js/public/GCAnnotations.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef js_GCAnnotations_h
   8 #define js_GCAnnotations_h
   9
  10 // Set of annotations for the rooting hazard analysis, used to categorize types
  11 // and functions.
  12 #ifdef XGILL_PLUGIN
  13
  14 #  define JS_EXPECT_HAZARDS __attribute__((annotate("Expect Hazards")))
  15
  16 // Mark a type as being a GC thing (eg js::gc::Cell has this annotation).
  17 #  define JS_HAZ_GC_THING __attribute__((annotate("GC Thing")))
  18
  19 // Mark a type as holding a pointer to a GC thing (eg JS::Value has this
  20 // annotation.) "Inherited" by templatized types with
  21 // MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS.
  22 #  define JS_HAZ_GC_POINTER __attribute__((annotate("GC Pointer")))
  23
  24 // Same as JS_HAZ_GC_POINTER, except additionally treat pointers to these
  25 // as GC pointers themselves in order to check references to them, since
  26 // the analysis cannot distinguish between pointers and references.
  27 #  define JS_HAZ_GC_REF __attribute__((annotate("GC Pointer or Reference")))
  28
  29 // Mark a type as a rooted pointer, suitable for use on the stack (eg all
  30 // Rooted<T> instantiations should have this.) "Inherited" by templatized types
  31 // with MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS.
  32 #  define JS_HAZ_ROOTED __attribute__((annotate("Rooted Pointer")))
  33
  34 // Mark a type as something that should not be held live across a GC, but which
  35 // is not itself a GC pointer. Note that this property is *not* inherited by
  36 // templatized types with MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS.
  37 #  define JS_HAZ_GC_INVALIDATED __attribute__((annotate("Invalidated by GC")))
  38
  39 // Mark a class as a base class of rooted types, eg CustomAutoRooter. All
  40 // descendants of this class will be considered rooted, though classes that
  41 // merely contain these as a field member will not be. "Inherited" by
  42 // templatized types with MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS
  43 #  define JS_HAZ_ROOTED_BASE __attribute__((annotate("Rooted Base")))
  44
  45 // Mark a type that would otherwise be considered a GC Pointer (eg because it
  46 // contains a JS::Value field) as a non-GC pointer. It is handled almost the
  47 // same in the analysis as a rooted pointer, except it will not be reported as
  48 // an unnecessary root if used across a GC call. This should rarely be used,
  49 // but makes sense for something like ErrorResult, which only contains a GC
  50 // pointer when it holds an exception (and it does its own rooting,
  51 // conditionally.)
  52 #  define JS_HAZ_NON_GC_POINTER \
  53     __attribute__((annotate("Suppressed GC Pointer")))
  54
  55 // Mark a function as something that runs a garbage collection, potentially
  56 // invalidating GC pointers.
  57 #  define JS_HAZ_GC_CALL __attribute__((annotate("GC Call")))
  58
  59 // Mark an RAII class as suppressing GC within its scope.
  60 #  define JS_HAZ_GC_SUPPRESSED __attribute__((annotate("Suppress GC")))
  61
  62 // Mark a function as one that can run script if called.  This obviously
  63 // subsumes JS_HAZ_GC_CALL, since anything that can run script can GC.`
  64 #  define JS_HAZ_CAN_RUN_SCRIPT __attribute__((annotate("Can run script")))
  65
  66 // Mark a function as able to call JSNatives. Otherwise, JSNatives don't show
  67 // up in the callgraph. This doesn't matter for the can-GC analysis, but it is
  68 // very nice for other uses of the callgraph.
  69 #  define JS_HAZ_JSNATIVE_CALLER __attribute__((annotate("Calls JSNatives")))
  70
  71 // Mark a variable as being "GC safe", i.e., it does not contain any
  72 // invalidatable pointers at the current point in the code. A typical
  73 // example might be a collection containing GC pointers, which at the
  74 // present time is empty. This property is only temporary; the next use
  75 // of the variable will invalidate it (on the assumption that a GC pointer
  76 // might be added to it.) Try to use this as early as possible, probably
  77 // immediately after construction, so that if future mutations through
  78 // the variable are added, they won't be covered by the annotation.
  79 #  define JS_HAZ_VALUE_IS_GC_SAFE(var) JS::detail::MarkVariableAsGCSafe(var)
  80
  81 #else
  82
  83 #  define JS_EXPECT_HAZARDS
  84 #  define JS_HAZ_GC_THING
  85 #  define JS_HAZ_GC_POINTER
  86 #  define JS_HAZ_GC_REF
  87 #  define JS_HAZ_ROOTED
  88 #  define JS_HAZ_GC_INVALIDATED
  89 #  define JS_HAZ_ROOTED_BASE
  90 #  define JS_HAZ_NON_GC_POINTER
  91 #  define JS_HAZ_GC_CALL
  92 #  define JS_HAZ_GC_SUPPRESSED
  93 #  define JS_HAZ_CAN_RUN_SCRIPT
  94 #  define JS_HAZ_JSNATIVE_CALLER
  95 #  define JS_HAZ_VALUE_IS_GC_SAFE(var)
  96
  97 #endif
  98
  99 #ifdef XGILL_PLUGIN
 100
 101 // Implemented by passing variable to a dummy function so that it shows up
 102 // in the control flow graph.
 103 namespace JS {
 104 namespace detail {
 105
 106 template <typename T>
 107 static inline void MarkVariableAsGCSafe(T& var) {
 108   asm("");
 109 }
 110
 111 }  // namespace detail
 112 }  // namespace JS
 113
 114 #endif
 115
 116 #endif /* js_GCAnnotations_h */