Re: Debug algorithms

[Jonathan Wakely <jwakely at redhat dot com>]

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.