Make util_rand thread safe

src/openrct2/Context.cpp

@@ -426,7 +426,6 @@ namespace OpenRCT2
             }
 
             gScenarioTicks = 0;
-            util_srand((uint32_t)time(nullptr));
             input_reset_place_obj_modifier();
             viewport_init_all();
 

src/openrct2/util/Util.cpp

@@ -23,8 +23,6 @@
 #include <ctime>
 #include <random>
 
-static std::mt19937 _prng;
-
 int32_t squaredmetres_to_squaredfeet(int32_t squaredMetres)
 {
     // 1 metre squared = 10.7639104 feet squared
@@ -529,13 +527,9 @@ bool str_is_null_or_empty(const char* str)
     return str == nullptr || str[0] == 0;
 }
 
-void util_srand(int32_t source)
-{
-    _prng.seed(source);
-}
-
 uint32_t util_rand()
 {
+    thread_local std::mt19937 _prng(std::random_device{}());
     return _prng();
 }
 

src/openrct2/util/Util.h

@@ -50,7 +50,6 @@ char* strcasestr(const char* haystack, const char* needle);
 bool utf8_is_bom(const char* str);
 bool str_is_null_or_empty(const char* str);
 
-void util_srand(int32_t source);
 uint32_t util_rand();
 
 uint8_t* util_zlib_deflate(const uint8_t* data, size_t data_in_size, size_t* data_out_size);

src/openrct2/world/MapGen.cpp

@@ -136,8 +136,6 @@ void mapgen_generate(mapgen_settings* settings)
     int32_t x, y, mapSize, floorTexture, wallTexture, waterLevel;
     TileElement* tileElement;
 
-    util_srand((int32_t)platform_get_ticks());
-
     mapSize = settings->mapSize;
     floorTexture = settings->floor;
     wallTexture = settings->wall;