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* [Bug libstdc++/107572] New: cartesian_product_view invokes the begin of input_range twice @ 2022-11-08 15:25 hewillk at gmail dot com 2022-11-08 15:35 ` [Bug libstdc++/107572] " redi at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: hewillk at gmail dot com @ 2022-11-08 15:25 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107572 Bug ID: 107572 Summary: cartesian_product_view invokes the begin of input_range twice Product: gcc Version: 13.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ Assignee: unassigned at gcc dot gnu.org Reporter: hewillk at gmail dot com Target Milestone: --- ranges#L8069: auto __it = __detail::__tuple_transform(ranges::begin, _M_bases); if (!__empty_tail) std::get<0>(__it) = __detail::__cartesian_common_arg_end(std::get<0>(_M_bases)); return _Iterator<false>{*this, std::move(__it)}; This *always* invokes begin twice for the first range, which is undefined behavior when it is an input_range. testcase (https://godbolt.org/z/7hfP8xM6a): #include <ranges> #include <fmt/ranges.h> #include <sstream> std::istringstream ints("0 1 2 3 4"); struct istream_range { auto begin() { return std::istream_iterator<int>{ints}; } auto end() { return std::istream_iterator<int>{}; } }; int main() { istream_range r; fmt::print("{}\n", std::views::cartesian_product(r)); // prints [(0), (2), (3), (4)] } ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/107572] cartesian_product_view invokes the begin of input_range twice 2022-11-08 15:25 [Bug libstdc++/107572] New: cartesian_product_view invokes the begin of input_range twice hewillk at gmail dot com @ 2022-11-08 15:35 ` redi at gcc dot gnu.org 2023-03-07 21:07 ` ppalka at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2022-11-08 15:35 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107572 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |ppalka at gcc dot gnu.org Ever confirmed|0 |1 Last reconfirmed| |2022-11-08 Status|UNCONFIRMED |NEW ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/107572] cartesian_product_view invokes the begin of input_range twice 2022-11-08 15:25 [Bug libstdc++/107572] New: cartesian_product_view invokes the begin of input_range twice hewillk at gmail dot com 2022-11-08 15:35 ` [Bug libstdc++/107572] " redi at gcc dot gnu.org @ 2023-03-07 21:07 ` ppalka at gcc dot gnu.org 2023-03-09 18:25 ` cvs-commit at gcc dot gnu.org 2023-03-09 18:27 ` ppalka at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: ppalka at gcc dot gnu.org @ 2023-03-07 21:07 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107572 Patrick Palka <ppalka at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |ppalka at gcc dot gnu.org ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/107572] cartesian_product_view invokes the begin of input_range twice 2022-11-08 15:25 [Bug libstdc++/107572] New: cartesian_product_view invokes the begin of input_range twice hewillk at gmail dot com 2022-11-08 15:35 ` [Bug libstdc++/107572] " redi at gcc dot gnu.org 2023-03-07 21:07 ` ppalka at gcc dot gnu.org @ 2023-03-09 18:25 ` cvs-commit at gcc dot gnu.org 2023-03-09 18:27 ` ppalka at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: cvs-commit at gcc dot gnu.org @ 2023-03-09 18:25 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107572 --- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>: https://gcc.gnu.org/g:3df9760d56662bdf38dd45f7398f003bbd64fdfe commit r13-6558-g3df9760d56662bdf38dd45f7398f003bbd64fdfe Author: Patrick Palka <ppalka@redhat.com> Date: Thu Mar 9 13:25:44 2023 -0500 libstdc++: extraneous begin in cartesian_product_view::end [PR107572] ranges::begin() isn't guaranteed to be equality-preserving for non-forward ranges, so in cartesian_product_view::end we need to avoid needlessly calling begin() on the first range (which could be non-forward) in the case where __empty_tail is false as per its specification. Since we're already using a variadic lambda to compute __empty_tail, we might as well use that same lambda to build up the tuple of iterators instead of building it separately via e.g. std::apply or __tuple_transform. PR libstdc++/107572 libstdc++-v3/ChangeLog: * include/std/ranges (cartesian_product_view::end): When building the tuple of iterators, avoid calling ranges::begin on the first range if __empty_tail is false. * testsuite/std/ranges/cartesian_product/1.cc (test07): New test. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/107572] cartesian_product_view invokes the begin of input_range twice 2022-11-08 15:25 [Bug libstdc++/107572] New: cartesian_product_view invokes the begin of input_range twice hewillk at gmail dot com ` (2 preceding siblings ...) 2023-03-09 18:25 ` cvs-commit at gcc dot gnu.org @ 2023-03-09 18:27 ` ppalka at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: ppalka at gcc dot gnu.org @ 2023-03-09 18:27 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107572 Patrick Palka <ppalka at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Target Milestone|--- |13.0 Status|ASSIGNED |RESOLVED Resolution|--- |FIXED --- Comment #2 from Patrick Palka <ppalka at gcc dot gnu.org> --- Should be fixed, thanks for catching this. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-03-09 18:27 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-11-08 15:25 [Bug libstdc++/107572] New: cartesian_product_view invokes the begin of input_range twice hewillk at gmail dot com 2022-11-08 15:35 ` [Bug libstdc++/107572] " redi at gcc dot gnu.org 2023-03-07 21:07 ` ppalka at gcc dot gnu.org 2023-03-09 18:25 ` cvs-commit at gcc dot gnu.org 2023-03-09 18:27 ` ppalka at gcc dot gnu.org
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