Error in the void print function - c++

Question

What I am trying to do is print out the elements that is dynamically allocated.
Here is my issue, I'm new in learning, and not understanding why this below cannot work? If you could please give a brief description why this is producing the error, I'm just trying to learn from my mistakes. I know I could just dynamically allocate the user input in the main function, but I wanted to see by trial and error if I could I just create an input function where I call it in my print function to produce the user elements after it is dynamically allocated.
Any suggestion on what I could do to make this work would be awesome, thanks.
void print(int* input, int size)
{
uinput(input,size);
for(int i=0; i<size;i++)
{
std::cout << " " << input[i];// Error -> Thread 1:EXC_BAD_ACCESS (code=1,address=0x0)
}
}
The entire code without the print function above
#include <iostream>
void print(int*, int);
void uinput(int*, int);
int* copy(const int*, int);
int main()
{
int size;
int* input;
std::cout << "Enter the size of the array";
std::cin >> size;
std::cout << "Original array:" << std::endl;
print(input,size);
int* expander = copy(input,size);
std::cout << "New array:" << std::endl;
print(expander,size);
delete [] input;
delete [] expander;
input= nullptr;
expander = nullptr;
return 0;
}
void uinput(int* input, int size)
{
int* uInput = new int[size];
for(int k=0; k <size;k++)
{
std::cin >> uInput[k];
}
}
int* copy(const int* input, int size)
{
int* newArray = new int[size*2];
int j =0;
for(int i = 0; i <size*2;i++)
{
if(j >i)
{
newArray[j]=newArray[i];
j++;
}
else
newArray[j]=0;
}
return newArray;
}
Update: I tried to modified where I just let it point to the size of uInput function, but that didn't work.
void uinput(int size)
{
int* uInput = new int[size];
for(int k=0; k <size;k++)
{
std::cin >> uInput[k];
}
}

Answer 1

Your uinput function allocates memory, but does not make use of the input parameter that you send it. As a result, trying to iterate over items supposedly pointed to by that pointer, which has not been initialized to point at anything, is undefined behavior, causing your program to crash, in this case.