Make a QSharedPointer like class thread-safe with signal/slots

[yayo56]

Hi,

I create a class named SyncronizedPointer, it look like a QSharedPointer except that "->" operator make that all call become thread Safe here a simple example of use.

class Foo
{
  void criticalMethod()
  {
    //All work done here is completely thred-safe
  }
};
 
int main()
{
 
  SyncronizedPointer<Foo> sp( new Foo() );
 
  sp->criticalMethod(); 
  /* This precedent line will automatically: 
     - Lock an mutex inside SyncronizedPointer object.
     - Call the criticalMethod
     - Unlock the mutex
   
    With this system it's easy to make the Foo class thread safe, I can use copy of the 
    SyncronizedPointer object in multiple thread, I am sure that no more than one thread can
    call a method inside Foo object at the same time.
 */
 
  return (0);
  /*
    The Foo object will be automatically delete using a reference counting inside SyncronizedPointer.
  */
}

class Foo
{
  void criticalMethod()
  {
    //All work done here is completely thred-safe
  }
};

int main()
{

  SyncronizedPointer<Foo> sp( new Foo() );
  
  sp->criticalMethod(); 
  /* This precedent line will automatically: 
     - Lock an mutex inside SyncronizedPointer object.
     - Call the criticalMethod
     - Unlock the mutex
   
    With this system it's easy to make the Foo class thread safe, I can use copy of the 
    SyncronizedPointer object in multiple thread, I am sure that no more than one thread can
    call a method inside Foo object at the same time.
 */

  return (0);
  /*
    The Foo object will be automatically delete using a reference counting inside SyncronizedPointer.
  */
}

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So my problem is when I am trying to use SyncronizedPointer with QObject like

class Foo : public QObject
{
  Q_OBJECT
 
  public:
 
  void criticalMethod();
 
  public slot:
 
   void criticalSlot();
}
 
int main()
{
  SyncronizedPointer<Foo> sp(new Foo());
 
  /*
     Here no problem I can send the sp var across thread, call to criticalMethod will stay 
     thread safe.
  */
 
  QTimer timer;
 
  /* 
     Now I want to connect the timer timeout signal to  the criticalSlot
     Note that call to this slot MUST be totaly thread safe
   */
  QObject::connect(&timer, SIGNAL(timeout()), sp->data(), SLOT(criticalSlot()));
 
  /*
    The precedent line does not protect the access to the Foo class because Qt signal system 
    will directly call the slot without locking the Mutex inside the SyncronizedPointer
 */
 
  return (0);
}

class Foo : public QObject
{
  Q_OBJECT

  public:

  void criticalMethod();

  public slot:
    
   void criticalSlot();
}

int main()
{
  SyncronizedPointer<Foo> sp(new Foo());

  /*
     Here no problem I can send the sp var across thread, call to criticalMethod will stay 
     thread safe.
  */

  QTimer timer;

  /* 
     Now I want to connect the timer timeout signal to  the criticalSlot
     Note that call to this slot MUST be totaly thread safe
   */
  QObject::connect(&timer, SIGNAL(timeout()), sp->data(), SLOT(criticalSlot()));

  /*
    The precedent line does not protect the access to the Foo class because Qt signal system 
    will directly call the slot without locking the Mutex inside the SyncronizedPointer
 */

  return (0);
}

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Is there a solution to make this work, for example by making Qt call the slot using the
SyncronizedPointer object ?


An easy way would be to put the mutex inside the Foo class and lock it inside both slot and method
but the code would be much less sexy


PS: Sorry if my English is not perfect.