Issue #2083 - Part 2: Remove use of RegExpGuard.

Based on Mozilla bug 1345177.
There were more uses of RegExpGuard in js/src/builtin/RegExp.cpp not found in
 the original bug's patch.

21 files changed, 92 insertions, 73 deletions

diff --git a/js/ipc/WrapperOwner.cpp b/js/ipc/WrapperOwner.cpp
index f8e4930ddf..92c6e409be 100644
--- a/js/ipc/WrapperOwner.cpp
+++ b/js/ipc/WrapperOwner.cpp
@@ -128,7 +128,8 @@ class CPOWProxyHandler : public BaseProxyHandler
     virtual bool isArray(JSContext* cx, HandleObject obj,
                          IsArrayAnswer* answer) const override;
     virtual const char* className(JSContext* cx, HandleObject proxy) const override;
-    virtual bool regexp_toShared(JSContext* cx, HandleObject proxy, RegExpGuard* g) const override;
+    virtual bool regexp_toShared(JSContext* cx, HandleObject proxy,
+                                 MutableHandle<RegExpShared*> shared) const override;
     virtual void finalize(JSFreeOp* fop, JSObject* proxy) const override;
     virtual void objectMoved(JSObject* proxy, const JSObject* old) const override;
     virtual bool isCallable(JSObject* obj) const override;
@@ -854,13 +855,14 @@ WrapperOwner::getPrototypeIfOrdinary(JSContext* cx, HandleObject proxy, bool* is
 }
 
 bool
-CPOWProxyHandler::regexp_toShared(JSContext* cx, HandleObject proxy, RegExpGuard* g) const
+CPOWProxyHandler::regexp_toShared(JSContext* cx, HandleObject proxy,
+                                  MutableHandle<RegExpShared*> shared) const
 {
-    FORWARD(regexp_toShared, (cx, proxy, g));
+    FORWARD(regexp_toShared, (cx, proxy, shared));
 }
 
 bool
-WrapperOwner::regexp_toShared(JSContext* cx, HandleObject proxy, RegExpGuard* g)
+WrapperOwner::regexp_toShared(JSContext* cx, HandleObject proxy, MutableHandle<RegExpShared*> shared)
 {
     ObjectId objId = idOf(proxy);
 
@@ -880,7 +882,7 @@ WrapperOwner::regexp_toShared(JSContext* cx, HandleObject proxy, RegExpGuard* g)
     if (!regexp)
         return false;
 
-    return js::RegExpToSharedNonInline(cx, regexp, g);
+    return js::RegExpToSharedNonInline(cx, regexp, shared);
 }
 
 void
diff --git a/js/ipc/WrapperOwner.h b/js/ipc/WrapperOwner.h
index 31291b5bfa..aee7111620 100644
--- a/js/ipc/WrapperOwner.h
+++ b/js/ipc/WrapperOwner.h
@@ -59,7 +59,8 @@ class WrapperOwner : public virtual JavaScriptShared
     bool getPrototypeIfOrdinary(JSContext* cx, JS::HandleObject proxy, bool* isOrdinary,
                                 JS::MutableHandleObject protop);
 
-    bool regexp_toShared(JSContext* cx, JS::HandleObject proxy, js::RegExpGuard* g);
+    bool regexp_toShared(JSContext* cx, JS::HandleObject proxy,
+                         js::MutableHandle<js::RegExpShared*> shared);
 
     nsresult instanceOf(JSObject* obj, const nsID* id, bool* bp);
 
diff --git a/js/public/Proxy.h b/js/public/Proxy.h
index 42973bdc37..e493f522c6 100644
--- a/js/public/Proxy.h
+++ b/js/public/Proxy.h
@@ -31,7 +31,7 @@ using JS::PrivateValue;
 using JS::PropertyDescriptor;
 using JS::Value;
 
-using RegExpGuard = JS::Rooted<RegExpShared*>;
+class RegExpShared;
 
 class JS_FRIEND_API(Wrapper);
 
