(svn r26105) -Codechange: add a lot of assertions to track/road functions that might eventually lead to become indices into tables

src/direction_func.h

@@ -14,198 +14,6 @@
 
 #include "direction_type.h"
 
-/**
- * Return the reverse of a direction
- *
- * @param d The direction to get the reverse from
- * @return The reverse Direction
- */
-static inline Direction ReverseDir(Direction d)
-{
-	return (Direction)(4 ^ d);
-}
-
-
-/**
- * Calculate the difference between to directions
- *
- * @param d0 The first direction as the base
- * @param d1 The second direction as the offset from the base
- * @return The difference how the second directions drifts of the first one.
- */
-static inline DirDiff DirDifference(Direction d0, Direction d1)
-{
-	/* Cast to uint so compiler can use bitmask. If the difference is negative
-	 * and we used int instead of uint, further "+ 8" would have to be added. */
-	return (DirDiff)((uint)(d0 - d1) % 8);
-}
-
-/**
- * Applies two differences together
- *
- * This function adds two differences together and return the resulting
- * difference. So adding two DIRDIFF_REVERSE together results in the
- * DIRDIFF_SAME difference.
- *
- * @param d The first difference
- * @param delta The second difference to add on
- * @return The resulting difference
- */
-static inline DirDiff ChangeDirDiff(DirDiff d, DirDiff delta)
-{
-	/* Cast to uint so compiler can use bitmask. Result can never be negative. */
-	return (DirDiff)((uint)(d + delta) % 8);
-}
-
-/**
- * Change a direction by a given difference
- *
- * This functions returns a new direction of the given direction
- * which is rotated by the given difference.
- *
- * @param d The direction to get a new direction from
- * @param delta The offset/drift applied to the direction
- * @return The new direction
- */
-static inline Direction ChangeDir(Direction d, DirDiff delta)
-{
-	/* Cast to uint so compiler can use bitmask. Result can never be negative. */
-	return (Direction)((uint)(d + delta) % 8);
-}
-
-
-/**
- * Returns the reverse direction of the given DiagDirection
- *
- * @param d The DiagDirection to get the reverse from
- * @return The reverse direction
- */
-static inline DiagDirection ReverseDiagDir(DiagDirection d)
-{
-	return (DiagDirection)(2 ^ d);
-}
-
-
-/**
- * Applies a difference on a DiagDirection
- *
- * This function applies a difference on a DiagDirection and returns
- * the new DiagDirection.
- *
- * @param d The DiagDirection
- * @param delta The difference to apply on
- * @return The new direction which was calculated
- */
-static inline DiagDirection ChangeDiagDir(DiagDirection d, DiagDirDiff delta)
-{
-	/* Cast to uint so compiler can use bitmask. Result can never be negative. */
-	return (DiagDirection)((uint)(d + delta) % 4);
-}
-
-/**
- * Convert a Direction to a DiagDirection.
- *
- * This function can be used to convert the 8-way Direction to
- * the 4-way DiagDirection. If the direction cannot be mapped its
- * "rounded clockwise". So DIR_N becomes DIAGDIR_NE.
- *
- * @param dir The direction to convert
- * @return The resulting DiagDirection, maybe "rounded clockwise".
- */
-static inline DiagDirection DirToDiagDir(Direction dir)
-{
-	return (DiagDirection)(dir >> 1);
-}
-
-/**
- * Convert a DiagDirection to a Direction.
- *
- * This function can be used to convert the 4-way DiagDirection
- * to the 8-way Direction. As 4-way are less than 8-way not all
- * possible directions can be calculated.
- *
- * @param dir The direction to convert
- * @return The resulting Direction
- */
-static inline Direction DiagDirToDir(DiagDirection dir)
-{
-	return (Direction)(dir * 2 + 1);
-}
-
-
-/**
- * Select the other axis as provided.
- *
- * This is basically the not-operator for the axis.
- *
- * @param a The given axis
- * @return The other axis
- */
-static inline Axis OtherAxis(Axis a)
-{
-	return (Axis)(a ^ 1);
-}
-
-
-/**
- * Convert a DiagDirection to the axis.
- *
- * This function returns the axis which belongs to the given
- * DiagDirection. The axis X belongs to the DiagDirection
- * north-east and south-west.
- *
- * @param d The DiagDirection
- * @return The axis which belongs to the direction
- */
-static inline Axis DiagDirToAxis(DiagDirection d)
-{
-	return (Axis)(d & 1);
-}
-
-
-/**
- * Converts an Axis to a DiagDirection
- *
- * This function returns the DiagDirection which
- * belongs to the axis. As 2 directions are mapped to an axis
- * this function returns the one which points to south,
- * either south-west (on X axis) or south-east (on Y axis)
- *
- * @param a The axis
- * @return The direction pointed to south
- */
-static inline DiagDirection AxisToDiagDir(Axis a)
-{
-	return (DiagDirection)(2 - a);
-}
-
-/**
- * Converts an Axis to a Direction
- *
- * This function returns the Direction which
- * belongs to the axis. As 2 directions are mapped to an axis
- * this function returns the one which points to south,
- * either south-west (on X axis) or south-east (on Y axis)
- *
- * @param a The axis
- * @return The direction pointed to south
- */
-static inline Direction AxisToDirection(Axis a)
-{
-	return (Direction)(5 - 2 * a);
-}
-
-/**
- * Convert an axis and a flag for north/south into a DiagDirection
- * @param xy axis to convert
- * @param ns north -> 0, south -> 1
- * @return the desired DiagDirection
- */
-static inline DiagDirection XYNSToDiagDir(Axis xy, uint ns)
-{
-	return (DiagDirection)(xy * 3 ^ ns * 2);
-}
-
 /**
  * Checks if an integer value is a valid DiagDirection
  *
@@ -239,6 +47,211 @@ static inline bool IsValidAxis(Axis d)
 	return d < AXIS_END;
 }
 
