Bug 1395509 - Add APIs to handle memory accounting while initializing object...

Bug 1395509 - Add APIs to handle memory accounting while initializing object pointers to malloc memory r=sfink?

Depends on D33313

Differential Revision: https://phabricator.services.mozilla.com/D33314

--HG--
extra : moz-landing-system : lando

js/src/gc/FreeOp.h

@@ -50,7 +50,11 @@ class FreeOp : public JSFreeOp {
 
   void free_(void* p) { js_free(p); }
 
-  // Free memory that was associated with a GC thing using js::AddCellMemory.
+  // Free memory associated with a GC thing and update the memory accounting.
+  //
+  // The memory should have been associated with the GC thing using
+  // js::InitReservedSlot or js::InitObjectPrivate, or possibly
+  // js::AddCellMemory.
   void free_(gc::Cell* cell, void* p, size_t nbytes, MemoryUse use);
 
   // Queue an allocation to be freed when the FreeOp is destroyed.
@@ -82,16 +86,23 @@ class FreeOp : public JSFreeOp {
     }
   }
 
-  // Delete a C++ object that was associated with a GC thing using
-  // js::AddCellMemory. The size is determined by the type T.
+  // Delete a C++ object that associated with a GC thing and update the memory
+  // accounting. The size is determined by the type T.
+  //
+  // The memory should have been associated with the GC thing using
+  // js::InitReservedSlot or js::InitObjectPrivate, or possibly
+  // js::AddCellMemory.
   template <class T>
   void delete_(gc::Cell* cell, T* p, MemoryUse use) {
     delete_(cell, p, sizeof(T), use);
   }
 
-  // Delete a C++ object that was associated with a GC thing using
-  // js::AddCellMemory. The size of the allocation is passed in to allow for
-  // allocations with trailing data after the object.
+  // Delete a C++ object that associated with a GC thing and update the memory
+  // accounting.
+  //
+  // The memory should have been associated with the GC thing using
+  // js::InitReservedSlot or js::InitObjectPrivate, or possibly
+  // js::AddCellMemory.
   template <class T>
   void delete_(gc::Cell* cell, T* p, size_t nbytes, MemoryUse use) {
     if (p) {

js/src/gc/ZoneAllocator.h

@@ -268,11 +268,15 @@ class ZoneAllocPolicy : public MallocProvider<ZoneAllocPolicy> {
   void decMemory(size_t nbytes) { zone_->decPolicyMemory(this, nbytes); }
 };
 
-// Convenience functions for memory accounting on the zone.
+// Functions for memory accounting on the zone.
 
-// Associate malloc memory with a GC thing. This call must be matched by a
+// Associate malloc memory with a GC thing. This call should be matched by a
 // following call to RemoveCellMemory with the same size and use. The total
 // amount of malloc memory associated with a zone is used to trigger GC.
+//
+// You should use InitReservedSlot / InitObjectPrivate in preference to this
+// where possible.
+
 inline void AddCellMemory(gc::TenuredCell* cell, size_t nbytes, MemoryUse use) {
   if (nbytes) {
     ZoneAllocator::from(cell->zone())->addCellMemory(cell, nbytes, use);
@@ -284,8 +288,9 @@ inline void AddCellMemory(gc::Cell* cell, size_t nbytes, MemoryUse use) {
   }
 }
 
-// Remove association between malloc memory and a GC thing. This call must
+// Remove association between malloc memory and a GC thing. This call should
 // follow a call to AddCellMemory with the same size and use.
+
 inline void RemoveCellMemory(gc::TenuredCell* cell, size_t nbytes,
                              MemoryUse use) {
   if (nbytes) {
@@ -299,6 +304,39 @@ inline void RemoveCellMemory(gc::Cell* cell, size_t nbytes, MemoryUse use) {
   }
 }
 
+// Initialize an object's reserved slot with a private value pointing to
+// malloc-allocated memory and associate the memory with the object.
+//
+// This call should be matched with a call to FreeOp::free_/delete_ in the
+// object's finalizer to free the memory and update the memory accounting.
+
+inline void InitReservedSlot(NativeObject* obj, uint32_t slot, void* ptr,
+                             size_t nbytes, MemoryUse use) {
+  AddCellMemory(obj, nbytes, use);
+  obj->initReservedSlot(slot, PrivateValue(ptr));
+}
+template <typename T>
+inline void InitReservedSlot(NativeObject* obj, uint32_t slot, T* ptr,
+                             MemoryUse use) {
+  InitReservedSlot(obj, slot, ptr, sizeof(T), use);
+}
+
+// Initialize an object's private slot with a pointer to malloc-allocated memory
+// and associate the memory with the object.
+//
+// This call should be matched with a call to FreeOp::free_/delete_ in the
+// object's finalizer to free the memory and update the memory accounting.
+
+inline void InitObjectPrivate(NativeObject* obj, void* ptr, size_t nbytes,
+                              MemoryUse use) {
+  AddCellMemory(obj, nbytes, use);
+  obj->initPrivate(ptr);
+}
+template <typename T>
+inline void InitObjectPrivate(NativeObject* obj, T* ptr, MemoryUse use) {
+  InitObjectPrivate(obj, ptr, sizeof(T), use);
+}
+
 }  // namespace js
 
 #endif  // gc_ZoneAllocator_h