@@ -328,7 +328,8 @@ class JS_FRIEND_API(BaseProxyHandler)
     virtual bool isArray(JSContext* cx, HandleObject proxy, JS::IsArrayAnswer* answer) const;
     virtual const char* className(JSContext* cx, HandleObject proxy) const;
     virtual JSString* fun_toString(JSContext* cx, HandleObject proxy, bool isToSource) const;
-    virtual bool regexp_toShared(JSContext* cx, HandleObject proxy, RegExpGuard* g) const;
+    virtual bool regexp_toShared(JSContext* cx, HandleObject proxy,
+                                 MutableHandle<js::RegExpShared*> shared) const;
     virtual bool boxedValue_unbox(JSContext* cx, HandleObject proxy, MutableHandleValue vp) const;
     virtual void trace(JSTracer* trc, JSObject* proxy) const;
     virtual void finalize(JSFreeOp* fop, JSObject* proxy) const;
diff --git a/js/src/builtin/RegExp.cpp b/js/src/builtin/RegExp.cpp
index 9b0e1a7cb6..33c2854dae 100644
--- a/js/src/builtin/RegExp.cpp
+++ b/js/src/builtin/RegExp.cpp
@@ -187,7 +187,7 @@ js::ExecuteRegExpLegacy(JSContext* cx, RegExpStatics* res, Handle<RegExpObject*>
                         HandleLinearString input, size_t* lastIndex, bool test,
                         MutableHandleValue rval)
 {
-    RegExpGuard shared(cx);
+    RootedRegExpShared shared(cx);
     if (!RegExpObject::getShared(cx, reobj, &shared))
         return false;
 
@@ -275,7 +275,7 @@ RegExpInitializeIgnoringLastIndex(JSContext* cx, Handle<RegExpObject*> obj,
 
     if (sharedUse == UseRegExpShared) {
         /* Steps 7-8. */
-        RegExpGuard re(cx);
+        RootedRegExpShared re(cx);
         if (!cx->compartment()->regExps.get(cx, pattern, flags, &re))
             return false;
 
@@ -381,7 +381,7 @@ regexp_compile_impl(JSContext* cx, const CallArgs& args)
         RegExpFlag flags;
         {
             // Step 3b.
-            RegExpGuard g(cx);
+            RootedRegExpShared g(cx);
             if (!RegExpToShared(cx, patternObj, &g))
                 return false;
 
@@ -476,7 +476,7 @@ js::regexp_construct(JSContext* cx, unsigned argc, Value* vp)
         RegExpFlag flags;
         {
             // Step 4.a.
-            RegExpGuard g(cx);
+            RootedRegExpShared g(cx);
             if (!RegExpToShared(cx, patternObj, &g))
                 return false;
             sourceAtom = g->getSource();
@@ -603,7 +603,7 @@ js::regexp_clone(JSContext* cx, unsigned argc, Value* vp)
     RootedAtom sourceAtom(cx);
     RegExpFlag flags;
     {
-        RegExpGuard g(cx);
+        RootedRegExpShared g(cx);
         if (!RegExpToShared(cx, from, &g))
             return false;
         sourceAtom = g->getSource();
@@ -985,7 +985,7 @@ ExecuteRegExp(JSContext* cx, HandleObject regexp, HandleString string,
     /* Steps 1-2 performed by the caller. */
     Rooted<RegExpObject*> reobj(cx, &regexp->as<RegExpObject>());
 
-    RegExpGuard re(cx);
+    RootedRegExpShared re(cx);
     if (!RegExpObject::getShared(cx, reobj, &re))
         return RegExpRunStatus_Error;
 
@@ -1070,7 +1070,7 @@ RegExpMatcherImpl(JSContext* cx, HandleObject regexp, HandleString string,
 
