[Bug libstdc++/103022] New: std::begin on empty std::valarray causes _GLIBCXX_DEBUG assertion

[Bug libstdc++/103022] New: std::begin on empty std::valarray causes _GLIBCXX_DEBUG assertion

[sbergman at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103022

            Bug ID: 103022
           Summary: std::begin on empty std::valarray causes
                    _GLIBCXX_DEBUG assertion
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sbergman at redhat dot com
  Target Milestone: ---

At least with GCC 11.2.1:

> $ cat test.cc
> #include <valarray>
> int main() {
>     std::valarray<double> v;
>     std::begin(v);
> }

> $ g++ -D_GLIBCXX_DEBUG test.cc
> $ ./a.out
> /usr/include/c++/11/valarray:594: _Tp& std::valarray<_Tp>::operator[](std::size_t) [with _Tp = double; std::size_t = long unsigned int]: Assertion '__i < this->size()' failed.
> Aborted

because the std::begin overload is implemented via

  return std::__addressof(__va[0]);

ever since
<https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=f67a9881a86bcdeb67fa52c0a8eb45ce9d4134d4>
"[multiple changes]" and the std::valarray subscript operator calls

  __glibcxx_requires_subscript(__i);

ever since
<https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=285b36d6a58c08792e78f9fedb3f84bdba3a4eee>
"[multiple changes]".

(See
<https://git.libreoffice.org/core/+/82047d042e9d5d24b334eba63fd7e4c5bbbb022e%5E%21>
"crashtesting: assert on conversion of fdo67521-1.odg to pdf" for an issue this
caused in LibreOffice.)

[Bug libstdc++/103022] std::begin on empty std::valarray causes _GLIBCXX_DEBUG assertion

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103022

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |redi at gcc dot gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-11-01

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The obvious solution is to not use std::valarray, like all sensible people :-P

[Bug libstdc++/103022] std::begin on empty std::valarray causes _GLIBCXX_DEBUG assertion

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103022

--- Comment #2 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:91bac9fed5d082f0b180834110ebc0f46f97599a

commit r12-4824-g91bac9fed5d082f0b180834110ebc0f46f97599a
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Nov 1 11:06:51 2021 +0000

    libstdc++: Fix range access for empty std::valarray [PR103022]

    The std::begin and std::end overloads for std::valarray are defined in
    terms of std::addressof(v[0]) which is undefined for an empty valarray.

    libstdc++-v3/ChangeLog:

            PR libstdc++/103022
            * include/std/valarray (begin, end): Do not dereference an empty
            valarray. Add noexcept and [[nodiscard]].
            * testsuite/26_numerics/valarray/range_access.cc: Check empty
            valarray. Check iterator properties. Run as well as compiling.
            * testsuite/26_numerics/valarray/range_access2.cc: Likewise.
            * testsuite/26_numerics/valarray/103022.cc: New test.

[Bug libstdc++/103022] std::begin on empty std::valarray causes _GLIBCXX_DEBUG assertion

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103022

--- Comment #3 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:0111975c07233512e63371b2bc99f88d9670bbc9

commit r11-9198-g0111975c07233512e63371b2bc99f88d9670bbc9
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Nov 1 11:06:51 2021 +0000

    libstdc++: Fix range access for empty std::valarray [PR103022]

    The std::begin and std::end overloads for std::valarray are defined in
    terms of std::addressof(v[0]) which is undefined for an empty valarray.

    libstdc++-v3/ChangeLog:

            PR libstdc++/103022
            * include/std/valarray (begin, end): Do not dereference an empty
            valarray. Add noexcept and [[nodiscard]].
            * testsuite/26_numerics/valarray/range_access.cc: Check empty
            valarray. Check iterator properties. Run as well as compiling.
            * testsuite/26_numerics/valarray/range_access2.cc: Likewise.
            * testsuite/26_numerics/valarray/103022.cc: New test.

    (cherry picked from commit 91bac9fed5d082f0b180834110ebc0f46f97599a)

[Bug libstdc++/103022] std::begin on empty std::valarray causes _GLIBCXX_DEBUG assertion

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103022

--- Comment #4 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:2374dfc907a9eb6ae2940c0d49de37bcf96bd5e5

commit r10-10246-g2374dfc907a9eb6ae2940c0d49de37bcf96bd5e5
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Nov 1 11:06:51 2021 +0000

    libstdc++: Fix range access for empty std::valarray [PR103022]

    The std::begin and std::end overloads for std::valarray are defined in
    terms of std::addressof(v[0]) which is undefined for an empty valarray.

    libstdc++-v3/ChangeLog:

            PR libstdc++/103022
            * include/std/valarray (begin, end): Do not dereference an empty
            valarray. Add noexcept and [[nodiscard]].
            * testsuite/26_numerics/valarray/range_access.cc: Check empty
            valarray. Check iterator properties. Run as well as compiling.
            * testsuite/26_numerics/valarray/range_access2.cc: Likewise.
            * testsuite/26_numerics/valarray/103022.cc: New test.

    (cherry picked from commit 91bac9fed5d082f0b180834110ebc0f46f97599a)

[Bug libstdc++/103022] std::begin on empty std::valarray causes _GLIBCXX_DEBUG assertion

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103022

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:12f7864eff882cba2720d8871d8b136bd7a1d3cd

commit r9-9807-g12f7864eff882cba2720d8871d8b136bd7a1d3cd
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Nov 1 11:06:51 2021 +0000

    libstdc++: Fix range access for empty std::valarray [PR103022]

    The std::begin and std::end overloads for std::valarray are defined in
    terms of std::addressof(v[0]) which is undefined for an empty valarray.

    libstdc++-v3/ChangeLog:

            PR libstdc++/103022
            * include/std/valarray (begin, end): Do not dereference an empty
            valarray. Add noexcept.
            * testsuite/26_numerics/valarray/range_access.cc: Check empty
            valarray. Check iterator properties. Run as well as compiling.
            * testsuite/26_numerics/valarray/range_access2.cc: Likewise.
            * testsuite/26_numerics/valarray/103022.cc: New test.

    (cherry picked from commit 91bac9fed5d082f0b180834110ebc0f46f97599a)

[Bug libstdc++/103022] std::begin on empty std::valarray causes _GLIBCXX_DEBUG assertion

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103022

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
   Target Milestone|---                         |9.5
             Status|ASSIGNED                    |RESOLVED

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 9.5, 10.4 and 11.3