Segment Fault Issue

Posted by Toy on Sat 04 Dec 2004 10:49 AM — 13 posts, 40,586 views.

Toy Sat 04 Dec 2004 10:49 AM #0

So after a nice compile, the game started up just fine. Problem is upon loading a character *Boom*. So I used gdb to track down where the issue is, and this is what i got.

(gdb)
game_loop () at comm.c:621
621 break;
(gdb)
635 if ( d == last_descriptor )
(gdb)
640 update_handler( );
(gdb)

Program received signal SIGSEGV, Segmentation fault.
0x004861df in get_char_room (ch=0xa229038, argument=0x239cb0 "someone") at handler.c:1864
warning: Source file is more recent than executable.

1864 if ( can_see( ch, rch )
(gdb)
0x7c90eaf0 in ntdll!LdrDisableThreadCalloutsForDll () from ntdll.dll
(gdb)
Single stepping until exit from function ntdll!LdrDisableThreadCalloutsForDll,
which has no line number information.
0x7c9377c1 in ntdll!LdrFindCreateProcessManifest () from ntdll.dll
(gdb)
Single stepping until exit from function ntdll!LdrFindCreateProcessManifest,
which has no line number information.
0x7c90390c in ntdll!RtlCheckRegistryKey () from ntdll.dll
(gdb)
Single stepping until exit from function ntdll!RtlCheckRegistryKey,
which has no line number information.
0x7c9377f0 in ntdll!LdrFindCreateProcessManifest () from ntdll.dll
(gdb)
Single stepping until exit from function ntdll!LdrFindCreateProcessManifest,
which has no line number information.
0x7c90392d in ntdll!RtlCheckRegistryKey () from ntdll.dll
(gdb)
Single stepping until exit from function ntdll!RtlCheckRegistryKey,
which has no line number information.
0x7c9377f5 in ntdll!LdrFindCreateProcessManifest () from ntdll.dll
(gdb)
Single stepping until exit from function ntdll!LdrFindCreateProcessManifest,
which has no line number information.
15 [main] smaug 3916 handle_exceptions: Exception: STATUS_ACCESS_VIOLATION
27214 [main] smaug 3916 open_stackdumpfile: Dumping stack trace to smaug.exe.stackdump

Program exited with code 0305400.
(gdb)

So I checked handler.c at 1864:

/* Find a char in the room. */
CHAR_DATA *get_char_room( CHAR_DATA *ch, char *argument )
{
    char arg[MAX_INPUT_LENGTH];
    CHAR_DATA *rch;
    int number, count, vnum;

    number = number_argument( argument, arg );
    	
	if ( !str_cmp( arg, "self" ) )
		return ch;

    if ( get_trust(ch) >= LEVEL_CODER && is_number( arg ) )
		vnum = atoi( arg );
    else
		vnum = -1;

    count  = 0;

    for ( rch = ch->in_room->first_person; rch; rch = rch->next_in_room )
	if ( can_see( ch, rch ) 
	&& (((nifty_is_name( arg, rch->name ) || (IS_NPC(rch) && nifty_is_name( arg, rch->pcdata->title ))) 
	|| (IS_NPC(rch) && vnum == rch->pIndexData->vnum))))
	{
	    if ( number == 0 && !IS_NPC(rch) )
			return rch;
	    else
	    if ( ++count == number )
			return rch;
	}
    	
	if ( vnum != -1 )
		return NULL;

/* If we didn't find an exact match, run through the list of characters
   again looking for prefix matching, ie gu == guard. Added by Narn, Sept/96 */
    count  = 0;

    for ( rch = ch->in_room->first_person; rch; rch = rch->next_in_room )
    {
		if ( !can_see( ch, rch ) || (!nifty_is_name_prefix( arg, rch->name ) 
		&& (IS_NPC(rch) || (!IS_NPC(rch) && !nifty_is_name_prefix( arg, rch->pcdata->title )))))
	    	continue;
	
		if ( number == 0 && !IS_NPC(rch) )
	    	return rch;
		else
		if ( ++count == number )
	    	return rch;
    }
	return NULL;
}

Error line is in bold. I'm guessing there is an issue with bool can_see, but I don't see it. I'll post can_see next.
Toy

Toy Sat 04 Dec 2004 10:54 AM #1


/* True if char can see victim. */
bool can_see( CHAR_DATA *ch, CHAR_DATA *victim )
{
    if ( !victim )            /* Gorog - panicked attempt to stop crashes */
       	return FALSE;
    
    if ( victim->position == POS_FIGHTING || victim->position < POS_SLEEPING )
		return TRUE;

    if ( !ch )
    {
      	if ( IS_AFFECTED(victim, AFF_INVISIBLE)
      	||   IS_AFFECTED(victim, AFF_HIDE)
      	||   xIS_SET(victim->act, PLR_WIZINVIS) ) 
			return FALSE;
      	else
			return TRUE;
    }

    if ( ch == victim )
		return TRUE;

    if ( !IS_NPC(victim)
    &&   xIS_SET(victim->act, PLR_WIZINVIS)
    &&   get_trust( ch ) < victim->pcdata->wizinvis )
		return FALSE;

    if ( victim->position == POS_FIGHTING || victim->position < POS_SLEEPING )
		return TRUE;
	
    if ( victim->position == POS_FIGHTING || victim->position < POS_SLEEPING )
		return TRUE;

