Hmmmm, this might be why:

 #0  0x00000000004031be in readfp (cx=0x18549c0, argc=<value optimised out>, vp=0x7f7559a0f130) at couch_js/main.c:166
         bytes = 0x7f7554001e70 "[\"reset\",{\"reduce_limit\":true}]\n"
         tmp = <value optimised out>
         byteslen = 256
         readlen = <value optimised out>
         used = 140141897195120
 #1  readline (cx=0x18549c0, argc=<value optimised out>, vp=0x7f7559a0f130) at couch_js/main.c:198
         str = <value optimised out>
         bytes = <value optimised out>
         tmp = <value optimised out>
         byteslen = <value optimised out>
 #2  0x00007f755e3760d3 in CallJSNative (cx=0x18549c0, entryFrame=0x7f7559a0f048, inlineCallCount=1, interpMode=JSINTERP_NORMAL) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jscntxtinlines.h:684
         ok = <value optimised out>
 #3  js::Interpret (cx=0x18549c0, entryFrame=0x7f7559a0f048, inlineCallCount=1, interpMode=JSINTERP_NORMAL) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jsinterp.cpp:4744
         ok = <value optimised out>
         ok = <value optimised out>
         callee = <value optimised out>
         flags = 0
         vp = 0x7f7559a0f130
         newfun = 0x7f7559817f80
         argc = 0
         normalJumpTable = {0x7f755e36e772, 0x7f755e36d9a9, 0x7f755e36c0e6, 0x7f755e36da54, 0x7f755e36db02, 0x7f755e36db35, 0x7f755e36c13e, 0x7f755e36db64, 0x7f755e36dbd3, 0x7f755e36f0ad, 0x7f755e36e254, 0x7f755e36e2d3, 0x7f755e36e6b7, 0x7f755e372fc1, 0x7f755e3730aa, 0x7f755e370157, 0x7f755e3701f2, 0x7f755e37028d, 0x7f755e370328, 0x7f755e36f263, 0x7f755e373bb3, 0x7f755e37322d, 0x7f755e373386, 0x7f755e3723b9, 0x7f755e3739b8, 0x7f755e373916, 0x7f755e373a5a, 0x7f755e3735d4, 0x7f755e373748, 0x7f755e37382f, 0x7f755e373d0c, 0x7f755e36e8f6, 0x7f755e36e9dd, 0x7f755e371eca, 0x7f755e371f32, 0x7f755e371bb5, 0x7f755e371bf7, 0x7f755e371cca, 0x7f755e371d8b, 0x7f755e36c554, 0x7f755e371b5b, 0x7f755e36f828, 0x7f755e371b9d, 0x7f755e371b93, 0x7f755e373b04, 0x7f755e371ba5, 0x7f755e371b98, 0x7f755e36f82d, 0x7f755e36bf98, 0x7f755e36be89, 0x7f755e36f832, 0x7f755e36bf98, 0x7f755e36be89, 0x7f755e36c2d0, 0x7f755e36bad0, 0x7f755e3712d4, 0x7f755e3727f1, 0x7f755e36bc37, 0x7f755e36c452, 0x7f755e36bc37, 0x7f755e36ea52, 0x7f755e36eab8, 0x7f755e36eca5, 0x7f755e36f06a, 0x7f755e36ece8, 0x7f755e3711f7, 0x7f755e36ed2b, 0x7f755e36ed6e, 0x7f755e36dca9, 0x7f755e36dd3b, 0x7f755e36edb1, 0x7f755e36f015, 0x7f755e373b51, 0x7f755e36f48a, 0x7f755e372974, 0x7f755e36e18c, 0x7f755e36e1ec, 0x7f755e36e353, 0x7f755e36c452, 0x7f755e373006, 0x7f755e36eb16, 0x7f755e36d9ec, 0x7f755e372702, 0x7f755e36f01f, 0x7f755e36c5de, 0x7f755e3722e9, 0x7f755e373eb9, 0x7f755e373e61, 0x7f755e3714c9, 0x7f755e36d64d, 0x7f755e36d899, 0x7f755e36cb8d, 0x7f755e36d764, 0x7f755e36f18c, 0x7f755e372e6e, 0x7f755e373b41, 0x7f755e372072, 0x7f755e373b26, 0x7f755e373557, 0x7f755e36e82d, 