diff --git a/src/activity_handlers.cpp b/src/activity_handlers.cpp
index 2fcdc891eb4b8..485e482989b8d 100644
--- a/src/activity_handlers.cpp
+++ b/src/activity_handlers.cpp
@@ -278,7 +278,6 @@ void set_up_butchery( player_activity &act, player &u, butcher_type action )
                 u.add_msg_if_player( m_info, _( "None of your tools are sharp and precise enough to do that." ) );
                 act.set_to_null();
                 return;
-                break;
             case 1:
                 u.add_msg_if_player( m_info, _( "You could use a better tool, but this will do." ) );
                 break;
@@ -1209,7 +1208,6 @@ void activity_handlers::butcher_finish( player_activity *act, player *p )
             }
             act->set_to_null();
             return;
-            break;
         case DISSECT:
             p->add_msg_if_player( m_good, _( "You finish dissecting the %s." ), corpse_item.tname().c_str() );
             g->m.i_rem( p->pos(), act->index );
diff --git a/src/bonuses.cpp b/src/bonuses.cpp
index cbc367f616111..a6c6bdba87e34 100644
--- a/src/bonuses.cpp
+++ b/src/bonuses.cpp
@@ -127,11 +127,10 @@ void bonus_container::load( JsonArray &jarr, bool mult )
     while( jarr.has_more() ) {
         JsonArray qualifiers = jarr.next_array();
 
-        affected_stat as;
         damage_type dt = DT_NULL;
 
         const std::string affected_stat_string = qualifiers.next_string();
-        as = affected_stat_from_string( affected_stat_string );
+        affected_stat as = affected_stat_from_string( affected_stat_string );
         if( as == AFFECTED_NULL ) {
             jarr.throw_error( "Invalid affected stat" );
         }
diff --git a/src/catacharset.cpp b/src/catacharset.cpp
index d517446da0eec..2a3365ec0f8d6 100644
--- a/src/catacharset.cpp
+++ b/src/catacharset.cpp
@@ -213,13 +213,12 @@ int cursorx_to_position( const char *line, int cursorx, int *prevpos, int maxlen
 
 std::string utf8_truncate( std::string s, size_t length )
 {
-    int last_pos;
 
     if( length == 0 || s.empty() ) {
         return s;
     }
 
-    last_pos = cursorx_to_position( s.c_str(), length, NULL, -1 );
+    int last_pos = cursorx_to_position( s.c_str(), length, NULL, -1 );
 
     return s.substr( 0, last_pos );
 }
diff --git a/src/clzones.cpp b/src/clzones.cpp
index b663a52927041..8787431e63219 100644
--- a/src/clzones.cpp
+++ b/src/clzones.cpp
@@ -232,7 +232,7 @@ void plot_options::deserialize( JsonObject &jo_zone )
     seed = jo_zone.get_string( "seed", "" );
 };
 
-cata::optional<std::string> zone_manager::query_name( std::string default_name ) const
+cata::optional<std::string> zone_manager::query_name( const std::string &default_name ) const
 {
     string_input_popup popup;
     popup
diff --git a/src/clzones.h b/src/clzones.h
index 369d9f1d4859f..2d23ca53d78d6 100644
--- a/src/clzones.h
+++ b/src/clzones.h
@@ -172,7 +172,7 @@ class zone_manager
         std::vector<zone_data> get_zones( const zone_type_id &type, const tripoint &where ) const;
         const zone_data *get_top_zone( const tripoint &where ) const;
         const zone_data *get_bottom_zone( const tripoint &where ) const;
-        cata::optional<std::string> query_name( std::string default_name = "" ) const;
+        cata::optional<std::string> query_name( const std::string &default_name = "" ) const;
         cata::optional<zone_type_id> query_type() const;
         void swap( zone_data &a, zone_data &b );
 
diff --git a/src/construction.cpp b/src/construction.cpp
index 26c76b4fdbc23..c5b62b9037e62 100644
--- a/src/construction.cpp
+++ b/src/construction.cpp
@@ -37,14 +37,10 @@
 
 static const skill_id skill_fabrication( "fabrication" );
 static const skill_id skill_electronics( "electronics" );
-static const skill_id skill_unarmed( "unarmed" );
-static const skill_id skill_throw( "throw" );
 
 static const trait_id trait_DEBUG_HS( "DEBUG_HS" );
-static const trait_id trait_NOPAIN( "NOPAIN" );
 static const trait_id trait_PAINRESIST_TROGLO( "PAINRESIST_TROGLO" );
 static const trait_id trait_STOCKY_TROGLO( "STOCKY_TROGLO" );
-static const trait_id trait_WEB_ROPE( "WEB_ROPE" );
 
 const trap_str_id tr_firewood_source( "tr_firewood_source" );
 
diff --git a/src/crafting_gui.cpp b/src/crafting_gui.cpp
index e41df8ced2f31..0fac10170b301 100644
--- a/src/crafting_gui.cpp
+++ b/src/crafting_gui.cpp
@@ -57,7 +57,6 @@ std::string get_cat_name( const std::string &prefixed_name )
 
 void load_recipe_category( JsonObject &jsobj )
 {
-    JsonArray subcats;
     std::string category = jsobj.get_string( "id" );
 
     if( category.find( "CC_" ) != 0 ) {
@@ -69,7 +68,7 @@ void load_recipe_category( JsonObject &jsobj )
     std::string cat_name = get_cat_name( category );
 
     craft_subcat_list[category] = std::vector<std::string>();
-    subcats = jsobj.get_array( "recipe_subcategories" );
+    JsonArray subcats = jsobj.get_array( "recipe_subcategories" );
     while( subcats.has_more() ) {
         std::string subcat_id = subcats.next_string();
         if( subcat_id.find( "CSC_" + cat_name + "_" ) != 0 && subcat_id != "CSC_ALL" ) {
diff --git a/src/creature_tracker.cpp b/src/creature_tracker.cpp
index 3d5f3cfafb178..6156fb09d9cd8 100644
--- a/src/creature_tracker.cpp
+++ b/src/creature_tracker.cpp
@@ -129,8 +129,6 @@ bool Creature_tracker::update_pos( const monster &critter, const tripoint &new_p
         rebuild_cache();
         return false;
     }
-
-    return false;
 }
 
 void Creature_tracker::remove_from_location_map( const monster &critter )
diff --git a/src/dependency_tree.h b/src/dependency_tree.h
index bcc1280dd3f6f..669e2c76a8b1b 100644
--- a/src/dependency_tree.h
+++ b/src/dependency_tree.h
@@ -77,7 +77,6 @@ class dependency_tree
         dependency_node *get_node( mod_id key );
 
         std::map<mod_id, dependency_node> master_node_map;
-    protected:
     private:
         // Don't need to be called directly. Only reason to call these are during initialization phase.
         void build_node_map( std::map<mod_id, std::vector<mod_id > > key_dependency_map );
diff --git a/src/dialogue.h b/src/dialogue.h
index 3758d2b3ae66d..0b6270b95d7ad 100644
--- a/src/dialogue.h
+++ b/src/dialogue.h
@@ -153,7 +153,7 @@ struct talk_response {
                 /**
                  * Sets an effect to a function object and consequence to explicitly given one.
                  */
-                void set_effect_consequence( effect_fun_t eff, dialogue_consequence con );
+                void set_effect_consequence( const effect_fun_t &eff, dialogue_consequence con );
                 void set_effect_consequence( std::function<void( npc &p )> ptr, dialogue_consequence con );
 
 
@@ -349,8 +349,6 @@ class json_talk_response
  */
 class json_talk_topic
 {
-    public:
-
     private:
         bool replace_built_in_responses = false;
         std::vector<json_talk_response> responses;
diff --git a/src/dialogue_win.cpp b/src/dialogue_win.cpp
index f8b27d28006dc..5955b75e45c34 100644
--- a/src/dialogue_win.cpp
+++ b/src/dialogue_win.cpp
@@ -109,8 +109,7 @@ bool dialogue_window::print_responses( int const yoffset, const std::vector<talk
     size_t const fold_width = xoffset - 2 - 2 - 2;
 
     int curline = min_line - ( int ) yoffset;
-    size_t i;
-    for( i = 0; i < responses.size() && curline <= max_line; i++ ) {
+    for( size_t i = 0; i < responses.size() && curline <= max_line; i++ ) {
         const std::vector<std::string> folded = foldstring( responses[i].second, fold_width );
         const nc_color &color = responses[i].first;
         for( size_t j = 0; j < folded.size(); j++, curline++ ) {
@@ -138,7 +137,8 @@ void dialogue_window::refresh_response_display()
     can_scroll_up = false;
 }
 
