Re: GHC 6.8.1 on powerpc OS X 10.5

15 Nov 2007

      Deborah Goldsmith wrote:
...
I asked internally at Apple about this and got the following response:
...
...
...
obvious symptom: stage2 compiler segfaults, gdb reports:
...
Program received signal SIGTRAP, Trace/breakpoint trap.
0x8fe0100c in __dyld__dyld_start ()
Ignore that. `continue` to actually run the program and get to the
real error.
Deborah
Ah, thanks.  It seems stage2/ghc-inplace may be a bit stripped, but
stage2/ghc-6.8.1 gives a legible backtrace:
...
pamac-cek10:stage2 chrisk$ gdb ghc-6.8.1
GNU gdb 6.3.50-20050815 (Apple version gdb-768) (Tue Oct  2 04:11:19 UTC 2007)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "powerpc-apple-darwin"...
warning: Unable to read symbols for
"GNUreadline.framework/Versions/A/GNUreadline" (file not found).
warning: Unable to read symbols for "GMP.framework/Versions/A/GMP" (file not
found).
Reading symbols for shared libraries ... done

...
(gdb) run --make /tmp/t.hs -o /tmp/t
Starting program:
/Users/chrisk/Documents/projects/haskell/build/ghc-6.8.1/ghc-6.8.1/compiler/stage2/ghc-6.8.1
--make /tmp/t.hs -o /tmp/t
Reading symbols for shared libraries +..+... done
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x4082000c
0x012ba9c8 in stg_ap_p_fast ()
...
(gdb) bt
#0  0x012ba9c8 in stg_ap_p_fast ()
#1  0x010d79ec in base_GHCziIOBase_noDuplicate_info ()
#2  0x01290e58 in schedule (initialCapability=0x41810070, task=0x38600000) at
Schedule.c:621
#3  0x012933c8 in scheduleWaitThread (tso=0x2680000, ret=0x0, cap=0x14c4318)
at Schedule.c:2500
#4  0x01285040 in rts_evalIO (cap=0x14c4318, p=0x13f40b4, ret=0x0) at RtsAPI.c:476
#5  0x0129d310 in ioManagerStart () at posix/Signals.c:151
#6  0x0128841c in hs_init (argc=0xbffff4a8, argv=0xbffff4ac) at RtsStartup.c:279
#7  0x01288464 in startupHaskell (argc=5, argv=0xbffff594, init_root=0x113cc
<__stginit_ZCMain>) at RtsStartup.c:290
#8  0x0127ebbc in real_main () at Main.c:57
#9  0x0127ed1c in main (argc=5, argv=0xbffff594) at Main.c:153
...
(gdb) disassemble
Dump of assembler code for function stg_ap_p_fast:
0x012ba9b0 :	andi.   r31,r14,3	
 And Immediate (to get the two least significant bits of r14)
0x012ba9b4 :	cmpwi   r31,1
 Equiv. to cmpi 0,0,r31,1
 Compare Immediate
0x012ba9b8 :	beq-    0x12ba9e0 
 Branch if equal
 (not taken, obviously, since the the next instructions are the fatal ones)
0x012ba9bc :	li      r31,-4
 Load Immediate (I believe -4 is the opposite bit pattern to 3)
0x012ba9c0 :	and     r14,r14,r31
 AND (to clear the two least significant bits of r14)
0x012ba9c4 :	lwz     r31,0(r14)
 Load Word and Zero
0x012ba9c8 :	lha     r31,-4(r31)
[ The error was for the above operation: Load Halfword Algebraic
  destination general purpose register r31
A quick descent of the stack prints the single source lines:

Initial frame selected; you cannot go up.
(gdb) down
#8  0x0127ebbc in real_main () at Main.c:57
57	    startupHaskell(progargc,progargv,__stginit_ZCMain);
(gdb) down
#7  0x01288464 in startupHaskell (argc=5, argv=0xbffff594, init_root=0x113cc
<__stginit_ZCMain>) at RtsStartup.c:290
290	    hs_init(&argc, &argv);
(gdb) down
#6  0x0128841c in hs_init (argc=0xbffff4a8, argv=0xbffff4ac) at RtsStartup.c:279
279	    ioManagerStart();
(gdb) down
#5  0x0129d310 in ioManagerStart () at posix/Signals.c:151
151		rts_evalIO(cap,&base_GHCziConc_ensureIOManagerIsRunning_closure,NULL);
(gdb) down
#4  0x01285040 in rts_evalIO (cap=0x14c4318, p=0x13f40b4, ret=0x0) at RtsAPI.c:476
476	    return scheduleWaitThread(tso,ret,cap);
(gdb) down

#3  0x012933c8 in scheduleWaitThread (tso=0x2680000, ret=0x0, cap=0x14c4318) at
Schedule.c:2500
2500	    cap = schedule(cap,task);
(gdb) down

