Use size_t, which is better for arrays of very large sizes.

src/main.c

@@ -5,7 +5,6 @@
 #include <gmp.h>
 
 #include "list.h"
-#include "types.h"
 
 static bool run;
 void leave();
@@ -43,7 +42,7 @@ int main(void) {
 		// Calculate half of `num'
 		mpz_fdiv_q_ui(halfNum, num, 2);
 		// Loop through found primes
-		for(ulli i = 0; i < primes.end; ++i) {
+		for(size_t i = 0; i < primes.end; ++i) {
 			if(mpz_cmp(primes.list[i], halfNum) > 0) break;
 			// If `num' is divisible by a prime then go to the next number
 			if(mpz_divisible_p(num, primes.list[i]) != 0)