     /* Steps 16-25 */
     Rooted<RegExpObject*> reobj(cx, &regexp->as<RegExpObject>());
-    RegExpGuard shared(cx);
+    RootedRegExpShared shared(cx);
     if (!RegExpObject::getShared(cx, reobj, &shared))
         return false;
     return CreateRegExpMatchResult(cx, *shared, string, matches, rval);
@@ -1117,7 +1117,7 @@ js::RegExpMatcherRaw(JSContext* cx, HandleObject regexp, HandleString input,
     // successful only if the pairs have actually been filled in.
     if (maybeMatches && maybeMatches->pairsRaw()[0] >= 0) {
       Rooted<RegExpObject*> reobj(cx, &regexp->as<RegExpObject>());
-      RegExpGuard shared(cx);
+      RootedRegExpShared shared(cx);
       if (!RegExpObject::getShared(cx, reobj, &shared))
           return false;
       return CreateRegExpMatchResult(cx, *shared, input, *maybeMatches, output);
diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index 2aec76dbd9..167cd28d60 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -6141,7 +6141,7 @@ JS_GetRegExpFlags(JSContext* cx, HandleObject obj)
     AssertHeapIsIdle(cx);
     CHECK_REQUEST(cx);
 
-    RegExpGuard shared(cx);
+    RootedRegExpShared shared(cx);
     if (!RegExpToShared(cx, obj, &shared))
         return false;
     return shared->getFlags();
@@ -6153,7 +6153,7 @@ JS_GetRegExpSource(JSContext* cx, HandleObject obj)
     AssertHeapIsIdle(cx);
     CHECK_REQUEST(cx);
 
-    RegExpGuard shared(cx);
+    RootedRegExpShared shared(cx);
     if (!RegExpToShared(cx, obj, &shared))
         return nullptr;
     return shared->getSource();
diff --git a/js/src/jsfriendapi.h b/js/src/jsfriendapi.h
index f42a4def5f..34ab6ca15e 100644
--- a/js/src/jsfriendapi.h
+++ b/js/src/jsfriendapi.h
@@ -1114,9 +1114,9 @@ extern JS_FRIEND_API(unsigned)
 GetEnterCompartmentDepth(JSContext* cx);
 #endif
 
-using RegExpGuard = JS::Rooted<RegExpShared*>;
 extern JS_FRIEND_API(bool)
-RegExpToSharedNonInline(JSContext* cx, JS::HandleObject regexp, RegExpGuard* shared);
+RegExpToSharedNonInline(JSContext* cx, JS::HandleObject regexp,
+                        JS::MutableHandle<RegExpShared*> shared);
 
 /* Implemented in jswrapper.cpp. */
 typedef enum NukeReferencesToWindow {
diff --git a/js/src/jswrapper.h b/js/src/jswrapper.h
index 3729ba884d..95f405e126 100644
--- a/js/src/jswrapper.h
+++ b/js/src/jswrapper.h
@@ -117,7 +117,7 @@ class JS_FRIEND_API(Wrapper) : public BaseProxyHandler
     virtual JSString* fun_toString(JSContext* cx, HandleObject proxy,
                                    bool isToSource) const override;
     virtual bool regexp_toShared(JSContext* cx, HandleObject proxy,
-                                 RegExpGuard* g) const override;
+                                 MutableHandle<RegExpShared*> shared) const override;
     virtual bool boxedValue_unbox(JSContext* cx, HandleObject proxy,
                                   MutableHandleValue vp) const override;
     virtual bool isCallable(JSObject* obj) const override;
@@ -211,7 +211,8 @@ class JS_FRIEND_API(CrossCompartmentWrapper) : public Wrapper
     virtual const char* className(JSContext* cx, HandleObject proxy) const override;
     virtual JSString* fun_toString(JSContext* cx, HandleObject wrapper,
                                    bool isToSource) const override;
-    virtual bool regexp_toShared(JSContext* cx, HandleObject proxy, RegExpGuard* g) const override;
+    virtual bool regexp_toShared(JSContext* cx, HandleObject proxy,
+                                 MutableHandle<RegExpShared*> shared) const override;
     virtual bool boxedValue_unbox(JSContext* cx, HandleObject proxy, MutableHandleValue vp) const override;
 
     // Allocate CrossCompartmentWrappers in the nursery.
@@ -312,7 +313,8 @@ class JS_FRIEND_API(SecurityWrapper) : public Base
                             const CallArgs& args) const override;
     virtual bool getBuiltinClass(JSContext* cx, HandleObject wrapper, ESClass* cls) const override;
     virtual bool isArray(JSContext* cx, HandleObject wrapper, JS::IsArrayAnswer* answer) const override;
-    virtual bool regexp_toShared(JSContext* cx, HandleObject proxy, RegExpGuard* g) const override;
+    virtual bool regexp_toShared(JSContext* cx, HandleObject proxy,
+                                 MutableHandle<RegExpShared*> shared) const override;
     virtual bool boxedValue_unbox(JSContext* cx, HandleObject proxy, MutableHandleValue vp) const override;
 
