On Wed, 17 Apr 2024, Michael Levine (BLOOMBERG/ 919 3RD A) wrote:
> This patch fixes GCC Bug 108760:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108760
> Before this patch, using std::ranges::iota required including <algorithm>
> when it should have been sufficient to only include <numeric>.
>
> When the patch is applied, the following code will compile:
> https://godbolt.org/z/33EPeqd1b
>
> I added a test case for this change as well.
>
> I built my local version of gcc using the following configuration: $
> ../gcc/configure --disable-bootstrap --prefix="$(pwd)/_pfx/"
> --enable-languages=c,c++,lto
>
> and I tested my changes by running: $ make check-c++ -jN -k
Nice, thanks for the patch!
>
> I ran this on the following OS:
>
> Virtualization: wsl
> Operating System: Ubuntu 20.04.6 LTS
> Kernel: Linux 5.15.146.1-microsoft-standard-WSL2
> Architecture: x86-64
> From bd04070c281572ed7a3b48e3d33543e25b8c8afe Mon Sep 17 00:00:00 2001
> From: Michael Levine <mlevin...@bloomberg.net>
> Date: Fri, 23 Feb 2024 14:13:13 -0500
> Subject: [PATCH 1/2] Fix the bug
>
> Signed-off-by: Michael Levine <mlevin...@bloomberg.net>
> ---
> libstdc++-v3/include/bits/ranges_algo.h | 52 ----------------------
> libstdc++-v3/include/bits/stl_numeric.h | 57 ++++++++++++++++++++++++-
> 2 files changed, 56 insertions(+), 53 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/ranges_algo.h
> b/libstdc++-v3/include/bits/ranges_algo.h
> index 62faff173bd..d258be0b93f 100644
> --- a/libstdc++-v3/include/bits/ranges_algo.h
> +++ b/libstdc++-v3/include/bits/ranges_algo.h
> @@ -3521,58 +3521,6 @@ namespace ranges
>
> #endif // __glibcxx_ranges_contains
>
> -#if __glibcxx_ranges_iota >= 202202L // C++ >= 23
> -
> - template<typename _Out, typename _Tp>
> - struct out_value_result
> - {
> - [[no_unique_address]] _Out out;
> - [[no_unique_address]] _Tp value;
> -
> - template<typename _Out2, typename _Tp2>
> - requires convertible_to<const _Out&, _Out2>
> - && convertible_to<const _Tp&, _Tp2>
> - constexpr
> - operator out_value_result<_Out2, _Tp2>() const &
> - { return {out, value}; }
> -
> - template<typename _Out2, typename _Tp2>
> - requires convertible_to<_Out, _Out2>
> - && convertible_to<_Tp, _Tp2>
> - constexpr
> - operator out_value_result<_Out2, _Tp2>() &&
> - { return {std::move(out), std::move(value)}; }
> - };
> -
> - template<typename _Out, typename _Tp>
> - using iota_result = out_value_result<_Out, _Tp>;
> -
> - struct __iota_fn
> - {
> - template<input_or_output_iterator _Out, sentinel_for<_Out> _Sent,
> weakly_incrementable _Tp>
> - requires indirectly_writable<_Out, const _Tp&>
> - constexpr iota_result<_Out, _Tp>
> - operator()(_Out __first, _Sent __last, _Tp __value) const
> - {
> - while (__first != __last)
> - {
> - *__first = static_cast<const _Tp&>(__value);
> - ++__first;
> - ++__value;
> - }
> - return {std::move(__first), std::move(__value)};
> - }
> -
> - template<weakly_incrementable _Tp, output_range<const _Tp&> _Range>
> - constexpr iota_result<borrowed_iterator_t<_Range>, _Tp>
> - operator()(_Range&& __r, _Tp __value) const
> - { return (*this)(ranges::begin(__r), ranges::end(__r),
> std::move(__value)); }
> - };
> -
> - inline constexpr __iota_fn iota{};
> -
> -#endif // __glibcxx_ranges_iota
> -
> #if __glibcxx_ranges_find_last >= 202207L // C++ >= 23
>
> struct __find_last_fn
> diff --git a/libstdc++-v3/include/bits/stl_numeric.h
> b/libstdc++-v3/include/bits/stl_numeric.h
> index fe911154ab7..1b06c26dc02 100644
> --- a/libstdc++-v3/include/bits/stl_numeric.h
> +++ b/libstdc++-v3/include/bits/stl_numeric.h
> @@ -59,7 +59,7 @@
> #include <bits/concept_check.h>
> #include <debug/debug.h>
> #include <bits/move.h> // For _GLIBCXX_MOVE
> -
> +#include <bits/ranges_base.h> // For _Range as used by std::ranges::iota
>
> namespace std _GLIBCXX_VISIBILITY(default)
> {
> @@ -102,6 +102,61 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> }
> #endif
>
> +namespace ranges
> +{
> +#if __glibcxx_ranges_iota >= 202202L // C++ >= 23
> +
> + template<typename _Out, typename _Tp>
> + struct out_value_result
> + {
> + [[no_unique_address]] _Out out;
> + [[no_unique_address]] _Tp value;
> +
> + template<typename _Out2, typename _Tp2>
> + requires convertible_to<const _Out&, _Out2>
> + && convertible_to<const _Tp&, _Tp2>
> + constexpr
> + operator out_value_result<_Out2, _Tp2>() const &
> + { return {out, value}; }
> +
> + template<typename _Out2, typename _Tp2>
> + requires convertible_to<_Out, _Out2>
> + && convertible_to<_Tp, _Tp2>
> + constexpr
> + operator out_value_result<_Out2, _Tp2>() &&
> + { return {std::move(out), std::move(value)}; }
> + };
IIUC out_value_result should continue to be available from <algorithm>, so we
probably don't want to move it to <numeric> (or one of its internal headers).