0x7f755e373b33, 0x7f755e3711ea, 0x7f755e36e794, 0x7f755e37013d, 0x7f755e36e3a4, 0x7f755e36e4f7, 0x7f755e36e645, 0x7f755e36da17, 0x7f755e36ffa8, 0x7f755e3712cf, 0x7f755e36fd31, 0x7f755e36e014, 0x7f755e372a4d, 0x7f755e372af8, 0x7f755e372f53, 0x7f755e3734df, 0x7f755e3729df, 0x7f755e36d965, 0x7f755e36d8bb, 0x7f755e36f4ef, 0x7f755e36c135, 0x7f755e37166b, 0x7f755e3725b7, 0x7f755e36d48f, 0x7f755e36d48f, 0x7f755e372db3, 0x7f755e36c973, 0x7f755e36c973, 0x7f755e36f775, 0x7f755e371883, 0x7f755e36fd73, 0x7f755e373040, 0x7f755e36d8dd, 0x7f755e373523, 0x7f755e36c82c, 0x7f755e36c82c, 0x7f755e36f10e, 0x7f755e373564, 0x7f755e3718c8, 0x7f755e36c1cf, 0x7f755e36ddad, 0x7f755e36de1c, 0x7f755e36df01, 0x7f755e36dfa2, 0x7f755e371ad2, 0x7f755e373155, 0x7f755e36c1c6, 0x7f755e36ee2a, 0x7f755e36eec4, 0x7f755e36cf75, 0x7f755e36cf75, 0x7f755e36fcec, 0x7f755e36c0e6, 0x7f755e36c009, 0x7f755e37351e, 0x7f755e3712ca, 0x7f755e372a43, 0x7f755e372a48, 0x7f755e36b83a, 0x7f755e36b840, 0x7f755e36eb89, 0x7f755e36e83d, 0x7f755e36e884, 0x7f755e3720a3, 0x7f755e372101, 0x7f755e36fc64, 0x7f755e372207, 0x7f755e3721a3, 0x7f755e36cc9e, 0x7f755e36cc9e, 0x7f755e36f837, 0x7f755e36f8ef, 0x7f755e36cd20, 0x7f755e36cde0, 0x7f755e36fa3b, 0x7f755e36fa8f, 0x7f755e36fb94, 0x7f755e36fbfc, 0x7f755e36f5b8, 0x7f755e370c20, 0x7f755e36c266, 0x7f755e370a7a, 0x7f755e370cc9, 0x7f755e37099a, 0x7f755e370e28, 0x7f755e36c63f, 0x7f755e36c63f, 0x7f755e36cde0, 0x7f755e37151e, 0x7f755e37162d, 0x7f755e36c5b3, 0x7f755e36c5b3, 0x7f755e36d8ff, 0x7f755e36d921, 0x7f755e36f620, 0x7f755e36c009, 0x7f755e36c2d0, 0x7f755e36cd20, 0x7f755e36c554, 0x7f755e370af8...}
         argv = 0x7f7559a0f0b0
         interpReturnOK = <value optimised out>
         len = <value optimised out>
         interruptJumpTable = {0x7f755e36e6f4 <repeats 249 times>}
         leaveOnSafePoint = false
         atoms = 0x19236f8
         op = <value optimised out>
         rt = 0x1829040
         jumpTable = 0x7f755e7f8240
         regs = {sp = 0x7f7559a0f140, pc = 0x19238a4 ":", fp = 0x7f7559a0f0b0}
         script = 0x1923640
         atomNotDefined = <value optimised out>
 #4  0x00007f755e3808ef in RunScript (cx=0x18549c0, chain=<value optimised out>, script=0x190dd10, prev=<value optimised out>, flags=<value optimised out>, result=0x7fff9e4f6048) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jsinterp.cpp:665
         status = 2818587871
 #5  js::Execute (cx=0x18549c0, chain=<value optimised out>, script=0x190dd10, prev=<value optimised out>, flags=<value optimised out>, result=0x7fff9e4f6048) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jsinterp.cpp:1008
         frame = {<js::FrameGuard> = {cx_ = 0x18549c0, seg_ = 0x7f7559a0f000, vp_ = 0x7f7559a0f038, fp_ = 0x7f7559a0f048}, regs_ = {sp = 0x7f7559a0f0a0, pc = 0x190def0 "\177", fp = 0x7f7559a0f048}}
         ok = <value optimised out>
