how to implement matrix functions in C - c

Question

I am trying to make some simple functions that does some operations on matrixes. But i can`t undestand why the following code is not working!. Can you please help me to understand what is wrong here and what should i do???
void create(int*** p, const int n)
{
*p = (int**)calloc(n, sizeof(int));
if(*p == NULL){
printf("Error1");
}
int i;
for(i = 0; i < n; i++){
(*(p[i]) = (int*)calloc(n, sizeof(int)));
if(*(p[i]) == NULL){
printf("Error2");
}
}
}
void initializeMatrix(int*** p, const int n)
{
int i, j;
for(i = 0; i < n; i++){
for(j = 0; j < n; j++){
scanf("%d", &((p[i][j])));
}
}
}
void show(const int** p, const int n)
{
int i, j;
for(i = 0; i < n; i++){
for(j = 0; j < n; j++){
printf("%d ", ((p)[i][j]));
}
printf("\n");
}
}
int main()
{
int** p = NULL;
create(&p, 2);
initializeMatrix(&p, 2);
show(p, 2);
return 0;
}

Answer 1

Problem 1
You are using *(p[i]) in create. it should be (*p)[i].
void create(int*** p, const int n)
{
*p = (int**)calloc(n, sizeof(int));
if(*p == NULL){
printf("Error1");
}
int i;
for(i = 0; i < n; i++){
// FIXED
(*p)[i] = (int*)calloc(n, sizeof(int)));
// FIXED
if( (*p)[i] == NULL){
printf("Error2");
}
}
}
Problem 2
You are passing the wrong size to first calloc in the function. You need to use sizeof(int*). After all, you want the returned value to be a pointer to n pointers to int, not a pointer to n objects of type int.
This is a critical error that leads to undefined behavior unless sizeof(int) is the same as sizeof(int*) on your platform.
Change the line to
*p = (int**)calloc(n, sizeof(int*));
More importantly, you can make that function a bit easier by returning a pointer. It will be easier to write such a function.
int** create(int n)
int **p = calloc(n, sizeof(*p));
if(p == NULL){
printf("Error1");
}
int i;
for(i = 0; i < n; i++){
p[i] = calloc(n, sizeof(*p[i])));
if( p[i] == NULL){
printf("Error2");
}
}
return p;
}
and use it as:
int** p = create(2);