Re: OpenBSD hangs / crashes with Suduku

[Fred Kiefer]

As Sebastian already pointed out not the exception is the problem here, 
but the way we currently implement it.

The exception itself is part of the algorithm of that application. It's 
a sort of structured long jump, when a solution is found somewhere deep 
down in the recursion it jumps back to the top of the stack. Not a very 
nice way to do this, but at least it pretends not to be a goto :-)

On 22.06.2011 11:04, Riccardo Mottola wrote:
> Hi,
>
> I am able to reproduce the problems Sebastian has on my own OpenBSD/x86
> box. I get this problem only on OpenBSD. I use gcc and its standard
> runtime. The same combination appears to work fine on NetBSD or Linux.
>
> The problem happens with "New" inside Sudoku (latest version from CVS of
> GAP).
>
> The happening is:
>
> 1) Sudoku is run normally (not in GDB). Sudokup.apps remains eternally
> at 99% of CPU usage and hangs
> 2) If run inside GDB, I get the same broken crash of Sebastian:
> #0 0x0d8ea287 in NSCountFrames () at NSDebug.m:1009
> #1 0x0d8edf19 in GSPrivateStackAddresses () at NSDebug.m:1112
> #2 0x0d902f5f in -[GSStackTrace init] (self=0x7d17a2e8, _cmd=0x2d8e89e8)
> at NSException.m:605
> #3 0x0d951942 in +[NSObject new] (self=0x2d8cfac0, _cmd=0x2d8cfb40)
> at NSObject.m:1281
> #4 0x0d90387c in -[NSException raise] (self=0x7d17a168, _cmd=0x2d8cfba8)
> at NSException.m:960
> #5 0x0d902e04 in +[NSException raise:format:arguments:] (self=0x2d8cf9c0,
> _cmd=0x2d8cfb90, name=0x3c00615c, format=0x3c006150,
> argList=0xcfbf0a80 "ðR÷\213h¾O'\027\003") at NSException.m:849
> #6 0x0d903cf3 in +[NSException raise:format:] (self=0x2d8cf9c0,
> _cmd=0x3c0060f8, name=0x3c00615c, format=0x3c006150) at NSException.m:835
> #7 0x1c0070ad in -[Sudoku doFind:] (self=0x7e509008, _cmd=0x3c0060d8,
> seen=0x87e36fc8) at Sudoku.m:457
> #8 0x1c006fbe in -[Sudoku doFind:] (self=0x7e509008, _cmd=0x3c0060d8,
> seen=0x87e36fc8) at Sudoku.m:524
> #9 0x1c006fbe in -[Sudoku doFind:] (self=0x7e509008, _cmd=0x3c0060d8,
> seen=0x87e36fc8) at Sudoku.m:524
> #10 0x1c006fbe in -[Sudoku doFind:] (self=0x7e509008, _cmd=0x3c0060d8,
> seen=0x87e36fc8) at Sudoku.m:524
> #11 0x1c006fbe in -[Sudoku doFind:] (self=0x7e509008, _cmd=0x3c0060d8,
> seen=0x87e36fc8) at Sudoku.m:524
>
>
> I can also put a breakpoint in NSException raise and get the similar
> output:
>
> #0 -[NSException raise] (self=0x7c139488, _cmd=0x2835eba8)
> at NSException.m:956
> #1 0x08391e04 in +[NSException raise:format:arguments:] (self=0x2835e9c0,
> _cmd=0x2835eb90, name=0x3c006174, format=0x3c006168,
> argList=0xcfbf01f0 "0÷\234\201h®\210&\027\003") at NSException.m:849
> #2 0x08392cf3 in +[NSException raise:format:] (self=0x2835e9c0,
> _cmd=0x3c0060f8, name=0x3c006174, format=0x3c006168) at NSException.m:835
> #3 0x1c006f80 in -[Sudoku doFind:] (self=0x84f0a008, _cmd=0x3c0060d8,
> seen=0x87651648) at Sudoku.m:452
> #4 0x1c006fbe in -[Sudoku doFind:] (self=0x84f0a008, _cmd=0x3c0060d8,
> seen=0x87651648) at Sudoku.m:524
> #5 0x1c006fbe in -[Sudoku doFind:] (self=0x84f0a008, _cmd=0x3c0060d8,
> seen=0x87651648) at Sudoku.m:524
> #6 0x1c006fbe in -[Sudoku doFind:] (self=0x84f0a008, _cmd=0x3c0060d8,
> seen=0x87651648) at Sudoku.m:524
> #7 0x1c006fbe in -[Sudoku doFind:] (self=0x84f0a008, _cmd=0x3c0060d8,
> seen=0x87651648) at Sudoku.m:524
> #8 0x1c006fbe in -[Sudoku doFind:] (self=0x84f0a008, _cmd=0x3c0060d8,
> seen=0x87651648) at Sudoku.m:524
> #9 0x1c006fbe in -[Sudoku doFind:] (self=0x84f0a008, _cmd=0x3c0060d8,
> seen=0x87651648) at Sudoku.m:524
> #10 0x1c006fbe in -[Sudoku doFind:] (self=0x84f0a008, _cmd=0x3c0060d8,
> seen=0x87651648) at Sudoku.m:524
>
> the exception is raised from line 452;
> [NSException raise:EX_COMPLETE format:EX_COMPLETE_FMT];
>
> line 524:
> [self doFind:seen];
>
> (which means indeed recursion)
>
>
> Seen as this it looks like a code problem, but if it happens only on
> OpenBSD I think of some kind of corruption. "placed" gets initialized
> before...
>
> Thanks,
> Riccardo
>
>
> and seq is an object instance variable, which makes me think of
> corruption in the object.