-void dialogue_window::display_responses( int const hilight_lines, std::vector<talk_data> responses,
+void dialogue_window::display_responses( int const hilight_lines,
+        const std::vector<talk_data> &responses,
         const long &ch )
 {
     if( text_only ) {
diff --git a/src/dialogue_win.h b/src/dialogue_win.h
index 02f161d4b2a4b..c7bb1def1a2e2 100644
--- a/src/dialogue_win.h
+++ b/src/dialogue_win.h
@@ -18,7 +18,8 @@ class dialogue_window
         bool text_only = false;
 
         void clear_window_texts();
-        void display_responses( int hilight_lines, std::vector<talk_data> responses, const long &ch );
+        void display_responses( int hilight_lines, const std::vector<talk_data> &responses,
+                                const long &ch );
         void refresh_response_display();
         /**
          * Folds and adds the folded text to @ref history. Returns the number of added lines.
diff --git a/src/faction_camp.cpp b/src/faction_camp.cpp
index 931718aba4b76..93d77f2a5f629 100644
--- a/src/faction_camp.cpp
+++ b/src/faction_camp.cpp
@@ -2302,7 +2302,7 @@ std::map<std::string, std::string> talk_function::camp_recipe_deck( const std::s
     return cooking_recipes;
 }
 
-int talk_function::camp_recipe_batch_max( const recipe making, const inventory &total_inv )
+int talk_function::camp_recipe_batch_max( const recipe &making, const inventory &total_inv )
 {
     int max_batch = 0;
     int max_checks = 9;
diff --git a/src/faction_camp.h b/src/faction_camp.h
index 028ed948d26ea..7ea034cdada41 100644
--- a/src/faction_camp.h
+++ b/src/faction_camp.h
@@ -222,7 +222,7 @@ std::string name_mission_tabs( npc &p, const std::string &id, const std::string
 /// Creats a map of all the recipes that are available to a building at om_cur, "ALL" for all possible
 std::map<std::string, std::string> camp_recipe_deck( const std::string &om_cur );
 /// Determines what the absolute max (out of 9999) that can be crafted using inventory and food supplies
-int camp_recipe_batch_max( const recipe making, const inventory &total_inv );
+int camp_recipe_batch_max( const recipe &making, const inventory &total_inv );
 
 /*
  * check if a companion survives a random encounter
diff --git a/src/game.cpp b/src/game.cpp
index 0394cff0da32d..a18b9ad14c2e8 100644
--- a/src/game.cpp
+++ b/src/game.cpp
@@ -4447,11 +4447,10 @@ int game::mon_info( const catacurses::window &w )
 
     // Print the symbols of all monsters in all directions.
     for( int i = 0; i < 8; i++ ) {
-        int symroom;
         point pr( xcoords[i] + widths[i] + 1, ycoords[i] + startrow );
 
         // The list of symbols needs a space on each end.
-        symroom = ( width / 3 ) - widths[i] - 2;
+        int symroom = ( width / 3 ) - widths[i] - 2;
         const int typeshere_npc = unique_types[i].size();
         const int typeshere_mon = unique_mons[i].size();
         const int typeshere = typeshere_mon + typeshere_npc;
@@ -5154,7 +5153,6 @@ void game::emp_blast( const tripoint &p )
     // TODO: Implement z part
     int x = p.x;
     int y = p.y;
-    int rn;
     const bool sight = g->u.sees( p );
     if( m.has_flag( "CONSOLE", x, y ) ) {
         if( sight ) {
@@ -5165,7 +5163,7 @@ void game::emp_blast( const tripoint &p )
     }
     // TODO: More terrain effects.
     if( m.ter( x, y ) == t_card_science || m.ter( x, y ) == t_card_military ) {
-        rn = rng( 1, 100 );
+        int rn = rng( 1, 100 );
         if( rn > 92 || rn < 40 ) {
             if( sight ) {
                 add_msg( _( "The card reader is rendered non-functional." ) );
@@ -5632,7 +5630,7 @@ void game::exam_vehicle( vehicle &veh, int cx, int cy )
     }
 }
 
-bool game::forced_door_closing( const tripoint &p, const ter_id door_type, int bash_dmg )
+bool game::forced_door_closing( const tripoint &p, const ter_id &door_type, int bash_dmg )
 {
     // TODO: Z
     const int &x = p.x;
@@ -6545,9 +6543,8 @@ void game::print_fields_info( const tripoint &lp, const catacurses::window &w_lo
         if( fld.first == fd_fire && ( m.has_flag( TFLAG_FIRE_CONTAINER, lp ) ||
                                       m.ter( lp ) == t_pit_shallow || m.ter( lp ) == t_pit ) ) {
             const int max_width = getmaxx( w_look ) - column - 2;
-            int lines;
-            lines = fold_and_print( w_look, ++line, column, max_width, cur.color(),
-                                    get_fire_fuel_string( lp ) ) - 1;
+            int lines = fold_and_print( w_look, ++line, column, max_width, cur.color(),
+                                        get_fire_fuel_string( lp ) ) - 1;
             line += lines;
         } else {
             mvwprintz( w_look, ++line, column, cur.color(), cur.name() );
@@ -8817,8 +8814,8 @@ void game::plthrow( int pos )
     m.draw( w_terrain, u.pos() );
 
     // target_ui() sets x and y, or returns empty vector if we canceled (by pressing Esc)
-    std::vector<tripoint> trajectory;
-    trajectory = target_handler().target_ui( u, TARGET_MODE_THROW, &thrown, range );
+    std::vector<tripoint> trajectory = target_handler().target_ui( u, TARGET_MODE_THROW, &thrown,
+                                       range );
     if( trajectory.empty() ) {
         return;
     }
@@ -10894,9 +10891,8 @@ void game::place_player( const tripoint &dest_loc )
                 }
                 int and_the_rest = 0;
                 for( size_t i = 0; i < names.size(); ++i ) {
-                    std::string fmt;
                     //~ number of items: "<number> <item>"
-                    fmt = ngettext( "%1$d %2$s", "%1$d %2$s", counts[i] );
+                    std::string fmt = ngettext( "%1$d %2$s", "%1$d %2$s", counts[i] );
                     names[i] = string_format( fmt, counts[i], names[i].c_str() );
                     // Skip the first two.
                     if( i > 1 ) {
@@ -12589,8 +12585,7 @@ void game::process_artifact( item &it, player &p )
 {
     const bool worn = p.is_worn( it );
     const bool wielded = ( &it == &p.weapon );
-    std::vector<art_effect_passive> effects;
-    effects = it.type->artifact->effects_carried;
+    std::vector<art_effect_passive> effects = it.type->artifact->effects_carried;
     if( worn ) {
         auto &ew = it.type->artifact->effects_worn;
         effects.insert( effects.end(), ew.begin(), ew.end() );
diff --git a/src/game.h b/src/game.h
index 4c0344f9629c6..fe6c8f994be28 100644
--- a/src/game.h
+++ b/src/game.h
@@ -850,7 +850,7 @@ class game
         // will do so, if bash_dmg is greater than 0, items won't stop the door
         // from closing at all.
         // If the door gets closed the items on the door tile get moved away or destroyed.
-        bool forced_door_closing( const tripoint &p, const ter_id door_type, int bash_dmg );
+        bool forced_door_closing( const tripoint &p, const ter_id &door_type, int bash_dmg );
 
         //pixel minimap management
         int pixel_minimap_option;
diff --git a/src/gamemode.h b/src/gamemode.h
index f957342854c57..30b80a5997639 100644
--- a/src/gamemode.h
+++ b/src/gamemode.h
@@ -138,14 +138,12 @@ struct defense_game : public special_game {
 
     private:
         void init_to_style( defense_style new_style );
-        void load_style( std::string style_name );
 
         void setup();
         void refresh_setup( const catacurses::window &w, int selection );
         void init_mtypes();
         void init_constructions();
         void init_map();
-        std::vector<itype_id> carvan_items( caravan_category cat );
 
         void spawn_wave();
         void caravan();
diff --git a/src/iexamine.cpp b/src/iexamine.cpp
index ebf3b33f4851b..9682915cde332 100644
--- a/src/iexamine.cpp
+++ b/src/iexamine.cpp
@@ -68,7 +68,6 @@ const efftype_id effect_sleep( "sleep" );
 static const trait_id trait_AMORPHOUS( "AMORPHOUS" );
 static const trait_id trait_ARACHNID_ARMS_OK( "ARACHNID_ARMS_OK" );
 static const trait_id trait_BADKNEES( "BADKNEES" );
-static const trait_id trait_BEAK_HUM( "BEAK_HUM" );
 static const trait_id trait_ILLITERATE( "ILLITERATE" );
 static const trait_id trait_INSECT_ARMS_OK( "INSECT_ARMS_OK" );
 static const trait_id trait_M_DEFENDER( "M_DEFENDER" );
@@ -77,7 +76,6 @@ static const trait_id trait_M_FERTILE( "M_FERTILE" );
 static const trait_id trait_M_SPORES( "M_SPORES" );
 static const trait_id trait_NOPAIN( "NOPAIN" );
 static const trait_id trait_PARKOUR( "PARKOUR" );
-static const trait_id trait_PROBOSCIS( "PROBOSCIS" );
 static const trait_id trait_THRESH_MARLOSS( "THRESH_MARLOSS" );
 static const trait_id trait_THRESH_MYCUS( "THRESH_MYCUS" );
 static const trait_id trait_BURROW( "BURROW" );
@@ -4127,10 +4125,8 @@ void iexamine::smoker_options( player &p, const tripoint &examp )
         case 1: //activate
             if ( active ) {
                 add_msg( _("It is already lit and smoking.") );
-                break;
             } else {
                 smoker_activate( p, examp );
-                break;
             }
             break;
         case 2: // load food
diff --git a/src/input.cpp b/src/input.cpp
index e4c0e055d0f08..2e60fa132f849 100644
--- a/src/input.cpp
+++ b/src/input.cpp
@@ -1343,7 +1343,7 @@ std::vector<std::string> input_context::filter_strings_by_phrase(
     return filtered_strings;
 }
 
