andypugh@dn2800:~/linuxcnc-dev$ gdb bin/rtapi_app core
GNU gdb (Ubuntu/Linaro 7.4-2012.04-0ubuntu2.1) 7.4-2012.04
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Reading symbols from /home/andypugh/linuxcnc-dev/bin/rtapi_app...done.

warning: core file may not match specified executable file.
[New LWP 1651]
Core was generated by `rtapi:0                                                           '.
Program terminated with signal 6, Aborted.
#0  0xb774a424 in __kernel_vsyscall ()
(gdb) bt
#0  0xb774a424 in __kernel_vsyscall ()
#1  0xb748f1df in ?? ()
#2  0xb7605ff4 in ?? ()
#3  <signal handler called>
#4  0x00000000 in ?? ()
#5  0xb7346192 in ?? ()
#6  0xb77352fc in ?? ()
#7  0xb733951d in ?? ()
#8  0x09202a68 in ?? ()
#9  0xb77325a2 in ?? ()
#10 0xb77352fc in ?? ()
#11 0xb741eb8f in ?? ()
#12 0x092028b8 in ?? ()
#13 0xb77326fd in ?? ()
#14 0xb77351c4 in ?? ()
#15 0x0804c14a in read_strings (fd=153102952) at rtapi/sim_rtapi_app.cc:295
#16 master (args=..., fd=0) at rtapi/sim_rtapi_app.cc:377
#17 main (argc=<error reading variable: Cannot access memory at address 0x1>, argv=<error reading variable: Cannot access memory at address 0x5>) at rtapi/sim_rtapi_app.cc:604