Dynamic Stack [Table Doubling]

// Table Doubling Program with Stack implementation //
#include <iostream>
using namespace std;

typedef struct{
    int *arr;
    int top;
    int size;
}stack;

void push(stack* sp,int num){
    if(sp->top == sp->size-1){
        int *temp;
        //double the size//
        temp = (int*)malloc(sizeof(int)*sp->size*2);
        if(temp == NULL){
            cout << "failed to allocate";
            return;
        }
        for(int i=0; i <= sp->top ;i++){
            temp[i] = sp->arr[i];
        }
        free(sp->arr);
        sp->arr = temp;
        sp->size *=2;
    }
    sp->top++;
    sp->arr[sp->top] = num;
    return;
}
int pop(stack* sp){
    if(sp->top == -1){
        cout << "Stack Empty\n";
        return -99;
    }
    int num = sp->arr[sp->top];
    sp->top--;
    return num;
}
void freemem(stack* sp){
    if(sp->arr != NULL){
        free(sp->arr);
        sp->top = -1;
        sp-> size = 0;
    }

}
void print(stack* sp){
    cout << "Size of Stack: " << sp->size << "\n\n";
    if(sp->top == -1){
        cout << "stack empty\n\n";
        return;
    }
    for (int i=0;i<= sp->top ;i++){
        cout << sp->arr[i] << "\t";
    }
    cout << "\n\n";
}
void __init__(stack* sp,int size){
    sp->top = -1;
    sp->arr = (int*)malloc(sizeof(int)*size);
    if(sp->arr == NULL){
    cout << "cant make allocations\n\n";
    return;
    }
    sp->size = size;
    return;
}
int main(){
    stack s1;
    __init__(&s1,5);
    int choice,num;
    while(1){
        cout << "1: push 2: pop 3: print 4: exit" <<endl;
        cin >> choice;
        switch(choice){
            case 1:
                cout << "num: ";
                cin >> num;
                push(&s1,num);
                break;
            case 2:
                num = pop(&s1);
                cout << num <<endl;
                break;
            case 3:
                print(&s1);
                break;
            case 4:
                freemem(&s1);
                exit(0);
            default:
                cout << "Invalid choice\n\n";
        }
    }
    return 0;
}