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fix invalid pointer dereference in morguemon

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On 3/23/2015 6:41 PM, a bug reporter wrote:
> If the game generates a graveyard, the graveyard places a normal
> demon, but all normal demons are extinct at the time, then morguemon (at
> mkroom.c line 423) indexes mons with NON_PM (the return value of
> ndemon() if it can't find a reference), which is an invalid pointer
> dereference. According to the testbench, this mostly seems to happen on
> dlvl 12.

This fixes the code violation, but the logic will now drop down to the
ghost/wraith/zombie code when that happens.

Is that desireable, or should something else happen (for variety)?
This commit is contained in:
nhmall
2015-03-24 19:20:14 -04:00
parent d787f45dcb
commit a1cc33d6ae
2 changed files with 14 additions and 4 deletions
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2
doc/fixes35.0
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@@ -880,6 +880,8 @@ message inconsistency: death message "swallowed <mon> whole" was preceded
by "You bite into"
improve the messaging when a monster you can't see is causing an obstruction
add option mention_walls, which gives feedback when bumping against a wall
fix invalid pointer dereference in morguemon if ndemon returns NON_PM
Platform- and/or Interface-Specific Fixes
-----------------------------------------

16
src/mkroom.c
View File

@@ -1,4 +1,4 @@
/* NetHack 3.5 mkroom.c $NHDT-Date$ $NHDT-Branch$:$NHDT-Revision$ */
/* NetHack 3.5 mkroom.c $NHDT-Date: 1427239202 2015/03/24 23:20:02 $ $NHDT-Branch: master $:$NHDT-Revision: 1.16 $ */
/* NetHack 3.5 mkroom.c $Date: 2012/01/10 17:47:19 $ $Revision: 1.15 $ */
/* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
/* NetHack may be freely redistributed. See license for details. */
@@ -408,9 +408,17 @@ morguemon()
{
register int i = rn2(100), hd = rn2(level_difficulty());
if(hd > 10 && i < 10)
return((Inhell || In_endgame(&u.uz)) ? mkclass(S_DEMON,0) :
&mons[ndemon(A_NONE)]);
if(hd > 10 && i < 10) {
if (Inhell || In_endgame(&u.uz)) {
return(mkclass(S_DEMON,0));
} else {
int ndemon_res = ndemon(A_NONE);
if (ndemon_res != NON_PM)
return(&mons[ndemon_res]);
/* else do what? As is, it will drop to ghost/wraith/zombie */
}
}
if(hd > 8 && i > 85)
return(mkclass(S_VAMPIRE,0));