For learning purposes, I'm attempting to create a primitive ArrayList class with the ability to add elements and resize itself when needed. Currently, I managed to create a constructor and overload the array access operator as well as add an append function to add elements to the back of the array. However, once the realloc is triggered, the program crashes with Segmentation Fault: 11. Oddly, though, if I change my code, the first time I execute it there is no segmentation fault; only when rerunning the executable does it fail, so I am suspicious my free() call is not working properly. All elements until the reallocation appear to be successfully added.
I have my class defined in a .cpp file because template definitions are unable to be split into a header and other file.
structures.cpp
#include <cstdlib>
#include <stdexcept>
template<typename T> class ArrayList {
private:
T* pointer;
unsigned short space;
public:
ArrayList();
~ArrayList();
T& operator[](unsigned short index);
const T& operator[](unsigned short index) const;
unsigned short length;
void append(T element);
};
template<typename T> ArrayList<T>::ArrayList() {
length = 0;
space = 10;
pointer = (T*)malloc(space*sizeof(T));
}
template<typename T> ArrayList<T>::~ArrayList() {
free(pointer);
}
template<typename T> T& ArrayList<T>::operator[](unsigned short index) {
if (index > length) throw std::out_of_range("Index out of bounds.");
return *(pointer + sizeof(T)*index);
}
template<typename T> void ArrayList<T>::append(T element) {
if (length == space) {
space *= 2;
pointer = (T*)realloc(pointer, sizeof(T)*space);
}
*(pointer + sizeof(T)*length) = element;
++length;
}
main.cpp
#include <iostream>
#include "structures.cpp"
int main(int argc, char** argv) {
ArrayList<unsigned> arr;
int l = 11;
for (int i = 0; i < l; ++i) {
std::cout << "Current index: " << i << std::endl;
arr.append(i);
}
std::cout << "Finished writing to array" << std::endl;
for (int i = 0; i < l; ++i) {
std::cout << "Index: " << i << " Value: " << arr[i] << std::endl;
}
return 0;
}
Output:
Current index: 0
Current index: 1
Current index: 2
Current index: 3
Current index: 4
Current index: 5
Current index: 6
Current index: 7
Current index: 8
Current index: 9
Current index: 10
Segmentation fault: 11