-void input_context::set_edittext( std::string s )
+void input_context::set_edittext( const std::string &s )
 {
     edittext = s;
 }
diff --git a/src/input.h b/src/input.h
index a8fe7f7219d8e..b6b9d1fcdc77e 100644
--- a/src/input.h
+++ b/src/input.h
@@ -264,8 +264,6 @@ class input_manager
          */
         void wait_for_any_key();
 
-        bool translate_to_window_position();
-
         /**
          * Sets global input polling timeout as appropriate for the current interface system.
          * Use `input_context::(re)set_timeout()` when possible so timeout will be properly
@@ -646,7 +644,7 @@ class input_context
         /**
         * Get/Set edittext to display IME unspecified string.
         */
-        void set_edittext( std::string s );
+        void set_edittext( const std::string &s );
         std::string get_edittext();
 
         void set_iso( bool mode = true );
diff --git a/src/inventory_ui.cpp b/src/inventory_ui.cpp
index 4a01a43685d88..3cb45b18b77de 100644
--- a/src/inventory_ui.cpp
+++ b/src/inventory_ui.cpp
@@ -1263,7 +1263,7 @@ inventory_selector::stat display_stat( const std::string &caption, int cur_value
 
 inventory_selector::stats inventory_selector::get_weight_and_volume_stats(
     units::mass weight_carried, units::mass weight_capacity,
-    units::volume volume_carried, units::volume volume_capacity )
+    const units::volume &volume_carried, const units::volume &volume_capacity )
 {
     return {
         {
diff --git a/src/inventory_ui.h b/src/inventory_ui.h
index c15d5e428d656..3f1a82193b8c5 100644
--- a/src/inventory_ui.h
+++ b/src/inventory_ui.h
@@ -492,7 +492,7 @@ class inventory_selector
 
         static stats get_weight_and_volume_stats(
             units::mass weight_carried, units::mass weight_capacity,
-            units::volume volume_carried, units::volume volume_capacity );
+            const units::volume &volume_carried, const units::volume &volume_capacity );
 
         /** Get stats to display in top right.
          *
@@ -551,7 +551,6 @@ class inventory_selector
             }
         }
         void toggle_navigation_mode();
-        void reassign_custom_invlets();
 
         /** Entry has been added */
         virtual void on_entry_add( const inventory_entry & ) {}
diff --git a/src/item.cpp b/src/item.cpp
index ee8ef65c6ddfe..d8793fc3a803e 100644
--- a/src/item.cpp
+++ b/src/item.cpp
@@ -626,7 +626,7 @@ bool item::merge_charges( const item &rhs )
     return true;
 }
 
-void item::put_in( item payload )
+void item::put_in( const item &payload )
 {
     contents.push_back( payload );
 }
diff --git a/src/item.h b/src/item.h
index bd918ea1e8861..7475912245606 100644
--- a/src/item.h
+++ b/src/item.h
@@ -624,7 +624,7 @@ class item : public visitable<item>
         /**
          * Puts the given item into this one, no checks are performed.
          */
-        void put_in( item payload );
+        void put_in( const item &payload );
 
         /** Stores a newly constructed item at the end of this item's contents */
         template<typename ... Args>
diff --git a/src/item_factory.h b/src/item_factory.h
index 07c793faec2a4..5418f638c63ef 100644
--- a/src/item_factory.h
+++ b/src/item_factory.h
@@ -331,7 +331,6 @@ class Item_factory
         void add_entry( Item_group &sg, JsonObject &obj );
 
         void load_basic_info( JsonObject &jo, itype &def, const std::string &src );
-        void tags_from_json( JsonObject &jo, std::string member, std::set<std::string> &tags );
         void set_qualities_from_json( JsonObject &jo, const std::string &member, itype &def );
         void set_properties_from_json( JsonObject &jo, const std::string &member, itype &def );
 
diff --git a/src/iuse.cpp b/src/iuse.cpp
index 226265420f9b5..500632cf5ed09 100644
--- a/src/iuse.cpp
+++ b/src/iuse.cpp
@@ -1440,15 +1440,12 @@ int petfood( player &p, const item &it, Petfood animal_food_type )
             case CATFOOD:
                 return feedpet( p, mon, MF_CATFOOD,
                                 _( "The %s seems to like you!  Or maybe it just tolerates your presence better.  It's hard to tell with felines." ) );
-                break;
             case CATTLEFODDER:
                 return feedpet( p, mon, MF_CATTLEFODDER,
                                 _( "The %s seems to like you!  It lets you pat its head and seems friendly." ) );
-                break;
             case BIRDFOOD:
                 return feedpet( p, mon, MF_BIRDFOOD,
                                 _( "The %s seems to like you!  It runs around your legs and seems friendly." ) );
-                break;
         }
 
     } else {
@@ -3548,8 +3545,6 @@ int iuse::shocktonfa_off( player *p, item *it, bool t, const tripoint &pos )
         case 0: {
             return iuse::tazer2( p, it, t, pos );
         }
-        break;
-
         case 1: {
             if( !it->ammo_sufficient() ) {
                 p->add_msg_if_player( m_info, _( "The batteries are dead." ) );
@@ -3581,8 +3576,6 @@ int iuse::shocktonfa_on( player *p, item *it, bool t, const tripoint &pos )
                 case 0: {
                     return iuse::tazer2( p, it, t, pos );
                 }
-                break;
-
                 case 1: {
                     p->add_msg_if_player( _( "You turn off the light." ) );
                     it->convert( "shocktonfa_off" ).active = false;
@@ -4327,7 +4320,6 @@ int iuse::torch_lit( player *p, item *it, bool t, const tripoint &pos )
                 }
                 return 0;
             }
-            break;
             case 1: {
                 tripoint temp = pos;
                 if( firestarter_actor::prep_firestarter_use( *p, temp ) ) {
@@ -4371,7 +4363,6 @@ int iuse::battletorch_lit( player *p, item *it, bool t, const tripoint &pos )
                 }
                 return 0;
             }
-            break;
             case 1: {
                 tripoint temp = pos;
                 if( firestarter_actor::prep_firestarter_use( *p, temp ) ) {
@@ -7706,14 +7697,12 @@ int iuse::washclothes( player *p, item *it, bool, const tripoint & )
     inv_s.add_character_items( *p );
     inv_s.set_title( _( "Multiclean" ) );
     inv_s.set_hint( _( "To clean x items, type a number before selecting." ) );
-    std::list<std::pair<int, int>> to_clean;
     if( inv_s.empty() ) {
         popup( std::string( _( "You have nothing to clean." ) ), PF_GET_KEY );
         return 0;
     }
-
-    to_clean = inv_s.execute();
-    if( to_clean.size() == 0 ) {
+    std::list<std::pair<int, int>> to_clean = inv_s.execute();
+    if( to_clean.empty() ) {
         return 0;
     }
     int required_water = 0;
diff --git a/src/iuse_actor.cpp b/src/iuse_actor.cpp
index ae3ef02b28ce0..520bc66ab9d37 100644
--- a/src/iuse_actor.cpp
+++ b/src/iuse_actor.cpp
@@ -1537,7 +1537,7 @@ bool cauterize_actor::cauterize_effect( player &p, item &it, bool force )
         return true;
     }
 
-    return 0;
+    return false;
 }
 
 long cauterize_actor::use( player &p, item &it, bool t, const tripoint & ) const
@@ -3200,9 +3200,6 @@ hp_part pick_part_to_heal(
             return healed_part;
         }
     }
-
-    // Won't happen?
-    return num_hp_parts;
 }
 
 hp_part heal_actor::use_healing_item( player &healer, player &patient, item &it, bool force ) const
diff --git a/src/iuse_software.cpp b/src/iuse_software.cpp
index a997c24205d05..5b7e234b86a4f 100644
--- a/src/iuse_software.cpp
+++ b/src/iuse_software.cpp
@@ -35,8 +35,6 @@ bool play_videogame( const std::string &function_name,
         }
 
         return foundkitten;
-
-        return true;
     } else if( function_name == "snake_game" ) {
         snake_game sg;
         int iScore = sg.start_game();
diff --git a/src/map.cpp b/src/map.cpp
index 57fabfb74fd0d..1bb13b30745ca 100644
--- a/src/map.cpp
+++ b/src/map.cpp
@@ -360,7 +360,6 @@ bool map::vehproceed()
     VehicleList vehs = get_vehicles();
     vehicle *cur_veh = nullptr;
     float max_of_turn = 0;
-    tripoint pt;
     // First horizontal movement
     for( auto &vehs_v : vehs ) {
         if( vehs_v.v->of_turn > max_of_turn ) {
@@ -1078,7 +1077,7 @@ bool map::displace_water( const tripoint &p )
 
