[apparmor] [RFC] [patch] Makefile automatically fallback to USE_SYSTEM=1

[John Johansen]

On 03/09/2014 09:36 AM, Christian Boltz wrote:
> Hello,
> 
> Am Freitag, 7. März 2014 schrieb John Johansen:
>> So this is a patch I have been using for a while to get around having
>> to specify USE_SYSTEM=1 every time I run the tests. Is it worth
>> upstreaming and applying to the other Makefiles that currently can
>> take USE_SYSTEM as a parameter
>>
>> If USE_SYSTEM=1 is NOT specified
>>   it tries to find a local build and if it can't find one, it sets
>>   USE_SYSTEM=1 and issues a warning message
>> If USE_SYSTEM=1 is specified
>>   it only tries building against the system libraries
> 
> I understand why you like this behaviour, but I don't like it too much 
> because it introduces some "surprising" behaviour. (And I doubt someone 
> reads the warning if the test succeeds ;-)
> 
I'm not sure why its a surprising behavior, but okay. Question is who
do you see the consumer as?

> 
> Thinking about it - can you implement an additional condition like 
> "file common/enable-auto-fallback-to-USE_SYSTEM exists" (or an 
> environment variable you set in .bashrc, but a file sounds better)?
> 
> That would mean people have to actively opt-in to the automatical 
> fallback by touch'ing the file once in their bzr checkout. This would 
> fix the "surprise" part.
> 
> With the opt-in file added, the patch looks good to me.
> 
using a file is possible, but how about opt-out instead? It would be
easy to add USE_SYSTEM=0, to opt-out. So if USE_SYSTEM is defined
(either 0 or 1) you get one or the other behavior other wise it tries
to build against one then the other