[issue9770] curses.isblank function doesn't match ctype.h
akira
report at bugs.python.org
Thu Jun 19 19:35:12 CEST 2014
akira added the comment:
I've fixed isblank to accept tab instead of backspace and added tests
for character classification functions from curses.ascii module that
have corresponding analogs in ctype.h. They've uncovered issues in
isblank, iscntrl, and ispunct functions.
Open questions:
- is it a security bug (backspace is treated as tab in isblank())?
If it is then 3.1, 3.2, 3.3 branches should also be updated
[devguide]. If not then only 2.7, 3.4, and default branches should
be changed.
[devguide]: http://hg.python.org/devguide/file/9794412fa62d/devcycle.rst#l105
- iscntrl() mistakenly returns false for 0x7f but c11 defines it as
a control character. Should iscntrl behavior (and its docs) be
changed to confirm? Should another issue be opened?
- ispunct() mistakenly returns true for control characters such as
'\n'. The documentation says (paraphrasing) 'any printable except
space and alnum'. string.printable includes '\n' but 'printing
character' in C11 does not include the newline. Moreover
curses.ascii.isprint follows C behavior and excludes control
characters. Should another issue be opened to return false from
ispunct() for control characters such as '\n'?
- ispunct() mistakenly returns true for non-ascii characters such as
0xff
- negative integer values: C functions are defined for EOF macros
(some negative value) and the behavior is undefined for any other
negative integer value. What should be curses.ascii.is* predicates
behavior? Should Python guarantee that False is returned?
- curses.ascii.isspace/.isblank doesn't raise TypeError for bytes,
None on Python 3
- should constants from string module be used? What is more
fundamental: string.digits or curses.ascii.isdigit?
- no tests for: isascii, isctrl, ismeta (they are not defined in
ctype.h). It is unclear what the behaviour should be e.g., isascii
mistakenly returns True for negative ints, ismeta returns True for
any non-ascii character including Unicode letters. It is not clear
how isctrl is different from iscntrl.
----------
keywords: +patch
nosy: +akira
Added file: http://bugs.python.org/file35693/curses_ascii_isblank_issue9770.patch
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