 // 2D overloads for furniture
 // To be removed once not needed
-void map::set( const int x, const int y, const ter_id new_terrain, const furn_id new_furniture )
+void map::set( const int x, const int y, const ter_id &new_terrain, const furn_id &new_furniture )
 {
     furn_set( x, y, new_furniture );
     ter_set( x, y, new_terrain );
@@ -1107,7 +1106,7 @@ furn_id map::furn( const int x, const int y ) const
     return current_submap->get_furn( lx, ly );
 }
 
-void map::furn_set( const int x, const int y, const furn_id new_furniture )
+void map::furn_set( const int x, const int y, const furn_id &new_furniture )
 {
     furn_set( tripoint( x, y, abs_sub.z ), new_furniture );
 }
@@ -1118,7 +1117,7 @@ std::string map::furnname( const int x, const int y )
 }
 // End of 2D overloads for furniture
 
-void map::set( const tripoint &p, const ter_id new_terrain, const furn_id new_furniture )
+void map::set( const tripoint &p, const ter_id &new_terrain, const furn_id &new_furniture )
 {
     furn_set( p, new_furniture );
     ter_set( p, new_terrain );
@@ -1160,7 +1159,7 @@ furn_id map::furn( const tripoint &p ) const
     return current_submap->get_furn( lx, ly );
 }
 
-void map::furn_set( const tripoint &p, const furn_id new_furniture )
+void map::furn_set( const tripoint &p, const furn_id &new_furniture )
 {
     if( !inbounds( p ) ) {
         return;
@@ -1254,7 +1253,7 @@ ter_id map::ter( const int x, const int y ) const
     return current_submap->get_ter( lx, ly );
 }
 
-bool map::ter_set( const int x, const int y, const ter_id new_terrain )
+bool map::ter_set( const int x, const int y, const ter_id &new_terrain )
 {
     return ter_set( tripoint( x, y, abs_sub.z ), new_terrain );
 }
@@ -1361,7 +1360,7 @@ bool map::is_harvestable( const tripoint &pos ) const
 /*
  * set terrain via string; this works for -any- terrain id
  */
-bool map::ter_set( const tripoint &p, const ter_id new_terrain )
+bool map::ter_set( const tripoint &p, const ter_id &new_terrain )
 {
     if( !inbounds( p ) ) {
         return false;
@@ -2356,13 +2355,13 @@ void map::make_rubble( const tripoint &p )
     make_rubble( p, f_rubble, false, t_dirt, false );
 }
 
-void map::make_rubble( const tripoint &p, const furn_id rubble_type, const bool items )
+void map::make_rubble( const tripoint &p, const furn_id &rubble_type, const bool items )
 {
     make_rubble( p, rubble_type, items, t_dirt, false );
 }
 
-void map::make_rubble( const tripoint &p, furn_id rubble_type, bool items, ter_id floor_type,
-                       bool overwrite )
+void map::make_rubble( const tripoint &p, const furn_id &rubble_type, const bool items,
+                       const ter_id &floor_type, bool overwrite )
 {
     if( overwrite ) {
         ter_set( p, floor_type );
@@ -3652,7 +3651,7 @@ bool map::open_door( const tripoint &p, const bool inside, const bool check_only
     return false;
 }
 
-void map::translate( const ter_id from, const ter_id to )
+void map::translate( const ter_id &from, const ter_id &to )
 {
     if( from == to ) {
         debugmsg( "map::translate %s => %s",
@@ -3674,7 +3673,7 @@ void map::translate( const ter_id from, const ter_id to )
 }
 
 //This function performs the translate function within a given radius of the player.
-void map::translate_radius( const ter_id from, const ter_id to, float radi, const tripoint &p,
+void map::translate_radius( const ter_id &from, const ter_id &to, float radi, const tripoint &p,
                             const bool same_submap )
 {
     if( from == to ) {
@@ -5467,8 +5466,6 @@ lit_level map::apparent_light_at( const tripoint &p, const visibility_variables
     } else {
         return LL_BLANK;
     }
-    // Is this ever supposed to happen?
-    return LL_DARK;
 }
 
 visibility_type map::get_visibility( const lit_level ll, const visibility_variables &cache ) const
diff --git a/src/map.h b/src/map.h
index 4b42a6252d387..c55acf4e41343 100644
--- a/src/map.h
+++ b/src/map.h
@@ -533,7 +533,7 @@ class map
         void move_vehicle( vehicle &veh, const tripoint &dp, const tileray &facing );
 
         // Furniture: 2D overloads
-        void set( const int x, const int y, const ter_id new_terrain, const furn_id new_furniture );
+        void set( const int x, const int y, const ter_id &new_terrain, const furn_id &new_furniture );
 
         std::string name( const int x, const int y );
         bool has_furn( const int x, const int y ) const;
@@ -541,11 +541,11 @@ class map
         // Furniture at coordinates (x, y); {x|y}=(0, SEE{X|Y}*3]
         furn_id furn( const int x, const int y ) const;
 
-        void furn_set( const int x, const int y, const furn_id new_furniture );
+        void furn_set( const int x, const int y, const furn_id &new_furniture );
 
         std::string furnname( const int x, const int y );
         // Furniture: 3D
-        void set( const tripoint &p, const ter_id new_terrain, const furn_id new_furniture );
+        void set( const tripoint &p, const ter_id &new_terrain, const furn_id &new_furniture );
 
         std::string name( const tripoint &p );
         std::string disp_name( const tripoint &p );
@@ -558,7 +558,7 @@ class map
 
         furn_id furn( const tripoint &p ) const;
 
-        void furn_set( const tripoint &p, const furn_id new_furniture );
+        void furn_set( const tripoint &p, const furn_id &new_furniture );
 
         std::string furnname( const tripoint &p );
         bool can_move_furniture( const tripoint &pos, player *p = nullptr );
@@ -566,7 +566,7 @@ class map
         // Terrain integer id at coordinates (x, y); {x|y}=(0, SEE{X|Y}*3]
         ter_id ter( const int x, const int y ) const;
 
-        bool ter_set( const int x, const int y, const ter_id new_terrain );
+        bool ter_set( const int x, const int y, const ter_id &new_terrain );
 
         std::string tername( const int x, const int y ) const; // Name of terrain at (x, y)
         // Terrain: 3D
@@ -581,7 +581,7 @@ class map
         const std::set<std::string> &get_harvest_names( const tripoint &p ) const;
         ter_id get_ter_transforms_into( const tripoint &p ) const;
 
-        bool ter_set( const tripoint &p, const ter_id new_terrain );
+        bool ter_set( const tripoint &p, const ter_id &new_terrain );
 
         std::string tername( const tripoint &p ) const;
 
@@ -694,10 +694,10 @@ class map
 
         /** Generates rubble at the given location, if overwrite is true it just writes on top of what currently exists
          *  floor_type is only used if there is a non-bashable wall at the location or with overwrite = true */
-        void make_rubble( const tripoint &p, furn_id rubble_type, bool items,
-                          ter_id floor_type, bool overwrite = false );
+        void make_rubble( const tripoint &p, const furn_id &rubble_type, const bool items,
+                          const ter_id &floor_type, bool overwrite = false );
         void make_rubble( const tripoint &p );
-        void make_rubble( const tripoint &p, furn_id rubble_type, bool items );
+        void make_rubble( const tripoint &p, const furn_id &rubble_type, const bool items );
 
         bool is_divable( const int x, const int y ) const;
         bool is_outside( const int x, const int y ) const;
@@ -743,9 +743,10 @@ class map
         void add_corpse( const tripoint &p );
 
