS::detail::MarkVariableAsGCSafe(var)
+
+#else
+
+#  define JS_EXPECT_HAZARDS
+#  define JS_HAZ_GC_THING
+#  define JS_HAZ_GC_POINTER
+#  define JS_HAZ_GC_REF
+#  define JS_HAZ_ROOTED
+#  define JS_HAZ_GC_INVALIDATED
+#  define JS_HAZ_ROOTED_BASE
+#  define JS_HAZ_NON_GC_POINTER
+#  define JS_HAZ_GC_CALL
+#  define JS_HAZ_GC_SUPPRESSED
+#  define JS_HAZ_CAN_RUN_SCRIPT
+#  define JS_HAZ_JSNATIVE_CALLER
+#  define JS_HAZ_VALUE_IS_GC_SAFE(var)
+
+#endif
+
+#ifdef XGILL_PLUGIN
+
+// Implemented by passing variable to a dummy function so that it shows up
+// in the control flow graph.
+namespace JS {
+namespace detail {
+
+template <typename T>
+static inline void MarkVariableAsGCSafe(T& var) {
+  asm("");
+}
+
+}  // namespace detail
+}  // namespace JS
+
+#endif
+
+#endif /* js_GCAnnotations_h */