This fixes the months-based addition for year_month when the year_month's month component is zero.
Successfully tested on x86_64-pc-linux-gnu, on the 'date' library's calendar and (now) on libcxx's calendar tests. Does this look OK to commit? libstdc++-v3/ChangeLog: * include/std/chrono (year_month::operator+): Properly handle a month value of 0 by casting the month value to int before subtracting 1 from it so that the difference is signed in the subsequent addition. * testsuite/std/time/year_month/1.cc: Test addition of months to a year_month whose month value is below and above the normalized range of [1,12]. --- libstdc++-v3/include/std/chrono | 2 +- libstdc++-v3/testsuite/std/time/year_month/1.cc | 12 ++++++++++++ 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/std/chrono b/libstdc++-v3/include/std/chrono index 417954d103b..398008c8f31 100644 --- a/libstdc++-v3/include/std/chrono +++ b/libstdc++-v3/include/std/chrono @@ -2133,7 +2133,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { // TODO: Optimize? auto __m = __ym.month() + __dm; - auto __i = unsigned{__ym.month()} - 1 + __dm.count(); + auto __i = int(unsigned{__ym.month()}) - 1 + __dm.count(); auto __y = (__i < 0 ? __ym.year() + years{(__i - 11) / 12} : __ym.year() + years{__i / 12}); diff --git a/libstdc++-v3/testsuite/std/time/year_month/1.cc b/libstdc++-v3/testsuite/std/time/year_month/1.cc index 007cfeb2f72..4c331dcdb50 100644 --- a/libstdc++-v3/testsuite/std/time/year_month/1.cc +++ b/libstdc++-v3/testsuite/std/time/year_month/1.cc @@ -83,4 +83,16 @@ constexpr_year_month() static_assert(2017y/33 + months{0} == 2019y/9); static_assert(2010y/January + months{-12} == 2009y/January); + + static_assert(2010y/month{0} + months{-1} == 2009y/November); + static_assert(2010y/month{0} + months{0} == 2009y/December); + static_assert(2010y/month{0} + months{1} == 2010y/January); + static_assert(2010y/month{0} + months{2} == 2010y/February); + static_assert(2010y/month{0} + months{11} == 2010y/November); + static_assert(2010y/month{0} + months{12} == 2010y/December); + static_assert(2010y/month{0} + months{13} == 2011y/January); + + static_assert(months{-1} + 2010y/month{37} == 2012y/December); + static_assert(months{0} + 2010y/month{37} == 2013y/January); + static_assert(months{1} + 2010y/month{37} == 2013y/February); } -- 2.28.0.337.ge9b77c84a0