         // Terrain changing functions
-        void translate( const ter_id from, const ter_id to ); // Change all instances of $from->$to
+        // Change all instances of $from->$to
+        void translate( const ter_id &from, const ter_id &to );
         // Change all instances $from->$to within this radius, optionally limited to locations in the same submap.
-        void translate_radius( const ter_id from, const ter_id to, const float radi, const tripoint &p,
+        void translate_radius( const ter_id &from, const ter_id &to, const float radi, const tripoint &p,
                                const bool same_submap = false );
         bool close_door( const tripoint &p, const bool inside, const bool check_only );
         bool open_door( const tripoint &p, const bool inside, const bool check_only = false );
@@ -1342,11 +1343,11 @@ class map
         void shift_traps( const tripoint &shift );
 
         void copy_grid( const tripoint &to, const tripoint &from );
-        void draw_map( const oter_id terrain_type, const oter_id t_north, const oter_id t_east,
-                       const oter_id t_south, const oter_id t_west, const oter_id t_neast,
-                       const oter_id t_seast, const oter_id t_swest, const oter_id t_nwest,
-                       const oter_id t_above, const oter_id t_below, const time_point &when, const float density,
-                       const int zlevel, const regional_settings *rsettings );
+        void draw_map( const oter_id &terrain_type, const oter_id &t_north, const oter_id &t_east,
+                       const oter_id &t_south, const oter_id &t_west, const oter_id &t_neast,
+                       const oter_id &t_seast, const oter_id &t_swest, const oter_id &t_nwest,
+                       const oter_id &t_above, const oter_id &t_below, const time_point &when,
+                       const float density, const int zlevel, const regional_settings *rsettings );
 
         void build_transparency_cache( int zlev );
     public:
@@ -1454,7 +1455,6 @@ class map
                               bool low_light, bool bright_light, bool inorder ) const;
 
         long determine_wall_corner( const tripoint &p ) const;
-        void cache_seen( const int fx, const int fy, const int tx, const int ty, const int max_range );
         // apply a circular light pattern immediately, however it's best to use...
         void apply_light_source( const tripoint &p, float luminance );
         // ...this, which will apply the light after at the end of generate_lightmap, and prevent redundant
diff --git a/src/mapgen.cpp b/src/mapgen.cpp
index e62d12015f928..0432bba9ccf57 100644
--- a/src/mapgen.cpp
+++ b/src/mapgen.cpp
@@ -106,7 +106,7 @@ const mtype_id mon_zombie_soldier( "mon_zombie_soldier" );
 const mtype_id mon_zombie_spitter( "mon_zombie_spitter" );
 const mtype_id mon_zombie_tough( "mon_zombie_tough" );
 
-bool connects_to( oter_id there, int dir_from_here );
+bool connects_to( const oter_id &there, int dir_from_here );
 void science_room( map *m, int x1, int y1, int x2, int y2, int z, int rotate );
 void set_science_room( map *m, int x1, int y1, bool faces_right, const time_point &when );
 void silo_rooms( map *m );
@@ -2212,16 +2212,14 @@ void mapgen_function_lua::generate( map *m, const oter_id &terrain_type, const m
 // track down what is and isn't supposed to be carried around between bits of code.
 // I suggest that we break the function down into smaller parts
 
-void map::draw_map( const oter_id terrain_type, const oter_id t_north, const oter_id t_east,
-                    const oter_id t_south, const oter_id t_west, const oter_id t_neast,
-                    const oter_id t_seast, const oter_id t_swest, const oter_id t_nwest,
-                    const oter_id t_above, const oter_id t_below, const time_point &when, const float density,
-                    const int zlevel, const regional_settings *rsettings )
+void map::draw_map( const oter_id &terrain_type, const oter_id &t_north, const oter_id &t_east,
+                    const oter_id &t_south, const oter_id &t_west, const oter_id &t_neast,
+                    const oter_id &t_seast, const oter_id &t_swest, const oter_id &t_nwest,
+                    const oter_id &t_above, const oter_id &t_below, const time_point &when,
+                    const float density, const int zlevel, const regional_settings *rsettings )
 {
     static const mongroup_id GROUP_ZOMBIE( "GROUP_ZOMBIE" );
     static const mongroup_id GROUP_LAB( "GROUP_LAB" );
-    static const mongroup_id GROUP_PUBLICWORKERS( "GROUP_PUBLICWORKERS" );
-    static const mongroup_id GROUP_DOMESTIC( "GROUP_DOMESTIC" );
     // Big old switch statement with a case for each overmap terrain type.
     // Many of these can be copied from another type, then rotated; for instance,
     //  "house_east" is identical to "house_north", just rotated 90 degrees to
@@ -7336,7 +7334,7 @@ void map::rotate( int turns )
 }
 
 // Hideous function, I admit...
-bool connects_to( oter_id there, int dir )
+bool connects_to( const oter_id &there, int dir )
 {
     switch( dir ) {
         case 2:
diff --git a/src/mapgen.h b/src/mapgen.h
index c52c6c6e635b9..433beb878f668 100644
--- a/src/mapgen.h
+++ b/src/mapgen.h
@@ -391,7 +391,7 @@ enum room_type {
 
 void house_room( map *m, room_type type, int x1, int y1, int x2, int y2, mapgendata &dat );
 // helpful functions
-bool connects_to( oter_id there, int dir );
+bool connects_to( const oter_id &there, int dir );
 void mapgen_rotate( map *m, oter_id terrain_type, bool north_is_down = false );
 // wrappers for map:: functions
 void line( map *m, const ter_id type, int x1, int y1, int x2, int y2 );
diff --git a/src/mapgen_functions.cpp b/src/mapgen_functions.cpp
index 6c268a868008a..7c4df1eaeb384 100644
--- a/src/mapgen_functions.cpp
+++ b/src/mapgen_functions.cpp
@@ -216,33 +216,24 @@ int &mapgendata::dir( int dir_in )
     switch( dir_in ) {
         case 0:
             return n_fac;
-            break;
         case 1:
             return e_fac;
-            break;
         case 2:
             return s_fac;
-            break;
         case 3:
             return w_fac;
-            break;
         case 4:
             return ne_fac;
-            break;
         case 5:
             return se_fac;
-            break;
         case 6:
             return sw_fac;
-            break;
         case 7:
             return nw_fac;
-            break;
         default:
             debugmsg( "Invalid direction for mapgendata::set_dir. dir_in = %d", dir_in );
             //return something just so the compiler doesn't freak out. Not really correct, though.
             return n_fac;
-            break;
     }
 }
 
diff --git a/src/martialarts.cpp b/src/martialarts.cpp
index 1c5a91c6cb60c..27b28d3d07f0f 100644
--- a/src/martialarts.cpp
+++ b/src/martialarts.cpp
@@ -886,7 +886,7 @@ bool player::can_melee() const
     } );
 }
 
-bool player::has_mabuff( mabuff_id id ) const
+bool player::has_mabuff( const mabuff_id &id ) const
 {
     return search_ma_buff_effect( *effects, [&id]( const ma_buff & b, const effect & ) {
         return b.id == id;
diff --git a/src/material.cpp b/src/material.cpp
index a1aadbe33ae8b..a74d057fa8531 100644
--- a/src/material.cpp
+++ b/src/material.cpp
@@ -145,22 +145,16 @@ int material_type::dam_resist( damage_type damtype ) const
     switch( damtype ) {
         case DT_BASH:
             return _bash_resist;
-            break;
         case DT_CUT:
             return _cut_resist;
-            break;
         case DT_ACID:
             return _acid_resist;
-            break;
         case DT_ELECTRIC:
             return _elec_resist;
-            break;
         case DT_HEAT:
             return _fire_resist;
-            break;
         default:
             return 0;
-            break;
     }
 }
 
diff --git a/src/melee.cpp b/src/melee.cpp
index 002d6721bb621..edb16b95e409e 100644
--- a/src/melee.cpp
+++ b/src/melee.cpp
@@ -40,7 +40,6 @@ static const skill_id skill_cutting( "cutting" );
 static const skill_id skill_unarmed( "unarmed" );
 static const skill_id skill_bashing( "bashing" );
 static const skill_id skill_melee( "melee" );
-static const skill_id skill_dodge( "dodge" );
 
 const efftype_id effect_badpoison( "badpoison" );
 const efftype_id effect_beartrap( "beartrap" );
@@ -370,7 +369,7 @@ void player::melee_attack( Creature &t, bool allow_special, const matec_id &forc
 
     if( hit_spread < 0 ) {
         int stumble_pen = stumble( *this, cur_weapon );
-        sfx::generate_melee_sound( pos(), t.pos(), 0, 0 );
+        sfx::generate_melee_sound( pos(), t.pos(), false, false );
         if( is_player() ) { // Only display messages if this is the player
 
             if( one_in( 2 ) ) {
@@ -460,7 +459,7 @@ void player::melee_attack( Creature &t, bool allow_special, const matec_id &forc
                     material = "steel";
                 }
             }
-            sfx::generate_melee_sound( pos(), t.pos(), 1, t.is_monster(), material );
+            sfx::generate_melee_sound( pos(), t.pos(), true, t.is_monster(), material );
             int dam = dealt_dam.total_damage();
 
