Path: utzoo!attcan!uunet!samsung!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!emory!gatech!prism!dali.gatech.edu!iansmith
From: iansmith@dali.gatech.edu (Ian E. Smith)
Newsgroups: comp.mail.mh
Subject: A possible bug in MH6.7
Message-ID: <1990Oct13.104529@dali.gatech.edu>
Date: 13 Oct 90 14:45:29 GMT
Sender: news@prism.gatech.EDU
Reply-To: iansmith@warhol.gatech.edu
Organization: the Software Engineering Research Center's Multimedia Lab
Lines: 53
Keywords:Next ;segmentation violation ; bug

Greetings.  I'm not sure if this is the right newsgroup, but I thought
I might give it a shot... 

I've just gotten MH 6.7 installed on my NeXT and it seemed to be 
working ok until I tried to use repl.  After generating the header
(or informing you that you already have a draft), it promptly gives a 
segmentation violation and crashes hard.  

I have traced the segmentation violation to the following place  in:
$DIST/uip/replsbr.c

    for (nxtbuf = compbuffers, i = ncomps; i--; )
        free (*nxtbuf++);  <-- signal 11 occurs here after a few times

I think that gdb told me it was line #240. I have also determined,
that this is because that the entires in the nxtbuff array (aliased from
compbuffers) beyond a certain value are not available... in other
words, indices above a threshold value are not in the availabe memory
area. I wrote some code to check for the fact the 
bug might be a bug in the code generator of gcc (not handling the
*nxtbuff++ right) :

    for (i=0; i<ncomps; ++i) {
      printf("my free and i is %d\n",i);
      free(nxtbuf[i]);
    }

But in fact it dies when i is 5 as expected.  Also, since ncomps is
generated by:
    ncomps = fmt_compile (cp, &fmt) + 1;

I think that ncomps is right.  (Otherwise, I would think that other
stuff that uses fmt_compile would die... )

The code that mallocs the space is:

    for (i = ncomps; i--; ) 
        if ((*nxtbuf++ = malloc( SBUFSIZ )) == NULL)
            adios (NULLCP, "unable to allocate component buffer");

And I checked and indeed it does iterate the correct number (ncomps)
times.  Now, my question is... what is wrong?

later,
ian

--
"Daddy what's regret?"
"Well son, all I can say is its always better to regret something you
have
done, than to regret something you haven't done. And, if you see you
mother
this afternoon..."  --Gibby