On Thu, Sep 19, 2002 at 01:54:34PM -0700, Matt Foltz wrote:
> A builder on my mud is making an area full of land
> mines. When a mob walks across a land mine, it
> triggers a program to make an asound and purge the
> mobs in the room. Problem is that I get these errors
> in the log files:
>
> BUG: Char_from_room: ch not found
> BUG: Extract_char: ch not found
>
> The first error puts all players into some weird
> state, where they don't receive any messages that
> require a descriptor lookup (possibly them simulate a
> non-switched NPC, basically). The second error flat
> out crashed the mud. I haven't changed mppurge,
> char_from_room, or extract_char from how the
> stock/patch is. Has anyone seen this before?
This is a logic bug. Without seeing your code, it is impossible to say
how to fix it. I can explain the problem in general terms and the
general solution to it, though:
In C, you have something like the following:
for ( victim = ch->in_room->people; victim ; victim = victim->next_in_room )
{
if (IS_NPC(victim))
extract_char(victim, TRUE);
}
The problem is that when you extract that first character, the
next_in_room pointer is now f'd up. This is bad, since it no longer
points to who the next person was in the room before you toasted that
one.
The solution? A temporary variable.
for ( victim = ch->in_room->people; victim ; victim = v_next )
{
v_next = victim->next_in_room;
if (IS_NPC(victim))
extract_char(victim, TRUE);
}
You will see this sort of construct all over ROM. Grep for '_next' for
examples.
How you fix your case would, again, depend on the code.