             // Practice melee and relevant weapon skill (if any) except when using CQB bionic
diff --git a/src/mission.cpp b/src/mission.cpp
index 782a1576ff7ef..fbbf0f5036601 100644
--- a/src/mission.cpp
+++ b/src/mission.cpp
@@ -270,13 +270,11 @@ bool mission::is_complete( const int _npc_id ) const
             const tripoint cur_pos = g->u.global_omt_location();
             return ( rl_dist( cur_pos, target ) <= 1 );
         }
-        break;
 
         case MGOAL_GO_TO_TYPE: {
             const auto cur_ter = overmap_buffer.ter( g->u.global_omt_location() );
             return is_ot_type( type->target_id.str(), cur_ter );
         }
-        break;
 
         case MGOAL_FIND_ITEM: {
             inventory tmp_inv = u.crafting_inventory();
@@ -338,7 +336,6 @@ bool mission::is_complete( const int _npc_id ) const
         default:
             return false;
     }
-    return false;
 }
 
 bool mission::has_deadline() const
diff --git a/src/mission_companion.cpp b/src/mission_companion.cpp
index 0b629f307abe0..5857b52ab07e2 100644
--- a/src/mission_companion.cpp
+++ b/src/mission_companion.cpp
@@ -1749,7 +1749,7 @@ std::vector<npc *> talk_function::companion_sort( std::vector<npc *> available,
     }
 
     struct companion_sort_skill {
-        companion_sort_skill( std::string skill_tested ) {
+        companion_sort_skill( const std::string &skill_tested ) {
             this->skill_tested = skill_tested;
         }
 
diff --git a/src/mod_manager_ui.cpp b/src/mod_manager_ui.cpp
index 98e7b9ddea38c..0f9ba678adc62 100644
--- a/src/mod_manager_ui.cpp
+++ b/src/mod_manager_ui.cpp
@@ -253,21 +253,16 @@ bool mod_ui::can_shift_down( long selection, const std::vector<mod_id> &active_l
     std::vector<mod_id> dependents = mm_tree.get_dependents_of_X_as_strings(
                                          active_list[selection] );
 
-    int newsel;
-    int oldsel;
-    mod_id selstring;
-    mod_id modstring;
-
     // figure out if we can move down!
     if( selection == ( int )active_list.size() - 1 ) {
         // can't move down, don't bother trying
         return false;
     }
-    newsel = selection;
-    oldsel = selection + 1;
+    int newsel = selection;
+    int oldsel = selection + 1;
 
-    modstring = active_list[newsel];
-    selstring = active_list[oldsel];
+    mod_id modstring = active_list[newsel];
+    mod_id selstring = active_list[oldsel];
 
     if( modstring->core ||
         std::find( dependents.begin(), dependents.end(), selstring ) != dependents.end() ) {
diff --git a/src/monattack.cpp b/src/monattack.cpp
index 898a361942ad0..e2327c25c7eb8 100644
--- a/src/monattack.cpp
+++ b/src/monattack.cpp
@@ -127,9 +127,7 @@ static const trait_id trait_THRESH_MYCUS( "THRESH_MYCUS" );
 // shared utility functions
 int within_visual_range( monster *z, int max_range )
 {
-    int dist;
-
-    dist = rl_dist( z->pos(), g->u.pos() );
+    int dist = rl_dist( z->pos(), g->u.pos() );
     if( dist > max_range || !z->sees( g->u ) ) {
         return -1;    // Out of range
     }
diff --git a/src/monfaction.cpp b/src/monfaction.cpp
index 2e0d65787071f..00cb6261643eb 100644
--- a/src/monfaction.cpp
+++ b/src/monfaction.cpp
@@ -222,10 +222,9 @@ void add_to_attitude_map( const std::set< std::string > &keys, mfaction_att_map
 void monfactions::load_monster_faction( JsonObject &jo )
 {
     // Factions inherit values from their parent factions - this is set during finalization
-    std::set< std::string > by_mood, neutral, friendly;
-    by_mood = jo.get_tags( "by_mood" );
-    neutral = jo.get_tags( "neutral" );
-    friendly = jo.get_tags( "friendly" );
+    std::set< std::string > by_mood = jo.get_tags( "by_mood" );
+    std::set< std::string > neutral = jo.get_tags( "neutral" );
+    std::set< std::string > friendly = jo.get_tags( "friendly" );
     // Need to make sure adding new factions won't invalidate our current faction's reference
     // That +1 is for base faction
     faction_list.reserve( faction_list.size() + by_mood.size() + neutral.size() + friendly.size() + 1 );
diff --git a/src/monster.cpp b/src/monster.cpp
index 8cd9fcdc3e2a0..2a34ac3aa4a44 100644
--- a/src/monster.cpp
+++ b/src/monster.cpp
@@ -2197,7 +2197,7 @@ void monster::make_ally( const monster &z )
     faction = z.faction;
 }
 
-void monster::add_item( item it )
+void monster::add_item( const item &it )
 {
     inv.push_back( it );
 }
diff --git a/src/monster.h b/src/monster.h
index 82f46e5540232..4008403385745 100644
--- a/src/monster.h
+++ b/src/monster.h
@@ -369,7 +369,8 @@ class monster : public Creature
         void make_friendly();
         /** Makes this monster an ally of the given monster. */
         void make_ally( const monster &z );
-        void add_item( item it );   // Add an item to inventory
+        // Add an item to inventory
+        void add_item( const item &it );
 
         /**
          * Makes monster react to heard sound
diff --git a/src/morale.cpp b/src/morale.cpp
index 1e9ffc5dc808c..29e7c01f738fb 100644
--- a/src/morale.cpp
+++ b/src/morale.cpp
@@ -24,9 +24,8 @@ static const efftype_id effect_took_prozac_bad( "took_prozac_bad" );
 
 namespace
 {
-static const std::string item_name_placeholder = "%s"; // Used to address an item name
 
-bool is_permanent_morale( const morale_type id )
+bool is_permanent_morale( const morale_type &id )
 {
     static const std::set<morale_type> permanent_morale = {{
             MORALE_PERM_OPTIMIST,
diff --git a/src/morale.h b/src/morale.h
index c5ab1a7e5095e..e4db4c16f5968 100644
--- a/src/morale.h
+++ b/src/morale.h
@@ -71,7 +71,7 @@ class player_morale
         {
             public:
                 morale_point(
-                    morale_type type = MORALE_NULL,
+                    const morale_type &type = MORALE_NULL,
                     const itype *item_type = nullptr,
                     int bonus = 0,
                     int max_bonus = 0,
diff --git a/src/newcharacter.cpp b/src/newcharacter.cpp
index 59df02ed6c8c8..1a9633ce93414 100644
--- a/src/newcharacter.cpp
+++ b/src/newcharacter.cpp
@@ -702,7 +702,7 @@ void draw_points( const catacurses::window &w, points_left &points, int netPoint
 }
 
 template <class Compare>
-void draw_sorting_indicator( const catacurses::window &w_sorting, input_context ctxt,
+void draw_sorting_indicator( const catacurses::window &w_sorting, const input_context &ctxt,
                              Compare sorter )
 {
     auto const sort_order = sorter.sort_by_points ? _( "points" ) : _( "name" );
diff --git a/src/npc.cpp b/src/npc.cpp
index 32e58276ab3f6..5e36c6ab0d452 100644
--- a/src/npc.cpp
+++ b/src/npc.cpp
@@ -301,7 +301,6 @@ void npc::randomize( const npc_class_id &type )
         debugmsg( "Invalid NPC class %s", type.c_str() );
         myclass = npc_class_id::NULL_ID();
     } else if( type.is_null() && !one_in( 5 ) ) {
-        npc_class_id typetmp;
         myclass = npc_class::random_common();
     } else {
         myclass = type;
diff --git a/src/npcmove.cpp b/src/npcmove.cpp
index 0bfe487ea5b08..f1af944f8e321 100644
--- a/src/npcmove.cpp
+++ b/src/npcmove.cpp
@@ -1305,16 +1305,12 @@ double npc::confidence_mult() const
     switch( rules.aim ) {
         case AIM_WHEN_CONVENIENT:
             return emergency() ? 1.5f : 1.0f;
-            break;
         case AIM_SPRAY:
             return 2.0f;
-            break;
         case AIM_PRECISE:
             return emergency() ? 1.0f : 0.75f;
-            break;
         case AIM_STRICTLY_PRECISE:
             return 0.5f;
-            break;
     }
 
     return 1.0f;
diff --git a/src/npctalk.cpp b/src/npctalk.cpp
index 75531edd8c13d..031c14fc9b056 100644
--- a/src/npctalk.cpp
+++ b/src/npctalk.cpp
@@ -1871,7 +1871,7 @@ void talk_response::effect_fun_t::set_change_faction_rep( int rep_change )
     };
 }
 
