diff --git a/crawl-ref/source/cluautil.cc b/crawl-ref/source/cluautil.cc
index 940c7a20dfbe..744712dec1e4 100644
--- a/crawl-ref/source/cluautil.cc
+++ b/crawl-ref/source/cluautil.cc
@@ -52,7 +52,7 @@ void luaopen_setmeta(lua_State *ls,
     luaL_newmetatable(ls, meta);
     lua_setglobal(ls, global);
 
-    luaL_openlib(ls, global, lua_lib, 0);
+    luaL_register(ls, global, lua_lib);
 
     // Do <global>.__index = <global>
     lua_pushstring(ls, "__index");
@@ -77,8 +77,9 @@ void clua_register_metatable(lua_State *ls, const char *tn,
         lua_settable(ls, -3);
     }
 
-    if (lr)
-        luaL_openlib(ls, nullptr, lr, 0);
+    if (lr) {
+        luaL_register(ls, NULL, lr);
+    }
 }
 
 int clua_pushcxxstring(lua_State *ls, const string &s)
diff --git a/crawl-ref/source/coord-circle.cc b/crawl-ref/source/coord-circle.cc
index f1de9daf4bf7..8008a14a2a8a 100644
--- a/crawl-ref/source/coord-circle.cc
+++ b/crawl-ref/source/coord-circle.cc
@@ -27,7 +27,7 @@ rectangle_iterator rect_def::iter() const
 }
 
 circle_def::circle_def()
-    : global_los_radius(true), check_bounds(false), origin(coord_def(0,0))
+    : global_los_radius(true), check_bounds(false), origin(coord_def(0,0)), radius(0)
 {
     // Set up bounding box and shape.
     init(LOS_RADIUS, C_SQUARE);
@@ -43,14 +43,14 @@ circle_def::circle_def(const coord_def& origin_, const circle_def& bds)
 }
 
 circle_def::circle_def(int param, circle_type ctype)
-    : global_los_radius(false), check_bounds(false), origin(coord_def(0,0))
+    : global_los_radius(false), check_bounds(false), origin(coord_def(0,0)), radius(0)
 {
     init(param, ctype);
 }
 
 circle_def::circle_def(const coord_def &origin_, int param,
                        circle_type ctype)
-    : global_los_radius(false), check_bounds(true), origin(origin_)
+    : global_los_radius(false), check_bounds(true), origin(origin_), radius(0)
 {
     init(param, ctype);
 }
diff --git a/crawl-ref/source/dbg-asrt.cc b/crawl-ref/source/dbg-asrt.cc
index 43bd306570b6..238f4d089bfd 100644
--- a/crawl-ref/source/dbg-asrt.cc
+++ b/crawl-ref/source/dbg-asrt.cc
@@ -187,7 +187,7 @@ static void _dump_player(FILE *file)
     {
         fprintf(file, "Delayed (%u):\n",
                 (unsigned int)you.delay_queue.size());
-        for (const auto delay : you.delay_queue)
+        for (const auto &delay : you.delay_queue)
         {
             fprintf(file, "    type:     %s", delay->name());
             fprintf(file, "\n");
diff --git a/crawl-ref/source/delay.cc b/crawl-ref/source/delay.cc
index 5c079ca987f9..abf0ae1fc9e6 100644
--- a/crawl-ref/source/delay.cc
+++ b/crawl-ref/source/delay.cc
@@ -314,7 +314,7 @@ bool is_being_drained(const item_def &item)
 
 bool is_being_butchered(const item_def &item, bool just_first)
 {
-    for (const auto delay : you.delay_queue)
+    for (const auto &delay : you.delay_queue)
     {
         if (delay->is_being_used(&item, OPER_BUTCHER))
             return true;
@@ -350,7 +350,7 @@ bool player_stair_delay()
  */
 bool already_learning_spell(int spell)
 {
-    for (const auto delay : you.delay_queue)
+    for (const auto &delay : you.delay_queue)
     {
         auto mem = dynamic_cast<MemoriseDelay*>(delay.get());
         if (!mem)
diff --git a/crawl-ref/source/dlua.cc b/crawl-ref/source/dlua.cc
index 1bc40f77cf49..0a9c2378872b 100644
--- a/crawl-ref/source/dlua.cc
+++ b/crawl-ref/source/dlua.cc
@@ -294,9 +294,9 @@ void init_dungeon_lua()
     dluaopen_wiz(dlua);
     #endif
 
