diff --git a/src/client/content_cao.cpp b/src/client/content_cao.cpp
index b169ba75f73d..cf22aa0ed534 100644
--- a/src/client/content_cao.cpp
+++ b/src/client/content_cao.cpp
@@ -1062,7 +1062,7 @@ void GenericCAO::updateTexturePos()
 	}
 }
 
-void GenericCAO::updateTextures(std::string mod)
+void GenericCAO::updateTextures(const std::string &modref)
 {
 	ITextureSource *tsrc = m_client->tsrc();
 
@@ -1071,9 +1071,21 @@ void GenericCAO::updateTextures(std::string mod)
 	bool use_anisotropic_filter = g_settings->getBool("anisotropic_filter");
 
 	m_previous_texture_modifier = m_current_texture_modifier;
-	m_current_texture_modifier = mod;
+	m_current_texture_modifier = modref;
 	m_glow = m_prop.glow;
 
+	// Create a reference to the copy of "modref" just created. The
+	// following code will then use this reference instead of the
+	// original parameter which was passed by reference. This is
+	// necessary as "modref" can be a class member and there is a swap on
+	// those class members which can get triggered by the rest of the
+	// code of this method. This is faster than passing the "mod" by
+	// value because it reuses the copy made by the assignment to
+	// m_current_texture_modifier for the "mod" instead of having two
+	// copies, one for "mod" and another one (created from "mod") for
+	// the m_current_texture_modifier class member.
+	const std::string &mod = m_current_texture_modifier;
+
 	video::E_MATERIAL_TYPE material_type = (m_prop.use_texture_alpha) ?
 		video::EMT_TRANSPARENT_ALPHA_CHANNEL : video::EMT_TRANSPARENT_ALPHA_CHANNEL_REF;
 
diff --git a/src/client/content_cao.h b/src/client/content_cao.h
index 3ce628d30c21..320607061dc2 100644
--- a/src/client/content_cao.h
+++ b/src/client/content_cao.h
@@ -225,9 +225,7 @@ class GenericCAO : public ClientActiveObject
 
 	void updateTexturePos();
 
-	// std::string copy is mandatory as mod can be a class member and there is a swap
-	// on those class members... do NOT pass by reference
-	void updateTextures(std::string mod);
+	void updateTextures(const std::string &modref);
 
 	void updateAnimation();
 
diff --git a/src/client/guiscalingfilter.cpp b/src/client/guiscalingfilter.cpp
index 3b4377da53ba..312f939398e9 100644
--- a/src/client/guiscalingfilter.cpp
+++ b/src/client/guiscalingfilter.cpp
@@ -39,7 +39,7 @@ std::map<io::path, video::ITexture *> g_txrCache;
 /* Manually insert an image into the cache, useful to avoid texture-to-image
  * conversion whenever we can intercept it.
  */
-void guiScalingCache(io::path key, video::IVideoDriver *driver, video::IImage *value)
+void guiScalingCache(const io::path &key, video::IVideoDriver *driver, video::IImage *value)
 {
 	if (!g_settings->getBool("gui_scaling_filter"))
 		return;
diff --git a/src/client/guiscalingfilter.h b/src/client/guiscalingfilter.h
index 4661bf8daff3..a5cd7851144a 100644
--- a/src/client/guiscalingfilter.h
+++ b/src/client/guiscalingfilter.h
@@ -23,7 +23,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 /* Manually insert an image into the cache, useful to avoid texture-to-image
  * conversion whenever we can intercept it.
  */
-void guiScalingCache(io::path key, video::IVideoDriver *driver, video::IImage *value);
+void guiScalingCache(const io::path &key, video::IVideoDriver *driver, video::IImage *value);
 
 // Manually clear the cache, e.g. when switching to different worlds.
 void guiScalingCacheClear();
diff --git a/src/client/hud.cpp b/src/client/hud.cpp
index 1a2287a13bc8..cb58fb500e4c 100644
--- a/src/client/hud.cpp
+++ b/src/client/hud.cpp
@@ -372,7 +372,7 @@ void Hud::drawLuaElements(const v3s16 &camera_offset)
 }
 