     /*
diff --git a/js/src/proxy/BaseProxyHandler.cpp b/js/src/proxy/BaseProxyHandler.cpp
index 6cd526d059..8c873d3c6a 100644
--- a/js/src/proxy/BaseProxyHandler.cpp
+++ b/js/src/proxy/BaseProxyHandler.cpp
@@ -327,7 +327,7 @@ BaseProxyHandler::fun_toString(JSContext* cx, HandleObject proxy, bool isToSourc
 
 bool
 BaseProxyHandler::regexp_toShared(JSContext* cx, HandleObject proxy,
-                                  RegExpGuard* g) const
+                                  MutableHandleRegExpShared shared) const
 {
     MOZ_CRASH("This should have been a wrapped regexp");
 }
diff --git a/js/src/proxy/CrossCompartmentWrapper.cpp b/js/src/proxy/CrossCompartmentWrapper.cpp
index bc698c8739..30f5ec14d8 100644
--- a/js/src/proxy/CrossCompartmentWrapper.cpp
+++ b/js/src/proxy/CrossCompartmentWrapper.cpp
@@ -437,9 +437,10 @@ CrossCompartmentWrapper::fun_toString(JSContext* cx, HandleObject wrapper, bool
 }
 
 bool
-CrossCompartmentWrapper::regexp_toShared(JSContext* cx, HandleObject wrapper, RegExpGuard* g) const
+CrossCompartmentWrapper::regexp_toShared(JSContext* cx, HandleObject wrapper,
+                                         MutableHandleRegExpShared shared) const
 {
-    RegExpGuard re(cx);
+    RootedRegExpShared re(cx);
     {
         AutoCompartment call(cx, wrappedObject(wrapper));
         if (!Wrapper::regexp_toShared(cx, wrapper, &re))
@@ -447,7 +448,7 @@ CrossCompartmentWrapper::regexp_toShared(JSContext* cx, HandleObject wrapper, Re
     }
 
     // Get an equivalent RegExpShared associated with the current compartment.
-    return cx->compartment()->regExps.get(cx, re->getSource(), re->getFlags(), g);
+    return cx->compartment()->regExps.get(cx, re->getSource(), re->getFlags(), shared);
 }
 
 bool
diff --git a/js/src/proxy/DeadObjectProxy.cpp b/js/src/proxy/DeadObjectProxy.cpp
index 34d9c3b04d..71c9787313 100644
--- a/js/src/proxy/DeadObjectProxy.cpp
+++ b/js/src/proxy/DeadObjectProxy.cpp
@@ -142,7 +142,8 @@ DeadObjectProxy::fun_toString(JSContext* cx, HandleObject proxy, bool isToSource
 }
 
 bool
-DeadObjectProxy::regexp_toShared(JSContext* cx, HandleObject proxy, RegExpGuard* g) const
+DeadObjectProxy::regexp_toShared(JSContext* cx, HandleObject proxy,
+                                 MutableHandle<RegExpShared*> shared) const
 {
     ReportDead(cx);
     return false;
diff --git a/js/src/proxy/DeadObjectProxy.h b/js/src/proxy/DeadObjectProxy.h
index bedec9c040..bed1c59a42 100644
--- a/js/src/proxy/DeadObjectProxy.h
+++ b/js/src/proxy/DeadObjectProxy.h
@@ -49,7 +49,8 @@ class DeadObjectProxy : public BaseProxyHandler
     virtual const char* className(JSContext* cx, HandleObject proxy) const override;
     virtual JSString* fun_toString(JSContext* cx, HandleObject proxy,
                                    bool isToSource) const override;
-    virtual bool regexp_toShared(JSContext* cx, HandleObject proxy, RegExpGuard* g) const override;
+    virtual bool regexp_toShared(JSContext* cx, HandleObject proxy,
+                                 MutableHandle<RegExpShared*> shared) const override;
 