         initialVarObj = <value optimised out>
         hookData = 0x0
 #6  0x00007f755e2f6ec6 in JS_ExecuteScript (cx=0x18549c0, obj=<value optimised out>, script=<value optimised out>, rval=<value optimised out>) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jsapi.cpp:4781
         ok = <value optimised out>
 #7  0x00000000004030f2 in execute_script (cx=0x18549c0, obj=0x7f7559803048, filename=<value optimised out>) at couch_js/main.c:274
         file = <value optimised out>
         script = 0x190dd10
         result = 6312992
 #8  0x00000000004033fb in main (argc=2, argv=0x7fff9e4f6188) at couch_js/main.c:355
         rt = 0x1829040
         cx = 0x18549c0
         global = 0x7f7559803048
         sp = <value optimised out>
StacktraceTop:
 readfp (cx=0x18549c0, argc=<value optimised out>, vp=0x7f7559a0f130) at couch_js/main.c:166
 readline (cx=0x18549c0, argc=<value optimised out>, vp=0x7f7559a0f130) at couch_js/main.c:198
 CallJSNative (cx=0x18549c0, entryFrame=0x7f7559a0f048, inlineCallCount=1, interpMode=JSINTERP_NORMAL) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jscntxtinlines.h:684
 js::Interpret (cx=0x18549c0, entryFrame=0x7f7559a0f048, inlineCallCount=1, interpMode=JSINTERP_NORMAL) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jsinterp.cpp:4744
 RunScript (cx=0x18549c0, chain=<value optimised out>, script=0x190dd10, prev=<value optimised out>, flags=<value optimised out>, result=0x7fff9e4f6048) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jsinterp.cpp:665
Tags: natty ubuntu-une
ThreadStacktrace:
 .
 Thread 2 (Thread 1087):
 #0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:162
 No locals.
 #1  0x00007f755c83252a in PR_WaitCondVar () from /usr/lib/libnspr4.so
 No symbol table info available.
 #2  0x00007f755e362a77 in threadLoop (arg=0x1829040) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jsgc.cpp:1995
 No locals.
 #3  js::GCHelperThread::threadMain (arg=0x1829040) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jsgc.cpp:1981
         rt = 0x1829040
 #4  0x00007f755c8380ca in ?? () from /usr/lib/libnspr4.so
 No symbol table info available.
 #5  0x00007f755ca52971 in start_thread (arg=<value optimised out>) at pthread_create.c:304
         __res = <value optimised out>
         pd = 0x7f755a60f710
         unwind_buf = {cancel_jmp_buf = {{jmp_buf = {140142004205328, 4116705332735556374, 140735849389872, 140142004206032, 140142078222400, 3, -4049917552398648554, -4049931259766850794}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
         not_first_call = <value optimised out>
         robust = <value optimised out>
         freesize = <value optimised out>
         __PRETTY_FUNCTION__ = "start_thread"
 #6  0x00007f755e01194d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
 No locals.
 #7  0x0000000000000000 in ?? ()
 No symbol table info available.
 .
