Debug algorithms

[François Dumont]

Hi

     Any final decision regarding this patch ?

     Note that __std_a namespace is optional, I can remove this change 
from the patch if you want.

François


On 18/07/2016 21:25, François Dumont wrote:
> On 13/07/2016 19:45, Jonathan Wakely wrote:
>> On 22/06/16 22:05 +0200, François Dumont wrote:
>>> Hi
>>>
>>>    Here is eventually the so long promized patch to introduce Debug 
>>> algos similarly to Debug containers.
>>
>> I'm trying to decide how much benefit this really gives us, and
>> whether the obfuscation to the code (even more namespaces involved,
>> and having to use __std_a:: instead of std::) is worth it. It also
>> means more code to maintain of course, with extra overloads.
>>
>>>    Why such an evolution:
>>> - More flexibility, debug algos can be used explicitely without 
>>> activating Debug mode.
>>
>> Although nice in theory, I doubt this will get much usage in practice.
>>
>>> - Performance: Debug algos can get rid of Debug layer on top of 
>>> container iterators to invoke normal algos. Operations on normal 
>>> iterators are faster and we also benefit from the same algos 
>>> specialization that sometimes exist on some container iterators 
>>> (like std::deque ones). Also normal algos are now using other normal 
>>> algos, Debug check won't be done several times.
>>> - It will be easier to implement new Debug checks without the 
>>> limitation to do so through some Debug macro
>>>
>>>    To do so I introduced a new namespace __cxx1998_a used for normal 
>>> algos when Debug mode is active. I couldn't reuse __cxx1998 cause 
>>> with current implementation of Debug containers __cxx1998 is exposed 
>>> and because of ADL we could then have ambiguity between Debug and 
>>> normal versions of the same algos. I also introduced a __std_a 
>>> namespace which control the kind of algos used within the library 
>>> mostly for containers implementation details.
>>
>>
>> I think I need to apply the patch locally and spend some time looking
>> at the new structure, to see what ends up calling what. I'm finding it
>> difficult to follow that just from reading the patch.
>>
>>
> This is definitely more code to maintain but I hope this code won't 
> require much maintenance as it only host the Debug logic and not the 
> algo logic itself. It relies on normal algo for algo logic.
>
> You can see this patch as a way to cleanup the normal mode too !
>
> If __cxx1998 namespace was perfectly encapsulated we could avoid the 
> __cxx1998_a but for the moment the boundary between normal and debug 
> mode is too tight.
>
> François
>