#2  0x01290e58 in schedule (initialCapability=0x41810070, task=0x38600000) at
Schedule.c:621
621		r = StgRun((StgFunPtr) stg_returnToStackTop, &cap->r);
(gdb) print r
$1 = (StgRegTable *) 0xabdffffc
(gdb) print &cap->r
$5 = (StgRegTable *) 0x7ddf7380
(gdb) print stg_returnToStackTop
$2 = {} 0x12b3784 
(gdb) down

#1  0x010d79ec in base_GHCziIOBase_noDuplicate_info ()
(gdb) down

#0  0x012ba9c8 in stg_ap_p_fast ()
(gdb) down
Bottom (i.e., innermost) frame selected; you cannot go down.

And disassemle the fatality

  source -4 displaced r31 ]
...
0x012ba9cc :	rlwinm  r31,r31,2,0,29
0x012ba9d0 :	addis   r31,r31,313
0x012ba9d4 :	lwz     r31,-28940(r31)
0x012ba9d8 :	mtctr   r31
0x012ba9dc :	bctr
0x012ba9e0 :	addi    r22,r22,0
0x012ba9e4 :	lwz     r31,-1(r14)
0x012ba9e8 :	mtctr   r31
0x012ba9ec :	bctr
0x012ba9f0 :	addi    r22,r22,-8
0x012ba9f4 :	stw     r15,4(r22)
0x012ba9f8 :	b       0x12b666c 
0x012ba9fc :	lwz     r31,0(r14)
0x012baa00 :	lha     r31,-10(r31)
0x012baa04 :	cmplwi  r31,0
0x012baa08 :	bgt-    0x12baa88 
0x012baa0c :	li      r3,0
0x012baa10 :	li      r4,2441
0x012baa14 :	bl      0x1287c80 <_assertFail>
0x012baa18 :	cmpwi   r31,1
0x012baa1c :	beq-    0x12baac8 
0x012baa20 :	addi    r22,r22,-8
0x012baa24 :	stw     r15,4(r22)
0x012baa28 :	cmplwi  r31,4
0x012baa2c :	blt-    0x12baa8c 
0x012baa30 :	li      r30,16
0x012baa34 :	add     r25,r25,r30
0x012baa38 :	cmplw   r25,r26
0x012baa3c :	bgt-    0x12baa94 
0x012baa40 :	addi    r29,r25,4
0x012baa44 :	subf    r30,r30,r29
0x012baa48 :	lis     r29,298
0x012baa4c :	ori     r29,r29,60928
0x012baa50 :	stw     r29,0(r30)
0x012baa54 :	addi    r31,r31,-1
0x012baa58 :	sth     r31,4(r30)
0x012baa5c :	stw     r14,8(r30)
0x012baa60 :	li      r31,1
0x012baa64 :	sth     r31,6(r30)
0x012baa68 :	li      r31,0
0x012baa6c :	cmplwi  r31,1
0x012baa70 :	blt-    0x12baaa8 
0x012baa74 :	mr      r14,r30
0x012baa78 :	addi    r22,r22,8
0x012baa7c :	lwz     r31,0(r22)
0x012baa80 :	mtctr   r31
0x012baa84 :	bctr
0x012baa88 :	b       0x12baa18 
0x012baa8c :	add     r14,r14,r31
0x012baa90 :	b       0x12baa30 
0x012baa94 :	stw     r30,112(r27)
0x012baa98 :	lis     r31,299
0x012baa9c :	ori     r31,r31,26220
0x012baaa0 :	stw     r31,0(r22)
0x012baaa4 :	b       0x12af8ac <__stg_gc_enter_1>
0x012baaa8 :	addi    r29,r31,1
0x012baaac :	rlwinm  r29,r29,2,0,29
0x012baab0 :	lwzx    r29,r22,r29
0x012baab4 :	addi    r28,r30,12
0x012baab8 :	rlwinm  r23,r31,2,0,29
0x012baabc :	stwx    r29,r28,r23
0x012baac0 :	addi    r31,r31,1
0x012baac4 :	b       0x12baa6c 
0x012baac8 :	addi    r22,r22,0
0x012baacc :	addi    r14,r14,1
0x012baad0 :	li      r31,-4
0x012baad4 :	and     r31,r14,r31
0x012baad8 :	lwz     r31,0(r31)
0x012baadc :	mtctr   r31
0x012baae0 :	bctr
0x012baae4 :	b       0x12baae4 
End of assembler dump.
Where was the evil value in r14 filled in? I look up the stack and
disassemble, but never find the instructions which assign to r14.  The
must be in another subroutine (?).

What about printing stuff?

