Re: [PATCH 2/3] libstdc++: Implement C++20 constrained algorithms

[Jonathan Wakely <jwakely at redhat dot com>]

On 05/02/20 19:39 +0100, François Dumont wrote:
> Hi
>
>     Is it me or the patch isn't an attachment ? It is far more 
> convenient to provide something easy to extract and apply locally.
>
> On 2/4/20 3:07 AM, Patrick Palka wrote:
> > This patch implements the C++20 ranges overloads for the algorithms in
> > [algorithms].  Most of the algorithms were reimplemented, with each of their
> > implementations very closely following the existing implementation in
> > bits/stl_algo.h and bits/stl_algobase.h.  The reason for reimplementing most of
> > the algorithms instead of forwarding to their STL-style overload is because
> > forwarding cannot be conformantly and efficiently performed for algorithms that
> > operate on non-random-access iterators.  But algorithms that operate on random
> > access iterators can safely and efficiently be forwarded to the STL-style
> > implementation, and this patch does so for push_heap, pop_heap, make_heap,
> > sort_heap, sort, stable_sort, nth_element, inplace_merge and stable_partition.
> >
> > What's missing from this patch is debug-iterator
>
> Always the 5th wheel of the car like we say in French :-)
>
> I'll be looking at this point once I manage to apply the patch.
>
> >  and container specializations
> > that are present for some of the STL-style algorithms that need to be ported
> > over to the ranges algos.  I marked them missing at TODO comments.  There are
> > also some other minor outstanding TODOs.
> >
> > The code that could use the most thorough review is ranges::__copy_or_move,
> > ranges::__copy_or_move_backward, ranges::__equal and
> > ranges::__lexicographical_compare.  In the tests, I tried to test the interface
> > of each new overload, as well as the correctness of the new implementation.
> >
> > diff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h
> > new file mode 100644
> > index 00000000000..2e177ce7f7a
> > --- /dev/null
> > +++ b/libstdc++-v3/include/bits/ranges_algo.h
> > @@ -0,0 +1,3640 @@
> > +// Core algorithmic facilities -*- C++ -*-
> > +
> > +// Copyright (C) 2019-2020 Free Software Foundation, Inc.
>
> Copyright for new files is wrong, should be only 2020. I know it is 
> painful to maintain that when you work on patch on several years.

I assume Patrick kept the 2019 date because his patch started from a
file I sent him with a few of the algos, and that was dated 2019.

I can't remember what the actual rule is for new files that contain
old code. The copyright on some of the new file *is* from 2019, even
if it wasn't added to the GCC repo yet.

New files containing new code should definitely only have the new date
(usually when I point out wrong dates in patch review it's because
somebody's just copied the comment header from an old testcase and so
the old dates are wrong).

I only wrote that code in December 2019 though, so it doesn't make a
lot of difference either way, 2020 is fine.