[libcxx-commits] [PATCH] D70346: [libc++] [LWG3321] Mark "year_month_day_last::day() specification does not cover !ok() values" issue as "Nothing to do", but add assertion.

[Marek Kurdej via Phabricator via libcxx-commits]

curdeius created this revision.
curdeius added reviewers: ldionne, mclow.lists, EricWF.
Herald added subscribers: libcxx-commits, dexonsmith, christof.
Herald added a project: libc++.

This LWG issue states that the result of `year_month_day_last::day()` is implementation defined if `ok()` is `false`.
However, from user perspective, calling `day()` in this situation will lead to a (possibly difficult to find) crash.
Hence, I have added an assertion to warn user at least when assertions are enabled.
I am however not aware of the libc++ stand on the desired behaviour.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70346

Files:
  libcxx/include/chrono
  libcxx/www/cxx2a_status.html


Index: libcxx/www/cxx2a_status.html
===================================================================
--- libcxx/www/cxx2a_status.html
+++ libcxx/www/cxx2a_status.html
@@ -409,7 +409,7 @@
 	<tr><td><a href="https://wg21.link/LWG3209">3209</a></td><td>Expression in <tt>year::ok()</tt> returns clause is ill-formed</td><td>Cologne</td><td>Complete</td></tr>
 
 	<tr><td></td><td></td><td></td><td></td></tr>
-	<tr><td><a href="https://wg21.link/LWG3231">3231</a></td><td><tt>year_month_day_last::day</tt> specification does not cover <tt>!ok()</tt> values</td><td>Belfast</td><td></td></tr>
+	<tr><td><a href="https://wg21.link/LWG3231">3231</a></td><td><tt>year_month_day_last::day</tt> specification does not cover <tt>!ok()</tt> values</td><td>Belfast</td><td><i>Nothing to do</i></td></tr>
 	<tr><td><a href="https://wg21.link/LWG3225">3225</a></td><td><tt>zoned_time</tt> converting constructor shall not be <tt>noexcept</tt></td><td>Belfast</td><td></td></tr>
 	<tr><td><a href="https://wg21.link/LWG3190">3190</a></td><td><tt>std::allocator::allocate</tt> sometimes returns too little storage</td><td>Belfast</td><td></td></tr>
 	<tr><td><a href="https://wg21.link/LWG3218">3218</a></td><td>Modifier for <tt>%d</tt> parse flag does not match POSIX and <tt>format</tt> specification</td><td>Belfast</td><td></td></tr>
Index: libcxx/include/chrono
===================================================================
--- libcxx/include/chrono
+++ libcxx/include/chrono
@@ -824,6 +824,7 @@
 */
 
 #include <__config>
+#include <__debug>
 #include <ctime>
 #include <type_traits>
 #include <ratio>
@@ -2454,6 +2455,7 @@
         chrono::day(31), chrono::day(31), chrono::day(30),
         chrono::day(31), chrono::day(30), chrono::day(31)
     };
+    _LIBCPP_ASSERT(ok(), "year_month_day_last::day(): year_month_day_last is invalid");
     return month() != February || !__y.is_leap() ?
         __d[static_cast<unsigned>(month()) - 1] : chrono::day{29};
 }


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