From c05982fda39bbfa9fa3641c7e5938f204a8b1bf5 Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Sat, 18 Jan 2025 10:37:31 +0100
Subject: [PATCH] q17::uninitialized_value_construct: use C++17/20 semantics of
 voidify

While LWG 3870 changed the const/static_cast'ing for C++23, this is
q17, so use the C++17/20 semantics of casting away const- and
volatile-ness.

Found in API-review.

Amends 364ac13a79a8fff0447a62e9af5588db397c0bfd.

Pick-to: 6.9
Change-Id: Ie11589cbc96b8c3c36deaa6101a897f527d92a46
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 src/corelib/global/q17memory.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/corelib/global/q17memory.h b/src/corelib/global/q17memory.h
index aef26b8f382..ae1c55272fd 100644
--- a/src/corelib/global/q17memory.h
+++ b/src/corelib/global/q17memory.h
@@ -16,6 +16,13 @@ namespace q17 {
 #if !defined(Q_OS_VXWORKS)
     using std::uninitialized_value_construct;
 #else
+    namespace _detail {
+        template <typename T>
+        void *voidify(T &t) {
+            // LWG3870 changed this for C++23, but this is q_17_, so use the C++17/20 version:
+            return const_cast<void*>(static_cast<const volatile void*>(std::addressof(t)));
+        }
+    } // namespace _detail
     // WindRiver confirmed that implementation of `std::uninitialized_value_construct` is not
     // working properly in VxWorks 24.03 (probably the same problem appears in older versions) with
     // defect VXHVP-9969
@@ -26,7 +33,7 @@ namespace q17 {
         using ValueType = typename std::iterator_traits<ForwardIt>::value_type;
         QT_TRY {
             for (; current != last; ++current)
-                ::new (static_cast<void *>(std::addressof(*current))) ValueType();
+                ::new (_detail::voidify(*current)) ValueType();
         } QT_CATCH(...) {
             std::destroy(first, current);
             QT_RETHROW;