+#include <ccan/tally/tally.c>
+#include <ccan/tap/tap.h>
+
+int main(void)
+{
+ struct tally *tally;
+ ssize_t total, overflow;
+ ssize_t min, max;
+
+ max = (ssize_t)~(1ULL << (sizeof(max)*CHAR_BIT - 1));
+ min = (ssize_t)(1ULL << (sizeof(max)*CHAR_BIT - 1));
+
+ plan_tests(15);
+
+ /* Simple case. */
+ tally = tally_new(0);
+ tally_add(tally, min);
+ ok1(tally_total(tally, NULL) == min);
+ ok1(tally_total(tally, &overflow) == min);
+ ok1(overflow == -1);
+
+ /* Underflow. */
+ tally_add(tally, min);
+ total = tally_total(tally, &overflow);
+ ok1(overflow == -1);
+ ok1((size_t)total == 0);
+ ok1(tally_total(tally, NULL) == min);
+ free(tally);
+
+ /* Simple case. */
+ tally = tally_new(0);
+ tally_add(tally, max);
+ ok1(tally_total(tally, NULL) == max);
+ ok1(tally_total(tally, &overflow) == max);
+ ok1(overflow == 0);
+
+ /* Overflow into sign bit... */
+ tally_add(tally, max);
+ total = tally_total(tally, &overflow);
+ ok1(overflow == 0);
+ ok1((size_t)total == 0xFFFFFFFE);
+ ok1(tally_total(tally, NULL) == max);
+
+ /* Overflow into upper size_t. */
+ tally_add(tally, max);
+ total = tally_total(tally, &overflow);
+ ok1(overflow == 1);
+ ok1((size_t)total == 0x7FFFFFFD);
+ ok1(tally_total(tally, NULL) == max);
+ free(tally);
+
+ return exit_status();
+}