[Python-Dev] 2.6.9 readline [Was: OS X 10.9 Mavericks -> 2.7.6/3.3.3 updates needed]

[Ned Deily]

In article <20131024094436.230220bf at anarchist>,
 Barry Warsaw <barry at python.org> wrote:
> On Oct 24, 2013, at 02:11 AM, Ned Deily wrote:
> >I don't know where any other potential 2.7.6 or 3.3.3 issues stand at this 
> >point.  But I'd like Benjamin and Georg to propose an aggressive schedule so 
> >we can get these fixes out there. 
> Does this problem affect 2.6?  2.6.9 final is scheduled for Monday, so if
> there's something we need to get in before then, please let me know asap.

Yes, this problem also affects 2.6.  There are some mitigating factors.  The 
support for libedit on OS X is only enabled when building for an OS X 10.5 or 
later ABI because in earlier releases, the readline emulation of libedit was 
judged too buggy.  In 2.6 as is also the case in 2.7, when building from 
source, ./configure defaults to using a 10.4 ABI unless certain universal 
build options are selected or the user explicitly sets 
MACOSX_DEPLOYMENT_TARGET=10.5 or higher when running configure.   With the 
default 10.4 setting, readline.so fails to build so there is no crash - no 
readline features, either.  Also, if one supplies a version of GNU readline 
(which Apple does not ship) as many people do, there is also no crash.

The 2.7 change of Issue18458 (http://hg.python.org/cpython/rev/1e03fd72e116) 
depends on some previous 2.7-only changes in Modules/readline.c so it does not 
apply cleanly to 2.6.  However, there aren't *that* many other earlier changes 
to 2.7 readline that are not in 2.6 and, for the most part, they have to do 
with fixing memory leaks, including some introduced by using newer versions of 
GNU readline, and I didn't see any new features.  Copying the current 2.7 tip 
of readline.c over to the current tip of 2.6 builds cleanly on 10.9.  
test_readline passes and the simple history scrolling seems to work without 
crashing.  I'd recommend either doing nothing or backporting everything.

-- 
 Ned Deily,
 nad at acm.org