[mercury-users] Crash on MacOS X

[Julien Fischer]

On Fri, 7 Nov 2008, Michael Day wrote:

> Hi Julien,
>
>> * Does disabling Mercury optimizations make the problem go away,
>>   e.g., compiling with MCFLASG = -O0?
>
> With -O0 the crash report is slightly different:
>
> Reason: KERN_INVALID_ADDRESS at address: 0xbf7fffc8
> 0x0021d77a in GC_clear_stack_inner ()
> (gdb) bt
> #0  0x0021d77a in GC_clear_stack_inner ()
> Cannot access memory at address 0xbf7fffc8
> Cannot access memory at address 0xbf7fffcc
>
>> * Does disabling optimizations at the C level make the problem go away,
>>   e.g. compiling with --cflags="-O0"?
>
> Still, crashes, but much much faster and earlier in the execution progress:
>
> Reason: KERN_INVALID_ADDRESS at address: 0xbf7ffc6c
> 0x00595988 in prepack__text__hyphenate_word_6_p_0 
> (prepack__text__Style_7=40981952, prepack__text__Buf0_8=0, 
> prepack__text__PrevNum0_9=0, prepack__text__Accum0_10=91898305, 
> prepack__text__Segs0_11=0, prepack__text__Segs_12=0xbf802a18) at 
> ../prepack/text.m:472
> 472	:- mode hyphenate_word(in, in, in, in, in, out) is det.
>
>> * What version of gcc are you using?
>
> i686-apple-darwin8-gcc-4.0.1 (GCC) 4.0.1 (Apple Computer, Inc. build 5367)
>
>> * Does the problem occur if you compile your program in none.gc?
>>   (note: `none' is the only low-level C base grade that works reliably
>>   on Mac OS / x86)
>
> It appears to work when compiled with none.gc. Further testing required. Do 
> you think that hlc.gc is not worth the risk on MacOS X?

No, hlc.gc is the preferred grade on Mac OS X; for one programs using
are (almost always) a lot quicker than none.gc.

Similar problems to the above have been reported on the GC list, see for
example:

<http://www.hpl.hp.com/hosted/linux/mail-archives/gc/2006-March/001224.html>

I would also note that there were a number of patches for Mac OS X / x86
added to version 7 alpha8 (and thereabouts).  (We are using alpha6.)

I suspect that fixing this will require using a newer version of the
collector.

Cheers,
Julien.
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