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

Sun Sep 28 18:31:27 EDT 2008

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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