[Python-Dev] Newly Built Python3 Binary Throws Segfault

Ryan Gonzalez rymg19 at gmail.com
Fri Jan 30 18:56:34 CET 2015 

I seriously doubt the issue is in that file; _PyMem_RawStrdup crashes when
calling strlen. It's that whatever is calling it is likely asking it to
duplicate a null pointer. Basically, it's probably the caller's fault.

You could always try modifying _PyMem_RawStrdup to return NULL when given a
null pointer and see where it then segfaults.

On Fri, Jan 30, 2015 at 11:53 AM, Cyd Haselton <chaselton at gmail.com> wrote:

> Alternatively, is there a hassle-free way to find out what changed in
> obmalloc.c between 2.7.x and 3.4.x?
>
>
> On Fri, Jan 30, 2015 at 9:29 AM, Cyd Haselton <chaselton at gmail.com> wrote:
> > There's a related strdup patch for readline.c, mentioned
> > here:http://bugs.python.org/issue21390 and here
> > https://github.com/rave-engine/python3-android/issues/2.
> > There's a patch, but I'm not sure how to modify it for obmalloc.c, as
> > (I think) the functions all belong to Python...they're all prefixed
> > with _PyXx
> >
> > On Fri, Jan 30, 2015 at 9:05 AM, Cyd Haselton <chaselton at gmail.com>
> wrote:
> >> Absolutely.  Good thing I have addr2line on device
> >>
> >> /bld/python/Python-3.4.2 $ addr2line -C -f -e /lib/libpython3.4m.so.1.0
> 0008bbc8
> >> _PyMem_RawStrdup
> >> /bld/python/Python-3.4.2/Objects/obmalloc.c:323
> >> /bld/python/Python-3.4.2 $
> >>
> >>
> >>
> >> On Thu, Jan 29, 2015 at 8:26 PM, Ryan <rymg19 at gmail.com> wrote:
> >>> Could you try the steps at http://stackoverflow.com/a/11369475/2097780?
> They
> >>> allow you to get a better idea of where libc is crashing.
> >>>
> >>> Cyd Haselton <chaselton at gmail.com> wrote:
> >>>>
> >>>> Managed to get this out of logcat:
> >>>> F(11914) Fatal signal 11 (SIGSEGV) at 0x00000000 (code=1), thread
> >>>> 11914 (python)  (libc)
> >>>>
> >>>> [ 01-29 19:30:55.855 23373:23373 F/libc     ]
> >>>> Fatal signal 11 (SIGSEGV) at 0x00000000 (code=1), thread 23373
> (python)
> >>>>
> >>>> Less detail than strace but it seems to be that python is segfaulting
> >>>> libc...
> >>>>
> >>>> On Wed, Jan 28, 2015 at 11:23 AM, Ryan Gonzalez <rymg19 at gmail.com>
> wrote:
> >>>>>
> >>>>>  On Wed, Jan 28, 2015 at 10:43 AM, Guido van Rossum <
> guido at python.org>
> >>>>> wrote:
> >>>>>>
> >>>>>>
> >>>>>>  What I see in the strace:
> >>>>>>
> >>>>>>  ... load libpython3.4m.so.1.0
> >>>>>>  ... load libm
> >>>>>>  ... open /dev/__properties__ and do something to it
> >>>>>> (what?)
> >>>>>>  ... get current time
> >>>>>>  ... allocate memory
> >>>>>>  ... getuid
> >>>>>>  ... segfault
> >>>>>>
> >>>>>>  That's not a lot to go on, but it doesn't look as if it has
> started to
> >>>>>>  load modules yet.
> >>>>>>
> >>>>>>  Does /dev/__properties__ ring a bell? Not to me.
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> https://android.googlesource.com/platform/system/core/+/tools_r22/init/property_service.c
> >>>>>  is the code that works with that file.
> >>>>>
> >>>>>  This explains it a bit (slides 24-29). Looks like something to do
> with
> >>>>>  interprocess communication. Likely has nothing to do with Python
> itself.
> >>>>>
> >>>>>  Maybe this would be useful?
> >>>>>
> >>>>>>
> >>>>>>  That stack trace would be really helpful.
> >>>>>>
> >>>>>>  On Wed, Jan 28, 2015 at 8:34 AM, Cyd Haselton <chaselton at gmail.com
> >
> >>>>>> wrote:
> >>>>>>>
> >>>>>>>
> >>>>>>>  Apologies...I'm not sure what a stack track is, but I do have the
> >>>>>>>  strace.  Nearest I can tell, it happens due to an open call,
