From: Louis Dionne <ldionne@apple.com>
Date: Tue, 9 Jun 2020 16:31:12 +0000 (-0400)
Subject: [libc++] Avoid UB in year_month_day_last::day() for incorrect months
X-Git-Tag: llvmorg-12-init~3594
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=1f48f8f6e289d3ae14d28ad9bd000ef5ba209fc0;p=platform%2Fupstream%2Fllvm.git

[libc++] Avoid UB in year_month_day_last::day() for incorrect months

This effectively implements the resolution of LWG3231, which mandates
that calling year_month_day_last::day() on an invalid year_month_day_last
is unspecified behavior. Before this change, it was undefined behavior.

Differential Revision: https://reviews.llvm.org/D81477
---

diff --git a/libcxx/include/chrono b/libcxx/include/chrono
index 6e5de39..117aab3 100644
--- a/libcxx/include/chrono
+++ b/libcxx/include/chrono
@@ -2454,7 +2454,7 @@ chrono::day year_month_day_last::day() const noexcept
         chrono::day(31), chrono::day(31), chrono::day(30),
         chrono::day(31), chrono::day(30), chrono::day(31)
     };
-    return month() != February || !__y.is_leap() ?
+    return (month() != February || !__y.is_leap()) && month().ok() ?
         __d[static_cast<unsigned>(month()) - 1] : chrono::day{29};
 }