🧹 Fix GCC complaints

[thorstenhater]

Tree

Fixes --- likely a spurious --- warning in tree.cpp:

[2/6] Building CXX object arbor/CMakeFiles/arbor.dir/tree.cpp.o
In file included from /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/algorithm:60,
                 from /Users/hater/src/arbor/arbor/tree.cpp:1:
In function 'typename __gnu_cxx::__enable_if<std::__is_scalar<_Tp>::__value, void>::__type std::__fill_a1(_ForwardIterator, _ForwardIterator, const _Tp&) [with _ForwardIterator = unsigned int*; _Tp = unsigned int]',
    inlined from 'void std::__fill_a(_FIte, _FIte, const _Tp&) [with _FIte = unsigned int*; _Tp = unsigned int]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_algobase.h:998:21,
    inlined from '_OutputIterator std::__fill_n_a(_OutputIterator, _Size, const _Tp&, random_access_iterator_tag) [with _OutputIterator = unsigned int*; _Size = long unsigned int; _Tp = unsigned int]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_algobase.h:1151:20,
    inlined from '_OI std::fill_n(_OI, _Size, const _Tp&) [with _OI = unsigned int*; _Size = long unsigned int; _Tp = unsigned int]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_algobase.h:1180:29,
    inlined from 'static _ForwardIterator std::__uninitialized_default_n_1<true>::__uninit_default_n(_ForwardIterator, _Size) [with _ForwardIterator = unsigned int*; _Size = long unsigned int]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_uninitialized.h:668:29,
    inlined from 'static _ForwardIterator std::__uninitialized_default_n_1<true>::__uninit_default_n(_ForwardIterator, _Size) [with _ForwardIterator = unsigned int*; _Size = long unsigned int]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_uninitialized.h:660:9,
    inlined from '_ForwardIterator std::__uninitialized_default_n(_ForwardIterator, _Size) [with _ForwardIterator = unsigned int*; _Size = long unsigned int]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_uninitialized.h:712:20,
    inlined from '_ForwardIterator std::__uninitialized_default_n_a(_ForwardIterator, _Size, allocator<_Tp>&) [with _ForwardIterator = unsigned int*; _Size = long unsigned int; _Tp = unsigned int]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_uninitialized.h:779:44,
    inlined from 'void std::vector<_Tp, _Alloc>::_M_default_initialize(size_type) [with _Tp = unsigned int; _Alloc = std::allocator<unsigned int>]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_vector.h:1720:36,
    inlined from 'std::vector<_Tp, _Alloc>::vector(size_type, const allocator_type&) [with _Tp = unsigned int; _Alloc = std::allocator<unsigned int>]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_vector.h:558:30,
    inlined from 'arb::tree::iarray arb::tree::select_new_root(int_type)' at /Users/hater/src/arbor/arbor/tree.cpp:219:34:
/opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_algobase.h:952:18: warning: 'void* __builtin_memset(void*, int, long unsigned int)' offset 4 is out of the bounds [0, 0] [-Warray-bounds=]
  952 |         *__first = __tmp;

Also use iota to generate contiguous indices.

Tests

test_simd.cpp

GCC doesn't acknowledge that simd v[i] = x for all i = 0 ... len(v) initializes v. Force initialization to zero.

test_network_generation.cpp

Compare across signs

test_distributed_for_each.cpp

Compare across signs; resolve by casting to correct type.   

test_range.cpp

GCC really turns the dial up to 11 here, complaining about oob access in

char str[] = "howdy";
auto rg = range_n(str, strlen(str)); // NOTE: Putting 5 here is OK, so is sizeof(str) - 1
util::sort(rg);

Same happens with std::sort(str, str + strlen(str)), so I am pretty sure this is not a real thing.
For reference:

/Users/hater/src/arbor/test/unit/test_range.cpp: In member function 'virtual void range_sort_Test::TestBody()':
/Users/hater/src/arbor/test/unit/test_range.cpp:446:14: note: at offset [8, 4611686018427387903] into object 'cstr' of size 6
  446 |         char cstr[] = "howdy";
      |              ^~~~
In function 'std::_Require<std::__not_<std::__is_tuple_like<_Tp> >, std::is_move_constructible<_Tp>, std::is_move_assignable<_Tp> > std::swap(_Tp&, _Tp&) [with _Tp = char]',
    inlined from 'void std::iter_swap(_ForwardIterator1, _ForwardIterator2) [with _ForwardIterator1 = char*; _ForwardIterator2 = char*]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_algobase.h:185:11,
    inlined from 'void std::__move_median_to_first(_Iterator, _Iterator, _Iterator, _Iterator, _Compare) [with _Iterator = char*; _Compare = __gnu_cxx::__ops::_Iter_less_iter]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_algo.h:91:20,
    inlined from '_RandomAccessIterator std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = char*; _Compare = __gnu_cxx::__ops::_Iter_less_iter]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_algo.h:1855:34,
    inlined from 'void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = char*; _Size = long int; _Compare = __gnu_cxx::__ops::_Iter_less_iter]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_algo.h:1889:38,
    inlined from 'void std::__sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = char*; _Compare = __gnu_cxx::__ops::_Iter_less_iter]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_algo.h:1905:25,
    inlined from 'void std::__sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = char*; _Compare = __gnu_cxx::__ops::_Iter_less_iter]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_algo.h:1900:5,
    inlined from 'void std::sort(_RAIter, _RAIter) [with _RAIter = char*]' at /opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/stl_algo.h:4771:18,
    inlined from 'std::enable_if_t<((bool)(! std::is_const<typename arb::util::impl_seqtrait::sequence_traits<Seq&&>::reference>::value))> arb::util::sort(Seq&&) [with Seq = range<char*, char*>]' at /Users/hater/src/arbor/arbor/util/rangeutil.hpp:154:14,
    inlined from 'virtual void range_sort_Test::TestBody()' at /Users/hater/src/arbor/test/unit/test_range.cpp:448:19:
/opt/homebrew/Cellar/gcc/14.2.0/include/c++/14/bits/move.h:223:11: warning: array subscript [8, 4611686018427387903] is outside array bounds of 'char [6]' [-Warray-bounds=]
  223 |       __b = _GLIBCXX_MOVE(__tmp);
      |           ^
/Users/hater/src/arbor/test/unit/test_range.cpp: In member function 'virtual void range_sort_Test::TestBody()':
/Users/hater/src/arbor/test/unit/test_range.cpp:446:14: note: at offset [8, 4611686018427387903] into object 'cstr' of size 6
  446 |         char cstr[] = "howdy";

I am still going to 'fix' this, since I am for warning free code and don't want to annotate with a pragma.

General

Remove spurious includes.

[boeschf]

using std::begin; using std::end; are brought in scope such that ADL works for types that have an overload for begin(), see https://en.cppreference.com/w/cpp/iterator/begin

[thorstenhater]

Good point! I think all of our containers use a member of begin, it's the proper way.

[boeschf]

Suggested change

	using std::begin;
	using std::begin;
	using std::end;