newterrain was unfit for unit testing.

bad test: insects cannot trade in deserts without castle.

src/economy.test.c

@@ -254,6 +254,7 @@ static void test_trade_insect(CuTest *tc) {
     CuAssertPtrEquals(tc, r, u->region);
     CuAssertPtrEquals(tc, (void *)it_luxury, (void *)r_luxury(u->region));
     produce(u->region);
+    CuAssertPtrEquals(tc, NULL, test_find_messagetype(u->faction->msgs, "error119"));
     CuAssertIntEquals(tc, 1, get_item(u, it_luxury));
     CuAssertIntEquals(tc, 5, get_item(u, it_silver));
 

src/kernel/region.c

@@ -1202,12 +1202,17 @@ void terraform_region(region * r, const terrain_type * terrain)
     }
 
     if (oldterrain == NULL || terrain->size != oldterrain->size) {
+        static int changed;
+        static const terrain_type *t_plain;
         int horses = 0, trees = 0;
+        if (terrain_changed(&changed)) {
+            t_plain = get_terrain(terrainnames[T_PLAIN]);
+        }
         if (terrain->size>0) {
             horses = rng_int() % (terrain->size / 50);
             trees = terrain->size * (30 + rng_int() % 40) / 1000;
         }
-        if (terrain == newterrain(T_PLAIN)) {
+        if (t_plain && terrain == t_plain) {
             rsethorses(r, horses);
             if (chance(0.4)) {
                 rsettrees(r, 2, trees);

src/kernel/terrain.c

@@ -38,7 +38,7 @@ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 #include <stdlib.h>
 #include <string.h>
 
-static const char *terrainnames[MAXTERRAINS] = {
+const char *terrainnames[MAXTERRAINS] = {
     "ocean",
     "plain",
     "swamp",
@@ -114,10 +114,14 @@ static terrain_type *terrain_find_i(const char *name)
     return terrain;
 }
 
-const terrain_type *get_terrain(const char *name) {
+static terrain_type *get_terrain_i(const char *name) {
     return terrain_find_i(name);
 }
 
+const terrain_type *get_terrain(const char *name) {
+    return get_terrain_i(name);
+}
+
 terrain_type * get_or_create_terrain(const char *name) {
     terrain_type *terrain = terrain_find_i(name);
     if (!terrain) {
@@ -127,7 +131,7 @@ terrain_type * get_or_create_terrain(const char *name) {
             terrain->_name = str_strdup(name);
             terrain->next = registered_terrains;
             registered_terrains = terrain;
-            if (strcmp("plain", name) == 0) {
+            if (strcmp(terrainnames[T_PLAIN], name) == 0) {
                 /* TODO: this is awful, it belongs in config */
                 terrain->name = &plain_name;
             }
@@ -136,19 +140,26 @@ terrain_type * get_or_create_terrain(const char *name) {
     return terrain;
 }
 
-static const terrain_type *newterrains[MAXTERRAINS];
+static terrain_type *newterrains[MAXTERRAINS];
 
 const struct terrain_type *newterrain(terrain_t t)
 {
+    static int changed;
     const struct terrain_type *result;
     if (t == NOTERRAIN) {
         return NULL;
     }
     assert(t >= 0);
     assert(t < MAXTERRAINS);
-    result = newterrains[t];
+    if (terrain_changed(&changed)) {
+        memset(newterrains, 0, sizeof(newterrains));
+        result = NULL;
+    }
+    else {
+        result = newterrains[t];
+    }
     if (!result) {
-        result = newterrains[t] = get_terrain(terrainnames[t]);
+        result = newterrains[t] = get_terrain_i(terrainnames[t]);
     }
     if (!result) {
         log_error("no such terrain: %s.", terrainnames[t]);
@@ -194,11 +205,11 @@ void init_terrains(void)
 {
     terrain_t t;
     for (t = 0; t != MAXTERRAINS; ++t) {
-        const terrain_type *newterrain = newterrains[t];
+        terrain_type *newterrain = newterrains[t];
         if (newterrain != NULL)
             continue;
         if (terrainnames[t] != NULL) {
-            newterrain = get_terrain(terrainnames[t]);
+            newterrain = get_terrain_i(terrainnames[t]);
             if (newterrain != NULL) {
                 newterrains[t] = newterrain;
             }

src/kernel/terrain.h

@@ -36,6 +36,8 @@ extern "C" {
 #define SWIM_INTO		     (1<<8)     /* man darf hierhin schwimmen */
 #define WALK_INTO		     (1<<9)     /* man darf hierhin laufen */
 
+    extern const char *terrainnames[];
+
     typedef struct production_rule {
         char *name;
         const struct resource_type *rtype;