 
-void Hud::drawStatbar(v2s32 pos, u16 corner, u16 drawdir, std::string texture,
+void Hud::drawStatbar(v2s32 pos, u16 corner, u16 drawdir, const std::string &texture,
 		s32 count, v2s32 offset, v2s32 size)
 {
 	const video::SColor color(255, 255, 255, 255);
diff --git a/src/client/hud.h b/src/client/hud.h
index e9bcdf4e23c3..693d2adee18a 100644
--- a/src/client/hud.h
+++ b/src/client/hud.h
@@ -81,7 +81,7 @@ class Hud
 	void drawLuaElements(const v3s16 &camera_offset);
 
 private:
-	void drawStatbar(v2s32 pos, u16 corner, u16 drawdir, std::string texture,
+	void drawStatbar(v2s32 pos, u16 corner, u16 drawdir, const std::string &texture,
 			s32 count, v2s32 offset, v2s32 size = v2s32());
 
 	void drawItems(v2s32 upperleftpos, v2s32 screen_offset, s32 itemcount,
diff --git a/src/client/tile.cpp b/src/client/tile.cpp
index 4911013aef08..72f7358b1c6a 100644
--- a/src/client/tile.cpp
+++ b/src/client/tile.cpp
@@ -131,7 +131,8 @@ std::string getTexturePath(const std::string &filename)
 		Check from texture_path
 	*/
 	for (const auto &path : getTextureDirs()) {
-		std::string testpath = path + DIR_DELIM + filename;
+		std::string testpath = path + DIR_DELIM;
+		testpath.append(filename);
 		// Check all filename extensions. Returns "" if not found.
 		fullpath = getImagePath(testpath);
 		if (!fullpath.empty())
diff --git a/src/gui/guiChatConsole.cpp b/src/gui/guiChatConsole.cpp
index 1ccb4e6d1f7f..42348beb3304 100644
--- a/src/gui/guiChatConsole.cpp
+++ b/src/gui/guiChatConsole.cpp
@@ -139,7 +139,7 @@ f32 GUIChatConsole::getDesiredHeight() const
 	return m_desired_height_fraction;
 }
 
-void GUIChatConsole::replaceAndAddToHistory(std::wstring line)
+void GUIChatConsole::replaceAndAddToHistory(const std::wstring &line)
 {
 	ChatPrompt& prompt = m_chat_backend->getPrompt();
 	prompt.addToHistory(prompt.getLine());
diff --git a/src/gui/guiChatConsole.h b/src/gui/guiChatConsole.h
index ef8a8767387c..7be40e27c147 100644
--- a/src/gui/guiChatConsole.h
+++ b/src/gui/guiChatConsole.h
@@ -60,7 +60,7 @@ class GUIChatConsole : public gui::IGUIElement
 	f32 getDesiredHeight() const;
 
 	// Replace actual line when adding the actual to the history (if there is any)
-	void replaceAndAddToHistory(std::wstring line);
+	void replaceAndAddToHistory(const std::wstring &line);
 
 	// Change how the cursor looks
 	void setCursor(
diff --git a/src/gui/guiEngine.cpp b/src/gui/guiEngine.cpp
index 6030a5bfb5d3..f0a8f40eb230 100644
--- a/src/gui/guiEngine.cpp
+++ b/src/gui/guiEngine.cpp
@@ -518,7 +518,7 @@ void GUIEngine::drawFooter(video::IVideoDriver *driver)
 }
 
 /******************************************************************************/
-bool GUIEngine::setTexture(texture_layer layer, std::string texturepath,
+bool GUIEngine::setTexture(texture_layer layer, const std::string &texturepath,
 		bool tile_image, unsigned int minsize)
 {
 	video::IVideoDriver *driver = RenderingEngine::get_video_driver();
@@ -593,7 +593,7 @@ void GUIEngine::updateTopLeftTextSize()
 }
 
