Thread: Code for int *growArray (int* p_values, int *size) is incorrect, Chapter 14, page 152

Code for int *growArray (int* p_values, int *size) is incorrect, Chapter 14, page 152 in the Jumping into C++

Code:

int *growArray (int* p_values, int *size)
{
*size *= 2;
int *p_new_values = new int[ *size ];


/* size has been changed by this time, so in the below for loop when you loop thru' o to size-1 and dereference the values in the original array p_values, once you go beyond the value of the original size -1 you go beyond the bounds of the original array and are dereferencing stuff that doesn't belong to the original array. You should save the original size and only loop from 0 to the size -1 of the original size value */

for ( int i = 0; i < *size; ++i )
{
p_new_values[ i ] = p_values[ i ];
}
delete [] p_values;
return p_new_values;
}
Sample Code 37: resize_array.cpp (continued)

So this is a completely over-engineered solution but this is a more C++11 version of what you have.

Code:

#include <array>
#include <memory>
#include <algorithm>


template <typename T>
auto grow_array(
    T const* const old_data, 
    size_t const old_size, 
    size_t const new_size)
-> std::unique_ptr<T[]>
{
    std::unique_ptr<T[]> data{new T[new_size]};
    std::uninitialized_copy(old_data, old_data + old_size, data.get());
    return data;
}


auto test(void) -> void
{
    std::array<int, 3> const x{0, 1, 2};


    auto data = grow_array(x.data(), x.size(), size_t{26});
}

godbolt

Compiled but not run.

For "over-engineered" read "completely retarded".

O_o

T_T

Well, such is life.

You're just lucky uninitialized_move is C++14/17 otherwise I would've even SFINAE'd it up and had separate overloads for movable classes vs non-movable classes :P

Also, you can just return unique_ptrs, how cool is that?