     virtual bool isCallable(JSObject* obj) const override;
     virtual bool isConstructor(JSObject* obj) const override;
diff --git a/js/src/proxy/Proxy.cpp b/js/src/proxy/Proxy.cpp
index d873717248..8f6a262106 100644
--- a/js/src/proxy/Proxy.cpp
+++ b/js/src/proxy/Proxy.cpp
@@ -488,10 +488,10 @@ Proxy::fun_toString(JSContext* cx, HandleObject proxy, bool isToSource)
 }
 
 bool
-Proxy::regexp_toShared(JSContext* cx, HandleObject proxy, RegExpGuard* g)
+Proxy::regexp_toShared(JSContext* cx, HandleObject proxy, MutableHandleRegExpShared shared)
 {
     JS_CHECK_RECURSION(cx, return false);
-    return proxy->as<ProxyObject>().handler()->regexp_toShared(cx, proxy, g);
+    return proxy->as<ProxyObject>().handler()->regexp_toShared(cx, proxy, shared);
 }
 
 bool
diff --git a/js/src/proxy/Proxy.h b/js/src/proxy/Proxy.h
index 4064b8a7f2..c2ba1afd48 100644
--- a/js/src/proxy/Proxy.h
+++ b/js/src/proxy/Proxy.h
@@ -59,7 +59,8 @@ class Proxy
     static bool isArray(JSContext* cx, HandleObject proxy, JS::IsArrayAnswer* answer);
     static const char* className(JSContext* cx, HandleObject proxy);
     static JSString* fun_toString(JSContext* cx, HandleObject proxy, bool isToSource);
-    static bool regexp_toShared(JSContext* cx, HandleObject proxy, RegExpGuard* g);
+    static bool regexp_toShared(JSContext* cx, HandleObject proxy,
+                                MutableHandle<RegExpShared*> shared);
     static bool boxedValue_unbox(JSContext* cx, HandleObject proxy, MutableHandleValue vp);
 
     static bool getElements(JSContext* cx, HandleObject obj, uint32_t begin, uint32_t end,
diff --git a/js/src/proxy/ScriptedProxyHandler.cpp b/js/src/proxy/ScriptedProxyHandler.cpp
index 5a219e2e3f..adb98edbdd 100644
--- a/js/src/proxy/ScriptedProxyHandler.cpp
+++ b/js/src/proxy/ScriptedProxyHandler.cpp
@@ -1265,7 +1265,8 @@ ScriptedProxyHandler::fun_toString(JSContext* cx, HandleObject proxy, bool isToS
 }
 
 bool
-ScriptedProxyHandler::regexp_toShared(JSContext* cx, HandleObject proxy, RegExpGuard* g) const
+ScriptedProxyHandler::regexp_toShared(JSContext* cx, HandleObject proxy,
+                                      MutableHandleRegExpShared shared) const
 {
     MOZ_CRASH("Should not end up in ScriptedProxyHandler::regexp_toShared");
     return false;
diff --git a/js/src/proxy/ScriptedProxyHandler.h b/js/src/proxy/ScriptedProxyHandler.h
index e464dc24e8..19120c0f4d 100644
--- a/js/src/proxy/ScriptedProxyHandler.h
+++ b/js/src/proxy/ScriptedProxyHandler.h
@@ -69,7 +69,7 @@ class ScriptedProxyHandler : public BaseProxyHandler
     virtual JSString* fun_toString(JSContext* cx, HandleObject proxy,
                                    bool isToSource) const override;
     virtual bool regexp_toShared(JSContext* cx, HandleObject proxy,
-                                 RegExpGuard* g) const override;
+                                 MutableHandle<RegExpShared*> shared) const override;
     virtual bool boxedValue_unbox(JSContext* cx, HandleObject proxy,
                                   MutableHandleValue vp) const override;
 
diff --git a/js/src/proxy/SecurityWrapper.cpp b/js/src/proxy/SecurityWrapper.cpp
index ef894ca772..75fe4dcb11 100644
--- a/js/src/proxy/SecurityWrapper.cpp
+++ b/js/src/proxy/SecurityWrapper.cpp
@@ -93,9 +93,10 @@ SecurityWrapper<Base>::isArray(JSContext* cx, HandleObject obj, JS::IsArrayAnswe
 
