From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id A52BC3858412; Mon, 24 Oct 2022 12:46:50 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org A52BC3858412
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1666615610;
	bh=qxefmpIcgSKN3TySeN7T291FGCgiyyWrfqdqI+TEIsA=;
	h=From:To:Subject:Date:From;
	b=J4H/WQh3n7oLNqUepHORTDqkIXbNebjk8v/6N9na18aiP/Ec8ApiglyKht4COpO4H
	 oESOStVwRvnd3xrPpBBC6zjCoafzV5sF0xpo42pPVJs7ApBiUhu17p3yZDRT8Pw2r6
	 jpbZbQIz/qCDvhmt9/zKaK4E31DoS++OvGxiDT6U=
From: "listcrawler at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/107376] New: regex executor requires allocator to be
 default constructible
Date: Mon, 24 Oct 2022 12:46:50 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: libstdc++
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: listcrawler at gmail dot com
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-107376-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107376

            Bug ID: 107376
           Summary: regex executor requires allocator to be default
                    constructible
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: listcrawler at gmail dot com
  Target Milestone: ---

To recreate problem:

#include <regex>
#include <memory>

template <typename T>
struct Alloc
{
    using value_type =3D T;

    T* allocate(std::size_t n)
    {
        return std::allocator<T>{}.allocate(n);
    }

    void deallocate(T* p, std::size_t n)
    {
        std::allocator<T>{}.deallocate(p, n);
    }

    ~Alloc() =3D default;
  //explicit Alloc() =3D default;
    explicit Alloc(int) {}

    Alloc(Alloc const&) =3D default;
    Alloc(Alloc     && rhs) =3D default;
    Alloc& operator=3D(Alloc const&) =3D default;
    Alloc& operator=3D(Alloc     && rhs) =3D default;

    template<typename U> Alloc(Alloc<U> const& rhs) {}
    template<typename U> Alloc(Alloc<U>     && rhs) {}
    template<typename U> Alloc& operator=3D(Alloc<U> const& rhs) {}
    template<typename U> Alloc& operator=3D(Alloc<U>     && rhs) {}
};

template<typename T, typename U>
bool operator=3D=3D(Alloc<T> const&, Alloc<U> const&)
{
    return true;
}

template<typename T, typename U>
bool operator!=3D(Alloc<T> const&, Alloc<U> const&)
{
    return false;
}

// =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D

template<typename T> using A =3D Alloc<T>;

using S        =3D std::string;
using SIt      =3D typename S::const_iterator;
using SubMatch =3D std::sub_match<SIt>;
using Match    =3D std::match_results<SIt, A<SubMatch>>;

int main()
{
    S          s {"foo"};
    Match      m {A<SubMatch>{0}};
    std::regex r {"foo"};
    std::regex_match(s, m, r);
}

Suggested patch:

diff --git a/libstdc++-v3/include/bits/regex_executor.h
b/libstdc++-v3/include/bits/regex_executor.h
index dc0878ce6..080a1134e 100644
--- a/libstdc++-v3/include/bits/regex_executor.h
+++ b/libstdc++-v3/include/bits/regex_executor.h
@@ -71,7 +71,8 @@ namespace __detail
                _ResultsVec&    __results,
                const _RegexT&  __re,
                _FlagT          __flags)
-      : _M_begin(__begin),
+      : _M_cur_results(__results.get_allocator())
+      , _M_begin(__begin),
       _M_end(__end),
       _M_re(__re),
       _M_nfa(*__re._M_automaton),=