OCB interfaces should be checked for null in enter() method

[wixiw]

I'm using an embedded environment without any RTTI available, so NULL pointer are not catched. It's quite painfull to have the board stucked in an HW error each time I forgot to map a new OCB interface.

It would be nice to check the interface mapping in the init() or enter() method.

[terfloth]

OK - checking the operation callbacks makes much sense...

[andreasmuelder]

the same applies to the Java Code Generator. The operation callbacks should be checked in the enter method. Init could break existing client code.

public void enter() {
if (!initialized) {
throw new IllegalStateException(
"The state machine needs to be initialized first by calling the init() function.");
}

	if(sCInterface.operationCallback == null) {
		throw new IllegalStateException("Operation callback for interface 'scInterface' must be set");
	}
	
	enterSequence_main_region_default();
}

[rherrmannr]

We could implement it like this:

void Default::enter()
{
#ifdef CHECK_UNIMPLEMENTED_VIRTUAL_METHODS
	// Check if methods are implemented
	// if not
	throw std::runtime_error( "Operation callback for interface XY must be set.");
#endif
	/* Default enter sequence for statechart default */
	enseq_main_region_default();
}

and define CHECK_UNIMPLEMENTED_VIRTUAL_METHODS in the StatemachineInterface.h file.
It can be deleted, if some IDE's are not supporting #include

What's your opinion @terfloth ?

[wixiw]

This wouldn't answer the need expressed at the issue opening. No RTTI being present you cannot use exceptions. If they where there, I would have had an exception on the NULL pointer.

I may agree that generating a clean runtime error is better than a NULL pointer exception, but it's still using exceptions.

What would fit is a return code to the enter method. It should not break existing code as the function is currently returning a void which is by definition not tested by user code.

[terfloth]

We have to add the checks to ::init() as operation callbacks may be used during variable initialization. Example:

operation getSomeValue(): integer
var x : integer = getSomeValue()

[rherrmannr]

Implemented in Java within the init() function.

[rherrmannr]

As an example I've implemented defines and changed the return type of the init function into the cpp generator.

The first four bits indicates, that an OCB is unimplemented. The four right handed bits indicates, which type of OCB is unimplemented. This can be discussed:
1 -> Internal OCB
2 -> Default Interface OCB
3 -> Any named Interface OCB

The defines in the sc_types.h:

#ifndef OCB_INTERNAL_INIT_ERROR
#define OCB_INTERNAL_INIT_ERROR 0b00010001
#endif	

#ifndef OCB_DEFAULT_INIT_ERROR
#define OCB_DEFAULT_INIT_ERROR 0b00010010
#endif

#ifndef OCB_NAMED_INIT_ERROR
#define OCB_NAMED_INIT_ERROR 0b00010011
#endif

The init function returns three possible errors. They are only generated, if the related interface is used:

sc_integer Default::init()
{
	if (this->iface_OCB == null) return OCB_DEFAULT_INIT_ERROR;
	if (this->ifaceNamed_OCB == null) return OCB_NAMED_INIT_ERROR;
	if (this->ifaceInternalSCI_OCB == null) return OCB_INTERNAL_INIT_ERROR;
      
        //...
	
	return 0;
}

[wixiw]

Great solution !