-    luaL_openlib(dlua, "feat", feat_dlib, 0);
-    luaL_openlib(dlua, "debug", debug_dlib, 0);
-    luaL_openlib(dlua, "los", los_dlib, 0);
+    luaL_register(dlua, "feat", feat_dlib);
+    luaL_register(dlua, "debug", debug_dlib);
+    luaL_register(dlua, "los", los_dlib);
 
     dlua.execfile("dlua/dungeon.lua", true, true);
     dlua.execfile("dlua/luamark.lua", true, true);
diff --git a/crawl-ref/source/god-abil.cc b/crawl-ref/source/god-abil.cc
index 2a928452d613..cc406664e4e3 100644
--- a/crawl-ref/source/god-abil.cc
+++ b/crawl-ref/source/god-abil.cc
@@ -5308,7 +5308,7 @@ static void _choose_arcana_mutations()
         = you.props[ARCANA_SAC_KEY].get_vector();
     ASSERT(current_arcane_sacrifices.empty());
 
-    for (const vector<mutation_type> arcane_sacrifice_list :
+    for (const vector<mutation_type> &arcane_sacrifice_list :
                                     _arcane_sacrifice_lists)
     {
         const mutation_type sacrifice =
@@ -5328,7 +5328,7 @@ static void _choose_arcana_mutations()
  */
 static bool _player_sacrificed_arcana()
 {
-    for (const vector<mutation_type> arcane_sacrifice_list :
+    for (const vector<mutation_type> &arcane_sacrifice_list :
                                     _arcane_sacrifice_lists)
     {
         for (mutation_type sacrifice : arcane_sacrifice_list)
diff --git a/crawl-ref/source/initfile.cc b/crawl-ref/source/initfile.cc
index 08876914c54d..330bc5f2cb9a 100644
--- a/crawl-ref/source/initfile.cc
+++ b/crawl-ref/source/initfile.cc
@@ -1520,7 +1520,7 @@ string find_crawlrc()
     // rc_dir_names list.
     for (const string &rc_dir : SysEnv.rcdirs)
     {
-        for (const string &rc_fn : rc_dir_filenames)
+        for (const char *rc_fn : rc_dir_filenames)
         {
             const string rc(catpath(rc_dir, rc_fn));
             if (file_exists(rc))
diff --git a/crawl-ref/source/json.cc b/crawl-ref/source/json.cc
index f90be8ec85c0..7d9e4b03c1de 100644
--- a/crawl-ref/source/json.cc
+++ b/crawl-ref/source/json.cc
@@ -413,7 +413,7 @@ char *json_encode(const JsonNode *node)
 
 char *json_encode_string(const char *str)
 {
-    SB sb;
+    SB sb = {};
     sb_init(&sb);
 
     emit_string(&sb, str);
@@ -423,7 +423,7 @@ char *json_encode_string(const char *str)
 
 char *json_stringify(const JsonNode *node, const char *space)
 {
-    SB sb;
+    SB sb = {};
     sb_init(&sb);
 
     if (space != nullptr)
@@ -844,7 +844,7 @@ static bool parse_object(const char **sp, JsonNode **out)
 bool parse_string(const char **sp, char **out)
 {
     const char *s = *sp;
-    SB sb;
+    SB sb = {};
     char throwaway_buffer[4];
         /* enough space for a UTF-8 character */
     char *b;
diff --git a/crawl-ref/source/kills.cc b/crawl-ref/source/kills.cc
index 44b040575c1c..c9c4c467b295 100644
--- a/crawl-ref/source/kills.cc
+++ b/crawl-ref/source/kills.cc
@@ -989,7 +989,7 @@ static const struct luaL_reg kill_lib[] =
 
 void cluaopen_kills(lua_State *ls)
 {
-    luaL_openlib(ls, "kills", kill_lib, 0);
+    luaL_register(ls, "kills", kill_lib);
 }
 
 #ifdef CLUA_BINDINGS
diff --git a/crawl-ref/source/l-colour.cc b/crawl-ref/source/l-colour.cc
index cd60eb309e62..43bdeb7a8c1b 100644
--- a/crawl-ref/source/l-colour.cc
+++ b/crawl-ref/source/l-colour.cc
@@ -110,5 +110,5 @@ static const struct luaL_reg colour_lib[] =
 
 void dluaopen_colour(lua_State *ls)
 {
-    luaL_openlib(ls, "colour", colour_lib, 0);
+    luaL_register(ls, "colour", colour_lib);
 }
diff --git a/crawl-ref/source/l-crawl.cc b/crawl-ref/source/l-crawl.cc
index 5210b43b324b..40e5e45c9b16 100644
--- a/crawl-ref/source/l-crawl.cc
+++ b/crawl-ref/source/l-crawl.cc
@@ -1493,7 +1493,7 @@ void cluaopen_crawl(lua_State *ls)
     clua_register_metatable(ls, MESSF_METATABLE, crawl_messf_ops,
                             lua_object_gc<message_filter>);
 
