[chuck-users] Assigning to appended array locations (bug?)

mike clemow gelfmuse at gmail.com
Sun Sep 28 22:09:28 EDT 2008


The garbage collection dicussion is way over my head at this point,
however, I want to thank you guys for taking a look at this issue.
The stack trace seems to be a lot more information than "bus error"
is.  I hope that Ge can make some sense of the underlying issues.

Back to my spaghetti...

Cheers,
Mike

On Sun, Sep 28, 2008 at 6:31 PM, Kassen <signal.automatique at gmail.com> wrote:
> Steve;
>
>> Yup, it probably needs some work, and at least I think reference-based
>> garbage collection is a little easier to get right than the "hunt
>> through memory for pointers" style.  Though each has its own downsides
>> if I recall, such as cyclical references.
>
> Well, anything is better then clogging up the whole CPU with periodic
> collection; we can't afford that.
>
>>
>> Well, I'm not sure if I understand what you're saying, but what's
>> happening is that 'f' references a new Foo, and then that foo is added
>> to the array.  When it's later replaced, it's not garbage collected
>> because 'f' still references it.  But when 'f' is made to point
>> somewhere else, *then* it gets garbage collected, which for some
>> reason causes an exception.
>>
>> Appended 'int f' doesn't make much sense though since the problem
>> doesn't lie with 'f', but with what 'f' points to.  It'll just say
>> that 'f' is already defined.
>
> I may have made a reasoning error but I wanted to test to see whether when
> the object under "f" is collected the reference, named "f", was still there.
> I knew this was a naive test but still wanted to run it.
>
> We're definitely having some kind of big-ish trouble here; I just saw ChucK
> spew out a amount of data at crashing. I've never seen it do anything like
> this before. Pasted below in case it means something to someone. At least I
> now got Mike's Unit-tests to go beyond where his comments say it gives a
> "bus error"... out of the frying pan and into the fire. I archived the state
> the code was in at this point in case this is relevant; zip-file on request.
>
> Yours,
> Kas.
>
> --------------------start paste----------------------------
> *** glibc detected *** chuck: double free or corruption (!prev): 0x0842b7e8
> ***
> ======= Backtrace: =========
> /lib/tls/i686/cmov/libc.so.6[0xb7bf2a85]
> /lib/tls/i686/cmov/libc.so.6(cfree+0x90)[0xb7bf64f0]
> /usr/lib/libstdc++.so.6(_ZdlPv+0x21)[0xb7e1eb11]
> /usr/lib/libstdc++.so.6(_ZdaPv+0x1d)[0xb7e1eb6d]
> chuck[0x8055f6f]
> chuck[0x80596da]
> chuck[0x809a652]
> chuck[0x805944e]
> chuck[0x80594d2]
> chuck[0x80c4ed5]
> chuck[0x80d2048]
> chuck[0x80cc8e8]
> /lib/tls/i686/cmov/libpthread.so.0[0xb7b744fb]
> /lib/tls/i686/cmov/libc.so.6(clone+0x5e)[0xb7c5de5e]
> ======= Memory map: ========
> 08048000-081ac000 r-xp 00000000 08:01 1165811    /usr/bin/chuck
> 081ac000-081d3000 rw-p 00164000 08:01 1165811    /usr/bin/chuck
> 081d3000-0845c000 rw-p 081d3000 00:00 0          [heap]
