Stack corruption ?

This is a discussion on Stack corruption ? within the C++ Programming forums, part of the General Programming Boards category; Hi everyone, Now every error seems weird, but this one _really_ does to me ;-) I have to classes, A ...

  1. #1
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    Stack corruption ?

    Hi everyone,

    Now every error seems weird, but this one _really_ does to me ;-)

    I have to classes, A and B. B is an interface for let's say B_a and B_b.
    'A' contains a pointer to 'B', pointing to an allocated object of either 'B_a' or 'B_b' (via some factory), and the 'B-object' contains a pointer to A (some pimpl implementation).
    Class 'A' also has a derived class, therefore some of it's member functions are virtual (and here's the problem).

    Code:
    class A;
    
    class B {
     public:
      B(A* p_a) : a_(p_a) {}
      virtual void read( 'file ') = 0;
     protected:
      A* a_;
    };
    
    class B_a : public B  // class implements 'read'
    class B_b : public B  // class implements 'read' in a similar way as B_a (see below)
    
    
    class A {
     public:
      A() : _b(new B_b(this)) {}  // or new B_a(this) , this is done in some factory method
      void read( 'file' ) { b_->read('file'); }
      virtual void f();
      virtual void g();
     protected:
      B* b_;
    };
    
    
    void B_a :: read( 'file' ) {
      // do a lot of things specific for B_a (or B_b)
      a_->f(); // someting weird happens here
    
      // do a lot of other things specific for B_a (or B_b)
      a_->g();
    }

    Now the weird thing is : the call 'a_->f()' does _not_ call 'A::f()' , but it call 'B::g()' !!

    If I remove the keyword 'virtual' (temporarily) for 'A::f()' it works, but then it produces a similar error for the call 'a_->g()' . Unless I remove the keyword 'virtual' ....

    ** I have verified the adresses of the pointers, that's all correct. I am debugging the correct code, I verified with some 'asserts'.
    ** calling 'a_->f()' from another context just just just before 'B_a::read', does not produce the problem.

    Is there somewhere a stack corruption ? If so, how could I detect it ?

    Thanks a lot !!!
    Last edited by MarkZWEERS; 01-31-2011 at 06:06 AM. Reason: indentation

  2. #2
    Algorithm Dissector iMalc's Avatar
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    There is no function B::g() in what you posted.
    Non-compileable bits like ('file') serve no useful purpose in this example. You may as well just leave out that parameter.
    Please fix your example.
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    Advice: Take only as directed - If symptoms persist, please see your debugger

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  3. #3
    Master Apprentice phantomotap's Avatar
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    O_o

    Your example makes baby kittens cry.

    Soma

  4. #4
    Super Moderator VirtualAce's Avatar
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    Yikes. Clean that code up and use more descriptive variable names, class names, and method names. The answer might jump out at you after you re-fector a bit for readability.

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