-    luaL_openlib(ls, "crawl", crawl_clib, 0);
+    luaL_register(ls, "crawl", crawl_clib);
 }
 
 //
@@ -1733,5 +1733,5 @@ static const struct luaL_reg crawl_dlib[] =
 
 void dluaopen_crawl(lua_State *ls)
 {
-    luaL_openlib(ls, "crawl", crawl_dlib, 0);
+    luaL_register(ls, "crawl", crawl_dlib);
 }
diff --git a/crawl-ref/source/l-dgn.cc b/crawl-ref/source/l-dgn.cc
index b7665b8f20fa..c1b506717616 100644
--- a/crawl-ref/source/l-dgn.cc
+++ b/crawl-ref/source/l-dgn.cc
@@ -1927,13 +1927,13 @@ void dluaopen_dgn(lua_State *ls)
 {
     _dgn_register_metatables(ls);
 
-    luaL_openlib(ls, "dgn", dgn_dlib, 0);
-    luaL_openlib(ls, "dgn", dgn_build_dlib, 0);
-    luaL_openlib(ls, "dgn", dgn_event_dlib, 0);
-    luaL_openlib(ls, "dgn", dgn_grid_dlib, 0);
-    luaL_openlib(ls, "dgn", dgn_item_dlib, 0);
-    luaL_openlib(ls, "dgn", dgn_level_dlib, 0);
-    luaL_openlib(ls, "dgn", dgn_mons_dlib, 0);
-    luaL_openlib(ls, "dgn", dgn_subvault_dlib, 0);
-    luaL_openlib(ls, "dgn", dgn_tile_dlib, 0);
+    luaL_register(ls, "dgn", dgn_dlib);
+    luaL_register(ls, "dgn", dgn_build_dlib);
+    luaL_register(ls, "dgn", dgn_event_dlib);
+    luaL_register(ls, "dgn", dgn_grid_dlib);
+    luaL_register(ls, "dgn", dgn_item_dlib);
+    luaL_register(ls, "dgn", dgn_level_dlib);
+    luaL_register(ls, "dgn", dgn_mons_dlib);
+    luaL_register(ls, "dgn", dgn_subvault_dlib);
+    luaL_register(ls, "dgn", dgn_tile_dlib);
 }
diff --git a/crawl-ref/source/l-file.cc b/crawl-ref/source/l-file.cc
index 71bf955cc87f..7023d6025d1a 100644
--- a/crawl-ref/source/l-file.cc
+++ b/crawl-ref/source/l-file.cc
@@ -22,7 +22,7 @@ static const struct luaL_reg file_clib[] =
 
 void cluaopen_file(lua_State *ls)
 {
-    luaL_openlib(ls, "file", file_clib, 0);
+    luaL_register(ls, "file", file_clib);
 }
 
 //
@@ -218,5 +218,5 @@ static const struct luaL_reg file_dlib[] =
 
 void dluaopen_file(lua_State *ls)
 {
-    luaL_openlib(ls, "file", file_dlib, 0);
+    luaL_register(ls, "file", file_dlib);
 }
diff --git a/crawl-ref/source/l-food.cc b/crawl-ref/source/l-food.cc
index 72765985bbcf..75341ecaa7d5 100644
--- a/crawl-ref/source/l-food.cc
+++ b/crawl-ref/source/l-food.cc
@@ -182,5 +182,5 @@ static const struct luaL_reg food_lib[] =
 
 void cluaopen_food(lua_State *ls)
 {
-    luaL_openlib(ls, "food", food_lib, 0);
+    luaL_register(ls, "food", food_lib);
 }
diff --git a/crawl-ref/source/l-item.cc b/crawl-ref/source/l-item.cc
index 672fd1e29467..df623d512a9e 100644
--- a/crawl-ref/source/l-item.cc
+++ b/crawl-ref/source/l-item.cc
@@ -1683,5 +1683,5 @@ void cluaopen_item(lua_State *ls)
     // Pop the metatable off the stack.
     lua_pop(ls, 1);
 
