https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107572
--- Comment #1 from CVS Commits ---
The master branch has been updated by Patrick Palka :
https://gcc.gnu.org/g:3df9760d56662bdf38dd45f7398f003bbd64fdfe
commit r13-6558-g3df9760d56662bdf38dd45f7398f003bbd64fdfe
Author: Patrick Palka
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.