Re: [PATCH v2 1/3] gdbsupport: add gdb::ranges::views::enumerate util

[Simon Marchi <simon.marchi@polymtl.ca>]

Ping.

On 2026-02-20 20:18, simon.marchi@polymtl.ca wrote:
> From: Simon Marchi <simon.marchi@polymtl.ca>
> 
> Add a "enumerate" utility, that acts pretty much like Python's
> enumerate().  It makes the code slightly nicer, for when you would
> otherwise need to handle the counter by hand.
> 
> It can be used like this:
> 
>   std::vector<int> my_vector;
>   for (auto [i, val] : gdb::ranges::views::enumerate (my_vector))
>     ...
> 
> `i` will hold the 0-based index of the current iteration, and `val` will
> be a reference to the value of the current iteration.
> 
> The name is chosen to match std::ranges::views::enumerate from C++23,
> making it easy to switch to that eventually.
> 
> Change-Id: I1870ab50537bcf54bba44a30a0b01ab397be16e3
> ---
>  gdb/Makefile.in                     |   1 +
>  gdb/unittests/enumerate-selftests.c | 154 ++++++++++++++++++++++++++++
>  gdbsupport/enumerate.h              | 121 ++++++++++++++++++++++
>  3 files changed, 276 insertions(+)
>  create mode 100644 gdb/unittests/enumerate-selftests.c
>  create mode 100644 gdbsupport/enumerate.h
> 
> diff --git a/gdb/Makefile.in b/gdb/Makefile.in
> index 2aa95be968ac..93701c962fed 100644
> --- a/gdb/Makefile.in
> +++ b/gdb/Makefile.in
> @@ -462,6 +462,7 @@ SELFTESTS_SRCS = \
>  	unittests/common-utils-selftests.c \
>  	unittests/copy_bitwise-selftests.c \
>  	unittests/enum-flags-selftests.c \
> +	unittests/enumerate-selftests.c \
>  	unittests/environ-selftests.c \
>  	unittests/filtered_iterator-selftests.c \
>  	unittests/format_pieces-selftests.c \
> diff --git a/gdb/unittests/enumerate-selftests.c b/gdb/unittests/enumerate-selftests.c
> new file mode 100644
> index 000000000000..ddda29f66251
> --- /dev/null
> +++ b/gdb/unittests/enumerate-selftests.c
> @@ -0,0 +1,154 @@
> +/* Self tests for the enumerate range adapter.
> +
> +   Copyright (C) 2026 Free Software Foundation, Inc.
> +
> +   This file is part of GDB.
> +
> +   This program 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 of the License, or
> +   (at your option) any later version.
> +
> +   This program 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 program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +#include "gdbsupport/selftest.h"
> +#include "gdbsupport/enumerate.h"
> +
> +#include <vector>
> +#include <array>
> +
> +namespace selftests {
> +
> +static void
> +test_enumerate ()
> +{
> +  /* Test basic enumeration over a vector.  */
> +  {
> +    std::vector<int> vec = { 10, 20, 30, 40 };
> +    std::vector<std::pair<std::size_t, int>> result;
> +    std::vector<std::pair<std::size_t, int>> expected {
> +      {0, 10},
> +      {1, 20},
> +      {2, 30},
> +      {3, 40}
> +    };
> +
> +    for (auto [i, val] : gdb::ranges::views::enumerate (vec))
> +      result.push_back ({ i, val });
> +
> +    SELF_CHECK (result == expected);
> +  }
> +
> +  /* Test enumeration over an std::array.  */
> +  {
> +    std::array<int, 3> arr = { 5, 6, 7 };
> +    std::vector<std::pair<std::size_t, int>> result;
> +    std::vector<std::pair<std::size_t, int>> expected {
> +      {0, 5},
> +      {1, 6},
> +      {2, 7}
> +    };
> +
> +    for (auto [i, val] : gdb::ranges::views::enumerate (arr))
> +      result.push_back ({ i, val });
> +
> +    SELF_CHECK (result == expected);
> +  }
> +
> +  /* Test enumeration over a C array.  */
> +  {
> +    int arr[] = { 8, 9, 10 };
> +    std::vector<std::pair<std::size_t, int>> result;
> +    std::vector<std::pair<std::size_t, int>> expected {
> +      {0, 8},
> +      {1, 9},
> +      {2, 10}
> +    };
> +
> +    for (auto [i, val] : gdb::ranges::views::enumerate (arr))
> +      result.push_back ({ i, val });
> +
> +    SELF_CHECK (result == expected);
> +  }
> +
> +  /* Test that enumeration allows modification of elements.  */
> +  {
> +    std::vector<int> vec = { 1, 2, 3 };
> +    std::vector<int> expected = { 10, 20, 30 };
> +
> +    for (auto [i, val] : gdb::ranges::views::enumerate (vec))
> +      val *= 10;
> +
> +    SELF_CHECK (vec == expected);
> +  }
> +
> +  /* Test enumeration over an empty container.  */
> +  {
> +    std::vector<int> vec;
> +    std::vector<std::pair<std::size_t, int>> result;
> +    std::vector<std::pair<std::size_t, int>> expected;
> +
> +    for (auto [i, val] : gdb::ranges::views::enumerate (vec))
> +      result.push_back ({ i, val });
> +
> +    SELF_CHECK (result == expected);
> +  }
> +
> +  /* Test enumeration over a single-element container.  */