-    luaL_openlib(ls, "items", item_lib, 0);
+    luaL_register(ls, "items", item_lib);
 }
diff --git a/crawl-ref/source/l-moninf.cc b/crawl-ref/source/l-moninf.cc
index 54aebd10faf4..4cdac513a24f 100644
--- a/crawl-ref/source/l-moninf.cc
+++ b/crawl-ref/source/l-moninf.cc
@@ -639,5 +639,5 @@ void cluaopen_moninf(lua_State *ls)
 {
     clua_register_metatable(ls, MONINF_METATABLE, moninf_lib,
                             lua_object_gc<monster_info>);
-    luaL_openlib(ls, "monster", mon_lib, 0);
+    luaL_register(ls, "monster", mon_lib);
 }
diff --git a/crawl-ref/source/l-spells.cc b/crawl-ref/source/l-spells.cc
index 1ba2458592fb..ab9b49049d02 100644
--- a/crawl-ref/source/l-spells.cc
+++ b/crawl-ref/source/l-spells.cc
@@ -291,5 +291,5 @@ static const struct luaL_reg spells_clib[] =
 
 void cluaopen_spells(lua_State *ls)
 {
-    luaL_openlib(ls, "spells", spells_clib, 0);
+    luaL_register(ls, "spells", spells_clib);
 }
diff --git a/crawl-ref/source/l-travel.cc b/crawl-ref/source/l-travel.cc
index 019e4b1eacdd..c4e87749e4d5 100644
--- a/crawl-ref/source/l-travel.cc
+++ b/crawl-ref/source/l-travel.cc
@@ -126,5 +126,5 @@ static const struct luaL_reg travel_lib[] =
 
 void cluaopen_travel(lua_State *ls)
 {
-    luaL_openlib(ls, "travel", travel_lib, 0);
+    luaL_register(ls, "travel", travel_lib);
 }
diff --git a/crawl-ref/source/l-view.cc b/crawl-ref/source/l-view.cc
index 042fa74abbd0..ba8481d8855d 100644
--- a/crawl-ref/source/l-view.cc
+++ b/crawl-ref/source/l-view.cc
@@ -223,5 +223,5 @@ static const struct luaL_reg view_lib[] =
 
 void cluaopen_view(lua_State *ls)
 {
-    luaL_openlib(ls, "view", view_lib, 0);
+    luaL_register(ls, "view", view_lib);
 }
diff --git a/crawl-ref/source/l-wiz.cc b/crawl-ref/source/l-wiz.cc
index 544a511f0e77..e699ede5282f 100644
--- a/crawl-ref/source/l-wiz.cc
+++ b/crawl-ref/source/l-wiz.cc
@@ -48,7 +48,7 @@ static const struct luaL_reg wiz_dlib[] =
 
 void dluaopen_wiz(lua_State *ls)
 {
-    luaL_openlib(ls, "wiz", wiz_dlib, 0);
+    luaL_register(ls, "wiz", wiz_dlib);
 }
 
 #endif
diff --git a/crawl-ref/source/l-you.cc b/crawl-ref/source/l-you.cc
index 5e64753d4452..9ab248f48339 100644
--- a/crawl-ref/source/l-you.cc
+++ b/crawl-ref/source/l-you.cc
@@ -1298,7 +1298,7 @@ static const struct luaL_reg you_clib[] =
 
 void cluaopen_you(lua_State *ls)
 {
-    luaL_openlib(ls, "you", you_clib, 0);
+    luaL_register(ls, "you", you_clib);
 }
 
 //
@@ -1604,5 +1604,5 @@ static const struct luaL_reg you_dlib[] =
 
 void dluaopen_you(lua_State *ls)
 {
-    luaL_openlib(ls, "you", you_dlib, 0);
+    luaL_register(ls, "you", you_dlib);
 }
diff --git a/crawl-ref/source/rltiles/tool/tile.cc b/crawl-ref/source/rltiles/tool/tile.cc
index f35788d247f6..1ccca7f20de1 100644
--- a/crawl-ref/source/rltiles/tool/tile.cc
+++ b/crawl-ref/source/rltiles/tool/tile.cc
@@ -293,7 +293,9 @@ void tile::copy(const tile &img)
     m_filename = img.m_filename;
     m_pixels   = new tile_colour[m_width * m_height];
     m_shrink   = img.m_shrink;
-    memcpy(m_pixels, img.m_pixels, m_width * m_height * sizeof(tile_colour));
+    for (int i = 0, iend = m_width * m_height; i < iend; ++i) {
+        m_pixels[i] = img.m_pixels[i];
+    }
 
