Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uwm.edu!rpi!rpi.edu!rodney
From: rodney@dali.ipl.rpi.edu (Rodney Peck II)
Newsgroups: gnu.g++
Subject: argument mixup -- register name typo?
Message-ID: <RODNEY.89Nov30212038@dali.ipl.rpi.edu>
Date: 1 Dec 89 02:20:46 GMT
Distribution: gnu
Organization: Rensselaer Polytechnic Institute Image Processing Lab, Troy NY
Lines: 78

Help!
I think I unwittingly found a program (maybe a typo?) in the argument passing
in g++.  Here's what happens...(I've got a conditional bkpt to catch the problem
here)

Starting program: /home/rodney/courses/paradigm/bank/main 

Bpt 1, enqueue_PSbqueue_PScitizen ($this=(struct bqueue *) 0x140ac, patron=(struct citizen *) 0x14) (bqueue.cc line 76)
(gdb) up
Reading in symbols for citizen.cc...done.
#1  0x2788 in enter_bank_PScitizen ($this=(struct citizen *) 0x15ed8) (citizen.cc line 71)
(gdb) print this
$1 = (struct citizen *) 0x15ed8
(gdb) down
#0  enqueue_PSbqueue_PScitizen ($this=(struct bqueue *) 0x140ac, patron=(struct citizen *) 0x14) (bqueue.cc line 76)
(gdb) print patron
$2 = (struct citizen *) 0x14
(gdb) print $i1
$3 = 89816
(gdb) print/x $i1
$4 = 0x00015ed8
(gdb) print/x $l1
$5 = 0x00000014
(gdb) 

---
portion of program...

bqueue.cc which is the code for bqueue::enqueue

void bqueue::enqueue(citizen *patron)
{
=>if (head == 0) tail = 0;
  for(node *P=tail;1;P=P->prev) {
    if ((P==0) || !condition((void *)patron,(void *)P->info))
      break;
  }
  insert_before(P,new node(patron));
  tickle_queue();
}

The breakpoint is where the arrow is pointing above.

void citizen::enter_bank() {
  if (type <= KNIGHT) schedule_entrance();
// get in line
  entrance_time = Events.time;	// set the time this one came in to now
// now, get in line.  The queue will alert the teller that I'm here
=>entrance.enqueue(this);
}

The part of citizen.cc which calls bqueue::enqueue.  Again, the arrow points
to the part in question.

As you can see from the prints and backtraces, when in enter_bank, `this' has
a proper value and should be passed to entrance.enqueue properly.  In enqueue,
however, it actually gets a 0x14.  This corresponds to register $i1 but
register $l1 has the actual value that should have been passed.   In fact, if
I put a conditional breakpoint in there and have it assign $l1 to $i1 and
continue, everything works fine.  Oddly, this problem doesn't always appear.
Sometimes, to make things worse, the program executes perfectly, but not often.



HELP!!!

Here's the version info:
dali.ipl.rpi.edu% g++ -v
g++ version 1.35.1-
dali.ipl.rpi.edu% gcc -v
gcc version 1.36
dali.ipl.rpi.edu% 


Please reply quickly if you have any idea what is happening, this project is
due tomorrow!
--
Rodney


Brought to you by Super Global Mega Corp .com