/* SB */
    if ( IS_NPC(victim)   
    &&   xIS_SET(victim->act, ACT_MOBINVIS)
    &&   get_trust( ch ) < victim->mobinvis )
        return FALSE;

    if ( !IS_NPC(ch) && xIS_SET(ch->act, PLR_HOLYLIGHT) )
		return TRUE;
	
/* The miracle cure for blindness? -- Altrag */
    if ( !IS_AFFECTED(ch, AFF_TRUESIGHT) )
    {
		if ( IS_AFFECTED(ch, AFF_BLIND) )
	  		return FALSE;

		if ( room_is_dark( ch->in_room ) && !IS_AFFECTED(ch, AFF_INFRARED) )
	  		return FALSE;

		if ( IS_AFFECTED(victim, AFF_INVISIBLE) && !IS_AFFECTED(ch, AFF_DETECT_INVIS) )
	  		return FALSE;

		if ( IS_AFFECTED(victim, AFF_HIDE)
		&&   !IS_AFFECTED(ch, AFF_DETECT_HIDDEN)
		&&   !victim->fighting
		&&   ( IS_NPC(ch) ? !IS_NPC(victim) : IS_NPC(victim) ) )
	  		return FALSE;
    }    
    return TRUE;
}

Any thoughts?

Toy

Zeno USA Sat 04 Dec 2004 01:30 PM #2

Loading a character? I'm going to say null rch. Can you reproduce that crash, and print ch and rch for me?

Toy Sun 05 Dec 2004 11:40 AM #3

2108 act( AT_ACTION, "$n has entered the game.", ch, NULL, NULL, TO_CANSEE )
;
(gdb)
2110 if ( ch->plr_home != NULL )
(gdb)
2185 if ( ch->pcdata->pet )
(gdb)
2191 do_look( ch, "auto" );
(gdb)
2192 mail_count(ch);
(gdb)
2193 check_loginmsg(ch);
(gdb)
2197 }
(gdb)
game_loop () at comm.c:621
621 break;
(gdb)
635 if ( d == last_descriptor )
(gdb)
640 update_handler( );
(gdb)

Program received signal SIGSEGV, Segmentation fault.
0x004861df in get_char_room (ch=0xa229038, argument=0x239cb0 "someone") at handler.c:1864
1864 if ( can_see( ch, rch )
(gdb)
0x7c90eaf0 in ntdll!LdrDisableThreadCalloutsForDll () from ntdll.dll
(gdb)
Single stepping until exit from function ntdll!LdrDisableThreadCalloutsForDll,
which has no line number information.
0x7c9377c1 in ntdll!LdrFindCreateProcessManifest () from ntdll.dll
(gdb)
Single stepping until exit from function ntdll!LdrFindCreateProcessManifest,
which has no line number information.
0x7c90390c in ntdll!RtlCheckRegistryKey () from ntdll.dll
(gdb)
Single stepping until exit from function ntdll!RtlCheckRegistryKey,
which has no line number information.
0x7c9377f0 in ntdll!LdrFindCreateProcessManifest () from ntdll.dll
(gdb)
Single stepping until exit from function ntdll!LdrFindCreateProcessManifest,
which has no line number information.
0x7c90392d in ntdll!RtlCheckRegistryKey () from ntdll.dll
(gdb)
Single stepping until exit from function ntdll!RtlCheckRegistryKey,
which has no line number information.
0x7c9377f5 in ntdll!LdrFindCreateProcessManifest () from ntdll.dll
(gdb)
Single stepping until exit from function ntdll!LdrFindCreateProcessManifest,
which has no line number information.
6 [main] smaug 2452 handle_exceptions: Exception: STATUS_ACCESS_VIOLATION
113065 [main] smaug 2452 open_stackdumpfile: Dumping stack trace to smaug.exe.stackdump

I can repeat the crash as many times as I want. Tried making a newbie, instead of using an old char. Same affect. Everything was fine through nanny until the update handler call.

As for the rest of what you're asking for, I'm not sure what you mean. :(

Toy

David Haley USA Sun 05 Dec 2004 11:47 AM #4

It means to just type 'print ch' and 'print rch' in gdb to show the values of the ch and rch variables.

Toy Sun 05 Dec 2004 07:40 PM #5

Program received signal SIGSEGV, Segmentation fault.
0x004861df in get_char_room (ch=0xa229038, argument=0x239cb0 "someone") at handler.c:1864
1864 if ( can_see( ch, rch )
(gdb) print ch
$6 = (CHAR_DATA *) 0xa229038
(gdb) print rch
$7 = (CHAR_DATA *) 0xa229038

this what you're looking for?

