c++ - Delete calling destructor but not deleting object? -

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so have been working c++ , pointers year , half now, , thought had them succeed. have called delete on objects many times before , objects got deleted, or @ least thought did.

the code below confusing hell out of me:

#include <iostream>  class myclass { public:     int a;      myclass() : a(10) {         std::cout << "constructor ran\n";     }      void method(std::string input_) {         std::cout << param_ << "\n";     }      ~myclass() {         std::cout << "destructor ran\n";     }  };  int main() {     myclass* ptr = new myclass;     ptr->method("1");     delete ptr;     ptr->method("2.5");  }

this code outputs:

constructor ran 1 destructor ran 2.5

i confused why not throwing error of sort - expecting memory out of bounds exception or alike, nothing. for loop in there incase there sort of hidden garbage collection, though far know there no garbage collection in c++.

can explain why code works, or going wrong code not give me error?

you're misunderstanding delete does. delete call destructor, , tell allocator that memory free. doesn't change actual pointer. beyond undefined.

in case, nothing actual data pointed to. pointer points same data pointed before, , calling methods on works fine. however, behavior not guaranteed; in fact, it's explicitly unspecified. delete 0 out data; or allocator allocate same memory else, or compiler refuse compile this.

c++ allows many unsafe things, in interest of performance. 1 of them. if want avoid kind of mistake, it's idea do:

delete ptr; ptr = null;

to ensure don't try reuse pointer, , crash if rather having undefined behavior.


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