[Bug libstdc++/100833] New: ranges::advance should return n when i == bound

[Bug libstdc++/100833] New: ranges::advance should return n when i == bound

[hewillk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100833

            Bug ID: 100833
           Summary: ranges::advance should return n when i == bound
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hewillk at gmail dot com
  Target Milestone: ---

This is specified in [range.iter.op.advance#7]:
"Returns: n - M, where M is the difference between the ending and starting
positions of i."


#include <ranges>

constexpr auto diff = [] {
  auto r = std::views::single(0) | 
           std::views::filter([](int) { return true; });
  auto it = r.begin();
  return std::ranges::advance(it, 100, r.begin());
}();

static_assert(diff == 100);

https://godbolt.org/z/6nh8xMWYd

[Bug libstdc++/100833] ranges::advance should return n when i == bound

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100833

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |10.4
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2021-06-01
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |redi at gcc dot gnu.org

[Bug libstdc++/100833] ranges::advance should return n when i == bound

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100833

--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:d8326291695c0f13124c232ddf4fd34e3310e649

commit r12-1146-gd8326291695c0f13124c232ddf4fd34e3310e649
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Jun 1 16:02:45 2021 +0100

    libstdc++: Fix return value of std::ranges::advance [PR 100833]

    The three-argument form of ranges::advance is supposed to return the
    difference between the second argument and the distance the iterator was
    advanced. When a non-random-access iterator is not advanced (because it
    already equals the sentinel) we were returning 0 rather than n - 0.

    libstdc++-v3/ChangeLog:

            PR libstdc++/100833
            * include/bits/ranges_base.h (ranges::advance(iter, n, sentinel)):
            Fix return value for no-op case.
            * testsuite/24_iterators/range_operations/advance.cc: Test
            return values of three-argument overload.

[Bug libstdc++/100833] ranges::advance should return n when i == bound

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100833

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:88ed4abb351117f3b7ef9174b3f538c73e6012c7

commit r11-8502-g88ed4abb351117f3b7ef9174b3f538c73e6012c7
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Jun 1 16:02:45 2021 +0100

    libstdc++: Fix return value of std::ranges::advance [PR 100833]

    The three-argument form of ranges::advance is supposed to return the
    difference between the second argument and the distance the iterator was
    advanced. When a non-random-access iterator is not advanced (because it
    already equals the sentinel) we were returning 0 rather than n - 0.

    libstdc++-v3/ChangeLog:

            PR libstdc++/100833
            * include/bits/ranges_base.h (ranges::advance(iter, n, sentinel)):
            Fix return value for no-op case.
            * testsuite/24_iterators/range_operations/advance.cc: Test
            return values of three-argument overload.

    (cherry picked from commit d8326291695c0f13124c232ddf4fd34e3310e649)

[Bug libstdc++/100833] ranges::advance should return n when i == bound

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100833

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:753c8680a46d371e179ff1ade36002486361095e

commit r10-9887-g753c8680a46d371e179ff1ade36002486361095e
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Jun 1 16:02:45 2021 +0100

    libstdc++: Fix return value of std::ranges::advance [PR 100833]

    The three-argument form of ranges::advance is supposed to return the
    difference between the second argument and the distance the iterator was
    advanced. When a non-random-access iterator is not advanced (because it
    already equals the sentinel) we were returning 0 rather than n - 0.

    libstdc++-v3/ChangeLog:

            PR libstdc++/100833
            * include/bits/range_access.h (ranges::advance(iter, n, sentinel)):
            Fix return value for no-op case.
            * testsuite/24_iterators/range_operations/advance.cc: Test
            return values of three-argument overload.

    (cherry picked from commit d8326291695c0f13124c232ddf4fd34e3310e649)

[Bug libstdc++/100833] ranges::advance should return n when i == bound

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100833

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 10.4 and 11.2