Problem with inheritance and object share use?

[tonnot]

This is the skeleton of my app.

- ClassA       has a    ClassE    * myclassE_inside_A    public var.
    - ClassB    Inherits ClassD 
    - ClassC    Inherits ClassD  
 
- ClassD has some funtions and  *ClassE public var.

- ClassA       has a    ClassE    * myclassE_inside_A    public var.
    - ClassB    Inherits ClassD 
    - ClassC    Inherits ClassD  

- ClassD has some funtions and  *ClassE public var.

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The idea was to deal with classE instance from class A, B and C. And use some common methods of ClassD from ClassB and ClassC.

Pseudocode that describes its operation.

Inside ClassA:
    ClassB my_classB;    
    my_classB.create;   (I have the *ClassE filled with data )
    myclassE_inside_A = my_classB.classE;
 
    ClassC my_classC;
    ClassC.set_classE(my_classE_insideA); 
    for(   ) 
    {  do some things with my_classE_inside_A ;
        classC.modify_some_things_on_classE }    
 
    -  classC.modify_some_things_on_classE uses own methods and one function  inheritated from classD.

Inside ClassA:
    ClassB my_classB;    
    my_classB.create;   (I have the *ClassE filled with data )
    myclassE_inside_A = my_classB.classE;

    ClassC my_classC;
    ClassC.set_classE(my_classE_insideA); 
    for(   ) 
    {  do some things with my_classE_inside_A ;
        classC.modify_some_things_on_classE }    

    -  classC.modify_some_things_on_classE uses own methods and one function  inheritated from classD.

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When I run the program I have a lot a heap error and a lot of crahes
HEAP: Free Heap block c977e28 modified at c977e5c after it was freed
(Internal error: pc 0x2ff in read in psymtab, but not in symtab.)
(Internal error: pc 0x2ff in read in psymtab, but not in symtab.)
(Internal error: pc 0x2ff in read in psymtab, but not in symtab.)
,,,,

The error was related with classC, after the first modification of classE object. the second time I use it (it is the same if I do it from myclassE_insideA or int classC) i have the crash.
I'm sure that I' forget to do something but I dont view it.

It is as If I can't use the classE object by pointer. ?

Any idea ?

[stampede]

I dont like this idea - who is responsible for deleting the classE object ?

ClassB my_classB;    
    my_classB.create;   (I have the *ClassE filled with data )
    myclassE_inside_A = my_classB.classE; // who owns the classE now ? this or my_classB
 
    ClassC my_classC;
    ClassC.set_classE(my_classE_insideA); // and now ? is ownership passed to my_classC ?

ClassB my_classB;    
    my_classB.create;   (I have the *ClassE filled with data )
    myclassE_inside_A = my_classB.classE; // who owns the classE now ? this or my_classB
 
    ClassC my_classC;
    ClassC.set_classE(my_classE_insideA); // and now ? is ownership passed to my_classC ?

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You can get lost here easily, passing around, modifying and storing pointer to an object created by temporary object (my_classB on stack) smells like crash sooner or later.

Free Heap block c977e28 modified at c977e5c after it was freed

I dont know who owns the created object, and it seems like you dont know either, because you want to access it after deleting it somewhere.
I gues you should rethink the design, because its not clear now, and will be very painful to modify and maintain this kind of code.

[wysota]

One of possible solutions is to do reference counting on "E" and copy it by value (with a shared reference counter of course) between those objects that use it. Or if you use Qt, QSharedPointer is the thing you want to use (if you don't but you use C++ you can use boost/std::shared_ptr). And for clarity E should be created outside B to avoid doubts related to ownership of E (since E can live longer than B if it is shared with another object). As for now you are trying to access an already deleted object.