-void talk_response::effect_t::set_effect_consequence( effect_fun_t fun, dialogue_consequence con )
+void talk_response::effect_t::set_effect_consequence( const effect_fun_t &fun, dialogue_consequence con )
 {
     effects.push_back( fun );
     guaranteed_consequence = std::max( guaranteed_consequence, con );
diff --git a/src/npctrade.h b/src/npctrade.h
index d98e3c0bbab5e..a511779cdcd0a 100644
--- a/src/npctrade.h
+++ b/src/npctrade.h
@@ -1,3 +1,7 @@
+#pragma once
+#ifndef NPCTRADE_H
+#define NPCTRADE_H
+
 #include "npc.h"
 #include "itype.h"
 #include "game.h"
@@ -27,3 +31,5 @@ inventory inventory_exchange( inventory &inv,
 std::vector<item_pricing> init_selling( npc &p );
 std::vector<item_pricing> init_buying( npc &p, player &u );
 bool trade( npc &p, int cost, const std::string &deal );
+
+#endif
diff --git a/src/path_info.cpp b/src/path_info.cpp
index 3694994c92cff..cdb0bf672f125 100644
--- a/src/path_info.cpp
+++ b/src/path_info.cpp
@@ -56,9 +56,7 @@ void PATH_INFO::init_user_dir( const char *ud )
 
 void PATH_INFO::update_pathname( const std::string &name, const std::string &path )
 {
-    std::map<std::string, std::string>::iterator iter;
-
-    iter = FILENAMES.find( name );
+    std::map<std::string, std::string>::iterator iter = FILENAMES.find( name );
     if( iter != FILENAMES.end() ) {
         FILENAMES[name] = path;
     } else {
diff --git a/src/player.cpp b/src/player.cpp
index 446c71dd13c75..a41dc46d562de 100644
--- a/src/player.cpp
+++ b/src/player.cpp
@@ -210,7 +210,6 @@ static const bionic_id bio_membrane( "bio_membrane" );
 static const bionic_id bio_memory( "bio_memory" );
 static const bionic_id bio_metabolics( "bio_metabolics" );
 static const bionic_id bio_noise( "bio_noise" );
-static const bionic_id bio_ods( "bio_ods" );
 static const bionic_id bio_plut_filter( "bio_plut_filter" );
 static const bionic_id bio_power_weakness( "bio_power_weakness" );
 static const bionic_id bio_purifier( "bio_purifier" );
@@ -256,7 +255,6 @@ static const trait_id trait_CEPH_EYES( "CEPH_EYES" );
 static const trait_id trait_CF_HAIR( "CF_HAIR" );
 static const trait_id trait_CHAOTIC( "CHAOTIC" );
 static const trait_id trait_CHEMIMBALANCE( "CHEMIMBALANCE" );
-static const trait_id trait_CHITIN( "CHITIN" );
 static const trait_id trait_CHITIN2( "CHITIN2" );
 static const trait_id trait_CHITIN3( "CHITIN3" );
 static const trait_id trait_CHITIN_FUR( "CHITIN_FUR" );
@@ -5995,8 +5993,7 @@ void player::suffer()
             slow_rad += ((tank_plut * 0.1) + (reactor_plut * 0.01));
             //begin power generation
             if (reactor_plut > 0) {
-                int power_gen;
-                power_gen = 0;
+                int power_gen = 0;
                 if (has_bionic( bio_advreactor ) ) {
                     if ((reactor_plut * 0.05) > 2000){
                         power_gen = 2000;
@@ -11216,7 +11213,7 @@ bool player::uncanny_dodge()
 tripoint player::adjacent_tile() const
 {
     std::vector<tripoint> ret;
-    int dangerous_fields;
+    int dangerous_fields = 0;
     for( const tripoint &p : g->m.points_in_radius( pos(), 1 ) ) {
         if( p == pos() ) {
             // Don't consider player position
diff --git a/src/player.h b/src/player.h
index 1126bc4bef14f..5d5a08570f550 100644
--- a/src/player.h
+++ b/src/player.h
@@ -444,7 +444,7 @@ class player : public Character
         void ma_ongethit_effects();
 
         /** Returns true if the player has any martial arts buffs attached */
-        bool has_mabuff( mabuff_id buff_id ) const;
+        bool has_mabuff( const mabuff_id &buff_id ) const;
         /** Returns true if the player has access to the entered martial art */
         bool has_martialart( const matype_id &ma_id ) const;
         /** Adds the entered martial art to the player's list */
diff --git a/src/ranged.cpp b/src/ranged.cpp
index edf858520eca0..a31164a86ecd9 100644
--- a/src/ranged.cpp
+++ b/src/ranged.cpp
@@ -43,7 +43,6 @@ const skill_id skill_launcher( "launcher" );
 const efftype_id effect_on_roof( "on_roof" );
 const efftype_id effect_hit_by_player( "hit_by_player" );
 
-static const trait_id trait_TRIGGERHAPPY( "TRIGGERHAPPY" );
 static const trait_id trait_HOLLOW_BONES( "HOLLOW_BONES" );
 static const trait_id trait_LIGHT_BONES( "LIGHT_BONES" );
 static const trait_id trait_PYROMANIA( "PYROMANIA" );
diff --git a/src/recipe_groups.cpp b/src/recipe_groups.cpp
index 9670d52c8aa78..74cad673416e2 100644
--- a/src/recipe_groups.cpp
+++ b/src/recipe_groups.cpp
@@ -36,8 +36,7 @@ generic_factory<recipe_group_data> recipe_groups_data( "recipe group type", "nam
 void recipe_group_data::load( JsonObject &jo, const std::string & )
 {
     building_type = jo.get_string( "building_type" );
-    JsonArray jsarr;
-    jsarr = jo.get_array( "recipes" );
+    JsonArray jsarr = jo.get_array( "recipes" );
     while( jsarr.has_more() ) {
         JsonObject ordering = jsarr.next_object();
         std::string name_id = ordering.get_string( "id" );
diff --git a/src/recipe_groups.h b/src/recipe_groups.h
index f23b6dd54cf20..4ba5206b01f5e 100644
--- a/src/recipe_groups.h
+++ b/src/recipe_groups.h
@@ -1,8 +1,9 @@
-#include "map.h"
 #pragma once
 #ifndef RECIPE_GROUPS_H
 #define RECIPE_GROUPS_H
 
+#include "map.h"
+
 #include <string>
 
 class JsonObject;
diff --git a/src/scent_map.cpp b/src/scent_map.cpp
index e9a6c768ed421..9c1045d0e0e93 100644
--- a/src/scent_map.cpp
+++ b/src/scent_map.cpp
@@ -193,9 +193,8 @@ void scent_map::update( const tripoint &center, map &m )
                 } else {
                     this_diffusivity = diffusivity / 5; //less air movement for REDUCE_SCENT square
                 }
-                int temp_scent;
                 // take the old scent and subtract what diffuses out
-                temp_scent = scent_here * ( 10 * 1000 - squares_used * this_diffusivity );
+                int temp_scent = scent_here * ( 10 * 1000 - squares_used * this_diffusivity );
                 // neighboring walls and reduce_scent squares absorb some scent
                 temp_scent -= scent_here * this_diffusivity * ( 90 - squares_used ) / 5;
                 // we've already summed neighboring scent values in the y direction in the previous
diff --git a/src/sdltiles.cpp b/src/sdltiles.cpp
index 29eca10b97707..beca8674ef2a9 100644
--- a/src/sdltiles.cpp
+++ b/src/sdltiles.cpp
@@ -159,7 +159,7 @@ class Font {
      * Draw character t at (x,y) on the screen,
      * using (curses) color.
      */
-    virtual void OutputChar(std::string ch, int x, int y, unsigned char color) = 0;
+    virtual void OutputChar(const std::string &ch, int x, int y, unsigned char color) = 0;
     virtual void draw_ascii_lines(unsigned char line_id, int drawx, int drawy, int FG) const;
     bool draw_window( const catacurses::window &win );
     bool draw_window( const catacurses::window &win, int offsetx, int offsety );
@@ -183,7 +183,7 @@ class CachedTTFFont : public Font {
     CachedTTFFont( int w, int h, std::string typeface, int fontsize, bool fontblending );
     ~CachedTTFFont() override = default;
 
-    virtual void OutputChar(std::string ch, int x, int y, unsigned char color) override;
+    virtual void OutputChar(const std::string &ch, int x, int y, unsigned char color) override;
 protected:
     SDL_Texture_Ptr create_glyph( const std::string &ch, int color );
 
@@ -219,7 +219,7 @@ class BitmapFont : public Font {
     BitmapFont( int w, int h, const std::string &path );
     ~BitmapFont() override = default;
 
-    virtual void OutputChar(std::string ch, int x, int y, unsigned char color) override;
+    virtual void OutputChar(const std::string &ch, int x, int y, unsigned char color) override;
     void OutputChar(long t, int x, int y, unsigned char color);
     virtual void draw_ascii_lines(unsigned char line_id, int drawx, int drawy, int FG) const override;
 protected:
@@ -690,7 +690,7 @@ SDL_Texture_Ptr CachedTTFFont::create_glyph( const std::string &ch, const int co
     return SDL_Texture_Ptr( SDL_CreateTextureFromSurface( renderer.get(), sglyph.get() ) );
 }
 
-void CachedTTFFont::OutputChar(std::string ch, int const x, int const y, unsigned char const color)
+void CachedTTFFont::OutputChar(const std::string &ch, int const x, int const y, unsigned char const color)
 {
     key_t    key {std::move(ch), static_cast<unsigned char>(color & 0xf)};
 
@@ -722,7 +722,7 @@ void CachedTTFFont::OutputChar(std::string ch, int const x, int const y, unsigne
 #endif
 }
 
