c++ - how to free malloc outside of function -

can't resolve problem - compiler allways tells me have troubles free(pointer) function. i'm not sure working of pointers debugging has shown works well. free function could't free memory.

    #include <stdio.h>              //bibliothek für input/output.     #include <stdlib.h>             //for malloc     #include <math.h>               //bibliothek für matchematische operationen.     #include <iostream>             //bibliothek für in/output in c++.     #include <stdbool.h>            //bibliothek für boolean      //prototypes int* readnumbers(int size); int sumupnumbers(int* sumpointer, int size);  //main function int main() {     int arraysize;  //size of malloc-array     int* pointer;   //pointer storing of malloc-address     int total;      //variable sumupnumbers function     pointer = null; //point on 0      //inform user before getting number him     std::cout << "please give size of array:" << std::endl;     fflush(stdout); //free output window     //get number size of array     scanf("%d", &arraysize);      //call readnumbers function , store first address of     //the malloc-array in pointer     pointer = readnumbers(arraysize);      //call sumupnumbers function , store number in total     total = sumupnumbers(pointer, arraysize);      fflush(stdout); //free output window     //show number total     printf("\n total of array:%d", total);      //call free function making memory of     //the malloc-array free again     free(pointer);      fflush(stdin);  //free keyboard buffer     getchar();      //wait feedback user     return 0;       //return 0 machine in case if works }   //this function has pointer extension because want work //array outside of function. give function size of array //we want build. function builds array , fills numbers //and gives first address of array. int* readnumbers(int size) {      int* array;         //pointer creating of malloc-array     int i;              //counter      //pointer storing of first address of array     int* helppointer;     array = null;       //set pointers     helppointer = null; //              on 0      //create array     array = (int *) malloc(size * sizeof(int));      //check value of array sure have created     //the array without errors     if(array != null)     {         //store first address of malloc-pointer         helppointer = array;         //give value parts of array         for(i=0; i<=size; i++)         {             //inform user             printf("\n give %d. nummber of array:\n", i+1);             fflush(stdout); //free output window             //read value             scanf("%d", array+i);         }          return helppointer; //return first address     }     //if went wrong creating of array, do:     else     {         //tell user, computer does't have enough memory         std::cout << "there no place saving data in mamory";         return 0;   //return failure     }  }  //the input of function pointer address of malloc-array //from readnumbers , size of array. function adds numbers //from array , gives result of additation back. int sumupnumbers(int* sumpointer, int size) {     int sum;    //variable storing of total value     int i;      //counter     sum = 0;    //set sum on 0 before work      //count values array     for(i=0; i<=size; i++)     {         //count 1 number after         sum = sum + *(sumpointer+i);     }     return sum; //return total value } 

the limits of for loops wrong. writing 1 position on end of array, might corrupt memory later program fails. change for loops to:

for(i=0; i<size; i++)