From d3c060defa29a7d1b5cc90fbb86d51adb226aa55 Mon Sep 17 00:00:00 2001
From: Ivan Solovev <ivan.solovev@qt.io>
Date: Fri, 24 May 2024 10:53:51 +0200
Subject: [PATCH] QDate: fix C++20 builds with MSVC

Commit c4f7dba81e43c11c1e71c19ef7f0b5acad119e60 reworked the C++20
QDate constructors and introduced a helper stdSysDaysToJulianDay()
method. However, the QT_POST_CXX17_API_IN_EXPORTED_CLASS was not used
on this new helper function.
As a result, an application which is built with C++20 but uses a
pre-built QtCore that is built with C++17 cannot call QDate constructors
with the new std::chorono types.

An obvious fix is to add the missing macro to the function.
However, we cannot do it directly, because the function is exported
in C++20 builds, and adding the macro will unexport it.

Use QT6_{DECL,CALL}_NEW_OVERLOAD_TAIL macros to add a new overload of
the stdSysDaysToJulianDay() function and mark it as
QT_POST_CXX17_API_IN_EXPORTED_CLASS.

Keep the old function under the QT_VERSION < Qt 7 check to keep BC.

Amends c4f7dba81e43c11c1e71c19ef7f0b5acad119e60.

Fixes: QTBUG-125610
Change-Id: I999354da51ee58c3691dbc1c0351be15a18a268b
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 88702cc87cf830b145c8bff5174748e3719364f9)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/corelib/time/qdatetime.h | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/corelib/time/qdatetime.h b/src/corelib/time/qdatetime.h
index 8bf2f9f7bfc..56601e5d783 100644
--- a/src/corelib/time/qdatetime.h
+++ b/src/corelib/time/qdatetime.h
@@ -35,28 +35,28 @@ public:
 #if __cpp_lib_chrono >= 201907L || defined(Q_QDOC)
     QT_POST_CXX17_API_IN_EXPORTED_CLASS
     Q_IMPLICIT constexpr QDate(std::chrono::year_month_day date) noexcept
-        : jd(date.ok() ? stdSysDaysToJulianDay(date) : nullJd())
+        : jd(date.ok() ? stdSysDaysToJulianDay(date QT6_CALL_NEW_OVERLOAD_TAIL) : nullJd())
     {}
 
     QT_POST_CXX17_API_IN_EXPORTED_CLASS
     Q_IMPLICIT constexpr QDate(std::chrono::year_month_day_last date) noexcept
-        : jd(date.ok() ? stdSysDaysToJulianDay(date) : nullJd())
+        : jd(date.ok() ? stdSysDaysToJulianDay(date QT6_CALL_NEW_OVERLOAD_TAIL) : nullJd())
     {}
 
     QT_POST_CXX17_API_IN_EXPORTED_CLASS
     Q_IMPLICIT constexpr QDate(std::chrono::year_month_weekday date) noexcept
-        : jd(date.ok() ? stdSysDaysToJulianDay(date) : nullJd())
+        : jd(date.ok() ? stdSysDaysToJulianDay(date QT6_CALL_NEW_OVERLOAD_TAIL) : nullJd())
     {}
 
     QT_POST_CXX17_API_IN_EXPORTED_CLASS
     Q_IMPLICIT constexpr QDate(std::chrono::year_month_weekday_last date) noexcept
-        : jd(date.ok() ? stdSysDaysToJulianDay(date) : nullJd())
+        : jd(date.ok() ? stdSysDaysToJulianDay(date QT6_CALL_NEW_OVERLOAD_TAIL) : nullJd())
     {}
 
     QT_POST_CXX17_API_IN_EXPORTED_CLASS
     static constexpr QDate fromStdSysDays(const std::chrono::sys_days &days) noexcept
     {
-        return QDate(stdSysDaysToJulianDay(days));
+        return QDate(stdSysDaysToJulianDay(days QT6_CALL_NEW_OVERLOAD_TAIL));
     }
 
     QT_POST_CXX17_API_IN_EXPORTED_CLASS
@@ -177,7 +177,9 @@ private:
     static constexpr inline qint64 unixEpochJd() { return Q_INT64_C(2440588); }
 
 #if __cpp_lib_chrono >= 201907L
-    static constexpr qint64 stdSysDaysToJulianDay(const std::chrono::sys_days &days) noexcept
+    QT_POST_CXX17_API_IN_EXPORTED_CLASS
+    static constexpr qint64
+    stdSysDaysToJulianDay(const std::chrono::sys_days &days QT6_DECL_NEW_OVERLOAD_TAIL) noexcept
     {
         const auto epochDays = days.time_since_epoch().count();
         // minJd() and maxJd() fit into 40 bits.
@@ -189,6 +191,13 @@ private:
         }
         return unixEpochJd() + epochDays;
     }
+
+#if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
+    static constexpr qint64 stdSysDaysToJulianDay(const std::chrono::sys_days &days) noexcept
+    {
+        return stdSysDaysToJulianDay(days QT6_CALL_NEW_OVERLOAD_TAIL);
+    }
+#endif // QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
 #endif // __cpp_lib_chrono >= 201907L
 
     qint64 jd;