[CrystalSpace] #929: Circular csRef/csWeakRef with explicit reset in destructor results in assert

#929: Circular csRef/csWeakRef with explicit reset in destructor results in
assert
---------------------+------------------------------------------------------
 Reporter:  thebolt  |       Owner:  admin
     Type:  defect   |      Status:  new  
 Priority:  major    |   Milestone:       
Component:  libs     |     Version:  V1.9 
 Keywords:           |  
---------------------+------------------------------------------------------
 The original code is csTextureHandleNull and csTextureManagerNull, where
 destruction of csTextureHandleNull results in following call chain, that
 ends up asserting (CS_ASSERT so only in debug-mode, probably does not
 cause any problem in release)

 {{{
 #3  0x0028a54c in CS::Debug::AssertMessage (expr=0xb55fe2 "scfRefCount !=
 0",
     filename=0xb55fbc "./include/csutil/scf_implementation.h", line=302,
     msg=0xb55ff4 "Refcount incremented from inside dtor") at
 /home/mos/src/CS/libs/csutil/csassert.cpp:80
 #4  0x00b54afb in scfImplementation<csTextureHandleNull>::IncRef
 (this=0xb565bba0)
     at ./include/csutil/scf_implementation.h:301
 #5  0x00b520b5 in csRef<iBase>::csRef<csTextureHandleNull>
 (this=0xbfffe98c, newobj=0xb565bba0)
     at ./include/csutil/ref.h:181
 #6  0x00b514cb in csWeakRef<csTextureHandleNull>::Get<csRef<iBase> >
 (this=0xbfffe9cc) at ./include/csutil/weakref.h:308
 #7  0x00b5036f in csWeakRef<csTextureHandleNull>::~csWeakRef
 (this=0xbfffe9cc, __in_chrg=<optimized out>)
     at ./include/csutil/weakref.h:180
 #8  0x00b4f70f in csTextureManagerNull::UnregisterTexture
 (this=0xb7d56758, handle=0xb565bba0)
     at /home/mos/src/CS/plugins/video/render3d/null/null_txt.cpp:206
 #9  0x00b4ef08 in csTextureHandleNull::~csTextureHandleNull
 (this=0xb565bba0, __in_chrg=<optimized out>,
     __vtt_parm=<optimized out>) at
 /home/mos/src/CS/plugins/video/render3d/null/null_txt.cpp:88
 #10 0x00b4efa1 in csTextureHandleNull::~csTextureHandleNull
 (this=0xb565bba0, __in_chrg=<optimized out>,
     __vtt_parm=<optimized out>) at
 /home/mos/src/CS/plugins/video/render3d/null/null_txt.cpp:89
 #11 0x00b54a84 in scfImplementation<csTextureHandleNull>::DecRef
 (this=0xb565bba0)
     at ./include/csutil/scf_implementation.h:295
 #12 0x080a6adf in csRef<iTextureHandle>::~csRef (this=0xb5b16648,
 __in_chrg=<optimized out>) at ./include/csutil/ref.h:206
 }}}

 A simplified code which exhibits the problem is

 {{{
 class Manager;

 class Client : public scfImplementation0<Client>
 {
 public:
   Client (Manager *b);
   ~Client ();

 private:
   Manager *b;
 };

 class Manager
 {
 public:
   void RegisterClient (Client *a);
   void UnregisterClient (Client *a);

 private:
   csWeakRefArray<Client> clientArray;
 };

 Client::Client (Manager *b)
   : scfImplementationType (this), b(b)
 {
 }

 Client::~Client ()
 {
   if (b) {
     b->UnregisterClient (this);
   }
 }

 void Manager::RegisterClient (Client *a)
 {
   clientArray.Push (a);
 }

 void Manager::UnregisterClient (Client *a)
 {
   size_t index = clientArray.Find (a);
   if (index != csArrayItemNotFound) clientArray.DeleteIndexFast (index);
 }

 void weakRefTest::testCyclicTeardown()
 {
   Manager *ourManager;
   Client *ourClient;

   ourManager = new Manager;
   ourClient = new Client (ourManager);

   ourManager->RegisterClient (ourClient);
   ourClient->DecRef ();

   // Clean up
   delete ourManager;

   CPPUNIT_ASSERT(1 == 1);
 }
 }}}

-- 
Ticket URL: <http://trac.crystalspace3d.org/trac/CS/ticket/929>
CrystalSpace <http://www.crystalspace3d.org/>
Free open-source 3D SDK.
------------------------------------------------------------------------------
Cloud Services Checklist: Pricing and Packaging Optimization
This white paper is intended to serve as a reference, checklist and point of 
discussion for anyone considering optimizing the pricing and packaging model 
of a cloud services business. Read Now!
http://www.accelacomm.com/jaw/sfnl/114/51491232/