+/**
+ * Return the reverse of a direction
+ *
+ * @param d The direction to get the reverse from
+ * @return The reverse Direction
+ */
+static inline Direction ReverseDir(Direction d)
+{
+	assert(IsValidDirection(d));
+	return (Direction)(4 ^ d);
+}
+
+
+/**
+ * Calculate the difference between to directions
+ *
+ * @param d0 The first direction as the base
+ * @param d1 The second direction as the offset from the base
+ * @return The difference how the second directions drifts of the first one.
+ */
+static inline DirDiff DirDifference(Direction d0, Direction d1)
+{
+	assert(IsValidDirection(d0));
+	assert(IsValidDirection(d1));
+	/* Cast to uint so compiler can use bitmask. If the difference is negative
+	 * and we used int instead of uint, further "+ 8" would have to be added. */
+	return (DirDiff)((uint)(d0 - d1) % 8);
+}
+
+/**
+ * Applies two differences together
+ *
+ * This function adds two differences together and return the resulting
+ * difference. So adding two DIRDIFF_REVERSE together results in the
+ * DIRDIFF_SAME difference.
+ *
+ * @param d The first difference
+ * @param delta The second difference to add on
+ * @return The resulting difference
+ */
+static inline DirDiff ChangeDirDiff(DirDiff d, DirDiff delta)
+{
+	/* Cast to uint so compiler can use bitmask. Result can never be negative. */
+	return (DirDiff)((uint)(d + delta) % 8);
+}
+
+/**
+ * Change a direction by a given difference
+ *
+ * This functions returns a new direction of the given direction
+ * which is rotated by the given difference.
+ *
+ * @param d The direction to get a new direction from
+ * @param delta The offset/drift applied to the direction
+ * @return The new direction
+ */
+static inline Direction ChangeDir(Direction d, DirDiff delta)
+{
+	assert(IsValidDirection(d));
+	/* Cast to uint so compiler can use bitmask. Result can never be negative. */
+	return (Direction)((uint)(d + delta) % 8);
+}
+
+
+/**
+ * Returns the reverse direction of the given DiagDirection
+ *
+ * @param d The DiagDirection to get the reverse from
+ * @return The reverse direction
+ */
+static inline DiagDirection ReverseDiagDir(DiagDirection d)
+{
+	assert(IsValidDiagDirection(d));
+	return (DiagDirection)(2 ^ d);
+}
+
+
+/**
+ * Applies a difference on a DiagDirection
+ *
+ * This function applies a difference on a DiagDirection and returns
+ * the new DiagDirection.
+ *
+ * @param d The DiagDirection
+ * @param delta The difference to apply on
+ * @return The new direction which was calculated
+ */
+static inline DiagDirection ChangeDiagDir(DiagDirection d, DiagDirDiff delta)
+{
+	assert(IsValidDiagDirection(d));
+	/* Cast to uint so compiler can use bitmask. Result can never be negative. */
+	return (DiagDirection)((uint)(d + delta) % 4);
+}
+
+/**
+ * Convert a Direction to a DiagDirection.
+ *
+ * This function can be used to convert the 8-way Direction to
+ * the 4-way DiagDirection. If the direction cannot be mapped its