> though I
> >>>>>>>  am probably wrong.
> >>>>>>>  Attaching the strace output to this email.  I'm going to head
> back to
> >>>>>>>  the documentation and to back out of some Android-related changes
> in
> >>>>>>>  _localemodule.c
> >>>>>>>
> >>>>>>>  On Wed, Jan 28, 2015 at 9:43 AM, Guido van Rossum <
> guido at python.org>
> >>>>>>>  wrote:
> >>>>>>>>
> >>>>>>>>  There could be a million differences relevant (unicode, ints,
> ...).
> >>>>>>>>  Perhaps
> >>>>>>>>  the importlib bootstrap is failing. Perhaps the dynamic loading
> code
> >>>>>>>>  changed. Did you get a stack track? (IIRC strace shows a syscall
> >>>>>>>> trace
> >>>>>>>>  --
> >>>>>>>>  also useful, but doesn't tell you precisely how
> >>>>>>>> it segfaulted.)
> >>>>>>>>
> >>>>>>>>  On Wed, Jan 28, 2015 at 6:43 AM, Cyd Haselton <
> chaselton at gmail.com>
> >>>>>>>>  wrote:
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>  All,
> >>>>>>>>>  I recently ditched my attempts to port Python 2.7.8 to Android
> in
> >>>>>>>>>  favor of Python 3.4.2.  Unfortunately, after using the same
> >>>>>>>>> configure
> >>>>>>>>>  options in the same environment, and modifying the setup.py as
> >>>>>>>>> needed,
> >>>>>>>>>  the newly built binary throws a segfault when the
> >>>>>>>>> generate-posix-vars
> >>>>>>>>>  portion of the build is reached...and when it is run as well
> (i.e.
> >>>>>>>>>  ./python --help, ./python -E -S -m sysconfig, or similar)
> >>>>>>>>>
> >>>>>>>>>  I took a strace of ./python, however I'm a bit lost when
> reviewing
> >>>>>>>>> it.
> >>>>>>>>>  Any ideas as to what may be going on...i.e. why Python 2.7
> works but
> >>>>>>>>>  3.x throws a segfault?
> >>>>>>>>>
> >>>>>>>>>  Thanks in advance,
> >>>>>>>>>  Cyd
> >>>>>>>>> ________________________________
> >>>>>>>>>
> >>>>>>>>>  Python-Dev mailing list
> >>>>>>>>>
> >>>>>>>>> Python-Dev at python.org
> >>>>>>>>>  https://mail.python.org/mailman/listinfo/python-dev
> >>>>>>>>>  Unsubscribe:
> >>>>>>>>>
> >>>>>>>>>
> https://mail.python.org/mailman/options/python-dev/guido%40python.org
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>  --
> >>>>>>>>  --Guido van Rossum (python.org/~guido)
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>  --
> >>>>>>  --Guido van Rossum (python.org/~guido)
> >>>>>>
> >>>>>> ________________________________
> >>>>>>
> >>>>>>  Python-Dev mailing list
> >>>>>>  Python-Dev at python.org
> >>>>>>  https://mail.python.org/mailman/listinfo/python-dev
> >>>>>>  Unsubscribe:
> >>>>>>
> https://mail.python.org/mailman/options/python-dev/rymg19%40gmail.com
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>  --
> >>>>>  Ryan
> >>>>>  If anybody ever asks me why I prefer C++ to C, my answer will be
> simple:
> >>>>>  "It's becauseslejfp23(@#Q*(E*EIdc-SEGFAULT. Wait, I don't think
> that was
> >>>>>  nul-terminated."
> >>>>>  Personal reality distortion fields are immune to contradictory
> evidence.
> >>>>> -
> >>>>>  srean
> >>>>>  Check out my website: http://kirbyfan64.github.io/
> >>>
> >>>
> >>> --
> >>> Sent from my Android phone with K-9 Mail. Please excuse my brevity.
> >>> Check out my website: http://kirbyfan64.github.io/
>



-- 
Ryan
If anybody ever asks me why I prefer C++ to C, my answer will be simple:
"It's becauseslejfp23(@#Q*(E*EIdc-SEGFAULT. Wait, I don't think that was
nul-terminated."
Personal reality distortion fields are immune to contradictory evidence. -
srean
Check out my website: http://kirbyfan64.github.io/
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