-void BitmapFont::OutputChar(std::string ch, int x, int y, unsigned char color)
+void BitmapFont::OutputChar(const std::string &ch, int x, int y, unsigned char color)
 {
     int len = ch.length();
     const char *s = ch.c_str();
@@ -1408,7 +1408,7 @@ int HandleDPad()
  * -1 when a ALT+number sequence has been started,
  * or something that a call to ncurses getch would return.
  */
-long sdl_keysym_to_curses( SDL_Keysym keysym )
+long sdl_keysym_to_curses( const SDL_Keysym &keysym )
 {
 
     if( get_option<bool>( "DIAG_MOVE_WITH_MODIFIERS" ) ) {
@@ -3180,7 +3180,7 @@ input_event input_manager::get_input_event() {
     else if (inputdelay > 0)
     {
         unsigned long starttime=SDL_GetTicks();
-        unsigned long endtime;
+        unsigned long endtime = 0;
         bool timedout = false;
         do
         {
@@ -3702,10 +3702,10 @@ Mix_Chunk *do_pitch_shift( Mix_Chunk *s, float pitch )
     result->abuf = ( Uint8 * )malloc( result->alen * sizeof( Uint8 ) );
     result->volume = s->volume;
     for( i = 0; i < s_out; i++ ) {
-        Sint16 lt;
-        Sint16 rt;
-        Sint16 lt_out;
-        Sint16 rt_out;
+        Sint16 lt = 0;
+        Sint16 rt = 0;
+        Sint16 lt_out = 0;
+        Sint16 rt_out = 0;
         Sint64 lt_avg = 0;
         Sint64 rt_avg = 0;
         Uint32 begin = ( Uint32 )( ( float )i / pitch_real );
diff --git a/src/sounds.h b/src/sounds.h
index 923b42744e65c..50e80fc3ea1ce 100644
--- a/src/sounds.h
+++ b/src/sounds.h
@@ -69,7 +69,7 @@ void play_ambient_variant_sound( const std::string &id, const std::string &varia
                                  int duration );
 void generate_gun_sound( const player &source, const item &firing );
 void generate_melee_sound( const tripoint &source, const tripoint &target, bool hit,
-                           bool targ_mon = 0, const std::string &material = "flesh" );
+                           bool targ_mon = false, const std::string &material = "flesh" );
 void do_hearing_loss( int turns = -1 );
 void remove_hearing_loss();
 void do_projectile_hit( const Creature &target );
diff --git a/src/string_formatter.h b/src/string_formatter.h
index 4ad0fef38239b..15bf0608d5c75 100644
--- a/src/string_formatter.h
+++ b/src/string_formatter.h
@@ -20,7 +20,7 @@ class string_formatter;
 [[noreturn]]
 void throw_error( const string_formatter &, const std::string & );
 // wrapper to access string_formatter::temp_buffer before the definition of string_formatter
-const char *string_formatter_set_temp_buffer( const string_formatter &, std::string );
+const char *string_formatter_set_temp_buffer( const string_formatter &, const std::string & );
 // Handle currently active exception from string_formatter and return it as string
 std::string handle_string_format_error();
 
@@ -210,7 +210,7 @@ class string_formatter
         /// for printing non-strings through "%s". It *only* works because this prints each format
         /// specifier separately, so the content of @ref temp_buffer is only used once.
         friend const char *string_formatter_set_temp_buffer( const string_formatter &sf,
-                std::string text ) {
+                const std::string &text ) {
             sf.temp_buffer = text;
             return sf.temp_buffer.c_str();
         }
@@ -287,7 +287,6 @@ class string_formatter
                                          std::forward<Args>( args )... ) );
                 default:
                     throw_error( "Unsupported format conversion: " + std::string( 1, c ) );
-                    break;
             }
         }
 
diff --git a/src/string_input_popup.cpp b/src/string_input_popup.cpp
index bcf0c0f7c257b..e075c848a07b5 100644
--- a/src/string_input_popup.cpp
+++ b/src/string_input_popup.cpp
@@ -442,7 +442,7 @@ void string_input_popup::edit( int &value )
     }
 }
 
-string_input_popup &string_input_popup::text( std::string value )
+string_input_popup &string_input_popup::text( const std::string &value )
 {
     _text = value;
     auto u8size = utf8_wrapper( _text ).size();
diff --git a/src/string_input_popup.h b/src/string_input_popup.h
index a1906b7ab6557..d2a237a8f34ec 100644
--- a/src/string_input_popup.h
+++ b/src/string_input_popup.h
@@ -92,7 +92,7 @@ class string_input_popup
          * It's optional default is an empty string.
          */
         /**@{*/
-        string_input_popup &text( std::string value );
+        string_input_popup &text( const std::string &value );
         const std::string &text() const {
             return _text;
         }
diff --git a/src/vehicle.cpp b/src/vehicle.cpp
index 75ed4d866c276..780edbf2063ec 100644
--- a/src/vehicle.cpp
+++ b/src/vehicle.cpp
@@ -1395,7 +1395,7 @@ bool vehicle::merge_rackable_vehicle( vehicle *carry_veh, const std::vector<int>
                 vehicle_part &carried_part = parts.back();
                 carried_part.mount = carry_map.carry_mount;
                 carried_part.carry_names.push( unique_id );
-                carried_part.enabled = 0;
+                carried_part.enabled = false;
                 carried_part.set_flag( vehicle_part::carried_flag );
                 parts[ carry_map.rack_part ].set_flag( vehicle_part::carrying_flag );
             }
diff --git a/src/wcwidth.h b/src/wcwidth.h
index f384e3feca3c7..6b84416703b77 100644
--- a/src/wcwidth.h
+++ b/src/wcwidth.h
@@ -73,7 +73,7 @@ struct interval {
 static uint32_t bisearch( uint32_t ucs, const struct interval *table, uint32_t max )
 {
     uint32_t min = 0;
-    uint32_t mid;
+    uint32_t mid = 0;
 
     if( ucs < table[0].first || ucs > table[max].last ) {
         return 0;
diff --git a/src/worldfactory.cpp b/src/worldfactory.cpp
index 028934082f7ad..d4206318139e2 100644
--- a/src/worldfactory.cpp
+++ b/src/worldfactory.cpp
@@ -154,7 +154,7 @@ WORLDPTR worldfactory::make_new_world( bool show_prompt, const std::string &worl
                                     iOffsetX );
 
         int curtab = 0;
-        int lasttab; // give placement memory to menus, sorta.
+        int lasttab = 0; // give placement memory to menus, sorta.
         const size_t numtabs = tabs.size();
         while( static_cast<size_t>( curtab ) < numtabs ) {
             lasttab = curtab;
diff --git a/src/worldfactory.h b/src/worldfactory.h
index 698102be73652..d4adefe8c89fb 100644
--- a/src/worldfactory.h
+++ b/src/worldfactory.h
@@ -128,7 +128,6 @@ class worldfactory
         static void draw_worldgen_tabs( const catacurses::window &win, size_t current );
         void show_active_world_mods( const std::vector<mod_id> &world_mods );
 
-    protected:
     private:
         std::map<std::string, WORLDPTR> all_worlds;
 
diff --git a/tests/map_memory.cpp b/tests/map_memory.cpp
index 77856802c3798..6bac5239051ff 100644
--- a/tests/map_memory.cpp
+++ b/tests/map_memory.cpp
@@ -12,7 +12,7 @@ TEST_CASE( "map_memory_defaults", "[map_memory]" )
     map_memory memory;
     CHECK( memory.get_symbol( p1 ) == 0 );
     memorized_terrain_tile default_tile = memory.get_tile( p1 );
-    CHECK( default_tile.tile == "" );
+    CHECK( default_tile.tile.empty() );
     CHECK( default_tile.subtile == 0 );
     CHECK( default_tile.rotation == 0 );
 }
diff --git a/tests/ranged_balance.cpp b/tests/ranged_balance.cpp
index 37d2ccb2f966e..63e4d33060808 100644
--- a/tests/ranged_balance.cpp
+++ b/tests/ranged_balance.cpp
@@ -82,8 +82,8 @@ static void equip_shooter( npc &shooter, const std::vector<std::string> &apparel
 
 std::array<double, 5> accuracy_levels = {{ accuracy_grazing, accuracy_standard, accuracy_goodhit, accuracy_critical, accuracy_headshot }};
 
-static std::array<firing_statistics, 5> firing_test( dispersion_sources dispersion, int range,
-        std::array<double, 5> thresholds )
+static std::array<firing_statistics, 5> firing_test( const dispersion_sources &dispersion,
+        int range, const std::array<double, 5> &thresholds )
 {
     std::array<firing_statistics, 5> firing_stats;
     bool threshold_within_confidence_interval = false;
diff --git a/tests/vehicle_split_test.cpp b/tests/vehicle_split_test.cpp
index ddc80e8d9c0fd..7711d8a1199d3 100644
--- a/tests/vehicle_split_test.cpp
+++ b/tests/vehicle_split_test.cpp
@@ -12,8 +12,7 @@ TEST_CASE( "vehicle_split_section" )
         tripoint test_origin( 15, 15, 0 );
         g->u.setpos( test_origin );
         tripoint vehicle_origin = tripoint( 10, 10, 0 );
-        VehicleList vehs;
-        vehs = g->m.get_vehicles();
+        VehicleList vehs = g->m.get_vehicles();
         vehicle *veh_ptr;
         for( auto &vehs_v : vehs ) {
             veh_ptr = vehs_v.v;