 Thread 1 (Thread 1079):
 #0  0x00000000004031be in readfp (cx=0x18549c0, argc=<value optimised out>, vp=0x7f7559a0f130) at couch_js/main.c:166
         bytes = 0x7f7554001e70 "[\"reset\",{\"reduce_limit\":true}]\n"
         tmp = <value optimised out>
         byteslen = 256
         readlen = <value optimised out>
         used = 140141897195120
 #1  readline (cx=0x18549c0, argc=<value optimised out>, vp=0x7f7559a0f130) at couch_js/main.c:198
         str = <value optimised out>
         bytes = <value optimised out>
         tmp = <value optimised out>
         byteslen = <value optimised out>
 #2  0x00007f755e3760d3 in CallJSNative (cx=0x18549c0, entryFrame=0x7f7559a0f048, inlineCallCount=1, interpMode=JSINTERP_NORMAL) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jscntxtinlines.h:684
         ok = <value optimised out>
 #3  js::Interpret (cx=0x18549c0, entryFrame=0x7f7559a0f048, inlineCallCount=1, interpMode=JSINTERP_NORMAL) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jsinterp.cpp:4744
         ok = <value optimised out>
         ok = <value optimised out>
         callee = <value optimised out>
         flags = 0
         vp = 0x7f7559a0f130
         newfun = 0x7f7559817f80
         argc = 0
         normalJumpTable = {0x7f755e36e772, 0x7f755e36d9a9, 0x7f755e36c0e6, 0x7f755e36da54, 0x7f755e36db02, 0x7f755e36db35, 0x7f755e36c13e, 0x7f755e36db64, 0x7f755e36dbd3, 0x7f755e36f0ad, 0x7f755e36e254, 0x7f755e36e2d3, 0x7f755e36e6b7, 0x7f755e372fc1, 0x7f755e3730aa, 0x7f755e370157, 0x7f755e3701f2, 0x7f755e37028d, 0x7f755e370328, 0x7f755e36f263, 0x7f755e373bb3, 0x7f755e37322d, 0x7f755e373386, 0x7f755e3723b9, 0x7f755e3739b8, 0x7f755e373916, 0x7f755e373a5a, 0x7f755e3735d4, 0x7f755e373748, 0x7f755e37382f, 0x7f755e373d0c, 0x7f755e36e8f6, 0x7f755e36e9dd, 0x7f755e371eca, 0x7f755e371f32, 0x7f755e371bb5, 0x7f755e371bf7, 0x7f755e371cca, 0x7f755e371d8b, 0x7f755e36c554, 0x7f755e371b5b, 0x7f755e36f828, 0x7f755e371b9d, 0x7f755e371b93, 0x7f755e373b04, 0x7f755e371ba5, 0x7f755e371b98, 0x7f755e36f82d, 0x7f755e36bf98, 0x7f755e36be89, 0x7f755e36f832, 0x7f755e36bf98, 0x7f755e36be89, 0x7f755e36c2d0, 0x7f755e36bad0, 0x7f755e3712d4, 0x7f755e3727f1, 0x7f755e36bc37, 0x7f755e36c452, 0x7f755e36bc37, 0x7f755e36ea52, 0x7f755e36eab8, 0x7f755e36eca5, 0x7f755e36f06a, 0x7f755e36ece8, 0x7f755e3711f7, 0x7f755e36ed2b, 0x7f755e36ed6e, 0x7f755e36dca9, 0x7f755e36dd3b, 0x7f755e36edb1, 0x7f755e36f015, 0x7f755e373b51, 0x7f755e36f48a, 0x7f755e372974, 0x7f755e36e18c, 0x7f755e36e1ec, 0x7f755e36e353, 0x7f755e36c452, 0x7f755e373006, 0x7f755e36eb16, 0x7f755e36d9ec, 0x7f755e372702, 0x7f755e36f01f, 0x7f755e36c5de, 0x7f755e3722e9, 0x7f755e373eb9, 0x7f755e373e61, 0x7f755e3714c9, 0x7f755e36d64d, 0x7f755e36d899, 0x7f755e36cb8d, 0x7f755e36d764, 0x7f755e36f18c, 0x7f755e372e6e, 0x7f755e373b41, 0x7f755e372072, 0x7f755e373b26, 0x7f755e373557, 0x7f755e36e82d, 0x7f755e373b33, 0x7f755e3711ea, 0x7f755e36e794, 0x7f755e37013d, 0x7f755e36e3a4, 0x7f755e36e4f7, 0x7f755e36e645, 0x7f755e36da17, 0x7f755e36ffa8, 0x7f755e3712cf, 0x7f755e36fd31, 0x7f755e36e014, 0x7f755e372a4d, 0x7f755e372af8, 0x7f755e372f53, 0x7f755e3734df, 0x7f755e3729df, 0x7f755e36d965, 0x7f755e36d8bb, 0x7f755e36f4ef, 0x7f755e36c135, 0x7f755e37166b, 0x7f755e3725b7, 