#2  0x01290e58 in schedule (initialCapability=0x41810070, task=0x38600000) at
Schedule.c:621
621		r = StgRun((StgFunPtr) stg_returnToStackTop, &cap->r);
(gdb) list
616		break;
617		
618	    case ThreadRunGHC:
619	    {
620		StgRegTable *r;
621		r = StgRun((StgFunPtr) stg_returnToStackTop, &cap->r);
622		cap = regTableToCapability(r);
623		ret = r->rRet;
624		break;
625	    }

#3  0x012933c8 in scheduleWaitThread (tso=0x2680000, ret=0x0, cap=0x14c4318) at
Schedule.c:2500
2500	    cap = schedule(cap,task);
(gdb) print *cap
$8 = {
  f = {
    stgGCEnter1 = 0x12af8ac <__stg_gc_enter_1>,
    stgGCFun = 0x12aff54 <__stg_gc_fun>
  },
  r = {
    rR1 = {
      w = 0,
      a = 0x0,
      c = 0,
      i8 = 0 '\0',
      f = 0,
      i = 0,
      p = 0x0,
      cl = 0x0,
      offset = 0,
      b = 0x0,
      t = 0x0
    },
    rR2 = {
      w = 0,
      a = 0x0,
      c = 0,
      i8 = 0 '\0',
      f = 0,
      i = 0,
      p = 0x0,
      cl = 0x0,
      offset = 0,
      b = 0x0,
      t = 0x0
    },
    rR3 = {
      w = 0,
      a = 0x0,
      c = 0,
      i8 = 0 '\0',
      f = 0,
      i = 0,
      p = 0x0,
      cl = 0x0,
      offset = 0,
      b = 0x0,
      t = 0x0
    },
    rR4 = {
      w = 0,
      a = 0x0,
      c = 0,
      i8 = 0 '\0',
      f = 0,
      i = 0,
      p = 0x0,
      cl = 0x0,
      offset = 0,
      b = 0x0,
      t = 0x0
    },
    rR5 = {
      w = 0,
      a = 0x0,
      c = 0,
      i8 = 0 '\0',
      f = 0,
      i = 0,
      p = 0x0,
      cl = 0x0,
      offset = 0,
      b = 0x0,
      t = 0x0
    },
    rR6 = {
      w = 0,
      a = 0x0,
      c = 0,
      i8 = 0 '\0',
      f = 0,
      i = 0,
      p = 0x0,
      cl = 0x0,
      offset = 0,
      b = 0x0,
      t = 0x0
    },
    rR7 = {
      w = 0,
      a = 0x0,
      c = 0,
      i8 = 0 '\0',
      f = 0,
      i = 0,
      p = 0x0,
      cl = 0x0,
      offset = 0,
      b = 0x0,
      t = 0x0
    },
    rR8 = {
      w = 0,
      a = 0x0,
      c = 0,
      i8 = 0 '\0',
      f = 0,
      i = 0,
      p = 0x0,
      cl = 0x0,
      offset = 0,
      b = 0x0,
      t = 0x0
    },
    rR9 = {
      w = 0,
      a = 0x0,
      c = 0,
      i8 = 0 '\0',
      f = 0,
      i = 0,
      p = 0x0,
      cl = 0x0,
      offset = 0,
      b = 0x0,
      t = 0x0
    },
    rR10 = {
      w = 0,
      a = 0x0,
      c = 0,
      i8 = 0 '\0',
      f = 0,
      i = 0,
      p = 0x0,
      cl = 0x0,
      offset = 0,
      b = 0x0,
      t = 0x0
    },
    rF1 = 0,
    rF2 = 0,
    rF3 = 0,
    rF4 = 0,
    rD1 = 0,
    rD2 = 0,
    rL1 = 0,
    rSp = 0x0,
    rSpLim = 0x0,
    rHp = 0x0,
    rHpLim = 0x0,
    rCurrentTSO = 0x2680000,
    rNursery = 0x24004d0,
    rCurrentNursery = 0x2600fe0,
    rCurrentAlloc = 0x2601000,
    rHpAlloc = 0,
    rmp_tmp_w = 0,
    rmp_tmp1 = {
      _mp_alloc = 0,
      _mp_size = 0,
      _mp_d = 0x0
    },
    rmp_tmp2 = {
      _mp_alloc = 0,
      _mp_size = 0,
      _mp_d = 0x0
    },
    rmp_result1 = {
      _mp_alloc = 0,
      _mp_size = 0,
      _mp_d = 0x0
    },
    rmp_result2 = {
      _mp_alloc = 0,
      _mp_size = 0,
      _mp_d = 0x0
    },
    rRet = 0,
    rSparks = {
      base = 0x2362000,
      lim = 0x2366000,
      hd = 0x2362000,
      tl = 0x2362000
    }
  },
  no = 0,
  running_task = 0x2400580,
  in_haskell = rtsTrue,
  run_queue_hd = 0x14076d0,
  run_queue_tl = 0x14076d0,
  suspended_ccalling_tasks = 0x0,
  mut_lists = 0x2400320,
  spare_workers = 0x0,
  lock = {
    __sig = 1297437784,
    __opaque = '\0' , "\b", '\0' 
  },
  returning_tasks_hd = 0x0,
  returning_tasks_tl = 0x0,
  wakeup_queue_hd = 0x14076d0,
  wakeup_queue_tl = 0x14076d0,
  free_tvar_watch_queues = 0x14076c0,
  free_invariant_check_queues = 0x14076c4,
  free_trec_chunks = 0x14076c8,
  free_trec_headers = 0x14076cc,
  transaction_tokens = 0
}