 /******************************************************************************/
-s32 GUIEngine::playSound(SimpleSoundSpec spec, bool looped)
+s32 GUIEngine::playSound(const SimpleSoundSpec &spec, bool looped)
 {
 	s32 handle = m_sound_manager->playSound(spec, looped);
 	return handle;
diff --git a/src/gui/guiEngine.h b/src/gui/guiEngine.h
index 409ba94c498a..0ff5030c0b93 100644
--- a/src/gui/guiEngine.h
+++ b/src/gui/guiEngine.h
@@ -247,7 +247,7 @@ class GUIEngine {
 	 * @param layer draw layer to specify texture
 	 * @param texturepath full path of texture to load
 	 */
-	bool setTexture(texture_layer layer, std::string texturepath,
+	bool setTexture(texture_layer layer, const std::string &texturepath,
 			bool tile_image, unsigned int minsize);
 
 	/**
@@ -296,7 +296,7 @@ class GUIEngine {
 	clouddata   m_cloud;
 
 	/** start playing a sound and return handle */
-	s32 playSound(SimpleSoundSpec spec, bool looped);
+	s32 playSound(const SimpleSoundSpec &spec, bool looped);
 	/** stop playing a sound started with playSound() */
 	void stopSound(s32 handle);
 
diff --git a/src/gui/guiFormSpecMenu.cpp b/src/gui/guiFormSpecMenu.cpp
index 92e6547659d9..e2aed420cf83 100644
--- a/src/gui/guiFormSpecMenu.cpp
+++ b/src/gui/guiFormSpecMenu.cpp
@@ -86,7 +86,7 @@ inline u32 clamp_u8(s32 value)
 GUIFormSpecMenu::GUIFormSpecMenu(JoystickController *joystick,
 		gui::IGUIElement *parent, s32 id, IMenuManager *menumgr,
 		Client *client, ISimpleTextureSource *tsrc, IFormSource *fsrc, TextDest *tdst,
-		std::string formspecPrepend,
+		const std::string &formspecPrepend,
 		bool remap_dbl_click):
 	GUIModalMenu(RenderingEngine::get_gui_env(), parent, id, menumgr),
 	m_invmgr(client),
diff --git a/src/gui/guiFormSpecMenu.h b/src/gui/guiFormSpecMenu.h
index d75a108d4a9a..33f88d8c03da 100644
--- a/src/gui/guiFormSpecMenu.h
+++ b/src/gui/guiFormSpecMenu.h
@@ -287,7 +287,7 @@ class GUIFormSpecMenu : public GUIModalMenu
 			ISimpleTextureSource *tsrc,
 			IFormSource* fs_src,
 			TextDest* txt_dst,
-			std::string formspecPrepend,
+			const std::string &formspecPrepend,
 			bool remap_dbl_click = true);
 
 	~GUIFormSpecMenu();
diff --git a/src/inventorymanager.cpp b/src/inventorymanager.cpp
index 51a472a569b4..24d1fa6ff470 100644
--- a/src/inventorymanager.cpp
+++ b/src/inventorymanager.cpp
@@ -93,7 +93,7 @@ void InventoryLocation::deSerialize(std::istream &is)
 	}
 }
 
-void InventoryLocation::deSerialize(std::string s)
+void InventoryLocation::deSerialize(const std::string &s)
 {
 	std::istringstream is(s, std::ios::binary);
 	deSerialize(is);
diff --git a/src/inventorymanager.h b/src/inventorymanager.h
index 30a82d4bf653..06517f40faaa 100644
--- a/src/inventorymanager.h
+++ b/src/inventorymanager.h
@@ -97,7 +97,7 @@ struct InventoryLocation
 	std::string dump() const;
 	void serialize(std::ostream &os) const;
 	void deSerialize(std::istream &is);
-	void deSerialize(std::string s);
+	void deSerialize(const std::string &s);
 };
 
 struct InventoryAction;
diff --git a/src/map.cpp b/src/map.cpp
index 0114867e09e2..3d1e7479043d 100644
--- a/src/map.cpp
+++ b/src/map.cpp
@@ -1717,7 +1717,7 @@ bool ServerMap::loadFromFolders() {
 	return false;
 }
 
