diff --git a/src/clientiface.cpp b/src/clientiface.cpp
index 33d07364a..c7166ce51 100644
--- a/src/clientiface.cpp
+++ b/src/clientiface.cpp
@@ -261,10 +261,9 @@ void RemoteClient::GetNextBlocks (
 			Get the border/face dot coordinates of a "d-radiused"
 			box
 		*/
-		std::vector<v3s16> list = FacePositionCache::getFacePositions(d);
+		const auto &list = FacePositionCache::getFacePositions(d);
 
-		std::vector<v3s16>::iterator li;
-		for (li = list.begin(); li != list.end(); ++li) {
+		for (auto li = list.begin(); li != list.end(); ++li) {
 			v3s16 p = *li + center;
 
 			/*
diff --git a/src/database/database-sqlite3.cpp b/src/database/database-sqlite3.cpp
index e73f9c77f..6f6ad341e 100644
--- a/src/database/database-sqlite3.cpp
+++ b/src/database/database-sqlite3.cpp
@@ -942,8 +942,8 @@ void ModStorageDatabaseSQLite3::listMods(std::vector<std::string> *res)
 			return 0;
 		}, (void *) res, &errmsg);
 	if (status != SQLITE_OK) {
-		DatabaseException e(std::string("Error trying to list mods with metadata: ") + errmsg);
+		auto msg = std::string("Error trying to list mods with metadata: ") + errmsg;
 		sqlite3_free(errmsg);
-		throw e;
+		throw DatabaseException(msg);
 	}
 }
diff --git a/src/inventory.cpp b/src/inventory.cpp
index c99147323..a0f0ea9a2 100644
--- a/src/inventory.cpp
+++ b/src/inventory.cpp
@@ -392,7 +392,7 @@ bool ItemStack::itemFits(ItemStack newitem,
 	return newitem.empty();
 }
 
-bool ItemStack::stacksWith(ItemStack other) const
+bool ItemStack::stacksWith(const ItemStack &other) const
 {
 	return (this->name == other.name &&
 			this->wear == other.wear &&
diff --git a/src/inventory.h b/src/inventory.h
index 3109246d4..64ca857fc 100644
--- a/src/inventory.h
+++ b/src/inventory.h
@@ -164,7 +164,7 @@ struct ItemStack
 
 	// Checks if another itemstack would stack with this one.
 	// Does not check if the item actually fits in the stack.
-	bool stacksWith(ItemStack other) const;
+	bool stacksWith(const ItemStack &other) const;
 
 	// Takes some items.
 	// If there are not enough, takes as many as it can.
diff --git a/src/mapgen/mg_schematic.cpp b/src/mapgen/mg_schematic.cpp
index 1e44ae34e..28a1abf83 100644
--- a/src/mapgen/mg_schematic.cpp
+++ b/src/mapgen/mg_schematic.cpp
@@ -625,7 +625,7 @@ void Schematic::condenseContentIds()
 			numids++;
 
 			m_nodenames.push_back(m_ndef->get(c).name);
-			nodeidmap.emplace(std::make_pair(c, id));
+			nodeidmap.emplace(c, id);
 		} else {
 			id = it->second;
 		}
diff --git a/src/script/cpp_api/s_mainmenu.cpp b/src/script/cpp_api/s_mainmenu.cpp
index 1e9ba3a41..290758e4a 100644
--- a/src/script/cpp_api/s_mainmenu.cpp
+++ b/src/script/cpp_api/s_mainmenu.cpp
@@ -21,7 +21,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "cpp_api/s_internal.h"
 #include "common/c_converter.h"
 
-void ScriptApiMainMenu::setMainMenuData(MainMenuDataForScript *data)
+void ScriptApiMainMenu::setMainMenuData(const MainMenuDataForScript *data)
 {
 	SCRIPTAPI_PRECHECKHEADER
 