     // enum explicitly not copied
     m_enumname.clear();
diff --git a/crawl-ref/source/rltiles/tool/tile_colour.cc b/crawl-ref/source/rltiles/tool/tile_colour.cc
index e7f00c920914..c45664e8d20b 100644
--- a/crawl-ref/source/rltiles/tool/tile_colour.cc
+++ b/crawl-ref/source/rltiles/tool/tile_colour.cc
@@ -23,16 +23,6 @@ bool tile_colour::operator!=(const tile_colour &rhs) const
     return r != rhs.r || g != rhs.g || b != rhs.b || a != rhs.a;
 }
 
-const tile_colour &tile_colour::operator=(const tile_colour &rhs)
-{
-    r = rhs.r;
-    g = rhs.g;
-    b = rhs.b;
-    a = rhs.a;
-
-    return *this;
-}
-
 unsigned char &tile_colour::operator[](int idx)
 {
     assert(idx >= 0 && idx <= 4);
diff --git a/crawl-ref/source/rltiles/tool/tile_colour.h b/crawl-ref/source/rltiles/tool/tile_colour.h
index 54419e5d7fca..b498c4115517 100644
--- a/crawl-ref/source/rltiles/tool/tile_colour.h
+++ b/crawl-ref/source/rltiles/tool/tile_colour.h
@@ -28,13 +28,13 @@ enum COLORS
 class tile_colour
 {
 public:
-    tile_colour() {};
+    tile_colour() : r(0), g(0), b(0), a(0) {};
     tile_colour(unsigned char _r, unsigned char _g, unsigned char _b,
         unsigned char _a) : r(_r), g(_g), b(_b), a(_a) {}
 
     bool operator==(const tile_colour &rhs) const;
     bool operator!=(const tile_colour &rhs) const;
-    const tile_colour &operator=(const tile_colour &rhs);
+    tile_colour &operator=(const tile_colour &rhs) = default;
 
     unsigned char &operator[](int idx);
     unsigned char operator[](int idx) const;
diff --git a/crawl-ref/source/rltiles/tool/tile_page.cc b/crawl-ref/source/rltiles/tool/tile_page.cc
index 718c305a266f..bfe753892525 100644
--- a/crawl-ref/source/rltiles/tool/tile_page.cc
+++ b/crawl-ref/source/rltiles/tool/tile_page.cc
@@ -137,7 +137,6 @@ bool tile_page::write_image(const char *filename)
     }
 
     tile_colour *pixels = new tile_colour[m_width * m_height];
-    memset(pixels, 0, m_width * m_height * sizeof(tile_colour));
 
     for (unsigned int i = 0; i < m_tiles.size(); i++)
     {
diff --git a/crawl-ref/source/tags.cc b/crawl-ref/source/tags.cc
index 7b6f61be17a4..8fc5322e40bf 100644
--- a/crawl-ref/source/tags.cc
+++ b/crawl-ref/source/tags.cc
@@ -2275,6 +2275,7 @@ void tag_read_char(reader &th, uint8_t format, uint8_t major, uint8_t minor)
         you.explore = unmarshallBoolean(th);
 }
 
+#if 0
 static void _cap_mutation_at(mutation_type mut, int cap)
 {
     if (you.mutation[mut] > cap)
@@ -2288,6 +2289,7 @@ static void _cap_mutation_at(mutation_type mut, int cap)
     if (you.innate_mutation[mut] > cap)
         you.innate_mutation[mut] = cap;
 }
+#endif
 
 static void tag_read_you(reader &th)
 {
diff --git a/crawl-ref/source/ui.h b/crawl-ref/source/ui.h
index ce1c11f79232..7b32d0b2f0ce 100644
--- a/crawl-ref/source/ui.h
+++ b/crawl-ref/source/ui.h
@@ -27,7 +27,7 @@ namespace ui {
 template <size_t N>
 struct vec {
     int items[N];
-    template <typename... Ts> vec<N> (Ts... l) : items{l...} {}
+    template <typename... Ts> vec(Ts... l) : items{l...} {}
     const int& operator[](int index) const { return items[index]; }
     int& operator[](int index) { return items[index]; }
     inline bool operator==(const vec<N>& rhs) {