Question

I’m trying to think of a method demonstrating a kind of memory error using Arrays and C++, that is hard to detect. The purpose is to motivate the usage of STL vector<> in combination with iterators.

Edit: The accepted answer is the answer i used to explain the advantages / disadvantages. I also used: this

Answer 1

A memory leak? IMO, vector in combination with iterators doesn’t particularly protect you from errors, such as going out of bounds or generally using an invalidated iterator (unless you have VC++ with iterator debugging); rather it is convenient because it implements a dynamically resizable array for you and takes care of memory management (NB! helps make your code more exception-safe).

void foo(const char* zzz)
{
    int* arr = new int[size];
    std::string s = zzz;
    //...
    delete[] arr;
}

Above can leak if an exception occurs (e.g when creating the string). Not with a vector.

Vector also makes it easier to reason about code because of its value semantics.

int* arr = new int[size];
int* second_ref = arr;
//...
delete [] arr; 
arr = 0; //play it safe :)

//...
second_ref[x] = y;
//...
delete [] second_ref;

But perhaps a vector doesn’t automatically satisfy 100% of dynamic array use cases. (For example, there’s also boost::shared_array and the to-be std::unique_ptr<T[]>)