@@ -38,7 +38,7 @@ void ScriptApiMainMenu::setMainMenuData(MainMenuDataForScript *data)
 	lua_pop(L, 1);
 }
 
-void ScriptApiMainMenu::handleMainMenuEvent(std::string text)
+void ScriptApiMainMenu::handleMainMenuEvent(const std::string &text)
 {
 	SCRIPTAPI_PRECHECKHEADER
 
diff --git a/src/script/cpp_api/s_mainmenu.h b/src/script/cpp_api/s_mainmenu.h
index 470577a29..7085c649b 100644
--- a/src/script/cpp_api/s_mainmenu.h
+++ b/src/script/cpp_api/s_mainmenu.h
@@ -29,13 +29,13 @@ public:
 	 * Hand over MainMenuDataForScript to lua to inform lua of the content
 	 * @param data the data
 	 */
-	void setMainMenuData(MainMenuDataForScript *data);
+	void setMainMenuData(const MainMenuDataForScript *data);
 
 	/**
 	 * process events received from formspec
 	 * @param text events in textual form
 	 */
-	void handleMainMenuEvent(std::string text);
+	void handleMainMenuEvent(const std::string &text);
 
 	/**
 	 * process field data received from formspec
diff --git a/src/script/lua_api/l_item.cpp b/src/script/lua_api/l_item.cpp
index c245ba5ba..c68046b5d 100644
--- a/src/script/lua_api/l_item.cpp
+++ b/src/script/lua_api/l_item.cpp
@@ -678,7 +678,7 @@ int ModApiItem::l_get_content_id(lua_State *L)
 
 	// If this is called at mod load time, NodeDefManager isn't aware of
 	// aliases yet, so we need to handle them manually
-	std::string alias_name = idef->getAlias(name);
+	const auto &alias_name = idef->getAlias(name);
 
 	content_t content_id;
 	if (alias_name != name) {
diff --git a/src/script/lua_api/l_mainmenu.cpp b/src/script/lua_api/l_mainmenu.cpp
index f3aa22ebc..eef3cd635 100644
--- a/src/script/lua_api/l_mainmenu.cpp
+++ b/src/script/lua_api/l_mainmenu.cpp
@@ -43,7 +43,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "common/c_converter.h"
 
 /******************************************************************************/
-std::string ModApiMainMenu::getTextData(lua_State *L, std::string name)
+std::string ModApiMainMenu::getTextData(lua_State *L, const std::string &name)
 {
 	lua_getglobal(L, "gamedata");
 
@@ -56,7 +56,7 @@ std::string ModApiMainMenu::getTextData(lua_State *L, std::string name)
 }
 
 /******************************************************************************/
-int ModApiMainMenu::getIntegerData(lua_State *L, std::string name,bool& valid)
+int ModApiMainMenu::getIntegerData(lua_State *L, const std::string &name, bool& valid)
 {
 	lua_getglobal(L, "gamedata");
 
@@ -65,14 +65,14 @@ int ModApiMainMenu::getIntegerData(lua_State *L, std::string name,bool& valid)
 	if(lua_isnil(L, -1)) {
 		valid = false;
 		return -1;
-		}
+	}
 
 	valid = true;
 	return luaL_checkinteger(L, -1);
 }
 
 /******************************************************************************/
-int ModApiMainMenu::getBoolData(lua_State *L, std::string name,bool& valid)
+int ModApiMainMenu::getBoolData(lua_State *L, const std::string &name, bool& valid)
 {
 	lua_getglobal(L, "gamedata");
 
@@ -81,7 +81,7 @@ int ModApiMainMenu::getBoolData(lua_State *L, std::string name,bool& valid)
 	if(lua_isnil(L, -1)) {
 		valid = false;
 		return false;
-		}
+	}
 
 	valid = true;
 	return readParam<bool>(L, -1);
@@ -553,7 +553,7 @@ int ModApiMainMenu::l_create_world(lua_State *L)
 	// Set the settings for world creation
 	// this is a bad hack but the best we have right now..
 	StringMap backup;
-	for (auto it : use_settings) {
+	for (auto &it : use_settings) {
 		if (g_settings->existsLocal(it.first))
 			backup[it.first] = g_settings->get(it.first);
 		g_settings->set(it.first, it.second);
@@ -569,7 +569,7 @@ int ModApiMainMenu::l_create_world(lua_State *L)
 	}
 