> +  {
> +    std::vector<int> vec = { 42 };
> +    std::vector<std::pair<std::size_t, int>> result;
> +    std::vector<std::pair<std::size_t, int>> expected {
> +      {0, 42}
> +    };
> +
> +    for (auto [i, val] : gdb::ranges::views::enumerate (vec))
> +      result.push_back ({ i, val });
> +
> +    SELF_CHECK (result == expected);
> +  }
> +
> +  /* Test enumeration over an rvalue container.  */
> +  {
> +    std::vector<std::pair<std::size_t, int>> result;
> +    std::vector<std::pair<std::size_t, int>> expected {
> +      {0, 17},
> +      {1, 38},
> +      {2, 99}
> +    };
> +
> +    for (auto [i, val] :
> +	 gdb::ranges::views::enumerate (std::vector<int> { 17, 38, 99 }))
> +      result.push_back ({ i, val });
> +
> +    SELF_CHECK (result == expected);
> +  }
> +
> +  /* Test enumeration with const container.  */
> +  {
> +    const std::vector<int> vec = { 100, 200 };
> +    std::vector<std::pair<std::size_t, int>> result;
> +    std::vector<std::pair<std::size_t, int>> expected {
> +      {0, 100},
> +      {1, 200}
> +    };
> +
> +    for (auto [i, val] : gdb::ranges::views::enumerate (vec))
> +      result.push_back ({ i, val });
> +
> +    SELF_CHECK (result == expected);
> +  }
> +}
> +
> +} /* namespace selftests */
> +
> +INIT_GDB_FILE (enumerate_selftests)
> +{
> +  selftests::register_test ("enumerate", selftests::test_enumerate);
> +}
> diff --git a/gdbsupport/enumerate.h b/gdbsupport/enumerate.h
> new file mode 100644
> index 000000000000..504d789f0ac3
> --- /dev/null
> +++ b/gdbsupport/enumerate.h
> @@ -0,0 +1,121 @@
> +/* An enumerate range adapter for GDB, the GNU debugger.
> +   Copyright (C) 2026 Free Software Foundation, Inc.
> +
> +   This file is part of GDB.
> +
> +   This program 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 of the License, or
> +   (at your option) any later version.
> +
> +   This program 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 program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +#ifndef GDBSUPPORT_ENUMERATE_H
> +#define GDBSUPPORT_ENUMERATE_H
> +
> +#include <cstddef>
> +#include <iterator>
> +#include <tuple>
> +#include <utility>
> +
> +namespace gdb::ranges::views
> +{
> +
> +/* An iterator that wraps another iterator and yields tuples containing
> +   both the index and the value.  */
> +
> +template<typename Iterator>
> +class enumerate_iterator
> +{
> +  using base_iterator = Iterator;
> +public:
> +  using value_type
> +    = std::tuple<std::size_t,
> +		 typename std::iterator_traits<base_iterator>::reference>;
> +
> +  explicit enumerate_iterator (Iterator it)
> +    : m_it (std::move (it))
> +  {}
> +
> +  value_type operator* () const
> +  { return { m_index, *m_it }; }
> +
> +  enumerate_iterator &operator++ ()
> +  {
> +    ++m_it;
> +    ++m_index;
> +    return *this;
> +  }
> +
> +  bool operator== (const enumerate_iterator &other) const
> +  { return m_it == other.m_it; }
> +
> +  bool operator!= (const enumerate_iterator &other) const
> +  { return m_it != other.m_it; }
> +
> +private:
> +  Iterator m_it;
> +  std::size_t m_index = 0;
> +};
> +
> +/* A range adapter that allows iteration on both index and value.  */
> +
> +template<typename Range>
> +class enumerate_range
> +{
> +  using base_iterator = decltype (std::begin (std::declval<Range &> ()));
> +
> +public:
> +  using iterator = enumerate_iterator<base_iterator>;
> +
> +  explicit enumerate_range (Range &&range)
> +    : m_range (std::forward<Range> (range))
> +  {}
> +
> +  iterator begin ()
> +  { return iterator (std::begin (m_range)); }
> +
> +  iterator end ()
> +  { return iterator (std::end (m_range)); }
> +
> +private:
> +  Range m_range;
> +};
> +
> +/* Return an enumerate_range for RANGE, allowing iteration with both
> +   index and value.
> +
> +   Example usage:
> +
> +     std::vector<int> vec = {10, 20, 30};
> +     for (auto [i, val] : gdb::ranges::views::enumerate (vec))
> +       printf ("%zu: %d\n", i, val);
> +
> +   This prints:
> +
> +     0: 10
> +     1: 20
> +     2: 30
> +
> +   The value is a reference to the element in the container, so
> +   modifications are possible:
> +
> +     for (auto [i, val] : gdb::ranges::views::enumerate (vec))
> +       val *= 2;  */
> +
> +template<typename Range>
> +enumerate_range<Range>
> +enumerate (Range &&range)
> +{
> +  return enumerate_range<Range> (std::forward<Range> (range));
> +}
> +
> +} /* namespace gdb::ranges::views */
> +
> +#endif /* GDBSUPPORT_ENUMERATE_H */
> 
> base-commit: 3049829f1e6dd849e5d3ca71d633990f8d799ae6