The C++ Language 4th edition - Subclassing vector for range checking.

Newsgroup: comp.lang.c++

Subject: The C++ Language 4th edition - Subclassing vector for range checking.

From: mrileyoscmp@...

Date: Sat, 13 Jul 2013 18:26:45 -0700 (PDT)



I was under the impression that it was generally a bad idea to subclass vector because the destructor is not virtual because if someone referenced an object of your class with a pointer and then deleted it with the base, the operation is undefined.



In The C++ Programing Language 4.4.1.2 Stroustrup says "... I often use a simple range-checking adaption of vector:"



template<typename T>

class Vec : public std::vector<T> {

public:

using vector<T>::vector;



T & operator[](int i)

{return vector<T>::at(i);}



const T & operator[](int i) const

{return vector<T>::at(i);}

};



I thought this was some what dangerous because if an user of the class (Maybe not the person who wrote it) writes:

Vector<T> * vectorObject = new Vec<int>(100);

delete vectorObject;



Results in undefined behavior.



Did something change in C++11? Is there some common idiom where people create classes that must be on the stack or they should know not to delete the base?



I ask because this seems like it would create error prone code.

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