Fix crash bug in satellite maps

The value of diffx() had the wrong sign when the arguments differed by
WORLD_X / 2.  Same for diffy() and WORLD_Y / 2.  satmap() used them to
find the vector from map center to ship or land unit to put on the
map, and got incorrect values for ships and land units directly
opposite to the center in x or y.  The bug made satmap() read a
pointer out bounds of its malloced radbuf[], and then write through
that with unpredictable consequences.

Broken in 4.2.12.  The original bug was in Empire 1.1: it
miscalculated where to put ships on the map (no crash).  An incomplete
fix for radmap() and satmap() appeared in Chainsaw 2 (still no crash).
radmap() got fixed correctly in Chainsaw 3, but satmap() was
forgotten.  That one got "fixed" in 4.2.7, and again in 4.2.12, but
both "fixes" were flawed and could crash.

Fix by backing out the flawed fixes and adopting the fix from radmap()
instead.
(cherry picked from commit 0cc474bd6dd095235330f4e15141c9d5e5adc4b4)

diff --git a/include/prototypes.h b/include/prototypes.h
index cc4fd26a914a970073ccfb0b4960ed4ba91ff839..450e69b758bdf1dbc6f5d0cf5141889ee1ed0ed1 100644 (file)
--- a/include/prototypes.h
+++ b/include/prototypes.h
@@ -282,8 +282,6 @@ extern int logreopen(void);
 extern void logerror(char *, ...) ATTRIBUTE((format (printf, 1, 2)));
 /* more in misc.h */
 /* mapdist.c */
-extern int diffx(int, int);
-extern int diffy(int, int);
 extern int deltax(int, int);
 extern int deltay(int, int);
 extern int mapdist(int, int, int, int);

diff --git a/src/lib/common/mapdist.c b/src/lib/common/mapdist.c
index cac702f454439f1a64544c68fe57276520b75670..50d90c00c8352e8390d3dab340216ec8567d3205 100644 (file)
--- a/src/lib/common/mapdist.c
+++ b/src/lib/common/mapdist.c
@@ -41,34 +41,6 @@
 #include "optlist.h"
 #include "prototypes.h"
 
-int
-diffx(int x1, int x2)
-{
-    int dx;
-
-    dx = x1 - x2;
-    dx = dx % WORLD_X;
-    if (dx > WORLD_X / 2)
-       dx = dx - WORLD_X;
-    if (dx < -WORLD_X / 2)
-       dx = dx + WORLD_X;
-    return dx;
-}
-
-int
-diffy(int y1, int y2)
-{
-    int dy;
-
-    dy = y1 - y2;
-    dy = dy % WORLD_Y;
-    if (dy > WORLD_Y / 2)
-       dy = dy - WORLD_Y;
-    if (dy < -WORLD_Y / 2)
-       dy = dy + WORLD_Y;
-    return dy;
-}
-
 int
 deltax(int x1, int x2)
 {

diff --git a/src/lib/subs/satmap.c b/src/lib/subs/satmap.c
index f4def5dfff43b4f890e9ec70b44fe18129e10acd..15a060201e013ec40119967ec0aae567740f17dd 100644 (file)
--- a/src/lib/subs/satmap.c
+++ b/src/lib/subs/satmap.c
@@ -177,15 +177,8 @@ satmap(int x, int y, int eff, int range, int flags, int type)
            }
            /* If we are imaging *and* drawing the map */
            if ((flags & P_I) && (type == EF_BAD)) {
-               /* Figure out where to put the ship */
-               /* First, figure out the distance from the two */
-               rx = diffx((int)ship.shp_x, x);
-               ry = diffy((int)ship.shp_y, y);
-               /* Next, determine which direction to add it to the center */
-               /* We can only do this if imaging and we have gotten the center
-                  up above by imaging the sectors. */
-               rx = deltax(x, ns.range.lx) + rx;
-               ry = deltay(y, ns.range.ly) + ry;
+               rx = deltx(&ns.range, ship.shp_x);
+               ry = delty(&ns.range, ship.shp_y);
                /* &~0x20 makes it a cap letter */
                rad[ry][rx] = (*mchr[(int)ship.shp_type].m_name) & ~0x20;
            }
@@ -230,15 +223,8 @@ satmap(int x, int y, int eff, int range, int flags, int type)
            }
            /* If we are imaging *and* drawing the map */
            if ((flags & P_I) && (type == EF_BAD)) {
-               /* Figure out where to put the unit */
-               /* First, figure out the distance from the two */
-               rx = diffx((int)land.lnd_x, x);
-               ry = diffy((int)land.lnd_y, y);
-               /* Next, determine which direction to add it to the center */
-               /* We can only do this if imaging and we have gotten the center
-                  up above by imaging the sectors. */
-               rx = deltax(x, ns.range.lx) + rx;
-               ry = deltay(y, ns.range.ly) + ry;
+               rx = deltx(&ns.range, land.lnd_x);
+               ry = delty(&ns.range, land.lnd_y);
                /* &~0x20 makes it a cap letter */
                rad[ry][rx] = (*lchr[(int)land.lnd_type].l_name) & ~0x20;
            }