Prevent duplicates in readline history

[smontanaro]

BPO	562492
Nosy	@gvanrossum, @smontanaro
Files	readline.diff

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/smontanaro'
closed_at = <Date 2002-06-11.14:33:37.000>
created_at = <Date 2002-05-30.17:47:33.000>
labels = ['extension-modules']
title = 'Prevent duplicates in readline history'
updated_at = <Date 2002-06-11.14:33:37.000>
user = 'https://github.com/smontanaro'

bugs.python.org fields:

activity = <Date 2002-06-11.14:33:37.000>
actor = 'skip.montanaro'
assignee = 'skip.montanaro'
closed = True
closed_date = None
closer = None
components = ['Extension Modules']
creation = <Date 2002-05-30.17:47:33.000>
creator = 'skip.montanaro'
dependencies = []
files = ['4311']
hgrepos = []
issue_num = 562492
keywords = ['patch']
message_count = 5.0
messages = ['40187', '40188', '40189', '40190', '40191']
nosy_count = 2.0
nosy_names = ['gvanrossum', 'skip.montanaro']
pr_nums = []
priority = 'normal'
resolution = 'accepted'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue562492'
versions = ['Python 2.3']

[smontanaro]

Someone complained awhile back on c.l.py that Python's readline
history gets duplicates when you ^P to reexecute the previous
command. I believe the attached patch fixes that. As far as I could
tell, the memory returned by history_get_history_state() is malloc'd,
though that's not documented in the version of the history docs I
have and I didn't have the source handy to check. Someone needs
to verify that before any such change is incorporated into the code
base. (I will download the readline/history source and check if
nobody else can confirm easily.)

Note that I also added a call to using_history() in setup_readline(). I
believe that's what the history docs indicate you should do, though it
doesn't seem to be strictly necessary.

Skip

[gvanrossum]

Logged In: YES
user_id=6380

I like this idea, but I suggest that you check the readline
source to confirm your hypothesis about the need to free
(state). You might want to check different versions of readline
too -- we're trying to be compatible with readline 2.2 through
4.x.

[smontanaro]

Logged In: YES
user_id=44345

I checked the readline 2.0 and 4.2a sources (the oldest and newest tarballs
available from ftp.gnu.org). The history_get_history_state function in both
versions malloc's the state.

Skip

[gvanrossum]

Logged In: YES
user_id=6380

OK, then go for it.

[smontanaro]

Logged In: YES
user_id=44345

incorporated as Modules/readline.c 2.50