+ * "rounded clockwise". So DIR_N becomes DIAGDIR_NE.
+ *
+ * @param dir The direction to convert
+ * @return The resulting DiagDirection, maybe "rounded clockwise".
+ */
+static inline DiagDirection DirToDiagDir(Direction dir)
+{
+	assert(IsValidDirection(dir));
+	return (DiagDirection)(dir >> 1);
+}
+
+/**
+ * Convert a DiagDirection to a Direction.
+ *
+ * This function can be used to convert the 4-way DiagDirection
+ * to the 8-way Direction. As 4-way are less than 8-way not all
+ * possible directions can be calculated.
+ *
+ * @param dir The direction to convert
+ * @return The resulting Direction
+ */
+static inline Direction DiagDirToDir(DiagDirection dir)
+{
+	assert(IsValidDiagDirection(dir));
+	return (Direction)(dir * 2 + 1);
+}
+
+
+/**
+ * Select the other axis as provided.
+ *
+ * This is basically the not-operator for the axis.
+ *
+ * @param a The given axis
+ * @return The other axis
+ */
+static inline Axis OtherAxis(Axis a)
+{
+	assert(IsValidAxis(a));
+	return (Axis)(a ^ 1);
+}
+
+
+/**
+ * Convert a DiagDirection to the axis.
+ *
+ * This function returns the axis which belongs to the given
+ * DiagDirection. The axis X belongs to the DiagDirection
+ * north-east and south-west.
+ *
+ * @param d The DiagDirection
+ * @return The axis which belongs to the direction
+ */
+static inline Axis DiagDirToAxis(DiagDirection d)
+{
+	assert(IsValidDiagDirection(d));
+	return (Axis)(d & 1);
+}
+
+
+/**
+ * Converts an Axis to a DiagDirection
+ *
+ * This function returns the DiagDirection which
+ * belongs to the axis. As 2 directions are mapped to an axis
+ * this function returns the one which points to south,
+ * either south-west (on X axis) or south-east (on Y axis)
+ *
+ * @param a The axis
+ * @return The direction pointed to south
+ */
+static inline DiagDirection AxisToDiagDir(Axis a)
+{
+	assert(IsValidAxis(a));
+	return (DiagDirection)(2 - a);
+}
+
+/**
+ * Converts an Axis to a Direction
+ *
+ * This function returns the Direction which
+ * belongs to the axis. As 2 directions are mapped to an axis
+ * this function returns the one which points to south,
+ * either south-west (on X axis) or south-east (on Y axis)
+ *
+ * @param a The axis
+ * @return The direction pointed to south
+ */
+static inline Direction AxisToDirection(Axis a)
+{
+	assert(IsValidAxis(a));
+	return (Direction)(5 - 2 * a);
+}
+
+/**
+ * Convert an axis and a flag for north/south into a DiagDirection
+ * @param xy axis to convert
+ * @param ns north -> 0, south -> 1
+ * @return the desired DiagDirection
+ */
+static inline DiagDirection XYNSToDiagDir(Axis xy, uint ns)
+{
+	assert(IsValidAxis(xy));
+	return (DiagDirection)(xy * 3 ^ ns * 2);
+}
+
 /**
  * Checks if a given Direction is diagonal.
  *
@@ -247,6 +260,7 @@ static inline bool IsValidAxis(Axis d)
  */
 static inline bool IsDiagonalDirection(Direction dir)
 {
+	assert(IsValidDirection(dir));
 	return (dir & 1) != 0;
 }
 

