*pointer was nullptr* error in C programming - c

Question

I have a serious problame.
at the line **c = (int*)malloc(size1 * sizeof(int*));
the compiler gives me this error which I don't really know what it says.
Unhandled exception thrown: read access violation.
c was nullptr. occurred
I don't know what I'm doing wrong..
I initialize every pointer like this.
void BuildMatrix(int ***, int, int);
void FreeMatrix(int ***, int);
void PrintMatrix(int **, int, int);
int **MultiplyMatrixes(int **, int**, int, int, int);
int main() {
int **matrix1 = NULL, **matrix2 = NULL, **matrix3 = NULL;
int * newCol = NULL;
int size1, size2, size3, newRow;
printf("-How many rows in the first matrix?: ");
scanf("%d", &size1);
printf("-How many columns in the first matrix and second?[size2, size3]: ");
scanf("%d %d", &size2, &size3); /*size2 = rows of matrix2.*/
/*Build both matrices*/
printf("-First matrix input.\n");
BuildMatrix(&matrix1, size1, size2);
PrintMatrix(matrix1, size1, size2);
printf("-Second matrix input.\n");
BuildMatrix(&matrix2, size2, size3);
PrintMatrix(matrix2, size2, size3);
/*Combine the 2 matrices to a new matrix*/
matrix3 = MultiplyMatrixes(matrix1, matrix2, size1, size2, size3);
FreeMatrix(&matrix2, size2); //Free the second matrix
printf("\n-Multiplied matrix: \n");
PrintMatrix(matrix3, size1, size3);
FreeMatrix(&matrix3, size1);
FreeMatrix(&matrix1, size1);
}
void BuildMatrix(int *** pMat, int row, int col) {
int i, j;
(*pMat) = (int **)malloc(row * sizeof(int*));
if (*pMat == NULL) {
free(pMat);
printf("*Not enough RAM.\nTerminating.\n");
exit(1);
}
for (i = 0; i < row; i++) {
(*pMat)[i] = (int *)malloc(col * sizeof(int*));
if ((*pMat)[i] == NULL) {
printf("*Not enough RAM.\nTerminating.\n");
FreeMatrix(pMat, row);
exit(1);
}
for (j = 0; j < col; j++) {
printf("-Enter %d element in %d row: ", j + 1, i + 1);
scanf("%d", &(*pMat)[i][j]);
}
printf("\n");
}
//FreeMatrix(pMat, row);
}
void PrintMatrix(int ** pMat, int row, int col) {
for (int i = 0; i < row; ++i) {
for (int j = 0; j < col; ++j) {
printf("%d ", pMat[i][j]);
}
printf("\n");
}
}
int** MultiplyMatrixes(int ** a, int ** b, int size1, int size2, int size3) {
int i, j, k, **c = NULL;
**c = (int*)malloc(size1 * sizeof(int*));
if (c == NULL) {
free(*c);
printf("*Not enough RAM.\nTerminating.\n");
exit(1);
}
for (i = 0; i < size1; i++) {
for (j = 0; j < size3; j++) {
c[i] = (int *)malloc(size3 * sizeof(int));
if (c[i] == NULL) {
printf("*Not enough RAM.\nTerminating.\n");
FreeMatrix(&c, size1);
exit(1);
}
for (k = 0; k < size2; k++) {
c[i][j] += (a[i][k] * b[k][j]);
}
}
}
return c;
}

Answer 1

(*pMat)[i] = (int *)malloc(col * sizeof(int*));
will be
(*pMat)[i] = malloc(col * sizeof(int));
You have allocated space for col number of int* where you are reading int-s.
Also
**c = (int*)malloc(size1 * sizeof(int*));
will be
c = malloc(size1 * sizeof(int*));
Otherwise you were trying to dereference NULL value which triggered the error you got.
Also the loop will be
for (i = 0; i < size1; i++) {
c[i] = malloc(size3 * sizeof(int));
if (c[i] == NULL) {
printf("*Not enough RAM.\nTerminating.\n");
FreeMatrix(&c, size1);
exit(1);
}
for (j = 0; j < size3; j++) {
c[i][j]=0;
for (k = 0; k < size2; k++) {
c[i][j] += (a[i][k] * b[k][j]);
}
}
}
Don't cast the return value of malloc.