[Python-Dev] Newly Built Python3 Binary Throws Segfault

Cyd Haselton chaselton at gmail.com
Fri Jan 30 19:34:18 CET 2015 

Ok...that makes sense.. apologies I do not do a lot of debugging. My
goal was to get Python (then spidermonkey) on my device then start
learning languages where i'd need to learn debugging.

Tried patch, see my reply, agree about Android's locale...at least
where native codeis concerned

On Fri, Jan 30, 2015 at 12:10 PM, Ryan Gonzalez <rymg19 at gmail.com> wrote:
> No, it returns NULL if malloc gives it a raw pointer. It unconditionally
> checks the length of the (possibly null) string argument first.
>
> Please try the patch I attached in the last email. It *might* fix the issue.
> Android has crappy locale handling.
>
> On Fri, Jan 30, 2015 at 12:09 PM, Cyd Haselton <chaselton at gmail.com> wrote:
>>
>>   Unless i'm reading something incorrectly,  _PyMem_RawStrdup is
>> currently returning NULL when given a null pointer.
>>
>> From obmalloc.c
>>
>> _PyMem_RawStrdup(const char *str)
>> {
>>     size_t size;
>> char *copy;
>>     size = strlen(str) + 1;
>>     copy = PyMem_RawMalloc(size);
>>     if (copy == NULL)
>>         return NULL;
>> memcpy(copy, str, size);
>> return copy;
>>           }
>>
>> On Fri, Jan 30, 2015 at 11:56 AM, Ryan Gonzalez <rymg19 at gmail.com> wrote:
>> > 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/
>
>
>
>
> --
> 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/

More information about the Python-Dev mailing list