-void ServerMap::createDirs(std::string path)
+void ServerMap::createDirs(const std::string &path)
 {
 	if (!fs::CreateAllDirs(path)) {
 		m_dout<<"ServerMap: Failed to create directory "
diff --git a/src/map.h b/src/map.h
index 7ef34b2792c7..251ac297fa8e 100644
--- a/src/map.h
+++ b/src/map.h
@@ -389,7 +389,7 @@ class ServerMap : public Map
 		Misc. helper functions for fiddling with directory and file
 		names when saving
 	*/
-	void createDirs(std::string path);
+	void createDirs(const std::string &path);
 	// returns something like "map/sectors/xxxxxxxx"
 	std::string getSectorDir(v2s16 pos, int layout = 2);
 	// dirname: final directory name
diff --git a/src/server.cpp b/src/server.cpp
index 496170da3f96..7167a6686fc1 100644
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -3207,7 +3207,7 @@ bool Server::hudSetHotbarItemcount(RemotePlayer *player, s32 hotbar_itemcount)
 	return true;
 }
 
-void Server::hudSetHotbarImage(RemotePlayer *player, std::string name)
+void Server::hudSetHotbarImage(RemotePlayer *player, const std::string &name)
 {
 	if (!player)
 		return;
@@ -3216,7 +3216,7 @@ void Server::hudSetHotbarImage(RemotePlayer *player, std::string name)
 	SendHUDSetParam(player->getPeerId(), HUD_PARAM_HOTBAR_IMAGE, name);
 }
 
-void Server::hudSetHotbarSelectedImage(RemotePlayer *player, std::string name)
+void Server::hudSetHotbarSelectedImage(RemotePlayer *player, const std::string &name)
 {
 	if (!player)
 		return;
diff --git a/src/server.h b/src/server.h
index 5e58ac9e6668..4232653ebcd9 100644
--- a/src/server.h
+++ b/src/server.h
@@ -296,8 +296,8 @@ class Server : public con::PeerHandler, public MapEventReceiver,
 	bool hudChange(RemotePlayer *player, u32 id, HudElementStat stat, void *value);
 	bool hudSetFlags(RemotePlayer *player, u32 flags, u32 mask);
 	bool hudSetHotbarItemcount(RemotePlayer *player, s32 hotbar_itemcount);
-	void hudSetHotbarImage(RemotePlayer *player, std::string name);
-	void hudSetHotbarSelectedImage(RemotePlayer *player, std::string name);
+	void hudSetHotbarImage(RemotePlayer *player, const std::string &name);
+	void hudSetHotbarSelectedImage(RemotePlayer *player, const std::string &name);
 
 	Address getPeerAddress(session_t peer_id);
 
diff --git a/src/translation.cpp b/src/translation.cpp
index 7ddd95591453..d17467ce7584 100644
--- a/src/translation.cpp
+++ b/src/translation.cpp
@@ -149,6 +149,8 @@ void Translations::loadTranslation(const std::string &data)
 			            << wide_to_utf8(oword1) << "\"" << std::endl;
 		}
 
-		m_translations[textdomain + L"|" + oword1] = oword2;
+		std::wstring translation_index = textdomain + L"|";
+		translation_index.append(oword1);
+		m_translations[translation_index] = oword2;
 	}
 }
diff --git a/src/unittest/test_areastore.cpp b/src/unittest/test_areastore.cpp
index 62d446f5c076..a6d4706e44d5 100644
--- a/src/unittest/test_areastore.cpp
+++ b/src/unittest/test_areastore.cpp
@@ -152,7 +152,7 @@ void TestAreaStore::testSerialization()
 			1 + 2 +
 			6 + 6 + 2 + 6 +
 			6 + 6 + 2 + 6);
-	UASSERTEQ(std::string, str, str_wanted);
+	UASSERTEQ(const std::string &, str, str_wanted);
 
 	std::istringstream is(str);
 	store.deserialize(is);