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Marlin/Marlin_main.cpp

@@ -4475,7 +4475,7 @@ inline void gcode_G28() {
             inInc = -1;
           }
 
-          zig = !zig; // zag
+          zig ^= true; // zag
 
           // Inner loop is Y with PROBE_Y_FIRST enabled
           for (int8_t PR_INNER_VAR = inStart; PR_INNER_VAR != inStop; PR_INNER_VAR += inInc) {
@@ -5799,7 +5799,7 @@ inline void gcode_M42() {
 #if ENABLED(AUTO_BED_LEVELING_UBL) && ENABLED(UBL_G26_MESH_EDITING)
 
   inline void gcode_M49() {
-    ubl.g26_debug_flag = !ubl.g26_debug_flag;
+    ubl.g26_debug_flag ^= true;
     SERIAL_PROTOCOLPGM("UBL Debug Flag turned ");
     serialprintPGM(ubl.g26_debug_flag ? PSTR("on.") : PSTR("off."));
   }

Marlin/ubl_G29.cpp

@@ -1551,7 +1551,7 @@
           inInc = -1;
         }
 
-        zig = !zig; // zag
+        zig ^= true; // zag
 
         // Inner loop is Y with PROBE_Y_FIRST enabled
         for (PR_INNER_VAR = inStart; PR_INNER_VAR != inStop; PR_INNER_VAR += inInc) {

Marlin/ultralcd.cpp

@@ -688,7 +688,7 @@ void kill_screen(const char* lcd_msg) {
     extern void update_case_light();
 
     void toggle_case_light() {
-      case_light_on = !case_light_on;
+      case_light_on ^= true;
       lcdDrawUpdate = LCDVIEW_CALL_REDRAW_NEXT;
       update_case_light();
     }
@@ -3196,7 +3196,7 @@ void kill_screen(const char* lcd_msg) {
 
   #endif //SDSUPPORT
 
-  void menu_action_setting_edit_bool(const char* pstr, bool* ptr) {UNUSED(pstr); *ptr = !(*ptr); lcdDrawUpdate = LCDVIEW_CLEAR_CALL_REDRAW; }
+  void menu_action_setting_edit_bool(const char* pstr, bool* ptr) {UNUSED(pstr); *ptr ^= true; lcdDrawUpdate = LCDVIEW_CLEAR_CALL_REDRAW; }
   void menu_action_setting_edit_callback_bool(const char* pstr, bool* ptr, screenFunc_t callback) {
     menu_action_setting_edit_bool(pstr, ptr);
     (*callback)();