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From: "redi 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 22:27:59 +0000 [thread overview] Message-ID: <bug-105838-4-igNdLnMV5B@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-105838-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105838 --- Comment #14 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Jason Merrill from comment #12) > 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 = 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. Which is potentially *much* more efficient, because it constructs the strings in place, instead of making unelidable copies of the initializer_list elements. > Jonathan, has anyone suggested adding generic init_list constructors to the > container classes? Not that I'm aware of. There might be concerns about introducing more ambiguities like the vector<int>{1,2} case. > What do you think about doing the above translation in the compiler? Is the > compiler allowed to do that? Good question. If the compiler first checked that the code as-written would call the initializer_list<value_type> constructor (and not some other constructor) then it should be safe to do it. In the general case, somebody would probably find a way to notice and complain. But if you're thinking of optimizing the specific case of vector<string> then I think it would be unobservable. The string copies can't be observed, because it's unspecified when and how often std::allocator calls operator new.
next prev parent reply other threads:[~2022-12-05 22:28 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-06-03 16:22 [Bug c++/105838] New: " eisjmbjdfcukqlaely at nthrl dot com 2022-06-13 12:47 ` [Bug c++/105838] " rguenth at gcc dot gnu.org 2022-06-13 12:52 ` rguenth at gcc dot gnu.org 2022-06-14 11:56 ` rguenth at gcc dot gnu.org 2022-06-14 13:10 ` [Bug c++/105838] [10/11/12/13 Regression] " rguenth at gcc dot gnu.org 2022-06-14 13:11 ` rguenth at gcc dot gnu.org 2022-06-14 13:37 ` jakub at gcc dot gnu.org 2022-06-28 10:49 ` jakub at gcc dot gnu.org 2022-07-10 20:39 ` pinskia at gcc dot gnu.org 2022-07-11 15:43 ` luydorarko at vusra dot com 2022-12-05 17:57 ` jason at gcc dot gnu.org 2022-12-05 18:30 ` jakub at gcc dot gnu.org 2022-12-05 20:50 ` jason at gcc dot gnu.org 2022-12-05 20:58 ` jason at gcc dot gnu.org 2022-12-05 22:27 ` redi at gcc dot gnu.org [this message] 2022-12-05 22:34 ` jakub at gcc dot gnu.org 2022-12-05 23:57 ` jason at gcc dot gnu.org 2022-12-08 18:34 ` cvs-commit at gcc dot gnu.org 2022-12-08 18:41 ` cvs-commit at gcc dot gnu.org 2022-12-08 18:45 ` cvs-commit at gcc dot gnu.org 2022-12-15 5:26 ` cvs-commit at gcc dot gnu.org 2023-01-09 22:41 ` cvs-commit at gcc dot gnu.org 2023-06-02 15:01 ` [Bug c++/105838] [10/11/12/13/14 " cvs-commit at gcc dot gnu.org 2023-06-12 8:57 ` [Bug c++/105838] [10/11/12 " cvs-commit at gcc dot gnu.org 2023-07-07 10:43 ` [Bug c++/105838] [11/12 " rguenth at gcc dot gnu.org 2023-08-19 9:22 ` fxcoudert at gcc dot gnu.org
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