gpsee_getRealm throws during finalizers called during shutdown

[GoogleCodeExporter]

Basically, when cx is grt->coreCx, we have no realm.

If we want to use the data store at realm->moduleData in a finalizer, we assert 
in gpsee_getRealm() if the finalized object is a property of the global object.

Proposed work around:  Make gpsee_getRealm() fallible, and return NULL when cx 
is grt->coreCx.  This can let module writers know that we are busy shutting 
down the module system if that is enough information for them. 

Program received signal SIGABRT, Aborted.
[Switching to Thread 1 (LWP 1)]
0xfef4155c in _lwp_kill () from /usr/lib/libc.so.1
(gdb) bt
#0  0xfef4155c in _lwp_kill () from /usr/lib/libc.so.1
#1  0xfeedff00 in raise () from /usr/lib/libc.so.1
#2  0xfeec0120 in abort () from /usr/lib/libc.so.1
#3  0xfed4618c in gpsee_assert (s=0xfed60e50 "realm", file=0xfed60e58 
"gpsee_realms.c", ln=118) at gpsee.c:92
#4  0xfed59b8c in gpsee_getRealm (cx=0x34b78) at gpsee_realms.c:118
#5  0xfe646d04 in mysqlEntry_Finalize (cx=0x34b78, obj=0xfe512040) at 
mysql/mysqlEntry.c:859
#6  0xff18fd30 in js_GC(JSContext*, JSGCInvocationKind) () from 
/var/surelynx/platform/SunOS-5.10-sun4u-sparc/lib/apr_surelynx/libmozjs.so
#7  0xfed5a158 in gpsee_destroyRealm (cx=0x34b78, realm=0x17a1b0) at 
gpsee_realms.c:285
#8  0xfed479ec in destroyRealm_cb (cx=0x34b78, key=0x17a1b0, value=0x0, 
private=0x0) at gpsee.c:638
#9  0xfed592f4 in gpsee_ds_forEach (cx=0x34b78, store=0x1795b0, cb=0xfed479c0 
<destroyRealm_cb>, private=0x0) at gpsee_datastores.c:371
#10 0xfed47bf4 in gpsee_destroyRuntime (grt=0x36438) at gpsee.c:680
#11 0xfed48a00 in gpsee_destroyInterpreter (jsi=0x289e0) at gpsee.c:981
#12 0x00013c84 in prmain (argc=2, argv=0xffbff774) at gsr.c:895
#13 0xff0bdd68 in PR_Initialize () from /usr/lib/mps/libnspr4.so
#14 0x00013cdc in main (argc=2, argv=0xffbff774) at gsr.c:903
(gdb)

Original issue reported on code.google.com by wes@page.ca on 15 Jun 2012 at 9:30