Avoid GCC compiler warnings

Author: Rangi42

src/main-window.cpp

@@ -711,7 +711,11 @@ void Main_Window::update_tileset_metadata() {
 		}
 		else {
 			char buffer[FL_PATH_MAX] = {};
-			sprintf(buffer, "%d files", _tilesets.size());
+#ifdef __GNUC__
+			sprintf(buffer, "%zu files", _tilesets.size());
+#else
+			sprintf(buffer, "%u files", _tilesets.size());
+#endif
 			_tileset_name->copy_label(buffer);
 		}
 	}

src/preferences.cpp

@@ -20,12 +20,11 @@ void Preferences::set(const char *key, int value) {
 std::string Preferences::get_string(const char *key) {
 	char *value;
 	global_prefs.get(key, value, "");
-	if (!value) { value = ""; }
-	std::string s(value);
+	std::string s(value ? value : "");
 	delete value;
 	return s;
 }
 
- void Preferences::set_string(const char *key, std::string &value) {
+void Preferences::set_string(const char *key, std::string &value) {
 	global_prefs.set(key, value.c_str());
 }

src/tile-buttons.cpp

@@ -106,8 +106,9 @@ void Tile_State::draw(int x, int y, bool active, bool selected) {
 		}
 	}
 	if (!gfx) {
-		char hi = (char)((id & 0xF0) >> 4), lo = (char)(id & 0x0F);
-		const char buffer[3] = {hi > 9 ? 'A' + hi - 10 : '0' + hi, lo > 9 ? 'A' + lo - 10 : '0' + lo, '\0'};
+		uint8_t hi = (id & 0xF0) >> 4, lo = id & 0x0F;
+		char l1 = (char)(hi > 9 ? 'A' + hi - 10 : '0' + hi), l2 = (char)(lo > 9 ? 'A' + lo - 10 : '0' + lo);
+		const char buffer[3] = {l1, l2, '\0'};
 		bool r = Config::rainbow_tiles();
 		Fl_Color bg = bg_colors[r ? lo : 0];
 		if (!active) { bg = fl_inactive(bg); }
@@ -120,7 +121,7 @@ void Tile_State::draw(int x, int y, bool active, bool selected) {
 	}
 	if (Config::attributes() && color > -1) {
 		sgb_color_images[color].draw(x, y, TILE_SIZE_2X, TILE_SIZE_2X);
-		const char buffer[2] = {'0' + (char)color, '\0'};
+		const char buffer[2] = {(char)('0' + color), '\0'};
 		fl_font(FL_COURIER_BOLD, s);
 		draw_outlined_text(buffer, x, y, TILE_SIZE_2X, TILE_SIZE_2X, FL_ALIGN_CENTER, sgb_colors[color]);
 	}

src/tile.h

@@ -19,4 +19,4 @@ bool is_blank_tile(Tile &tile);
 bool are_identical_tiles(Tile &t1, Tile &t2, Tilemap_Format fmt, bool &x_flip, bool &y_flip);
 Tile *get_image_tiles(Fl_RGB_Image *img, size_t &n);
 
-#endif TILE_H
+#endif