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segfaults calling warnings.warn() with non-string message #47889
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dalcinl commented
on Aug 21, 2008 dalcinlmannequinMannequinAuthorfrom warnings import warn warn("hello world") # -> Success warn(UserWarning) # -> Segmentation fault warn(None) # -> Segmentation fault warn(1) # -> Segmentation fault
devdanzin commented
on Aug 22, 2008 devdanzinmannequinMannequinTwo small clues.
First, a backtrace:
#0 0xb7df102a in strcmp () from /lib/tls/i686/cmov/libc.so.6 #1 0x0809e678 in warn_explicit (category=0x81dd140, message=0xb7ac58f4, filename=0xb7acced0, lineno=1, module=0xb7f53300, registry=0xb7ac9e94, sourceline=0x0) at Python/_warnings.c:393 #2 0x0809f1df in do_warn (message=0x81fbd78, category=0x81dd140, stack_level=1) at Python/_warnings.c:606 #3 0x0809f37d in warnings_warn (self=0xb7aceab4, args=0xb7af0a7c, kwds=0x0) at Python/_warnings.c:628 #4 0x081624ee in PyCFunction_Call (func=0xb7acace4, arg=0xb7af0a7c, kw=0x0) at Objects/methodobject.c:84 #5 0x080b3633 in call_function (pp_stack=0xbfd51f44, oparg=1) at Python/ceval.c:3403 #6 0x080ae776 in PyEval_EvalFrameEx (f=0x82b5e6c, throwflag=0) at Python/ceval.c:2205 #7 0x080b1ac8 in PyEval_EvalCodeEx (co=0xb7ade988, globals=0xb7f4f5d4, locals=0xb7f4f5d4, args=0x0, argcount=0, kws=0x0, kwcount=0, defs=0x0, defcount=0, kwdefs=0x0, closure=0x0) at Python/ceval.c:2840 #8 0x080a686f in PyEval_EvalCode (co=0xb7ade988, globals=0xb7f4f5d4, locals=0xb7f4f5d4) at Python/ceval.c:519 #9 0x080df486 in run_mod (mod=0x82ba910, filename=0x81a09e4 "<stdin>", globals=0xb7f4f5d4, locals=0xb7f4f5d4, flags=0xbfd52370, arena=0x8216df8) at Python/pythonrun.c:1553 #10 0x080dd67e in PyRun_InteractiveOneFlags (fp=0xb7ec7440, filename=0x81a09e4 "<stdin>", flags=0xbfd52370) at Python/pythonrun.c:958 #11 0x080dd1e0 in PyRun_InteractiveLoopFlags (fp=0xb7ec7440, filename=0x81a09e4 "<stdin>", flags=0xbfd52370) at Python/pythonrun.c:870 #12 0x080dd038 in PyRun_AnyFileExFlags (fp=0xb7ec7440, filename=0x81a09e4 "<stdin>", closeit=0, flags=0xbfd52370) at Python/pythonrun.c:839 #13 0x080ef6ba in Py_Main (argc=1, argv=0xb7f22028) at Modules/main.c:592 #14 0x0805a689 in main (argc=1, argv=0xbfd534c4) at ./Modules/python.c:57
Then, this behavior: Python 3.0b3+ (py3k:65930M, Aug 21 2008, 21:23:08) [GCC 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import _warnings [40709 refs] >>> _warnings.warn(0) __main__:1: UserWarning: 0 [40739 refs] >>> _warnings.warn(12345) __main__:1: UserWarning: 12345 [40744 refs] >>> _warnings.warn(AttributeError) __main__:1: UserWarning: <class 'AttributeError'> [40750 refs] >>> import warnings [41483 refs] >>> warnings.warn(0) [41483 refs] >>> warnings.warn(12345) [41483 refs] >>> warnings.warn(10101) Segmentation fault
That is, _warnings.warn(spam) works OK and avoids the
warnings.warn(spam) crash for values already called by the former.If you search for _PyUnicode_AsString() in Python/_warnings.c you will
find several places that assume that the proper measures have been taken
to make sure the object is a string. All of those places need to be
fixed so that if a string is not passed in then one is grabbed.And the reason this turned out as a segfault is for a missing error
return value just before the strcmp() call.devdanzin commented
on Aug 22, 2008 devdanzinmannequinMannequinBrett,
I don't think I know C (and CPython) enough to fix this. I was able to
get rid of this specific segfault with this:-
const char \*text_char = \_PyUnicode_AsString(text);
+ const char *text_char =
_PyUnicode_AsString(PyObject_Str(text));But I have no idea whether I should also incref/decref the PyObject_Str.
-
On Fri, Aug 22, 2008 at 8:03 AM, Daniel Diniz <report@bugs.python.org> wrote:
Daniel Diniz <ajaksu@gmail.com> added the comment:
Brett,
I don't think I know C (and CPython) enough to fix this. I was able to
get rid of this specific segfault with this:-
const char \*text_char = \_PyUnicode_AsString(text);
-
const char \*text_char =
_PyUnicode_AsString(PyObject_Str(text));
But I have no idea whether I should also incref/decref the PyObject_Str.
That's along the lines of what needs to be done (and what I was
planning on doing), although you need to do more error checking on the
return values. Plus the patch I am cooking up adds more checks in the
code for the return value of _PyUnicode_AsString().-
The patch doesn't actually bother with a translation as the code causing
issue is only there to prevent infinite recursion. So if the object
being used is not a string, then there is no need to worry as it is not
part of the infinite recursion problem.I also added a bunch of missing error checks.
Brett, is this patch ready for review?
That's why the keyword is set. =)
On Fri, Aug 22, 2008 at 2:59 PM, Brett Cannon <report@bugs.python.org> wrote:
Brett Cannon <brett@python.org> added the comment:
That's why the keyword is set. =)
Ah. I missed that. :) The patch looks fine.
Python tracker <report@bugs.python.org>
<http://bugs.python.org/issue3639\>
--
Cheers,
Benjamin Peterson
"There's no place like 127.0.0.1."Checked in r66140.
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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