Here is what is happening to me:
novoselt@zv5000-lmde ~/sage/devel/sage-main $ sage
----------------------------------------------------------------------
| Sage Version 5.2.rc0, Release Date: 2012-07-17 |
| Type "notebook()" for the browser-based notebook interface. |
| Type "help()" for help. |
----------------------------------------------------------------------
**********************************************************************
* *
* Warning: this is a prerelease version, and it may be unstable. *
* *
**********************************************************************
sage: notebook()
The notebook files are stored in: sage_notebook.sagenb
**************************************************
* *
* Open your web browser to http://localhost:8080 *
* *
**************************************************
2012-07-19 08:16:42-0600 [-] Log opened.
2012-07-19 08:16:42-0600 [-] twistd 12.1.0
(/home/novoselt/sage-5.2.rc0/local/bin/python 2.7.3) starting up.
2012-07-19 08:16:42-0600 [-] reactor class:
twisted.internet.epollreactor.EPollReactor.
2012-07-19 08:16:42-0600 [-] QuietSite starting on 8080
2012-07-19 08:16:42-0600 [-] Starting factory <__builtin__.QuietSite
instance at 0x61c8440>
^C2012-07-19 08:16:51-0600 [-] Quitting all running worksheets...
2012-07-19 08:16:51-0600 [-] Saving notebook...
2012-07-19 08:16:51-0600 [-] Notebook cleanly saved.
2012-07-19 08:16:51-0600 [-] (TCP Port 8080 Closed)
2012-07-19 08:16:51-0600 [-] Stopping factory <__builtin__.QuietSite
instance at 0x61c8440>
2012-07-19 08:16:51-0600 [-] Main loop terminated.
2012-07-19 08:16:51-0600 [-] Server Shut Down.
/home/novoselt/sage-5.2.rc0/local/lib/libcsage.so(print_backtrace+0x31)[0x7 ffc1ba25c47]
/home/novoselt/sage-5.2.rc0/local/lib/libcsage.so(sigdie+0x14)[0x7ffc1ba25c 79]
/home/novoselt/sage-5.2.rc0/local/lib/libcsage.so(sage_signal_handler+0x216 )[0x7ffc1ba25856]
/lib/x86_64-linux-gnu/libpthread.so.0(+0xf030)[0x7ffc21935030]
/lib/x86_64-linux-gnu/libc.so.6(cfree+0x19)[0x7ffc20f90799]
/home/novoselt/sage-5.2.rc0/local/lib/libcsage.so(+0xad85)[0x7ffc1ba25d85]
/home/novoselt/sage-5.2.rc0/local/lib/libcsage.so(sage_mpir_free+0x1c)[0x7f fc1ba25e31]
/home/novoselt/sage-5.2.rc0/local/lib/libgivaro.so.0(_ZN7IntegerD2Ev+0x18)[ 0x7ffc08e30e9c]
/home/novoselt/sage-5.2.rc0/local/lib/libgivaro.so.0(_ZN8RationalD2Ev+0x1d) [0x7ffc08e3b47b]
/lib/x86_64-linux-gnu/libc.so.6(+0x36df2)[0x7ffc20f4cdf2]
/lib/x86_64-linux-gnu/libc.so.6(+0x36e45)[0x7ffc20f4ce45]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x104)[0x7ffc20f34eb4]
python[0x4006a1]
------------------------------------------------------------------------
Unhandled SIGSEGV: A segmentation fault occurred in Sage.
This probably occurred because a *compiled* component of Sage has a bug
in it and is not properly wrapped with sig_on(), sig_off(). You might
want to run Sage under gdb with 'sage -gdb' to debug this.
Sage will now terminate.
------------------------------------------------------------------------
Segmentation fault
True
sage: 1 + 3
4
sage:
This does happen every time on this machine (8 years old notebook on
Athlon64, 2Gb RAM, never had such issues before).
I have also opened
http://trac.sagemath.org/sage_trac/ticket/13270
for automatic reenabling of user registration.
Andrey