 template <class Base>
 bool
-SecurityWrapper<Base>::regexp_toShared(JSContext* cx, HandleObject obj, RegExpGuard* g) const
+SecurityWrapper<Base>::regexp_toShared(JSContext* cx, HandleObject obj,
+                                       MutableHandle<RegExpShared*> shared) const
 {
-    return Base::regexp_toShared(cx, obj, g);
+    return Base::regexp_toShared(cx, obj, shared);
 }
 
 template <class Base>
diff --git a/js/src/proxy/Wrapper.cpp b/js/src/proxy/Wrapper.cpp
index 314409bba1..5ce1f22c9a 100644
--- a/js/src/proxy/Wrapper.cpp
+++ b/js/src/proxy/Wrapper.cpp
@@ -267,10 +267,10 @@ Wrapper::fun_toString(JSContext* cx, HandleObject proxy, bool isToSource) const
 }
 
 bool
-Wrapper::regexp_toShared(JSContext* cx, HandleObject proxy, RegExpGuard* g) const
+Wrapper::regexp_toShared(JSContext* cx, HandleObject proxy, MutableHandleRegExpShared shared) const
 {
     RootedObject target(cx, proxy->as<ProxyObject>().target());
-    return RegExpToShared(cx, target, g);
+    return RegExpToShared(cx, target, shared);
 }
 
 bool
diff --git a/js/src/vm/RegExpObject.cpp b/js/src/vm/RegExpObject.cpp
index 4cc2b539aa..cd085efb69 100644
--- a/js/src/vm/RegExpObject.cpp
+++ b/js/src/vm/RegExpObject.cpp
@@ -122,14 +122,15 @@ VectorMatchPairs::allocOrExpandArray(size_t pairCount)
 /* RegExpObject */
 
 /* static */ bool
-RegExpObject::getShared(JSContext* cx, Handle<RegExpObject*> regexp, RegExpGuard* g)
+RegExpObject::getShared(JSContext* cx, Handle<RegExpObject*> regexp,
+                        MutableHandleRegExpShared shared)
 {
     if (regexp->hasShared()) {
-        g->set(regexp->sharedRef());
+        shared.set(regexp->sharedRef());
         return true;
     }
 
-    return createShared(cx, regexp, g);
+    return createShared(cx, regexp, shared);
 }
 
 /* static */ bool
@@ -278,13 +279,14 @@ RegExpObject::create(ExclusiveContext* cx, HandleAtom source, RegExpFlag flags,
 }
 
 /* static */ bool
-RegExpObject::createShared(JSContext* cx, Handle<RegExpObject*> regexp, RegExpGuard* g)
+RegExpObject::createShared(JSContext* cx, Handle<RegExpObject*> regexp,
+                           MutableHandleRegExpShared shared)
 {
     MOZ_ASSERT(!regexp->hasShared());
-    if (!cx->compartment()->regExps.get(cx, regexp->getSource(), regexp->getFlags(), g))
+    if (!cx->compartment()->regExps.get(cx, regexp->getSource(), regexp->getFlags(), shared))
         return false;
 
-    regexp->setShared(**g);
+    regexp->setShared(*shared);
     return true;
 }
 
@@ -891,11 +893,11 @@ RegExpShared::dumpBytecode(JSContext* cx, bool match_only, HandleLinearString in
 RegExpObject::dumpBytecode(JSContext* cx, Handle<RegExpObject*> regexp,
                            bool match_only, HandleLinearString input)
 {
-    RegExpGuard g(cx);
-    if (!getShared(cx, regexp, &g))
+    RootedRegExpShared shared(cx);
+    if (!getShared(cx, regexp, &shared))
         return false;
 
-    return g->dumpBytecode(cx, match_only, input);
+    return shared->dumpBytecode(cx, match_only, input);
 }
 #endif
 
