c++ - Unusable derived class std::map member -

please observe following code:

class foo

class foo: {    public:      foo();      ~foo(); } 

class c

class c {     public:       c();       ~c();       void seta(a* a) { m_a = a; }       a* geta() { return m_a; }      private:     a* m_a; } 

abstract class a:

class { public:     // constructor, destructor     (c* c) : parent (c)     virtual ~a();      // relevant pure abstract methods     void addfoo(foo* f, std::string& id) = 0;     foo* getfoo(std::string id)= 0;  protected:     c* parent;     std::map< std::string, foo* > m_foos; }; 

in b.h

class b : public { public:     // constructor, destructor ...     b(c* c);     virtual ~b();     // definition of pure relevant methods     virtual void addfoo(foo* f, std::string& id);     virtual foo* getfoo(std::string id);         }; 

in b.cpp

// methods implementation ... b::b(c* c) : a(c) { }  foo* b::getfoo(std::string id) {     return m_foos[id]; }  b::setfoo( foo* f, std::string& id ) {     m_foos[id] = f; } 

and then, in different part of code running smoothly until decided make m_foos inheritable:

   c* c = new c();    c->seta(new b(c)); 

this executed beyond doubt before:

foo* f = new foo(); ... c->geta()->setfoo(f); 

program crashes when trying access m_foos inside setfoo. reason can't yet understand, m_foos not correctly initialized in b (running m_foos.size() instance returns crazy values). mind error @ runtime, not @ compilation time.

edit: weird, since adding protected member variable of type int in class allows modification , reading in b::setfoo()...

my psychic debugging skills tell me b either null pointer, hasn't actually been constructed, or prematurely destructed.

did accidentally create on stack , store pointer it?

edit: given adding member a changes behavior, somewhere in code you're getting undefined behavior. need see more of code more general guesses.