(gdb) print task
$10 = (Task *) 0x2400580
(gdb) print *task
$11 = {
  id = 0xa032c074,
  cap = 0x14c4318,
  stopped = rtsFalse,
  suspended_tso = 0x0,
  tso = 0x2680000,
  stat = NoStatus,
  ret = 0x0,
  cond = {
    __sig = 1129270852,
    __opaque = '\0' , "\002"
  },
  lock = {
    __sig = 1297437784,
    __opaque = '\0' , "\b", '\0' 
  },
  wakeup = rtsFalse,
  elapsedtimestart = 1195167550991792,
  muttimestart = 12791,
  mut_time = 0,
  mut_etime = 0,
  gc_time = 0,
  gc_etime = 0,
  prev = 0x0,
  next = 0x0,
  return_link = 0x0,
  all_link = 0x0,
  prev_stack = 0x0
}
(gdb) print *tso
$13 = {
  header = {
    info = 0x12b3464
  },
  link = 0x14076d0,
  global_link = 0x14076d0,
  what_next = 1,
  why_blocked = 0,
  flags = 1,
  block_info = {
    closure = 0x0,
    tso = 0x0,
    fd = 0,
    target = 0
  },
  id = 1,
  saved_errno = 0,
  bound = 0x2400580,
  cap = 0x14c4318,
  trec = 0x14076cc,
  blocked_exceptions = 0x14076d0,
  stack_size = 241,
  max_stack_size = 2080753,
  sp = 0x26803ec,
  stack = 0x268003c
}
(gdb) list (with list - and list -)
2475	    Task *task;
2476	
2477	    // We already created/initialised the Task
2478	    task = cap->running_task;
2479	
2480	    // This TSO is now a bound thread; make the Task and TSO
2481	    // point to each other.
2482	    tso->bound = task;
2483	    tso->cap = cap;
2484	
2485	    task->tso = tso;
2486	    task->ret = ret;
2487	    task->stat = NoStatus;
2488	
2489	    appendToRunQueue(cap,tso);
2490	
2491	    debugTrace(DEBUG_sched, "new bound thread (%lu)", (unsigned long)tso->id);
2492	
2493	#if defined(GRAN)
2494	    /* GranSim specific init */
2495	    CurrentTSO = m->tso;                // the TSO to run
2496	    procStatus[MainProc] = Busy;        // status of main PE
2497	    CurrentProc = MainProc;             // PE to run it on
2498	#endif
2499	
2500	    cap = schedule(cap,task);
2501	
2502	    ASSERT(task->stat != NoStatus);
2503	    ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
2504	

#4  0x01285040 in rts_evalIO (cap=0x14c4318, p=0x13f40b4, ret=0x0) at RtsAPI.c:476
476	    return scheduleWaitThread(tso,ret,cap);
(gdb) print p
$16 = (HaskellObj) 0x13f40b4
(gdb) print *p
$17 = {
  header = {
    info = 0x12b3324
  },
  payload = 0x13f40b8
}
(gdb) list
471	rts_evalIO (Capability *cap, HaskellObj p, /*out*/HaskellObj *ret)
472	{
473	    StgTSO* tso;
474	
475	    tso = createStrictIOThread(cap, RtsFlags.GcFlags.initialStkSize, p);
476	    return scheduleWaitThread(tso,ret,cap);
477	}
478	
479	/*
480	 * rts_evalStableIO() is suitable for calling from Haskell.  It

#5  0x0129d310 in ioManagerStart () at posix/Signals.c:151
151		rts_evalIO(cap,&base_GHCziConc_ensureIOManagerIsRunning_closure,NULL);
(gdb) list
146	{
147	    // Make sure the IO manager thread is running
148	    Capability *cap;
149	    if (io_manager_pipe < 0) {
150		cap = rts_lock();
151		rts_evalIO(cap,&base_GHCziConc_ensureIOManagerIsRunning_closure,NULL);
152		rts_unlock(cap);
153	    }
154	}
155	#endif

And this is the limit of what I can do with gdb for now.

Re: GHC 6.8.1 on powerpc OS X 10.5

Chris Kuklewicz