[apparmor] [patch] rewrite set_profile_flags() to use write_header()

[Christian Boltz]

Hello,

Am Donnerstag, 2. April 2015 schrieb Seth Arnold:
> On Thu, Apr 02, 2015 at 12:03:40PM -0700, Steve Beattie wrote:
> > > The difference is this:
> > > 
> > > $ python2.7 -c "print(len('   ')/2)"
> > > 1

Seriously?

if 3/2 == 1:
    print("old python inside")

> > > $ python3 -c "print(len('   ')/2)"
> > > 1.5
> 
> Argh. I still can't believe that made it into a relese..

At least the new version does what sane people and math teachers expect.

> > So importing division from __future__ gives floating point division
> > by default in python 2.7, to match the behavior of division in
> > python3. Adding it to apparmor/aa.py lets the tests that were
> > failing only under python 2.7 pass, but I'm a little leery of
> > adding it, as grepping for> 
> > division in aa.py gives at least:
> >                 data += write_methods[segs](prof_data, int(depth /
> >                 2))
> >                 
> >                         data += write_header(write_prof_data[name],
> >                         int(depth / 2), name, False, include_flags)>                     
> >                     depth = int(len(line) - len(line.lstrip()) / 2)
> >                     + 1
> >                     depth = int((len(line) - len(line.lstrip())) /
> >                     2)
> > 
> > so I'm concerned we'd be introducing other changes by doing
> > so... though getting consistent behavior across python2 and python3
> > would be a benefit, I'd say.
> 
> It looks like those other cases are prepared for it, the int()
> wrappers look like they are bringing back the usual truncation on
> division.

I also checked and agree - all divisions have an int() call around. 
BTW: the only divisions we do are for depth (number of leading spaces), 
and funnily we later undo this with a multiplication ;-)

Besides that - I'm using the tools with py3 since quite some time and 
didn't notice any division-related crash.

> I think importing division from future makes sense here.

Agreed. To make it more formal:


Tell python2 about math

if 3/2 == 1:
    print("python2 inside")

Add "from __future__ import division" so that python2 returns the
correct result (if needed, as float)

On related news: At least python3 knows how to calculate correctly.


I propose this patch for trunk and 2.9.


[ 21a-tell-python2-about-math.diff ]

=== modified file utils/apparmor/aa.py
--- utils/apparmor/aa.py        2015-04-02 12:01:55.401784901 +0200
+++ utils/apparmor/aa.py        2015-04-02 21:34:02.886805899 +0200
@@ -13,7 +13,7 @@
 #
 # 
----------------------------------------------------------------------
 # No old version logs, only 2.6 + supported
-from __future__ import with_statement
+from __future__ import division, with_statement
 import inspect
 import os
 import re



Regards,

Christian Boltz
-- 
Yeah, I always need to have a sick bag handy when thinking about
web apps ;-)  [Ludwig Nussel in opensuse-packaging]