Issue 762455: Python segfaults when sys.stdout is changed in getattr (original) (raw)
Created on 2003-06-28 18:24 by hyeshik.chang, last changed 2022-04-10 16:09 by admin. This issue is now closed.
Messages (9)
Author: Hyeshik Chang (hyeshik.chang) * 
Date: 2003-06-28 18:24
Reproducible source digest:
import sys class StdoutGuard: def getattr(self, attr): sys.stdout = sys.stdout raise RuntimeError("Premature access to sys.stdout.%s" % attr) sys.stdout = StdoutGuard() print "Oops!"
and Backtrace:
(gdb) bt #0 0x00000002 in ?? () #1 0x08055ba6 in PyObject_GetAttrString (v=0x814b9e0, name=0x2 <Error reading address 0x2: Bad address>) at Objects/object.c:1066 #2 0x080a57d2 in PyFile_WriteObject (v=0x817d180, f=0x8178a8c, flags=135760524) at Objects/fileobject.c:1691 #3 0x08071493 in eval_frame (f=0x8121c0c) at Python/ceval.c:1371 #4 0x080730be in PyEval_EvalCodeEx (co=0x8126500, globals=0x2, locals=0x2, args=0x0, argcount=0, kws=0x0, kwcount=0, defs=0x0, defcount=0, closure=0x0) at Python/ceval.c:2595 #5 0x080702da in PyEval_EvalCode (co=0x8126500, globals=0x812fd0c, locals=0x812fd0c) at Python/ceval.c:481 #6 0x08089891 in run_node (n=0x8178a80, filename=0xbfbff648 "test.py", globals=0x812fd0c, locals=0x812fd0c, flags=0xbfbff4d8) at Python/pythonrun.c:1067 #7 0x08088af7 in PyRun_SimpleFileExFlags (fp=0x282c3780, filename=0xbfbff648 "test.py", closeit=1, flags=0xbfbff4d8) at Python/pythonrun.c:673 #8 0x08052a77 in Py_Main (argc=1, argv=0xbfbff538) at Modules/main.c:367 #9 0x080525cf in main (argc=2, argv=0xbfbff538) at Modules/python.c:10 #10 0x08052505 in _start () (gdb) f 2 #2 0x080a57d2 in PyFile_WriteObject (v=0x817d180, f=0x8178a8c, flags=135760524) at Objects/fileobject.c:1691 1691 writer = PyObject_GetAttrString(f, "write"); (gdb) p *f $22 = {ob_refcnt = 1000843696, ob_type = 0x814b9e0}
Author: Hyeshik Chang (hyeshik.chang) *
Date: 2003-06-28 18:26
Logged In: YES user_id=55188
import sys class StdoutGuard: def getattr(self, attr): sys.std out = sys.stdout raise RuntimeError("Premature access to sys.stdout.%s" % attr) sys.stdout = StdoutGuard() print "Oops!"
Author: Neal Norwitz (nnorwitz) *
Date: 2003-06-29 02:48
Logged In: YES user_id=33168
Attached is a patch which fixes the problem. I'm not entirely sure the comment is accurate. 2.2.3 doesn't crash, but goes into an infinite loop. Tim should this go into 2.3b2?
Author: Raymond Hettinger (rhettinger) *
Date: 2003-06-29 03:38
Logged In: YES user_id=80475
This looks like a clean fix to me and ought to go into 2.3b2 so it can be shaken out further.
Please use filefault.py to create a unittest.
Author: Neal Norwitz (nnorwitz) *
Date: 2003-06-29 04:58
Logged In: YES user_id=33168
I couldn't get the test working. It always passed, before and after the fix. I would like to have a test for this, but no time now.
Author: Raymond Hettinger (rhettinger) *
Date: 2003-06-29 05:27
Logged In: YES user_id=80475
filefault.py fails for me before the patch and succeeds after the patch.
If you go ahead and apply the patch, I'll write the test. Do you have an idea which test_*.py is the best place for it?
Author: Tim Peters (tim.peters) *
Date: 2003-06-29 05:56
Logged In: YES user_id=31435
I can't make time to analyze the problem, but the comment sounds plausible .
The fix isn't quite right, though: because w can be NULL, you have to use Py_XINCREF and Py_XDECREF instead of Py_INCREF and Py_DECREF. The latter will probably segfault when w is NULL.
Author: Neal Norwitz (nnorwitz) *
Date: 2003-06-29 14:57
Logged In: YES user_id=33168
Checked in as:
- Python/ceval.c 2.367 & 2.301.4.9
Assigned to Raymond to make a test.
As for the test, in test_descr.specials() there is some stdout handling at the end of the function (around line 1881). I don't know of a better place than that.
Author: Raymond Hettinger (rhettinger) *
Date: 2003-06-29 15:45
Logged In: YES user_id=80475
Done. See test_descr.py 1.196