src/road_func.h

@@ -37,6 +37,16 @@ static inline bool IsValidRoadType(RoadType rt)
 	return rt == ROADTYPE_ROAD || rt == ROADTYPE_TRAM;
 }
 
+/**
+ * Whether the given roadtype is valid.
+ * @param rt the roadtype to check for validness
+ * @return true if and only if valid
+ */
+static inline bool IsValidRoadBits(RoadBits r)
+{
+	return r < ROAD_END;
+}
+
 /**
  * Maps a RoadType to the corresponding RoadTypes value
  *
@@ -45,6 +55,7 @@ static inline bool IsValidRoadType(RoadType rt)
  */
 static inline RoadTypes RoadTypeToRoadTypes(RoadType rt)
 {
+	assert(IsValidRoadType(rt));
 	return (RoadTypes)(1 << rt);
 }
 
@@ -73,6 +84,7 @@ static inline RoadTypes ComplementRoadTypes(RoadTypes r)
  */
 static inline RoadBits ComplementRoadBits(RoadBits r)
 {
+	assert(IsValidRoadBits(r));
 	return (RoadBits)(ROAD_ALL ^ r);
 }
 
@@ -86,6 +98,7 @@ static inline RoadBits ComplementRoadBits(RoadBits r)
  */
 static inline RoadBits MirrorRoadBits(RoadBits r)
 {
+	assert(IsValidRoadBits(r));
 	return (RoadBits)(GB(r, 0, 2) << 2 | GB(r, 2, 2));
 }
 
@@ -100,6 +113,7 @@ static inline RoadBits MirrorRoadBits(RoadBits r)
  */
 static inline RoadBits RotateRoadBits(RoadBits r, DiagDirDiff rot)
 {
+	assert(IsValidRoadBits(r));
 	for (; rot > (DiagDirDiff)0; rot--) {
 		r = (RoadBits)(GB(r, 0, 1) << 3 | GB(r, 1, 3));
 	}
@@ -114,6 +128,7 @@ static inline RoadBits RotateRoadBits(RoadBits r, DiagDirDiff rot)
  */
 static inline bool IsStraightRoad(RoadBits r)
 {
+	assert(IsValidRoadBits(r));
 	return (r == ROAD_X || r == ROAD_Y);
 }
 
@@ -128,6 +143,7 @@ static inline bool IsStraightRoad(RoadBits r)
  */
 static inline RoadBits DiagDirToRoadBits(DiagDirection d)
 {
+	assert(IsValidDiagDirection(d));
 	return (RoadBits)(ROAD_NW << (3 ^ d));
 }
 
@@ -142,6 +158,7 @@ static inline RoadBits DiagDirToRoadBits(DiagDirection d)
  */
 static inline RoadBits AxisToRoadBits(Axis a)
 {
+	assert(IsValidAxis(a));
 	return a == AXIS_X ? ROAD_X : ROAD_Y;
 }
 
@@ -154,7 +171,7 @@ static inline RoadBits AxisToRoadBits(Axis a)
  */
 static inline Money RoadMaintenanceCost(RoadType roadtype, uint32 num)
 {
-	assert(roadtype < ROADTYPE_END);
+	assert(IsValidRoadType(roadtype));
 	return (_price[PR_INFRASTRUCTURE_ROAD] * (roadtype == ROADTYPE_TRAM ? 3 : 2) * num * (1 + IntSqrt(num))) >> 9; // 2 bits fraction for the multiplier and 7 bits scaling.
 }
 

src/track_func.h

@@ -14,6 +14,7 @@
 
 #include "core/bitmath_func.hpp"
 #include "track_type.h"
+#include "direction_func.h"
 #include "slope_func.h"
 
 /**
@@ -27,6 +28,42 @@
  */
 #define FOR_EACH_SET_TRACK(var, track_bits) FOR_EACH_SET_BIT_EX(Track, var, TrackBits, track_bits)
 
