Disable nested execute. The execute protocol is flawed and cannot be

implemented correctly by asynchronous clients --- unless a client
waits for a prompt after sending the execute command and its argument,
it is prone to send more input before the C_EXECUTE arrives.  That
input overtakes the contents of the script file.  This is almost
certain to happen when the execute is in a script file.  Disabling
that is probably more useful and certainly less painful than
documenting this mess.  The client rejects nested execute since
servcmd.c rev. 1.42.
(EXEC): new.
(player_coms): Require it for execute.
(player_set_nstat): Set it in nstat.
(execute): Clear it in nstat.

include/player.h

@@ -46,6 +46,7 @@
 #define SANCT		(bit(1) | VIS)
 #define NORM		(bit(2) | VIS)
 #define GOD		(bit(3) | NORM | VIS)
+#define EXEC		bit(5)
 #define	CAP		bit(6)
 #define	MONEY		bit(7)
 

src/lib/player/empmod.c

@@ -100,7 +100,7 @@ struct cmndstr player_coms[] = {
      0, edit, C_MOD, GOD},
     {"enable", 0, enab, C_MOD, GOD},
     {"enlist <SECTS> <NUM>", 2, enli, C_MOD, NORM + MONEY + CAP},
-    {"execute <INPUT FILE>", 0, execute, 0, VIS},
+    {"execute <INPUT FILE>", 0, execute, 0, VIS + EXEC },
     {"explore <c|m> <SECT> <NUM> <PATH|DESTINATION>",
      1, explore, C_MOD, NORM + MONEY + CAP},
     {"financial", 0, fina, 0, NORM},

src/lib/player/init_nats.c

@@ -82,5 +82,6 @@ player_set_nstat(struct player *pl, struct natstr *np)
 	pl->nstat |= MONEY;
     if (np->nat_stat == STAT_ACTIVE && !influx(np))
 	pl->nstat |= CAP;
+    pl->nstat |= EXEC;
     return pl->nstat;
 }

src/lib/player/player.c

@@ -261,6 +261,7 @@ execute(void)
     prexec(p);
 
     while (!failed && status()) {
+	player->nstat &= ~EXEC;
 	if (recvclient(buf, sizeof(buf)) < 0)
 	    break;
 	if (parse(buf, scanspace, player->argp, player->comtail,
@@ -278,6 +279,7 @@ execute(void)
     if (failed) {
 	while (recvclient(buf, sizeof(buf)) >= 0) ;
     }
+
     pr("Execute : %s\n", failed ? "aborted" : "terminated");
     player->eof = 0;
     return RET_OK;