c++ - vector related memory allocation question -

i encountering following bug.

• i have class foo . instances of class stored in std::vector vec of class b.
• in class foo, creating instance of class allocating memory using new , deleting object in ~foo().

the code compiles, crash @ runtime. if disable delete my_a desstructor of class foo. code runs fine (but there going memory leak).

could please explain going wrong here , suggest fix?

thank you!

class a{       public:           a(int val);           ~a(){};           int val_a;  };  a::a(int val){        val_a = val;        };  class foo {             public:              foo();              ~foo();              void createa();              a* my_a; };  foo::foo(){     createa(); };  void foo::createa(){     my_a = new a(20); };  foo::~foo(){     delete my_a;  };    class b {       public:              vector<foo> vec;                           void createfoo();                          b(){};              ~b(){}; };   void b::createfoo(){     vec.push_back(foo()); };   int main(){     b b;      int  =0;     (i = 0; < 5; ++){         std::cout<<"\n creating foo";         b.createfoo();            std::cout<<"\n foo created";         }     std::cout<<"\ndone foo creation";      std::cout << "\npress return continue...";     std::cin.get();      return 0; } 

you need implement copy constructor , assignment operator foo. whenever find need destructor, alnmost need these 2 well. used in many places, putting objects standard library containers.

the copy constructor should this:

foo :: foo( const foo & f ) : my_a( new a( * f.my_a ) ) { } 

and assignment operator:

foo & foo :: operator=( const foo & f ) {     delete my_a;     my_a = new a( * f.my_a );     return * this; } 

or better still, don't create instance in foo class dynamically:

class foo {             public:              foo();              ~foo();              void createa();              my_a; };  foo::foo() : my_a( 20 ) { };