Better would be to move it to <bits/ranges_algobase.h> I think.
> +
> + template<typename _Out, typename _Tp>
> + using iota_result = out_value_result<_Out, _Tp>;
> +
> + struct __iota_fn
> + {
> + template<input_or_output_iterator _Out, sentinel_for<_Out> _Sent,
> weakly_incrementable _Tp>
> + requires indirectly_writable<_Out, const _Tp&>
> + constexpr iota_result<_Out, _Tp>
> + operator()(_Out __first, _Sent __last, _Tp __value) const
> + {
> + while (__first != __last)
> + {
> + *__first = static_cast<const _Tp&>(__value);
> + ++__first;
> + ++__value;
> + }
> + return {std::move(__first), std::move(__value)};
> + }
> +
> + template<weakly_incrementable _Tp, output_range<const _Tp&> _Range>
> + constexpr iota_result<borrowed_iterator_t<_Range>, _Tp>
> + operator()(_Range&& __r, _Tp __value) const
> + { return (*this)(ranges::begin(__r), ranges::end(__r),
> std::move(__value)); }
> + };
> +
> + inline constexpr __iota_fn iota{};
> +
> +#endif // __glibcxx_ranges_iota
And it might be cleaner to move ranges::iota directly into <numeric>
instead (and then include <bits/ranges_algobase.h> directly from <numeric>
to bring in <bits/ranges_base.h> and out_value_result) since
<bits/stl_numeric.h> has other users besides <numeric> which would
otherwise get unnecessarily bloated.
> +}
> +
> _GLIBCXX_END_NAMESPACE_VERSION
>
> _GLIBCXX_BEGIN_NAMESPACE_ALGO
> --
> 2.25.1
>
>
> From c52c8d79fb3c7dc9d2512d1635712ffcd3dea07c Mon Sep 17 00:00:00 2001
> From: Michael Levine <mlevin...@bloomberg.net>
> Date: Tue, 16 Apr 2024 16:45:37 -0400
> Subject: [PATCH 2/2] Added a test to verify that the bug has been fixed
>
> Signed-off-by: Michael Levine <mlevin...@bloomberg.net>
> ---
> .../testsuite/std/ranges/iota/108760.cc | 41 +++++++++++++++++++
> 1 file changed, 41 insertions(+)
> create mode 100644 libstdc++-v3/testsuite/std/ranges/iota/108760.cc
>
> diff --git a/libstdc++-v3/testsuite/std/ranges/iota/108760.cc
> b/libstdc++-v3/testsuite/std/ranges/iota/108760.cc
> new file mode 100644
> index 00000000000..4f71383687c
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/std/ranges/iota/108760.cc
> @@ -0,0 +1,41 @@
> +// Copyright (C) 2020-2024 Free Software Foundation, Inc.
> +//
> +// This file is part of the GNU ISO C++ Library. This library is free
> +// software; you can redistribute it and/or modify it under the
> +// terms of the GNU General Public License as published by the
> +// Free Software Foundation; either version 3, or (at your option)
> +// any later version.
> +
> +// This library is distributed in the hope that it will be useful,
> +// but WITHOUT ANY WARRANTY; without even the implied warranty of
> +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> +// GNU General Public License for more details.
> +
> +// You should have received a copy of the GNU General Public License along
> +// with this library; see the file COPYING3. If not see
> +// <http://www.gnu.org/licenses/>.
> +
> +// Fixes https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108760
> +// { dg-do run { target c++23 } }
> +
> +#include <numeric>
> +#include <testsuite_hooks.h>
> +
> +const int ARR_SIZE = 4;
> +
> +void
> +test01()
> +{
> + int expected_arr[ARR_SIZE] = {0, 1, 2, 3};
> + int input_arr[ARR_SIZE] = {0, 0, 0, 0};
> + std::ranges::iota(input_arr, 0);
> + for (int i = 0; i < ARR_SIZE; i++) {
> + VERIFY( input_arr[i] == expected_arr[i]);
> + }
> +}
> +
> +int
> +main()
> +{
> + test01();
> +}
Instead of adding a new test, perhaps we should just move the
existing test libstdc++-v3/testsuite/25_algorithms/iota/1.cc
to libstdc++-v3/testsuite/26_numerics/iota/1.cc and change it
to include <numeric> instead of <algorithm>?
> --
> 2.25.1
>