 	// Restore previous settings
-	for (auto it : use_settings) {
+	for (auto &it : use_settings) {
 		auto it2 = backup.find(it.first);
 		if (it2 == backup.end())
 			g_settings->remove(it.first); // wasn't set before
diff --git a/src/script/lua_api/l_mainmenu.h b/src/script/lua_api/l_mainmenu.h
index 6cb8b6d2c..a5fff3872 100644
--- a/src/script/lua_api/l_mainmenu.h
+++ b/src/script/lua_api/l_mainmenu.h
@@ -34,7 +34,7 @@ private:
 	 * @param name name of variable to read
 	 * @return string value of requested variable
 	 */
-	static std::string getTextData(lua_State *L, std::string name);
+	static std::string getTextData(lua_State *L, const std::string &name);
 
 	/**
 	 * read an integer variable from gamedata table within lua stack
@@ -42,7 +42,7 @@ private:
 	 * @param name name of variable to read
 	 * @return integer value of requested variable
 	 */
-	static int getIntegerData(lua_State *L, std::string name,bool& valid);
+	static int getIntegerData(lua_State *L, const std::string &name, bool& valid);
 
 	/**
 	 * read a bool variable from gamedata table within lua stack
@@ -50,7 +50,7 @@ private:
 	 * @param name name of variable to read
 	 * @return bool value of requested variable
 	 */
-	static int getBoolData(lua_State *L, std::string name,bool& valid);
+	static int getBoolData(lua_State *L, const std::string &name ,bool& valid);
 
 	/**
 	 * Checks if a path may be modified. Paths in the temp directory or the user
diff --git a/src/settings.cpp b/src/settings.cpp
index b537005aa..8b89bf489 100644
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -403,7 +403,7 @@ bool Settings::updateConfigFile(const char *filename)
 
 
 bool Settings::parseCommandLine(int argc, char *argv[],
-		std::map<std::string, ValueSpec> &allowed_options)
+		const std::map<std::string, ValueSpec> &allowed_options)
 {
 	int nonopt_index = 0;
 	for (int i = 1; i < argc; i++) {
@@ -424,8 +424,7 @@ bool Settings::parseCommandLine(int argc, char *argv[],
 
 		std::string name = arg_name.substr(2);
 
-		std::map<std::string, ValueSpec>::iterator n;
-		n = allowed_options.find(name);
+		auto n = allowed_options.find(name);
 		if (n == allowed_options.end()) {
 			errorstream << "Unknown command-line parameter \""
 					<< arg_name << "\"" << std::endl;
diff --git a/src/settings.h b/src/settings.h
index 4b0787343..1aeec0255 100644
--- a/src/settings.h
+++ b/src/settings.h
@@ -147,7 +147,7 @@ public:
 	bool updateConfigFile(const char *filename);
 	// NOTE: Types of allowed_options are ignored.  Returns success.
 	bool parseCommandLine(int argc, char *argv[],
-			std::map<std::string, ValueSpec> &allowed_options);
+			const std::map<std::string, ValueSpec> &allowed_options);
 	bool parseConfigLines(std::istream &is);
 	void writeLines(std::ostream &os, u32 tab_depth=0) const;
 
diff --git a/src/texture_override.cpp b/src/texture_override.cpp
index 88f754f88..7dc9dfa8c 100644
--- a/src/texture_override.cpp
+++ b/src/texture_override.cpp
@@ -46,7 +46,7 @@ static const std::map<std::string, OverrideTarget> override_LUT = {
 	{ "*", OverrideTarget::ALL_FACES }
 };
 
