[Python-Dev] Newly Built Python3 Binary Throws Segfault

Ryan Gonzalez rymg19 at gmail.com
Fri Jan 30 19:10:57 CET 2015 

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/
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