Faulty Dynamic memory allocation for larger values - c

Question

In the code below, i am taking n as a user input, and depending on its value i have allocated memory to the pointer array (both n and pointer array are a part of a structure). The whole code works well for values of n below 4, anything 4 or beyond, its giving a segmentation fault while inputting values in the pointer array.
I can imagine that it might be because the memory isn't getting allocated but why its only beyond 4 I don't understand
Here is a snippet where the problem is happening.
#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
// static int n;
typedef struct test_case {
int n;
int *test[];
} testCase;
int maxsc(testCase *test_case_ptr);
int find_maximum(int *ptr, int n);
int main() {
int T;
int x = 0;
int temp;
testCase *test_case_ptr;
printf("T = ");
scanf("%d", &T);
printf("\n");
for (int i = 0; i < T; i++) {
printf("N = ");
scanf("%d", &test_case_ptr->n);
temp = test_case_ptr->n;
printf("\n");
test_case_ptr = (testCase *)malloc(sizeof(struct test_case));
for (int i = 0; i < temp; i++) {
test_case_ptr->test[i] = malloc(sizeof(int *) * test_case_ptr->n);
}
test_case_ptr->n = temp;
// printf("%d\n", test_case_ptr->n);
printf("give values\n");
for (int j = 0; j < test_case_ptr->n; j++) {
for (int k = 0; k < test_case_ptr->n; k++) {
scanf("%d", &test_case_ptr->test[j][k]);
}
}
int max_score = maxsc(test_case_ptr);
printf("\n");
printf("The max_score_%d = %d \n", x++, max_score);
}
}

Answer 1

First, you try to use the test_case_ptr struct before allocating mem for it. Second, when using a flexible array, you need to alloc the mem for it when you malloc the mem for the struct.
scanf("%d", &temp);
// Allocate mem for the struct plus the array
test_case_ptr = malloc(sizeof(struct test_case) + sizeof(int *) * temp);
test_case_ptr->n = temp;
// Allocate each row in the array
for (int i = 0; i < test_case_ptr->n; i++) {
test_case_ptr->test[i] = malloc(sizeof(int) * test_case_ptr->n);
}
// .....