more strictly define what it means to be the owner of the show, and when it is transferred.

mostly copied from building_owner.
test coverage is a wonderful thing.

src/kernel/building.c

@@ -500,7 +500,6 @@ static building *deleted_buildings;
 void remove_building(building ** blist, building * b)
 {
   unit *u;
-  direction_t d;
   static const struct building_type *bt_caravan, *bt_dam, *bt_tunnel;
   static boolean init = false;
 
@@ -527,15 +526,19 @@ void remove_building(building ** blist, building * b)
    * gebaute Straße zur Hälfte vernichtet */
   if (b->type == bt_caravan || b->type == bt_dam || b->type == bt_tunnel) {
     region *r = b->region;
-    for (d = 0; d != MAXDIRECTIONS; ++d)
-      if (rroad(r, d) > 0) {
-        rsetroad(r, d, rroad(r, d) / 2);
+    int d;
+    for (d = 0; d != MAXDIRECTIONS; ++d) {
+      direction_t dir = (direction_t)d;
+      if (rroad(r, dir) > 0) {
+        rsetroad(r, dir, rroad(r, dir) / 2);
       }
+    }
   }
 
   /* Stattdessen nur aus Liste entfernen, aber im Speicher halten. */
-  while (*blist && *blist != b)
+  while (*blist && *blist != b) {
     blist = &(*blist)->next;
+  }
   *blist = b->next;
   b->region = NULL;
   b->next = deleted_buildings;
@@ -630,7 +633,7 @@ void building_set_owner(struct building *b, struct unit * owner)
   b->_owner = owner;
 }
 
-static unit *building_owner_ex(const building * bld, const faction * last_owner)
+static unit *building_owner_ex(const building * bld, const struct faction * last_owner)
 {
   unit *u, *heir = 0;
 

src/kernel/ship.c

@@ -291,31 +291,40 @@ void ship_set_owner(ship * sh, unit * u) {
   sh->_owner = u;
 }
 
-unit *ship_owner(const ship * sh)
+static unit * ship_owner_ex(const ship * sh, const struct faction * last_owner)
 {
-  unit *owner = sh->_owner;
-  if (owner && (owner->ship!=sh || owner->number<=0)) {
-    unit *u, *heir = 0;
+  unit *u, *heir = 0;
 
-    owner->ship = 0;
-    /* Prüfen ob Eigentümer am leben. */
-    for (u = sh->region->units; u; u = u->next) {
-      if (u->ship == sh) {
-        if (u->number > 0) {
-          if (u->faction==owner->faction) {
-            heir = u;
-            break;
-          }
-          else if (!heir) {
-            heir = u; /* you'll do in an emergency */
-          }
+  /* Eigentümer tot oder kein Eigentümer vorhanden. Erste lebende Einheit
+    * nehmen. */
+  for (u = sh->region->units; u; u = u->next) {
+    if (u->ship == sh) {
+      if (u->number > 0) {
+        if (heir && last_owner && heir->faction!=last_owner && u->faction==last_owner) {
+          heir = u;
+          break; /* we found someone from the same faction who is not dead. let's take this guy */
+        }
+        else if (!heir) {
+          heir = u; /* you'll do in an emergency */
         }
       }
     }
-    owner = heir;
   }
-  /* Eigentümer tot oder kein Eigentümer vorhanden. Erste lebende Einheit
-   * nehmen. */
+  return heir;
+}
+
+void ship_update_owner(ship * sh) {
+  unit * owner = sh->_owner;
+  sh->_owner = ship_owner_ex(sh, owner?owner->faction:0);
+}
+
+unit *ship_owner(const ship * sh)
+{
+  unit *owner = sh->_owner;
+  if (!owner || (owner->ship!=sh || owner->number<=0)) {
+    unit * heir = ship_owner_ex(sh, owner?owner->faction:0);
+    return (heir && heir->number>0) ? heir : 0;
+  }
   return owner;
 }
 

src/kernel/ship.h

@@ -97,6 +97,8 @@ extern "C" {
   extern void damage_ship(struct ship * sh, double percent);
   extern void ship_set_owner(struct ship * sh, struct unit * u);
   extern struct unit *ship_owner(const struct ship *sh);
+  extern void ship_update_owner(struct ship * sh);
+
   extern const char *shipname(const struct ship *self);
   extern int shipcapacity(const struct ship *sh);
   extern void getshipweight(const struct ship *sh, int *weight, int *cabins);

src/kernel/ship_test.c

@@ -54,7 +54,7 @@ static void test_ship_set_owner(CuTest * tc)
   CuAssertPtrEquals(tc, u2, ship_owner(sh));
 }
 
