Fix march not to wipe out concurrent updates

March code reads the land units into a land unit list, and writes them
back when it changes them, e.g. when a land unit stops.  If a land
unit changes in the land unit file while it is in such a land unit
list, the copy in the land unit list becomes stale, and must not be
used.

To that end, do_unit_move() calls lnd_mar() after prompting for path
or destination.  lnd_mar() re-reads all the land units.
Unfortunately, it still writes back stale copies in certain
circumstances.  Known ways to trigger such writes:

* Deity loads land unit onto a ship or land unit

* Land unit's crew killed just right, e.g. by collateral damage from
  interdiction, followed by additional updates, such as shell fire
  damage

* Sector no longer owned or allied, e.g. allied sector captured by an
  enemy (own sector would kill or retreat the land unit)

Writing a stale copy wipes out the updates that made the copy stale,
and triggers a seqno mismatch oops.  For instance, damage that follows
killing of all crew by collateral damage from interdiction is wiped
out.  If no damage follows, we still get a generation oops.

diff --git a/src/lib/subs/lndsub.c b/src/lib/subs/lndsub.c
index 9a414b90b5417b5080b6ec8fa3b604c96d200250..5bc2c329adaba507713563b4c8a08650859c103e 100644 (file)
--- a/src/lib/subs/lndsub.c
+++ b/src/lib/subs/lndsub.c
@@ -460,8 +460,8 @@ lnd_mar(struct emp_qelem *list, double *minmobp, double *maxmobp,
     struct emp_qelem *qp;
     struct emp_qelem *next;
     struct ulist *llp;
     struct emp_qelem *qp;
     struct emp_qelem *next;
     struct ulist *llp;

+    struct lndstr *lp;

     struct sctstr sect;
     struct sctstr sect;

-    struct lndstr land;

     coord allx;
     coord ally;
     int first = 1;
     coord allx;
     coord ally;
     int first = 1;


@@ -473,54 +473,54 @@ lnd_mar(struct emp_qelem *list, double *minmobp, double *maxmobp,
     for (qp = list->q_back; qp != list; qp = next) {
        next = qp->q_back;
        llp = (struct ulist *)qp;
     for (qp = list->q_back; qp != list; qp = next) {
        next = qp->q_back;
        llp = (struct ulist *)qp;

-       getland(llp->unit.land.lnd_uid, &land);
-       if (land.lnd_own != actor) {
+       lp = &llp->unit.land;
+       getland(lp->lnd_uid, lp);
+       if (lp->lnd_own != actor) {

            mpr(actor, "%s was disbanded at %s\n",
            mpr(actor, "%s was disbanded at %s\n",

-               prland(&land), xyas(land.lnd_x, land.lnd_y, actor));
+               prland(lp), xyas(lp->lnd_x, lp->lnd_y, actor));

            emp_remque((struct emp_qelem *)llp);
            free(llp);
            continue;
        }
            emp_remque((struct emp_qelem *)llp);
            free(llp);
            continue;
        }

-       if (land.lnd_ship >= 0) {
+       if (lp->lnd_ship >= 0) {

            lnd_stays(actor, "is on a ship", llp);
            continue;
        }
            lnd_stays(actor, "is on a ship", llp);
            continue;
        }

-       if (land.lnd_land >= 0) {
+       if (lp->lnd_land >= 0) {

            lnd_stays(actor, "is on a unit", llp);
            continue;
        }
            lnd_stays(actor, "is on a unit", llp);
            continue;
        }

-       if (!getsect(land.lnd_x, land.lnd_y, &sect)) {
+       if (!getsect(lp->lnd_x, lp->lnd_y, &sect)) {

            lnd_stays(actor, "was sucked into the sky by a strange looking spaceland", llp);    /* heh -KHS */
            continue;
        }
            lnd_stays(actor, "was sucked into the sky by a strange looking spaceland", llp);    /* heh -KHS */
            continue;
        }

-       if (!(lchr[(int)llp->unit.land.lnd_type].l_flags & L_SPY) &&
-           !(lchr[(int)llp->unit.land.lnd_type].l_flags & L_TRAIN) &&
-           llp->unit.land.lnd_item[I_MILIT] == 0) {
+       if (!(lchr[lp->lnd_type].l_flags & L_SPY) &&
+           !(lchr[lp->lnd_type].l_flags & L_TRAIN) &&
+           lp->lnd_item[I_MILIT] == 0) {

            lnd_stays(actor, "has no mil on it to guide it", llp);
            continue;
        }
        if (relations_with(sect.sct_own, actor) != ALLIED &&
            lnd_stays(actor, "has no mil on it to guide it", llp);
            continue;
        }
        if (relations_with(sect.sct_own, actor) != ALLIED &&

-           !(lchr[(int)llp->unit.land.lnd_type].l_flags & L_SPY) &&
+           !(lchr[lp->lnd_type].l_flags & L_SPY) &&

            sect.sct_own) {
            sprintf(mess, "has been kidnapped by %s", cname(sect.sct_own));
            lnd_stays(actor, mess, llp);
            continue;
        }
        if (first) {
            sect.sct_own) {
            sprintf(mess, "has been kidnapped by %s", cname(sect.sct_own));
            lnd_stays(actor, mess, llp);
            continue;
        }
        if (first) {

-           allx = land.lnd_x;
-           ally = land.lnd_y;
+           allx = lp->lnd_x;
+           ally = lp->lnd_y;

            first = 0;
        }
            first = 0;
        }

-       if (land.lnd_x != allx || land.lnd_y != ally)
+       if (lp->lnd_x != allx || lp->lnd_y != ally)

            *togetherp = 0;
            *togetherp = 0;

-       if (land.lnd_mobil + 1 < (int)llp->mobil) {
-           llp->mobil = land.lnd_mobil;
+       if (lp->lnd_mobil + 1 < (int)llp->mobil) {
+           llp->mobil = lp->lnd_mobil;

        }
        if (llp->mobil < *minmobp)
            *minmobp = llp->mobil;
        if (llp->mobil > *maxmobp)
            *maxmobp = llp->mobil;
        }
        if (llp->mobil < *minmobp)
            *minmobp = llp->mobil;
        if (llp->mobil > *maxmobp)
            *maxmobp = llp->mobil;

-       llp->unit.land = land;

     }
 }
 
     }
 }