Fix and improve G-code queue (#21122)

Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>

Marlin/src/core/bug_on.h

@@ -0,0 +1,37 @@
+/**
+ * Marlin 3D Printer Firmware
+ * Copyright (c) 2021 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
+ *
+ * Copyright (c) 2021 X-Ryl669 [https://blog.cyril.by]
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ */
+#pragma once
+
+// We need SERIAL_ECHOPAIR and macros.h
+#include "serial.h"
+
+#if ENABLED(POSTMORTEM_DEBUGGING)
+  // Useful macro for stopping the CPU on an unexpected condition
+  // This is used like SERIAL_ECHOPAIR, that is: a key-value call of the local variables you want
+  // to dump to the serial port before stopping the CPU.
+  #define BUG_ON(V...) do { SERIAL_ECHOPAIR(ONLY_FILENAME, __LINE__, ": "); SERIAL_ECHOLNPAIR(V); SERIAL_FLUSHTX(); *(char*)0 = 42; } while(0)
+#elif ENABLED(MARLIN_DEV_MODE)
+  // Don't stop the CPU here, but at least dump the bug on the serial port
+  #define BUG_ON(V...) do { SERIAL_ECHOPAIR(ONLY_FILENAME, __LINE__, ": BUG!\n"); SERIAL_ECHOLNPAIR(V); SERIAL_FLUSHTX(); } while(0)
+#else
+  // Release mode, let's ignore the bug
+  #define BUG_ON(V...) NOOP
+#endif