From 363f324179b608d3be5eabcb0e964ee8a9d0b2ab Mon Sep 17 00:00:00 2001
From: Teemo Vaas <teemo@digiwood.ee>
Date: Fri, 22 Dec 2023 06:47:36 +0200
Subject: [PATCH] =?UTF-8?q?=F0=9F=9A=B8=20Fix=20G4=20Dwell=20overflow?=
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---
 Marlin/src/core/millis_t.h | 5 ++++-
 Marlin/src/gcode/gcode.cpp | 8 ++++----
 Marlin/src/gcode/gcode.h   | 2 +-
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/Marlin/src/core/millis_t.h b/Marlin/src/core/millis_t.h
index e7032a2e55..7c00b91a5b 100644
--- a/Marlin/src/core/millis_t.h
+++ b/Marlin/src/core/millis_t.h
@@ -30,5 +30,8 @@ typedef uint32_t millis_t;
 #define MS_TO_SEC(N) millis_t((N)/1000UL)
 #define MS_TO_SEC_PRECISE(N) (float(N)/1000.0f)
 
-#define PENDING(NOW,SOON) ((int32_t)(NOW-(SOON))<0)
+#define FUTURE(START,DURA) (millis_t(millis()-(START))<(DURA))
+#define PAST(START,DURA) (!FUTURE(START,DURA))
+
+#define PENDING(NOW,SOON) (int32_t((NOW)-(SOON))<0)
 #define ELAPSED(NOW,SOON) (!PENDING(NOW,SOON))
diff --git a/Marlin/src/gcode/gcode.cpp b/Marlin/src/gcode/gcode.cpp
index 881149fb52..69d77e875e 100644
--- a/Marlin/src/gcode/gcode.cpp
+++ b/Marlin/src/gcode/gcode.cpp
@@ -242,11 +242,11 @@ void GcodeSuite::get_destination_from_command() {
 }
 
 /**
- * Dwell waits immediately. It does not synchronize. Use M400 instead of G4
+ * Dwell waits immediately. It does not synchronize.
  */
-void GcodeSuite::dwell(millis_t time) {
-  time += millis();
-  while (PENDING(millis(), time)) idle();
+void GcodeSuite::dwell(const millis_t time) {
+  const millis_t startMillis = millis();
+  while (FUTURE(startMillis, time)) idle();
 }
 
 /**
diff --git a/Marlin/src/gcode/gcode.h b/Marlin/src/gcode/gcode.h
index e86a58d85d..1f3ccba37c 100644
--- a/Marlin/src/gcode/gcode.h
+++ b/Marlin/src/gcode/gcode.h
@@ -503,7 +503,7 @@ public:
     #define KEEPALIVE_STATE(N) NOOP
   #endif
 
-  static void dwell(millis_t time);
+  static void dwell(const millis_t time);
 
 private: