Debug algorithms

[François Dumont]

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