Bugs item #3085651, was opened at 2010-10-11 21:21
Message generated for change (Tracker Item Submitted) made by kthomases
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Ken Thomases (kthomases)
Assigned to: Nobody/Anonymous (nobody)
Summary: Unsafe NSLog in PyObjCTools.Debugging.nsLogPythonException
Initial Comment:
In PyObjCTools.Debugging.nsLogPythonException, the exception is formatted into a string, which is then passed as the first/only argument to NSLog. The problem is that NSLog treats its first argument as a format string. The formatted exception may contain percent ('%') characters, which will be interpreted as format specifiers. Since there are no arguments for those specifiers, an exception is thrown (during logging of an exception).
It results in something like this:
*** Exception occurred during exception handler ***
Traceback (most recent call last):
File "/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/PyObjCTools/Debugging.py", line 83, in exceptionHandler_shouldLogException_mask_
File "/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/PyObjCTools/Debugging.py", line 47, in nsLogPythonException
ValueError: Too few arguments for format string [cur:1/len:1]
2010-10-11 20:47:03.946 CrossOver[497:903] NSExceptionHandler has recorded the following exception:
OC_PythonException -- <type 'exceptions.KeyError'>: u'Key needs_download does not exist'
Stack trace: 0x96155d24 0x97082509 0x98c2a9f1 0x150b2cb8 0x1508c5fe 0x331d4 0x33500 0x32f73 0x97f8cf1e 0x9806c699 0x98068146 0x9806743d 0x980bca61 0x98065e93 0x98063e9c 0x97f7caff 0x255f06 0x97f105bb 0x97f085ed 0x25e676 0x83b10 0x2c92 0x1
When I add a proper format string (u'%@') to the NSLog call, the same path through my code produces a properly-logged exception:
2010-10-11 20:54:26.587 CrossOver[760:903] *** Python exception discarded!
Traceback (most recent call last):
File "/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/PyObjC/PyObjCTools/KeyValueCoding.py", line 213, in getKey
raise KeyError, "Key %s does not exist" % (key,)
KeyError: u'Key needs_download does not exist'
You can see the '%s' in the traceback which is the "bomb" for the unsafe NSLog call.
It's probably a good idea to review all uses of NSLog for similar unsafe calling. The first argument should always be a constant, not a run-time-computed string.
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