+/**
+ * Checks if a Track is valid.
+ *
+ * @param track The value to check
+ * @return true if the given value is a valid track.
+ * @note Use this in an assert()
+ */
+static inline bool IsValidTrack(Track track)
+{
+	return track < TRACK_END;
+}
+
+/**
+ * Checks if a Trackdir is valid for road vehicles.
+ *
+ * @param trackdir The value to check
+ * @return true if the given value is a valid Trackdir
+ * @note Use this in an assert()
+ */
+static inline bool IsValidTrackdirForRoadVehicle(Trackdir trackdir)
+{
+	return trackdir < TRACKDIR_END;
+}
+
+/**
+ * Checks if a Trackdir is valid for non-road vehicles.
+ *
+ * @param trackdir The value to check
+ * @return true if the given value is a valid Trackdir
+ * @note Use this in an assert()
+ */
+static inline bool IsValidTrackdir(Trackdir trackdir)
+{
+	return (1 << trackdir & TRACKDIR_BIT_MASK) != 0;
+}
+
 /**
  * Convert an Axis to the corresponding Track
  * AXIS_X -> TRACK_X
@@ -38,6 +75,7 @@
  */
 static inline Track AxisToTrack(Axis a)
 {
+	assert(IsValidAxis(a));
 	return (Track)a;
 }
 
@@ -48,6 +86,7 @@ static inline Track AxisToTrack(Axis a)
  */
 static inline TrackBits TrackToTrackBits(Track track)
 {
+	assert(IsValidTrack(track));
 	return (TrackBits)(1 << track);
 }
 
@@ -74,8 +113,6 @@ static inline TrackBits CornerToTrackBits(Corner corner)
 	return _corner_to_trackbits[corner];
 }
 
-
-
 /**
  * Maps a Trackdir to the corresponding TrackdirBits value
  * @param trackdir the track direction to convert
@@ -83,6 +120,7 @@ static inline TrackBits CornerToTrackBits(Corner corner)
  */
 static inline TrackdirBits TrackdirToTrackdirBits(Trackdir trackdir)
 {
+	assert(IsValidTrackdir(trackdir));
 	return (TrackdirBits)(1 << trackdir);
 }
 
@@ -103,6 +141,7 @@ static inline TrackdirBits TrackdirToTrackdirBits(Trackdir trackdir)
 static inline Track RemoveFirstTrack(TrackBits *tracks)
 {
 	if (*tracks != TRACK_BIT_NONE && *tracks != INVALID_TRACK_BIT) {
+		assert((*tracks & ~TRACK_BIT_MASK) == TRACK_BIT_NONE);
 		Track first = (Track)FIND_FIRST_BIT(*tracks);
 		ClrBit(*tracks, first);
 		return first;
@@ -127,6 +166,7 @@ static inline Track RemoveFirstTrack(TrackBits *tracks)
 static inline Trackdir RemoveFirstTrackdir(TrackdirBits *trackdirs)
 {
 	if (*trackdirs != TRACKDIR_BIT_NONE && *trackdirs != INVALID_TRACKDIR_BIT) {
+		assert((*trackdirs & ~TRACKDIR_BIT_MASK) == TRACKDIR_BIT_NONE);
 		Trackdir first = (Trackdir)FindFirstBit2x64(*trackdirs);
 		ClrBit(*trackdirs, first);
 		return first;
@@ -184,31 +224,6 @@ static inline Trackdir FindFirstTrackdir(TrackdirBits trackdirs)
 	return (trackdirs != TRACKDIR_BIT_NONE) ? (Trackdir)FindFirstBit2x64(trackdirs) : INVALID_TRACKDIR;
 }
 
-/**
- * Checks if a Track is valid.
- *
- * @param track The value to check
- * @return true if the given value is a valid track.
- * @note Use this in an assert()
- */
-static inline bool IsValidTrack(Track track)
-{
-	return track < TRACK_END;
-}
-
-/**
- * Checks if a Trackdir is valid.
- *
- * @param trackdir The value to check
- * @return true if the given value is a valid Trackdir
- * @note Use this in an assert()
- */
-static inline bool IsValidTrackdir(Trackdir trackdir)
-{
-	return (TrackdirToTrackdirBits(trackdir) & TRACKDIR_BIT_MASK) != 0;
-}
-
-
 /*
  * Functions describing logical relations between Tracks, TrackBits, Trackdirs
  * TrackdirBits, Direction and DiagDirections.
@@ -225,7 +240,7 @@ static inline bool IsValidTrackdir(Trackdir trackdir)
  */
 static inline Track TrackToOppositeTrack(Track t)
 {
-	assert(t != INVALID_TRACK);
+	assert(IsValidTrack(t));
 	return (Track)(t ^ 1);
 }
 
