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Title: Bugs in curses.ascii predicates
Type: behavior Stage: resolved
Components: Library (Lib) Versions: Python 3.6, Python 3.5, Python 2.7
Status: closed Resolution: fixed
Dependencies: Superseder:
Assigned To: serhiy.storchaka Nosy List: akira, serhiy.storchaka, twouters
Priority: normal Keywords: patch

Created on 2016-05-21 20:09 by serhiy.storchaka, last changed 2022-04-11 14:58 by admin. This issue is now closed.

File name Uploaded Description Edit
curses_ascii.patch serhiy.storchaka, 2016-05-21 20:09 review
Messages (5)
msg266020 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * (Python committer) Date: 2016-05-21 20:09
Most curses.ascii predicates corresponds C functions declared in <ctype.h>. But there are some differences:

1. isblank() returns True for space and backspace instead of space and tab.

2. ispunct() returns True for non-ASCII and control characters.

3. iscntrl() returns False for '\x7f'. Note that there is different function isctrl().

These differences look as bugs. Proposed patch fixes them and adds tests for all curses.ascii functions.
msg268825 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * (Python committer) Date: 2016-06-18 19:14
Committed with wrong commit message (damn two clipboards on X11) in ac8338546ca8, d7b6c07bc713, d03c8d0a6a73.
msg269562 - (view) Author: Akira Li (akira) * Date: 2016-06-30 08:08
There is an overlapping issue from 2010: "curses.ascii.isblank() function is broken. It confuses backspace (BS 0x08) with tab (0x09)" 

Your patch fixes it too (it should be closed). Note: the patch does not pass tests from Lib/test/ attached to issue9770 (even if the code: `if char_class_name in ('cntrl', 'punct') test = unittest.expectedFailure(test)` is removed) e.g., iscntrl(-1) should be False but it returns True:

  $ ./python
  >>> import curses.ascii
  >>> curses.ascii.iscntrl(-1) #XXX expected False

If we ignore negative ints then isblank, ispunct, iscntrl provided in the curses_ascii.patch are ok.
msg269573 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * (Python committer) Date: 2016-06-30 10:50
Since screen.getch() can return -1, it looks reasonable to make curses.ascii predicates to work with negative integers.

Do you want to open a new issue and write a patch Akira?
msg269679 - (view) Author: Akira Li (akira) * Date: 2016-07-01 16:59
I'm not sure anything should be done (e.g., it is "undefined behavior" to pass a negative value such as CHAR_MIN (if *char* type is signed) to a character classification function in C. Though EOF value (-1 traditionally) should be handled).

If you want to explore it further; I've enumerated open questions in 2014 (inconsistent TypeError, ord(c) > 0x100, negative ints handling, etc)
Date User Action Args
2022-04-11 14:58:31adminsetgithub: 71266
2016-07-01 16:59:23akirasetmessages: + msg269679
2016-06-30 10:50:56serhiy.storchakasetmessages: + msg269573
2016-06-30 08:08:44akirasetnosy: + akira
messages: + msg269562
2016-06-18 19:14:55serhiy.storchakasetstatus: open -> closed
resolution: fixed
messages: + msg268825

stage: patch review -> resolved
2016-06-18 19:01:02serhiy.storchakasetassignee: serhiy.storchaka
2016-05-21 20:09:59serhiy.storchakacreate