-TextureOverrideSource::TextureOverrideSource(std::string filepath)
+TextureOverrideSource::TextureOverrideSource(const std::string &filepath)
 {
 	std::ifstream infile(filepath.c_str());
 	std::string line;
@@ -115,7 +115,7 @@ TextureOverrideSource::TextureOverrideSource(std::string filepath)
 }
 
 //! Get all overrides that apply to item definitions
-std::vector<TextureOverride> TextureOverrideSource::getItemTextureOverrides()
+std::vector<TextureOverride> TextureOverrideSource::getItemTextureOverrides() const
 {
 	std::vector<TextureOverride> found_overrides;
 
@@ -128,7 +128,7 @@ std::vector<TextureOverride> TextureOverrideSource::getItemTextureOverrides()
 }
 
 //! Get all overrides that apply to node definitions
-std::vector<TextureOverride> TextureOverrideSource::getNodeTileOverrides()
+std::vector<TextureOverride> TextureOverrideSource::getNodeTileOverrides() const
 {
 	std::vector<TextureOverride> found_overrides;
 
diff --git a/src/texture_override.h b/src/texture_override.h
index 237efcba1..19e55689c 100644
--- a/src/texture_override.h
+++ b/src/texture_override.h
@@ -70,13 +70,13 @@ struct TextureOverride
 class TextureOverrideSource
 {
 public:
-	TextureOverrideSource(std::string filepath);
+	TextureOverrideSource(const std::string &filepath);
 
 	//! Get all overrides that apply to item definitions
-	std::vector<TextureOverride> getItemTextureOverrides();
+	std::vector<TextureOverride> getItemTextureOverrides() const;
 
 	//! Get all overrides that apply to node definitions
-	std::vector<TextureOverride> getNodeTileOverrides();
+	std::vector<TextureOverride> getNodeTileOverrides() const;
 
 private:
 	std::vector<TextureOverride> m_overrides;
diff --git a/src/util/enriched_string.cpp b/src/util/enriched_string.cpp
index 941f8b08d..7edbf8eb7 100644
--- a/src/util/enriched_string.cpp
+++ b/src/util/enriched_string.cpp
@@ -59,10 +59,11 @@ void EnrichedString::clear()
 	m_background = irr::video::SColor(0, 0, 0, 0);
 }
 
-void EnrichedString::operator=(const wchar_t *str)
+EnrichedString &EnrichedString::operator=(const wchar_t *str)
 {
 	clear();
 	addAtEnd(translate_string(std::wstring(str)), m_default_color);
+	return *this;
 }
 
 void EnrichedString::addAtEnd(const std::wstring &s, SColor initial_color)
diff --git a/src/util/enriched_string.h b/src/util/enriched_string.h
index 4e249eac5..b48408ac6 100644
--- a/src/util/enriched_string.h
+++ b/src/util/enriched_string.h
@@ -34,7 +34,7 @@ public:
 		const video::SColor &color = video::SColor(255, 255, 255, 255));
 	EnrichedString(const std::wstring &string,
 		const std::vector<video::SColor> &colors);
-	void operator=(const wchar_t *str);
+	EnrichedString &operator=(const wchar_t *str);
 
 	void clear();
 
diff --git a/src/util/string.cpp b/src/util/string.cpp
index 52b7c71ff..1ac295bb4 100644
--- a/src/util/string.cpp
+++ b/src/util/string.cpp
@@ -846,7 +846,7 @@ std::string sanitizeDirName(const std::string &str, const std::string &optional_
 {
 	std::wstring safe_name = utf8_to_wide(str);
 
-	for (std::wstring disallowed_name : disallowed_dir_names) {
+	for (auto &disallowed_name : disallowed_dir_names) {
 		if (str_equal(safe_name, disallowed_name, true)) {
 			safe_name = utf8_to_wide(optional_prefix) + safe_name;
 			break;