@@ -241,7 +256,7 @@ static inline Track TrackToOppositeTrack(Track t)
  */
 static inline Trackdir ReverseTrackdir(Trackdir trackdir)
 {
-	assert(trackdir != INVALID_TRACKDIR);
+	assert(IsValidTrackdirForRoadVehicle(trackdir));
 	return (Trackdir)(trackdir ^ 8);
 }
 
@@ -256,6 +271,7 @@ static inline Trackdir ReverseTrackdir(Trackdir trackdir)
  */
 static inline Track TrackdirToTrack(Trackdir trackdir)
 {
+	assert(IsValidTrackdir(trackdir));
 	return (Track)(trackdir & 0x7);
 }
 
@@ -272,6 +288,7 @@ static inline Track TrackdirToTrack(Trackdir trackdir)
  */
 static inline Trackdir TrackToTrackdir(Track track)
 {
+	assert(IsValidTrack(track));
 	return (Trackdir)track;
 }
 
@@ -373,6 +390,7 @@ static inline TrackStatus CombineTrackStatus(TrackdirBits trackdirbits, Trackdir
  */
 static inline Trackdir NextTrackdir(Trackdir trackdir)
 {
+	assert(IsValidTrackdir(trackdir));
 	extern const Trackdir _next_trackdir[TRACKDIR_END];
 	return _next_trackdir[trackdir];
 }
@@ -389,6 +407,7 @@ static inline Trackdir NextTrackdir(Trackdir trackdir)
  */
 static inline TrackBits TrackCrossesTracks(Track track)
 {
+	assert(IsValidTrack(track));
 	extern const TrackBits _track_crosses_tracks[TRACK_END];
 	return _track_crosses_tracks[track];
 }
@@ -407,6 +426,7 @@ static inline TrackBits TrackCrossesTracks(Track track)
  */
 static inline DiagDirection TrackdirToExitdir(Trackdir trackdir)
 {
+	assert(IsValidTrackdirForRoadVehicle(trackdir));
 	extern const DiagDirection _trackdir_to_exitdir[TRACKDIR_END];
 	return _trackdir_to_exitdir[trackdir];
 }
@@ -428,6 +448,8 @@ static inline DiagDirection TrackdirToExitdir(Trackdir trackdir)
  */
 static inline Trackdir TrackExitdirToTrackdir(Track track, DiagDirection diagdir)
 {
+	assert(IsValidTrack(track));
+	assert(IsValidDiagDirection(diagdir));
 	extern const Trackdir _track_exitdir_to_trackdir[TRACK_END][DIAGDIR_END];
 	return _track_exitdir_to_trackdir[track][diagdir];
 }
@@ -451,6 +473,8 @@ static inline Trackdir TrackExitdirToTrackdir(Track track, DiagDirection diagdir
  */
 static inline Trackdir TrackEnterdirToTrackdir(Track track, DiagDirection diagdir)
 {
+	assert(IsValidTrack(track));
+	assert(IsValidDiagDirection(diagdir));
 	extern const Trackdir _track_enterdir_to_trackdir[TRACK_END][DIAGDIR_END];
 	return _track_enterdir_to_trackdir[track][diagdir];
 }
@@ -461,6 +485,8 @@ static inline Trackdir TrackEnterdirToTrackdir(Track track, DiagDirection diagdi
  */
 static inline Trackdir TrackDirectionToTrackdir(Track track, Direction dir)
 {
+	assert(IsValidTrack(track));
+	assert(IsValidDirection(dir));
 	extern const Trackdir _track_direction_to_trackdir[TRACK_END][DIR_END];
 	return _track_direction_to_trackdir[track][dir];
 }
@@ -473,6 +499,7 @@ static inline Trackdir TrackDirectionToTrackdir(Track track, Direction dir)
  */
 static inline Track DiagDirToDiagTrack(DiagDirection diagdir)
 {
+	assert(IsValidDiagDirection(diagdir));
 	return (Track)(diagdir & 1);
 }
 