Toy

Zeno USA Sun 05 Dec 2004 07:57 PM #6

Yeah. Hmm, so neither is null. What is line 1864 of can_see?

Toy Mon 06 Dec 2004 01:34 AM #7

Line 1864 is called to handler.c in get_char_room on the line:

if ( can_see( ch, rch )

as I posted earlier. what's odd though is there's a call to "someone", but there is no word "someone" in handler.c. Could my description macro's be causing it?

/* Description macros. */
#define DISGUISE(ch)            ((!nifty_is_name(ch->name, ch->pcdata->title)) ?   \
								1 : 0)
#define PERS(ch, looker)		( can_see( (looker), (ch) ) ?		\
								( IS_NPC(ch) ? (ch)->short_descr	\
								: ((get_trust(looker) <= LEVEL_IMMORTAL) ? (DISGUISE(ch) ? ch->pcdata->title : (ch)->name ) : (ch)->name)) : ( IS_IMMORTAL(ch) ? "A Great One" : "someone" ))

#define MORPHPERS(ch, looker)   ( can_see( (looker), (ch) ) ?           \
                                (ch)->morph->morph->short_desc       \
                                : "someone" )

Toy

David Haley USA Mon 06 Dec 2004 02:19 AM #8

Quote:
Program received signal SIGSEGV, Segmentation fault.
0x004861df in get_char_room (ch=0xa229038, argument=0x239cb0 "someone") at handler.c:1864
warning: Source file is more recent than executable.

Might want to fix that, too, otherwise your gdb running will be out of synch with your actual code.

Also...

Quote:
Program received signal SIGSEGV, Segmentation fault.
0x004861df in get_char_room (ch=0xa229038, argument=0x239cb0 "someone") at handler.c:1864
1864 if ( can_see( ch, rch )
(gdb)

Here, you should type 'bt' to do a backtrace - that'll show you what's dying where. Single stepping after a segfault is useless.

Toy Mon 06 Dec 2004 12:58 PM #9

I made sure to update the .exe. Didn't notice that, but the problem still exists. I I did a bt like suggested:

Program received signal SIGSEGV, Segmentation fault.
0x004861df in get_char_room (ch=0xa229038, argument=0x239cb0 "someone") at handler.c:1864
1864 if ( can_see( ch, rch )
(gdb) bt
#0 0x004861df in get_char_room (ch=0xa229038, argument=0x239cb0 "someone") at handler.c:1864
#1 0x004b8865 in do_mpechoat (ch=0xa229038,
argument=0x23b97c "A burlap sack, some clothes, and a torch are given to you. Use")
at mud_comm.c:477
#2 0x0049b957 in interpret (ch=0xa229038,
argument=0x23b974 "Someone A burlap sack, some clothes, and a torch are given to you. Use")
at interp.c:681
#3 0x004bff12 in mprog_do_command (
cmnd=0x23c281 "mea $n A burlap sack, some clothes, and a torch are given to you. Use",
mob=0xa229038, actor=0xa2685b8, obj=0x0, vo=0x0, rndm=0x0, ignore=0 '\0',
ignore_ors=0 '\0') at mud_prog.c:2362
#4 0x004bfa81 in mprog_driver (
com_list=0xa118a90 "mpoload 123 1\n\rmpoload 367 1\n\rmpoload 113 1\n\rgive sack 0.$n\n\rgi
ve clothes 0.$n\n\rgive torch 0.$n\n\rmea $n A burlap sack, some clothes, and a torch are given
to you. Use\n\rmea $n these items to help you o"..., mob=0xa229038, actor=0xa2685b8,
obj=0x0, vo=0x0, single_step=0 '\0') at mud_prog.c:2059
#5 0x004c02f7 in mprog_wordlist_check (
arg=0xa268f10 "A Great One has entered the game.\n\r", mob=0xa229038, actor=0xa2685b8,
obj=0x0, vo=0x0, type=0) at mud_prog.c:2471
#6 0x005036ef in aggr_update () at update.c:2104
#7 0x005042ff in update_handler () at update.c:2508
#8 0x0045cfb1 in game_loop () at comm.c:640
#9 0x0045c726 in main (argc=1, argv=0xa052020) at comm.c:291
(gdb)

I'm currently looking at everything from the backtrace right now to see if I can find the issue. Anyone notice anything?

Toy

Zeno USA Mon 06 Dec 2004 01:17 PM #10

#0 0x004861df in get_char_room (ch=0xa229038, argument=0x239cb0 "someone") at handler.c:1864

That looks wrong. It's trying to find a character in the room by the name of "someone". I would think that would make rch null, but that may not be the problem.

Toy Mon 06 Dec 2004 01:50 PM #11

Ok... I just found a weird issue. I tried looking into my area files for that mob program it was calling to and removed it. Now I can log in just fine. Gonna play around witn mob programs some and see if that's the issue.

Toy

David Haley USA Mon 06 Dec 2004 07:53 PM #12

Looks like your mob couldn't see the player in question. Strange that it would crash, though. Look at how $n evaluates to 'Someone'.