0x7f755e36d48f, 0x7f755e36d48f, 0x7f755e372db3, 0x7f755e36c973, 0x7f755e36c973, 0x7f755e36f775, 0x7f755e371883, 0x7f755e36fd73, 0x7f755e373040, 0x7f755e36d8dd, 0x7f755e373523, 0x7f755e36c82c, 0x7f755e36c82c, 0x7f755e36f10e, 0x7f755e373564, 0x7f755e3718c8, 0x7f755e36c1cf, 0x7f755e36ddad, 0x7f755e36de1c, 0x7f755e36df01, 0x7f755e36dfa2, 0x7f755e371ad2, 0x7f755e373155, 0x7f755e36c1c6, 0x7f755e36ee2a, 0x7f755e36eec4, 0x7f755e36cf75, 0x7f755e36cf75, 0x7f755e36fcec, 0x7f755e36c0e6, 0x7f755e36c009, 0x7f755e37351e, 0x7f755e3712ca, 0x7f755e372a43, 0x7f755e372a48, 0x7f755e36b83a, 0x7f755e36b840, 0x7f755e36eb89, 0x7f755e36e83d, 0x7f755e36e884, 0x7f755e3720a3, 0x7f755e372101, 0x7f755e36fc64, 0x7f755e372207, 0x7f755e3721a3, 0x7f755e36cc9e, 0x7f755e36cc9e, 0x7f755e36f837, 0x7f755e36f8ef, 0x7f755e36cd20, 0x7f755e36cde0, 0x7f755e36fa3b, 0x7f755e36fa8f, 0x7f755e36fb94, 0x7f755e36fbfc, 0x7f755e36f5b8, 0x7f755e370c20, 0x7f755e36c266, 0x7f755e370a7a, 0x7f755e370cc9, 0x7f755e37099a, 0x7f755e370e28, 0x7f755e36c63f, 0x7f755e36c63f, 0x7f755e36cde0, 0x7f755e37151e, 0x7f755e37162d, 0x7f755e36c5b3, 0x7f755e36c5b3, 0x7f755e36d8ff, 0x7f755e36d921, 0x7f755e36f620, 0x7f755e36c009, 0x7f755e36c2d0, 0x7f755e36cd20, 0x7f755e36c554, 0x7f755e370af8...}
         argv = 0x7f7559a0f0b0
         interpReturnOK = <value optimised out>
         len = <value optimised out>
         interruptJumpTable = {0x7f755e36e6f4 <repeats 249 times>}
         leaveOnSafePoint = false
         atoms = 0x19236f8
         op = <value optimised out>
         rt = 0x1829040
         jumpTable = 0x7f755e7f8240
         regs = {sp = 0x7f7559a0f140, pc = 0x19238a4 ":", fp = 0x7f7559a0f0b0}
         script = 0x1923640
         atomNotDefined = <value optimised out>
 #4  0x00007f755e3808ef in RunScript (cx=0x18549c0, chain=<value optimised out>, script=0x190dd10, prev=<value optimised out>, flags=<value optimised out>, result=0x7fff9e4f6048) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jsinterp.cpp:665
         status = 2818587871
 #5  js::Execute (cx=0x18549c0, chain=<value optimised out>, script=0x190dd10, prev=<value optimised out>, flags=<value optimised out>, result=0x7fff9e4f6048) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jsinterp.cpp:1008
         frame = {<js::FrameGuard> = {cx_ = 0x18549c0, seg_ = 0x7f7559a0f000, vp_ = 0x7f7559a0f038, fp_ = 0x7f7559a0f048}, regs_ = {sp = 0x7f7559a0f0a0, pc = 0x190def0 "\177", fp = 0x7f7559a0f048}}
         ok = <value optimised out>
         initialVarObj = <value optimised out>
         hookData = 0x0
 #6  0x00007f755e2f6ec6 in JS_ExecuteScript (cx=0x18549c0, obj=<value optimised out>, script=<value optimised out>, rval=<value optimised out>) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jsapi.cpp:4781
         ok = <value optimised out>
 #7  0x00000000004030f2 in execute_script (cx=0x18549c0, obj=0x7f7559803048, filename=<value optimised out>) at couch_js/main.c:274
         file = <value optimised out>
         script = 0x190dd10
         result = 6312992
 #8  0x00000000004033fb in main (argc=2, argv=0x7fff9e4f6188) at couch_js/main.c:355
         rt = 0x1829040
         cx = 0x18549c0
         global = 0x7f7559803048
         sp = <value optimised out>

I guess that's for me to fix