-static void test_shipowner_goes_to_next_after_death(CuTest * tc)
+static void test_shipowner_goes_to_next_when_empty(CuTest * tc)
 {
   struct region *r;
   struct ship *sh;
@@ -88,7 +88,7 @@ static void test_shipowner_goes_to_next_after_death(CuTest * tc)
   CuAssertPtrEquals(tc, u2, ship_owner(sh));
 }
 
-static void test_shipowner_goes_to_other_after_death(CuTest * tc)
+static void test_shipowner_goes_to_other_when_empty(CuTest * tc)
 {
   struct region *r;
   struct ship *sh;
@@ -122,7 +122,7 @@ static void test_shipowner_goes_to_other_after_death(CuTest * tc)
   CuAssertPtrEquals(tc, u2, ship_owner(sh));
 }
 
-static void test_shipowner_goes_to_same_faction_after_death(CuTest * tc)
+static void test_shipowner_goes_to_same_faction_when_empty(CuTest * tc)
 {
   struct region *r;
   struct ship *sh;
@@ -270,7 +270,7 @@ static void test_shipowner_goes_to_same_faction_after_leave(CuTest * tc)
   CuAssertPtrEquals(tc, 0, ship_owner(sh));
 }
 
-static void test_shipowner_resets_when_dead(CuTest * tc)
+static void test_shipowner_resets_when_empty(CuTest * tc)
 {
   struct region *r;
   struct ship *sh;
@@ -300,6 +300,49 @@ static void test_shipowner_resets_when_dead(CuTest * tc)
   CuAssertPtrEquals(tc, u, ship_owner(sh));
   u->number = 0;
   CuAssertPtrEquals(tc, 0, ship_owner(sh));
+  u->number = 1;
+  CuAssertPtrEquals(tc, u, ship_owner(sh));
+}
+
+void test_shipowner_goes_to_empty_unit_after_leave(CuTest * tc)
+{
+  struct region *r;
+  struct ship *sh;
+  struct unit *u1, *u2, *u3;
+  struct faction *f1;
+  const struct ship_type *stype;
+  const struct race *human;
+
+  test_cleanup();
+  test_create_world();
+
+  human = rc_find("human");
+  CuAssertPtrNotNull(tc, human);
+
+  stype = st_find("boat");
+  CuAssertPtrNotNull(tc, stype);
+
+  f1 = test_create_faction(human);
+  r = findregion(0, 0);
+
+  sh = test_create_ship(r, stype);
+  CuAssertPtrNotNull(tc, sh);
+
+  u1 = test_create_unit(f1, r);
+  u2 = test_create_unit(f1, r);
+  u3 = test_create_unit(f1, r);
+  u_set_ship(u1, sh);
+  u_set_ship(u2, sh);
+  u_set_ship(u3, sh);
+
+  CuAssertPtrEquals(tc, u1, ship_owner(sh));
+  u2->number = 0;
+  leave_ship(u1);
+  CuAssertPtrEquals(tc, u3, ship_owner(sh));
+  leave_ship(u3);
+  CuAssertPtrEquals(tc, 0, ship_owner(sh));
+  u2->number = 1;
+  CuAssertPtrEquals(tc, u2, ship_owner(sh));
 }
 
 CuSuite *get_ship_suite(void)
@@ -307,12 +350,13 @@ CuSuite *get_ship_suite(void)
   CuSuite *suite = CuSuiteNew();
   SUITE_ADD_TEST(suite, test_register_ship);
   SUITE_ADD_TEST(suite, test_ship_set_owner);
-  SUITE_ADD_TEST(suite, test_shipowner_resets_when_dead);
-  SUITE_ADD_TEST(suite, test_shipowner_goes_to_next_after_death);
-  SUITE_ADD_TEST(suite, test_shipowner_goes_to_other_after_death);
-  SUITE_ADD_TEST(suite, test_shipowner_goes_to_same_faction_after_death);
+  SUITE_ADD_TEST(suite, test_shipowner_resets_when_empty);
+  SUITE_ADD_TEST(suite, test_shipowner_goes_to_next_when_empty);
+  SUITE_ADD_TEST(suite, test_shipowner_goes_to_other_when_empty);
+  SUITE_ADD_TEST(suite, test_shipowner_goes_to_same_faction_when_empty);
   SUITE_ADD_TEST(suite, test_shipowner_goes_to_next_after_leave);
   SUITE_ADD_TEST(suite, test_shipowner_goes_to_other_after_leave);
   SUITE_ADD_TEST(suite, test_shipowner_goes_to_same_faction_after_leave);
+  SUITE_ADD_TEST(suite, test_shipowner_goes_to_empty_unit_after_leave);
   return suite;
 }

src/kernel/unit.c

@@ -798,6 +798,7 @@ void leave_ship(unit * u)
 
   u->ship = 0;
   if (sh->_owner==u) {
+    ship_update_owner(sh);
     sh->_owner = ship_owner(sh);
   }
   set_leftship(u, sh);