Allow USE_GCODE_SUBCODES for debugging

Marlin/src/gcode/geometry/G92.cpp

 
   bool sync_E = false, sync_XYZ = false;
 
-  #if USE_GCODE_SUBCODES
+  #if ENABLED(USE_GCODE_SUBCODES)
     const uint8_t subcode_G92 = parser.subcode;
   #else
     constexpr uint8_t subcode_G92 = 0;

Marlin/src/gcode/parser.cpp

 char GCodeParser::command_letter;
 int GCodeParser::codenum;
 
-#if USE_GCODE_SUBCODES
+#if ENABLED(USE_GCODE_SUBCODES)
   uint8_t GCodeParser::subcode;
 #endif
 
 #if ENABLED(GCODE_MOTION_MODES)
   int16_t GCodeParser::motion_mode_codenum = -1;
-  #if USE_GCODE_SUBCODES
+  #if ENABLED(USE_GCODE_SUBCODES)
     uint8_t GCodeParser::motion_mode_subcode;
   #endif
 #endif
   string_arg = nullptr;                 // No whole line argument
   command_letter = '?';                 // No command letter
   codenum = 0;                          // No command code
-  #if USE_GCODE_SUBCODES
+  #if ENABLED(USE_GCODE_SUBCODES)
     subcode = 0;                        // No command sub-code
   #endif
   #if ENABLED(FASTER_GCODE_PARSER)
       do { codenum *= 10, codenum += *p++ - '0'; } while (NUMERIC(*p));
 
       // Allow for decimal point in command
-      #if USE_GCODE_SUBCODES
-      if (*p == '.') {
-        p++;
-        while (NUMERIC(*p))
-        subcode *= 10, subcode += *p++ - '0';
-      }
+      #if ENABLED(USE_GCODE_SUBCODES)
+        if (*p == '.') {
+          p++;
+          while (NUMERIC(*p))
+          subcode *= 10, subcode += *p++ - '0';
+        }
       #endif
 
       // Skip all spaces to get to the first argument, or nul
                              )
         ) {
           motion_mode_codenum = codenum;
-          #if USE_GCODE_SUBCODES
+          #if ENABLED(USE_GCODE_SUBCODES)
             motion_mode_subcode = subcode;
           #endif
         }
         if (motion_mode_codenum < 0) return;
         command_letter = 'G';
         codenum = motion_mode_codenum;
-        #if USE_GCODE_SUBCODES
+        #if ENABLED(USE_GCODE_SUBCODES)
           subcode = motion_mode_subcode;
         #endif
         p--; // Back up one character to use the current parameter

Marlin/src/gcode/parser.h

               *string_arg,                // string of command line
               command_letter;             // G, M, or T
   static int codenum;                     // 123
-  #if USE_GCODE_SUBCODES
+  #if ENABLED(USE_GCODE_SUBCODES)
     static uint8_t subcode;               // .1
   #endif
 
   #if ENABLED(GCODE_MOTION_MODES)
     static int16_t motion_mode_codenum;
-    #if USE_GCODE_SUBCODES
+    #if ENABLED(USE_GCODE_SUBCODES)
       static uint8_t motion_mode_subcode;
     #endif
     FORCE_INLINE static void cancel_motion_mode() { motion_mode_codenum = -1; }

Marlin/src/inc/Conditionals_post.h

 #endif
 
 // Add commands that need sub-codes to this list
-#define USE_GCODE_SUBCODES ANY(G38_PROBE_TARGET, CNC_COORDINATE_SYSTEMS, POWER_LOSS_RECOVERY)
+#if ANY(G38_PROBE_TARGET, CNC_COORDINATE_SYSTEMS, POWER_LOSS_RECOVERY)
+  #define USE_GCODE_SUBCODES
+#endif
 
 // Parking Extruder
 #if ENABLED(PARKING_EXTRUDER)