bugfix(projectile): Fix out-of-bounds access in DumbProjectile which causes mismatch with very high speed weapons at small hit distances (TheSuperHackers#2087)

Author: Caball009

GeneralsMD/Code/GameEngine/Source/GameLogic/Object/Behavior/DumbProjectileBehavior.cpp

@@ -446,7 +446,10 @@ Bool DumbProjectileBehavior::calcFlightPath(Bool recalcNumSegments)
 		Real flightDistance = flightCurve.getApproximateLength();
 		m_flightPathSegments = ceil( flightDistance / m_flightPathSpeed );
 	}
-	flightCurve.getSegmentPoints( m_flightPathSegments, &m_flightPath );
+
+	// TheSuperHackers @info The way flight paths are used requires at least two curve points.
+	// DumbProjectileBehavior::update has been modified to handle cases where the flight path consists of one or zero curve points.
+	flightCurve.getSegmentPoints(m_flightPathSegments, &m_flightPath);
 	DEBUG_ASSERTCRASH(m_flightPathSegments == m_flightPath.size(), ("m_flightPathSegments mismatch"));
 
 #if defined(RTS_DEBUG)
@@ -584,6 +587,7 @@ UpdateSleepTime DumbProjectileBehavior::update()
 		return UPDATE_SLEEP_NONE;
 	}
 
+	// TheSuperHackers @info This check also covers the case where the flight path consists of zero curve points.
 	if( m_currentFlightPathStep >= m_flightPath.size() )
 	{
 		// No more steps to use. Would go out of bounds on vector, so have to do something.
@@ -648,8 +652,28 @@ UpdateSleepTime DumbProjectileBehavior::update()
       //long, blurry projectile graphics which look badly oriented on step 0 of the flight path
       // so lets orient it the same as if it were on frame 1!
     {
-		  Coord3D prevPos = m_flightPath[0];
-		  Coord3D curPos = m_flightPath[1];
+			// TheSuperHackers @bugfix Caball009 10/01/2026 Check vector size before accessing the second element to prevent out of bounds access.
+			// The non-deterministic behavior for retail clients cannot be fixed, so this will remain a source of potential mismatches in retail compatibility mode.
+			// Use the flight path start and end coordinates if needed, so that the behavior is deterministic for patched clients.
+			Coord3D prevPos;
+			Coord3D curPos;
+
+			if (m_flightPath.size() >= 2)
+			{
+				prevPos = m_flightPath[0];
+				curPos = m_flightPath[1];
+			}
+			else
+			{
+#if RETAIL_COMPATIBLE_CRC
+				DEBUG_CRASH(("A mismatch is likely to happen if this code path is used in a match with unpatched clients."
+					" Vector is expected to contain two or more elements; check the weapon speed value."));
+#endif
+
+				prevPos = m_flightPathStart;
+				curPos = m_flightPathEnd;
+				flightStep = m_flightPathEnd;
+			}
 
 		  Vector3 curDir(curPos.x - prevPos.x, curPos.y - prevPos.y, curPos.z - prevPos.z);
 		  curDir.Normalize();	// buildTransformMatrix wants it this way