fopen() gives me malloc(): corrupted top size - c++

Question

I am trying to write the contents of an array, to a binary file, but it gives the following errors when I run the file.
malloc(): corrupted top size
Process finished with exit code 134 (interrupted by signal 6: SIGABRT)
Here is my code
#include <iostream>
#include <time.h>
#include <fstream>
#include <iostream>
using namespace std;
#define ONE 1
#define TWO 2
#define THREE 3
#define FOUR 4
#define FIVE 5
#define SIX 6
#define SEVEN 7
int getArrayLength();
void initializeArray(int *array, int length);
void printArray(int *array, int length);
void menu(int *array, int length);
void userChoice(int userInput, int *array, int length);
void serialSearch(int *array, int length, int givenNumber);
void quickSort(int *array, int start, int end);
int partition(int *array, int start, int end);
void substitute(int *firstElement, int *secondElement);
int binarySearch(int *array, int start, int end, int userChoice);
void arrayConcatenation(int *firstArray, int *secondArray, int *concatenatedArray, int length, int doubleLength);
int main() {
int arrayLength = getArrayLength();
int *randomNumbersArray = (int *) malloc(arrayLength * sizeof (int));
initializeArray(randomNumbersArray, arrayLength);
printArray(randomNumbersArray, arrayLength);
menu(randomNumbersArray, arrayLength);
return 0;
}
int getArrayLength()
{
int size;
cout<<"Please give the size of the array: ";
cin>>size;
return size;
}
void initializeArray(int *array, int length)
{
srand(time(nullptr));
for(int i = 0; i < length; i++)
*(array + i) = 30 + rand() % 21;
}
void printArray(int *array, int length)
{
for(int i = 0; i < length; i++)
cout<<*(array + i)<<" ";
cout<<endl;
}
void menu(int *array, int length)
{
int userInput;
cout<<" Array Functions"<<"\n"<<endl;
do {
cout<<"1. Serial Search"<<endl;
cout<<"2. Array Classification"<<endl;
cout<<"3. Binary Search (classifies the array automatically)"<<endl;
cout<<"4. Concatenation of classified arrays"<<endl;
cout<<"5. Print"<<endl;
cout<<"6. Save and read array with binary file"<<endl;
cout<<"7. Exit"<<"\n"<<endl;
cout<<"Please enter your choice: ";
cout<<endl;
cin>>userInput;
userChoice(userInput, array, length);
} while (userInput != SEVEN);
}
void userChoice(int userInput, int *array, int length)
{
FILE *myFile;
int mergedLength = 2 * length;
int *secondArray = (int *) malloc(length * sizeof (int));
int *mergedArray = (int *) malloc(length * sizeof (int));
initializeArray(secondArray, length);
initializeArray(mergedArray, mergedLength);
switch(userInput)
{
case ONE:
{
int givenNumber;
serialSearch(array, length, givenNumber);
break;
}
case TWO:
{
quickSort(array, 0, length-ONE);
cout<<"This is the sorted array."<<endl;
printArray(array, length);
break;
}
case THREE:
{
int choice, existence;
cout<<"What number you want?"<<endl;
cin>>choice;
quickSort(array, 0, length-ONE);
existence = binarySearch(array, 0, length-ONE, choice);
if (existence == -ONE)
cout<<"The chosen number is not in the array."<<endl;
else
cout<<"The number is at index "<<existence<<"."<<endl;
break;
}
case FOUR:
{
quickSort(array, 0, length-ONE);
quickSort(secondArray, 0, length-ONE);
arrayConcatenation(array, secondArray, mergedArray, length, mergedLength);
quickSort(mergedArray, 0, mergedLength - ONE);
cout<<"This is the first array in order"<<endl;
printArray(array, length);
cout<<"This is the second array in order."<<endl;
printArray(secondArray, length);
cout<<"This is the merged array in order."<<endl;
printArray(mergedArray, mergedLength);
myFile = fopen("binarydata.dat", "wb");
if(myFile == NULL)
{
cout<<"Error in file opening."<<endl;
exit(0);
}
fwrite(array, sizeof (int ), length, myFile);
fclose(myFile);
break;
}
}
free(secondArray);
free(mergedArray);
}
void serialSearch(int *array, int length, int givenNumber)
{
int flag = -ONE;
cout<<"Please give the number that you want to find in the array: ";
cin>>givenNumber;
for(int i = 0; i < length; i++)
{
if(*(array + i) == givenNumber)
{
cout<<"The number was found at position: "<<i<<"\n"<<endl;
flag = 0;
break;
}
}
if(flag == -1)
cout<<"The number is not in the array."<<"\n"<<endl;
}
void quickSort(int *array, int start, int end)
{
if (start < end)
{
int driver = partition(array, start, end);
quickSort(array, start, driver-ONE);
quickSort(array, driver+ONE, end);
}
}
int partition(int *array, int start, int end)
{
int key = *(array + end);
int i = start - ONE;
for(int j = start; j < end; j++)
{
if(*(array + j) <= key)
{
i++;
substitute((array + i), (array + j));
}
}
substitute((array +i + ONE), (array + end));
return(i + ONE);
}
void substitute(int *firstElement, int *secondElement)
{
int temp = *firstElement;
*firstElement = *secondElement;
*secondElement = temp;
}
int binarySearch(int *array, int start, int end, int userChoice)
{
if(end >= start)
{
int middle = start + (end - start)/2;
if(*(array + middle) == userChoice)
return middle;
if(*(array + middle) > userChoice)
return binarySearch(array, start, middle-1, userChoice);
return binarySearch(array, middle+1, end,userChoice);
}
return -1;
}
void arrayConcatenation(int *firstArray, int *secondArray, int *concatenatedArray, int length, int doubleLength)
{
for(int i = 0; i < length; i++)
*(concatenatedArray + i) = *(firstArray + i);
for(int i = 0; i < length; i++)
*(concatenatedArray + i + length) = *(secondArray + i);
}
The problem is in the case FOUR of the switch case part of the code.