Chapter 20 // Exercise 15 - Principles & Practice Using C++

In this exercise I am using Visual Studio 2019 and a modified version of the std_lib_facilities header found here.

Chapter 20 // Exercise 15

Define a pvector to be like a vector of pointers except that it contains pointers to objects and its destructor deletes each object.

Github: https://github.com/l-paz91/principles-practice/blob/master/Chapter%2020/Exercise%2015

I found the wording on this one really confusing. Like does he mean a vector of pointers to anything (like vector<void*>) or like a vector<int*> where each object is just a standard type. I understand what he's getting us to do though because a vector doesn't call the destructor for a plain pointer. So whereas string will clean itself up when it goes out of scope, a pointer to a string won't call strings destructor when it goes out of scope (because raw pointers don't have destructors) and then a memory leak is created.

At first I tried to inherit from std::vector and add a new destructor but I have no idea what a _Compressed_pair<_Alty, _Scary_val> _MyPair is and just calling delete[] _MyPair wouldn't compile so I gave up as it was completely beyond me. Also I learnt that std::vectors destructor is not virtual so I can't modify it anyway. Google says it's best to not inherit from std::vector unless absolutely necessary.

I ended up creating a class that has a std::vector as a member variable and implementing most std::vector methods with the destructor explicitly calling delete on each pointer element. Using my best friend _CrtDumpMemoryLeaks() at the end of main shows how PVector cleans up after itself and a std::vector leaks memory:

I then added a static_assert to the class to prevent it from compiling if the type given is not a pointer.