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 E868E3949090; Mon,  5 Dec 2022 20:50:57 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org E868E3949090
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1670273457;
	bh=V5bIC5vvx3AYwGlV6yth2DwxQk/yNnkC44hFxTWACMs=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=ZeahU0Wn5PVQXThAV/bLXmm30lNELJiqcjiCgGjzEacgIJQkFZ6qn/4787STQ0Uth
	 mLTsiPWa8ANe4fyy1bMY6b/GQC9I20RIv1wPnruG71a3nKf6WqZcYCAFJVq/8Yn8Tl
	 XuZybwy7cn+sfFkqwRNmoxrxoTsJHVDA5pbekQ2o=
From: "jason at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/105838] [10/11/12/13 Regression] g++ 12.1.0 runs out of
 memory or time when building const std::vector of std::strings
Date: Mon, 05 Dec 2022 20:50:57 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 12.1.0
X-Bugzilla-Keywords: compile-time-hog, memory-hog
X-Bugzilla-Severity: normal
X-Bugzilla-Who: jason at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 10.5
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-105838-4-kQj0aE68Wx@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-105838-4@http.gcc.gnu.org/bugzilla/>
References: <bug-105838-4@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=3D105838

--- Comment #12 from Jason Merrill <jason at gcc dot gnu.org> ---
Another significant part of the problem is that vector<string> doesn't have=
 a
generic initializer_list constructor.  Adding

      template <typename __elt>
      _GLIBCXX20_CONSTEXPR
      vector(initializer_list<__elt> __l,
             const allocator_type& __a =3D allocator_type())
      : _Base(__a)
      {
        _M_range_initialize(__l.begin(), __l.end(),
                            random_access_iterator_tag());
      }

so that it can construct from initializer_list<const char *> makes the
construction into a simple loop over a static array.

Users can do this optimization manually by writing e.g.

  auto init =3D {
  "aahing", "aaliis", "aarrgh", "abacas", "abacus", "abakas", "abamps",
"abands", "abased", "abaser", "abases", "abasia",
  };
  const std::vector<std::string> lst (init.begin(), init.end());

and so using the (template) iterator constructor instead of the (non-templa=
te)
initializer_list constructor.  But that shouldn't be necessary.

Jonathan, has anyone suggested adding generic init_list constructors to the
container classes?

What do you think about doing the above translation in the compiler?  Is the
compiler allowed to do that?=