@@ -1351,11 +1353,12 @@ RegExpCompartment::sweep(JSRuntime* rt)
 }
 
 bool
-RegExpCompartment::get(JSContext* cx, JSAtom* source, RegExpFlag flags, RegExpGuard* g)
+RegExpCompartment::get(JSContext* cx, JSAtom* source, RegExpFlag flags,
+                       MutableHandleRegExpShared result)
 {
     DependentAddPtr<Set> p(cx, set_.get(), Key(source, flags));
     if (p) {
-        g->set(*p);
+        result.set(*p);
         return true;
     }
 
@@ -1370,18 +1373,19 @@ RegExpCompartment::get(JSContext* cx, JSAtom* source, RegExpFlag flags, RegExpGu
         return false;
     }
 
-    g->set(shared);
+    result.set(shared);
     return true;
 }
 
 bool
-RegExpCompartment::get(JSContext* cx, HandleAtom atom, JSString* opt, RegExpGuard* g)
+RegExpCompartment::get(JSContext* cx, HandleAtom atom, JSString* opt,
+                       MutableHandleRegExpShared shared)
 {
     RegExpFlag flags = RegExpFlag(0);
     if (opt && !ParseRegExpFlags(cx, opt, &flags))
         return false;
 
-    return get(cx, atom, flags, g);
+    return get(cx, atom, flags, shared);
 }
 
 size_t
@@ -1410,12 +1414,12 @@ js::CloneRegExpObject(JSContext* cx, JSObject* obj_)
 
     Rooted<JSAtom*> source(cx, regex->getSource());
 
-    RegExpGuard g(cx);
-    if (!RegExpObject::getShared(cx, regex, &g))
+    RootedRegExpShared shared(cx);
+    if (!RegExpObject::getShared(cx, regex, &shared))
         return nullptr;
 
-    clone->initAndZeroLastIndex(source, g->getFlags(), cx);
-    clone->setShared(*g);
+    clone->initAndZeroLastIndex(source, shared->getFlags(), cx);
+    clone->setShared(*shared);
 
     return clone;
 }
@@ -1554,9 +1558,9 @@ js::CloneScriptRegExpObject(JSContext* cx, RegExpObject& reobj)
 }
 
 JS_FRIEND_API(bool)
-js::RegExpToSharedNonInline(JSContext* cx, HandleObject obj, js::RegExpGuard* g)
+js::RegExpToSharedNonInline(JSContext* cx, HandleObject obj, MutableHandleRegExpShared shared)
 {
-    return RegExpToShared(cx, obj, g);
+    return RegExpToShared(cx, obj, shared);
 }
 
 JS::ubi::Node::Size
diff --git a/js/src/vm/RegExpObject.h b/js/src/vm/RegExpObject.h
index 16ba7f41fd..41f5e623ae 100644
--- a/js/src/vm/RegExpObject.h
+++ b/js/src/vm/RegExpObject.h
@@ -32,10 +32,8 @@
  *
  * To save memory, a RegExpShared is not created for a RegExpObject until it is
  * needed for execution. When a RegExpShared needs to be created, it is looked
- * up in a per-compartment table to allow reuse between objects. Lastly, on
- * GC, every RegExpShared (that is not active on the callstack) is discarded.
- * Because of the last point, any code using a RegExpShared (viz., by executing
- * a regexp) must indicate the RegExpShared is active via RegExpGuard.
+ * up in a per-compartment table to allow reuse between objects. Lastly, on GC,
+ * every RegExpShared that is not in active use is discarded.
  */
 namespace js {
 
@@ -251,6 +249,10 @@ class RegExpShared : public gc::TenuredCell
 #endif
 };
 
+using RootedRegExpShared = JS::Rooted<RegExpShared*>;
+using HandleRegExpShared = JS::Handle<RegExpShared*>;
+using MutableHandleRegExpShared = JS::MutableHandle<RegExpShared*>;
+
 class RegExpCompartment
 {
     struct Key {
@@ -321,10 +323,11 @@ class RegExpCompartment
 
     bool empty() { return set_.empty(); }
 
-    bool get(JSContext* cx, JSAtom* source, RegExpFlag flags, RegExpGuard* g);
+    bool get(JSContext* cx, JSAtom* source, RegExpFlag flags, MutableHandleRegExpShared shared);
 
