Bug 1874739 - Part 13: Introduce the IRefCountedProtocol type, r=ipc-reviewers,mccr8

This acts as a new class between IProtocol and IToplevelProtocol which just
introduces the AddRef and Release virtual methods. It's used to allow generic
code to hold a strong reference to an actor which is structurally known to be
reference counted, and generally will have limited use elsewhere.

Differential Revision: https://phabricator.services.mozilla.com/D198623

Author: mystor

ipc/glue/ProtocolUtils.cpp

@@ -629,7 +629,7 @@ void IProtocol::DestroySubtree(ActorDestroyReason aWhy) {
 
 IToplevelProtocol::IToplevelProtocol(const char* aName, ProtocolId aProtoId,
                                      Side aSide)
-    : IProtocol(aProtoId, aSide),
+    : IRefCountedProtocol(aProtoId, aSide),
       mOtherPid(base::kInvalidProcessId),
       mLastLocalId(0),
       mChannel(aName, this) {

ipc/glue/ProtocolUtils.h

@@ -156,6 +156,7 @@ typedef IPCMessageStart ProtocolId;
 // Generated by IPDL compiler
 const char* ProtocolIdToName(IPCMessageStart aId);
 
+class IRefCountedProtocol;
 class IToplevelProtocol;
 class ActorLifecycleProxy;
 class WeakActorLifecycleProxy;
@@ -409,13 +410,23 @@ class Endpoint;
 template <class PFooSide>
 class ManagedEndpoint;
 
+/**
+ * All refcounted protocols should inherit this class.
+ */
+class IRefCountedProtocol : public IProtocol {
+ public:
+  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+  using IProtocol::IProtocol;
+};
+
 /**
  * All top-level protocols should inherit this class.
  *
  * IToplevelProtocol tracks all top-level protocol actors created from
  * this protocol actor.
  */
-class IToplevelProtocol : public IProtocol {
+class IToplevelProtocol : public IRefCountedProtocol {
   template <class PFooSide>
   friend class Endpoint;
 
@@ -425,9 +436,6 @@ class IToplevelProtocol : public IProtocol {
   ~IToplevelProtocol() = default;
 
  public:
-  // All top-level protocols are refcounted.
-  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
-
   // Shadow methods on IProtocol which are implemented directly on toplevel
   // actors.
   int32_t Register(IProtocol* aRouted);

ipc/ipdl/ipdl/lower.py

@@ -1305,12 +1305,6 @@ def _subtreeUsesShmem(p):
 
 
 class Protocol(ipdl.ast.Protocol):
-    def managerInterfaceType(self, ptr=False):
-        return Type("mozilla::ipc::IProtocol", ptr=ptr)
-
-    def openedProtocolInterfaceType(self, ptr=False):
-        return Type("mozilla::ipc::IToplevelProtocol", ptr=ptr)
-
     def _ipdlmgrtype(self):
         assert 1 == len(self.decl.type.managers)
         for mgr in self.decl.type.managers:
@@ -3625,11 +3619,12 @@ def visitProtocol(self, p):
                 hasAsyncReturns = True
                 break
 
-        inherits = []
         if ptype.isToplevel():
-            inherits.append(Inherit(p.openedProtocolInterfaceType(), viz="public"))
+            inherits = [Inherit(Type("mozilla::ipc::IToplevelProtocol"))]
+        elif ptype.isRefcounted():
+            inherits = [Inherit(Type("mozilla::ipc::IRefCountedProtocol"))]
         else:
-            inherits.append(Inherit(p.managerInterfaceType(), viz="public"))
+            inherits = [Inherit(Type("mozilla::ipc::IProtocol"))]
 
         if ptype.isToplevel() and self.side == "parent":
             self.hdrfile.addthings(
@@ -3812,11 +3807,12 @@ def visitProtocol(self, p):
                 )
             ]
         else:
-            ctor.memberinits = [
-                ExprMemberInit(
-                    ExprVar("mozilla::ipc::IProtocol"), [_protocolId(ptype), side]
-                )
-            ]
+            baseCtor = (
+                ExprVar("mozilla::ipc::IRefCountedProtocol")
+                if ptype.isRefcounted()
+                else ExprVar("mozilla::ipc::IProtocol")
+            )
+            ctor.memberinits = [ExprMemberInit(baseCtor, [_protocolId(ptype), side])]
 
         ctor.addcode("MOZ_COUNT_CTOR(${clsname});\n", clsname=self.clsname)
         self.cls.addstmts([ctor, Whitespace.NL])
@@ -3853,12 +3849,6 @@ def visitProtocol(self, p):
             )
 
         if ptype.isRefcounted():
-            if not ptype.isToplevel():
-                self.cls.addcode(
-                    """
-                    NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
-                    """
-                )
             # Perform AddRef/Release in ActorAlloc/ActorDealloc if refcounted.
             actoralloc.addcode("AddRef();\n")
             actordealloc.addcode("Release();\n")