From:	Chris Frolik <frolikcc AT indy DOT net>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Getting useful information from the traceback
Date:	Mon, 15 Dec 1997 22:43:29 -0500
Organization:	IndyNet - Indys Internet Gateway (info AT indy DOT net)
Lines:	37
Message-ID:	<3495F8E1.1C87@indy.net>
NNTP-Posting-Host:	ip75-108.ts.indy.net
Mime-Version:	1.0
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

I am writing a program with DJGPP + Allegro, and I have a bug in my
program which causes the program to crash and print the registers and
traceback onto the screen.  Thanks to the wonderful symify utility, I
can locate exactly which line number and which file the problem occurs
in.  However, now that I know *where* the problem occurs, I am still not
sure *why*.  Is there any useful information I can get out of the
traceback to tell me what's happening?  For example, am I dividing by
zero, writing beyond the bounds of an array, etc?  Is there any way to
determine this?  Here is the traceback:

Shutting down Allegro
Exiting due to signal SIGSEGV
Page fault at eip=0000e5c7, error=0006
eax=fff607b8 ebx=00000000 ecx=c6047600 edx=00000000 esi=7fc7c0bb
edi=00000000
ebp=fff608dc esp=fff607b8 program=C:\CHRIS\CPP\SPACEWAR\MAPED.EXE
cs: sel=00a7  base=828fc000  limit=fff60fff
ds: sel=00af  base=828fc000  limit=fff60fff
es: sel=00af  base=828fc000  limit=fff60fff
fs: sel=00bf  base=00000000  limit=ffffffff
gs: sel=00bf  base=00000000  limit=ffffffff
ss: sel=00af  base=828fc000  limit=fff60fff

Call frame traceback EIPs:
  0x0000e5c7   _test_seg_size__12galaxy_tableiii+131, line 162 of
tiles.cc
  0x0000e65b   _select_seg_size__12galaxy_tableii+55, line 178 of
tiles.cc
  0x00005fc8   _save_map__FP8PACKFILEPc+228, line 40 of save.cc
  0x000041b6   _save_file__Fv+382, line 386 of file.cc


------
Thanks,

-Chris Frolik
frolikcc AT indy DOT net

- Raw text -