> b6200000-b6221000 rw-p b6200000 00:00 0
> b6221000-b6300000 ---p b6221000 00:00 0
> b6311000-b6312000 ---p b6311000 00:00 0
> b6312000-b6b12000 rw-p b6312000 00:00 0
> b6b12000-b6b13000 ---p b6b12000 00:00 0
> b6b13000-b7313000 rw-p b6b13000 00:00 0
> b7313000-b7314000 ---p b7313000 00:00 0
> b7314000-b7b16000 rw-p b7314000 00:00 0
> b7b16000-b7b1a000 r-xp 00000000 08:01 1165578    /usr/lib/libogg.so.0.5.3
> b7b1a000-b7b1b000 rw-p 00003000 08:01 1165578    /usr/lib/libogg.so.0.5.3
> b7b1b000-b7b6e000 r-xp 00000000 08:01 1165787    /usr/lib/libFLAC.so.8.2.0
> b7b6e000-b7b6f000 rw-p 00052000 08:01 1165787    /usr/lib/libFLAC.so.8.2.0
> b7b6f000-b7b83000 r-xp 00000000 08:01 3965681
> /lib/tls/i686/cmov/libpthread-2.7.so
> b7b83000-b7b85000 rw-p 00013000 08:01 3965681
> /lib/tls/i686/cmov/libpthread-2.7.so
> b7b85000-b7b87000 rw-p b7b85000 00:00 0
> b7b87000-b7cd0000 r-xp 00000000 08:01 3965649
> /lib/tls/i686/cmov/libc-2.7.so
> b7cd0000-b7cd1000 r--p 00149000 08:01 3965649
> /lib/tls/i686/cmov/libc-2.7.so
> b7cd1000-b7cd3000 rw-p 0014a000 08:01 3965649
> /lib/tls/i686/cmov/libc-2.7.so
> b7cd3000-b7cd7000 rw-p b7cd3000 00:00 0
> b7cd7000-b7ce1000 r-xp 00000000 08:01 3932228    /lib/libgcc_s.so.1
> b7ce1000-b7ce2000 rw-p 0000a000 08:01 3932228    /lib/libgcc_s.so.1
> b7ce2000-b7d05000 r-xp 00000000 08:01 3965653
> /lib/tls/i686/cmov/libm-2.7.so
> b7d05000-b7d07000 rw-p 00023000 08:01 3965653
> /lib/tls/i686/cmov/libm-2.7.so
> b7d07000-b7d5d000 r-xp 00000000 08:01 1165274
> /usr/lib/libsndfile.so.1.0.17
> b7d5d000-b7d5e000 rw-p 00056000 08:01 1165274
> /usr/lib/libsndfile.so.1.0.17
> b7d5e000-b7d63000 rw-p b7d5e000 00:00 0
> b7d63000-b7d65000 r-xp 00000000 08:01 3965652
> /lib/tls/i686/cmov/libdl-2.7.so
> b7d65000-b7d67000 rw-p 00001000 08:01 3965652
> /lib/tls/i686/cmov/libdl-2.7.so
> b7d67000-b7e4f000 r-xp 00000000 08:01 1164012    /usr/lib/libstdc++.so.6.0.9
> b7e4f000-b7e52000 r--p 000e8000 08:01 1164012    /usr/lib/libstdc++.so.6.0.9
> b7e52000-b7e54000 rw-p 000eb000 08:01 1164012    /usr/lib/libstdc++.so.6.0.9
> b7e54000-b7e5a000 rw-p b7e54000 00:00 0
> b7e5a000-b7f19000 r-xp 00000000 08:01 1165782    /usr/lib/libasound.so.2.0.0
> b7f19000-b7f1d000 rw-p 000be000 08:01 1165782    /usr/lib/libasound.so.2.0.0
> b7f1d000-b7f1e000 rw-p b7f1d000 00:00 0
> b7f2b000-b7f2c000 rw-s 81000000 00:0e 11361      /dev/snd/pcmC0D0c
> b7f2c000-b7f2d000 r--s 80000000 00:0e 11361      /dev/snd/pcmC0D0c
> b7f2d000-b7f2e000 rw-s 81000000 00:0e 11354      /dev/snd/pcmC0D0p
> b7f2e000-b7f2f000 r--s 80000000 00:0e 11354      /dev/snd/pcmC0D0p
> b7f2f000-b7f30000 rw-p b7f2f000 00:00 0
> b7f30000-b7f31000 r-xp b7f30000 00:00 0          [vdso]
> b7f31000-b7f4b000 r-xp 00000000 08:01 3932197    /lib/ld-2.7.so
> b7f4b000-b7f4d000 rw-p 00019000 08:01 3932197    /lib/ld-2.7.so
> bfbe3000-bfbf8000 rw-p bffeb000 00:00 0          [stack]
> Aborted
>
> --------------------------end paste------------------------
>
>
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