@@ -484,6 +511,7 @@ static inline Track DiagDirToDiagTrack(DiagDirection diagdir)
  */
 static inline TrackBits DiagDirToDiagTrackBits(DiagDirection diagdir)
 {
+	assert(IsValidDiagDirection(diagdir));
 	return TrackToTrackBits(DiagDirToDiagTrack(diagdir));
 }
 
@@ -496,6 +524,7 @@ static inline TrackBits DiagDirToDiagTrackBits(DiagDirection diagdir)
  */
 static inline Trackdir DiagDirToDiagTrackdir(DiagDirection diagdir)
 {
+	assert(IsValidDiagDirection(diagdir));
 	extern const Trackdir _dir_to_diag_trackdir[DIAGDIR_END];
 	return _dir_to_diag_trackdir[diagdir];
 }
@@ -513,6 +542,7 @@ static inline Trackdir DiagDirToDiagTrackdir(DiagDirection diagdir)
  */
 static inline TrackdirBits DiagdirReachesTrackdirs(DiagDirection diagdir)
 {
+	assert(IsValidDiagDirection(diagdir));
 	extern const TrackdirBits _exitdir_reaches_trackdirs[DIAGDIR_END];
 	return _exitdir_reaches_trackdirs[diagdir];
 }
@@ -541,6 +571,7 @@ static inline TrackBits DiagdirReachesTracks(DiagDirection diagdir) { return Tra
  */
 static inline TrackdirBits TrackdirReachesTrackdirs(Trackdir trackdir)
 {
+	assert(IsValidTrackdir(trackdir));
 	extern const TrackdirBits _exitdir_reaches_trackdirs[DIAGDIR_END];
 	return _exitdir_reaches_trackdirs[TrackdirToExitdir(trackdir)];
 }
@@ -562,6 +593,7 @@ static inline TrackdirBits TrackdirReachesTrackdirs(Trackdir trackdir)
  */
 static inline TrackdirBits TrackdirCrossesTrackdirs(Trackdir trackdir)
 {
+	assert(IsValidTrackdirForRoadVehicle(trackdir));
 	extern const TrackdirBits _track_crosses_trackdirs[TRACKDIR_END];
 	return _track_crosses_trackdirs[TrackdirToTrack(trackdir)];
 }
@@ -574,6 +606,7 @@ static inline TrackdirBits TrackdirCrossesTrackdirs(Trackdir trackdir)
  */
 static inline bool IsDiagonalTrack(Track track)
 {
+	assert(IsValidTrack(track));
 	return (track == TRACK_X) || (track == TRACK_Y);
 }
 
@@ -585,6 +618,7 @@ static inline bool IsDiagonalTrack(Track track)
  */
 static inline bool IsDiagonalTrackdir(Trackdir trackdir)
 {
+	assert(IsValidTrackdir(trackdir));
 	return IsDiagonalTrack(TrackdirToTrack(trackdir));
 }
 
@@ -626,6 +660,7 @@ static inline bool TrackOverlapsTracks(TrackBits tracks, Track track)
  */
 static inline bool IsReversingRoadTrackdir(Trackdir dir)
 {
+	assert(IsValidTrackdirForRoadVehicle(dir));
 	return (dir & 0x07) >= 6;
 }
 
@@ -636,6 +671,7 @@ static inline bool IsReversingRoadTrackdir(Trackdir dir)
  */
 static inline bool IsStraightRoadTrackdir(Trackdir dir)
 {
+	assert(IsValidTrackdirForRoadVehicle(dir));
 	return (dir & 0x06) == 0;
 }
 
@@ -651,6 +687,7 @@ static inline bool IsStraightRoadTrackdir(Trackdir dir)
  */
 static inline bool IsUphillTrackdir(Slope slope, Trackdir dir)
 {
+	assert(IsValidTrackdirForRoadVehicle(dir));
 	extern const TrackdirBits _uphill_trackdirs[];
 	return HasBit(_uphill_trackdirs[RemoveHalftileSlope(slope)], dir);
 }