segmentation fault when using clock() function - c

Question

My following code gives segmentation fault: 11 only when I add the clock() function to calculate the time elapsed (When I comment clock(), I get results with no issues!!! ):
typedef struct heap_strct *Sort;
struct heap_strct {
int count;
int size;
int *queue;
};
int main() {
time_t start = clock();
Sort h; // Sort is a structure
initi(h);
parse(h);
time_t end = clock();
double time_elapsed = (double)(end - start) / CLOCKS_PER_SEC;
printf("Time = %f", time_elapsed);
}
I am using #include <time.h> but I don't know why such a fault appears! Kindly, can someone tell me why?

Answer 1

You pass an uninitialized pointer to function initi(). If this function modifies the structure, you invoke undefined behavior.
It is a very bad habit to hide pointers behind typedefs. The comment is completely misleading: Sort is not a structure!
Define a structure directly and pass its address:
#include <time.h>
struct heap_strct {
int count;
int size;
int *queue;
};
int main(void) {
clock_t start = clock();
struct heap_strct h; // h is a structure for real now!
initi(&h);
parse(&h);
time_t end = clock();
double time_elapsed = (double)(end - start) / CLOCKS_PER_SEC;
printf("Time = %f\n", time_elapsed);
return 0;
}

Answer 2

clock() is a proven library function and will not cause a segfault.
You pass a pointer h to initi but there is no storage for h allocated. Then you pass the same pointer to parse. But there still is no storage for the structure!
When you comment clock() out, the call is not made so the stack is not changed. On the stack is also h, an uninitialized local variable.