     /* Like 'get', but compile 'maybeOpt' (if non-null). */
-    bool get(JSContext* cx, HandleAtom source, JSString* maybeOpt, RegExpGuard* g);
+    bool get(JSContext* cx, HandleAtom source, JSString* maybeOpt,
+             MutableHandleRegExpShared shared);
 
     /* Get or create template object used to base the result of .exec() on. */
     ArrayObject* getOrCreateMatchResultTemplateObject(JSContext* cx) {
@@ -447,7 +450,7 @@ class RegExpObject : public NativeObject
     static bool isOriginalFlagGetter(JSNative native, RegExpFlag* mask);
 
     static MOZ_MUST_USE bool getShared(JSContext* cx, Handle<RegExpObject*> regexp,
-                                       RegExpGuard* g);
+                                       MutableHandleRegExpShared shared);
 
     bool hasShared() {
         return !!sharedRef();
@@ -479,7 +482,7 @@ class RegExpObject : public NativeObject
      * Side effect: sets the private field.
      */
     static MOZ_MUST_USE bool createShared(JSContext* cx, Handle<RegExpObject*> regexp,
-                                          RegExpGuard* g);
+                                          MutableHandleRegExpShared shared);
 
     ReadBarriered<RegExpShared*>& sharedRef() {
         auto& ref = NativeObject::privateRef(PRIVATE_SLOT);
@@ -501,12 +504,12 @@ ParseRegExpFlags(JSContext* cx, JSString* flagStr, RegExpFlag* flagsOut);
 
 /* Assuming GetBuiltinClass(obj) is ESClass::RegExp, return a RegExpShared for obj. */
 inline bool
-RegExpToShared(JSContext* cx, HandleObject obj, RegExpGuard* g)
+RegExpToShared(JSContext* cx, HandleObject obj, MutableHandleRegExpShared shared)
 {
     if (obj->is<RegExpObject>())
-        return RegExpObject::getShared(cx, obj.as<RegExpObject>(), g);
+        return RegExpObject::getShared(cx, obj.as<RegExpObject>(), shared);
 
-    return Proxy::regexp_toShared(cx, obj, g);
+    return Proxy::regexp_toShared(cx, obj, shared);
 }
 
 template<XDRMode mode>
diff --git a/js/src/vm/RegExpStatics.cpp b/js/src/vm/RegExpStatics.cpp
index 6445bdd440..27bc988db6 100644
--- a/js/src/vm/RegExpStatics.cpp
+++ b/js/src/vm/RegExpStatics.cpp
@@ -80,8 +80,8 @@ RegExpStatics::executeLazy(JSContext* cx)
     MOZ_ASSERT(lazyIndex != size_t(-1));
 
     /* Retrieve or create the RegExpShared in this compartment. */
-    RegExpGuard g(cx);
-    if (!cx->compartment()->regExps.get(cx, lazySource, lazyFlags, &g))
+    RootedRegExpShared shared(cx);
+    if (!cx->compartment()->regExps.get(cx, lazySource, lazyFlags, &shared))
         return false;
 
     /*
@@ -91,7 +91,7 @@ RegExpStatics::executeLazy(JSContext* cx)
 
     /* Execute the full regular expression. */
     RootedLinearString input(cx, matchesInput);
-    RegExpRunStatus status = g->execute(cx, input, lazyIndex, &this->matches, nullptr);
+    RegExpRunStatus status = shared->execute(cx, input, lazyIndex, &this->matches, nullptr);
     if (status == RegExpRunStatus_Error)
         return false;
 
diff --git a/js/src/vm/StructuredClone.cpp b/js/src/vm/StructuredClone.cpp
index 9cd4f1e072..26e57976fc 100644
--- a/js/src/vm/StructuredClone.cpp
+++ b/js/src/vm/StructuredClone.cpp
@@ -1402,7 +1402,7 @@ JSStructuredCloneWriter::startWrite(HandleValue v)
             return false;
 
         if (cls == ESClass::RegExp) {
-            RegExpGuard re(context());
+            RootedRegExpShared re(context());
             if (!RegExpToShared(context(), obj, &re))
                 return false;
             return out.writePair(SCTAG_REGEXP_OBJECT, re->getFlags()) &&