Bugs item #1072182, was opened at 2004-11-23 18:35
Message generated for change (Settings changed) made by rhettinger
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Category: Python Library
Group: Python 2.3
Status: Open
Resolution: None
Priority: 5
Submitted By: Greg McFarlane (gregm)
>Assigned to: Raymond Hettinger (rhettinger)
Summary: bad arg type to isspace in struct module
Initial Comment:
For characters greater than 0x7f, the calls to
isspace() in Modules/structmodule.c can return random
values. For example, on Solaris I got this (incorrect)
output:
>>> import struct
>>> struct.calcsize('10d\xfed')
88
>>>
After changing the three occurrences of
"isspace((int)c)" to "isspace((unsigned char)c)", this
was the (correct) output:
>>> import struct
>>> struct.calcsize('10d\xfed')
Traceback (most recent call last):
File "<stdin>", line 1, in ?
struct.error: bad char in struct format
>>>
Reason: the '\xfe' is taken as a signed char. The code
(int)c converts this to a signed int (-2). The system
isspace macro uses this as an index into the __ctype
array. The array is only defined for the values 0 to
255 and so -2 is out-of-bounds. The value returned by
isspace depends on what happens to be at that location
in memory.
NOTE: There may be other occurrences of this bug in
other parts of the python code. Please check.
----------------------------------------------------------------------
Comment By: Erik Demaine (edemaine)
Date: 2004-11-23 23:52
Message:
Logged In: YES
user_id=265183
Looking at other instances of isspace and friends, I think
this is the point of calling Py_CHARMASK, which is used to
"Convert a possibly signed character to a nonnegative int"
(depending on whether 'char' is signed or unsigned).
In other words, I believe the three instances of
isspace((int)c) in Modules/structmodule.c should be changed
to isspace(Py_CHARMASK(c)).
`grep isspace */*.c | grep -v CHARMASK` suggests some other
potential bugs:
- Modules/posixmodule.c:466 (os2_formatmsg): isspace(*lastc)
- Modules/socketmodule.c:504 (set_error): isspace(*lastc)
`egrep
'isalnum|isalpha|isascii|isblank|iscntrl|isdigit|isgraph|islower|isprint|isprint|ispunct|isupper|isxdigit'
*/*.c | grep -v Py_CHARMASK` suggest the following further bugs:
- Modules/_hotshot.c:1431 (get_version_string):
isdigit((int)*rev) [unlikely to cause trouble, but wrong in
the same way...]
- Modules/_tkinter.c:639 (Tkapp_New): isupper((int)argv0[0])
- Modules/pyexpat.c:1800 (get_version_string):
isdigit((int)*rev) [again unlikely a problem]
- Modules/stropmodule.c:760 (strop_atoi): isalnum((int)end[-1])
ye
- Parser/grammar.c:183 (translabel):
isalpha((int)(lb->lb_str[1]))
- Parser/tokenizer.c:232 (get_coding_spec): isalnum((int)t[0])
- Parser/atof.c:16 (atof): (c = *s++) != '\0' && isdigit(c)
[same problem appears three times in the same function]
- Python/compile.c:1721,1727 (parsestr): int quote = *s; ...
isalpha(quote)
- Python/dynload_aix.c:147 (aix_loaderror): isdigit(*message[i])
- Python/getargs.c:141 (vgetargs1): int c = *format++ (and
later, isalpha(c))
- Python/getargcs.c:258 (vgetargs1): isalpha((int)(*format))
- Python/getargs.c:336 (converttuple): int c = *format++
(and later, isalpha(c))
- Python/getargs.c:1222 (vgetargskeyword): i = *format++
(and later, isalpha(i))
That's all that I could find.
----------------------------------------------------------------------
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