From a248d8daf5d12795c2891c3ac8978b1f728e43e8 Mon Sep 17 00:00:00 2001
From: Ulf Hermann <ulf.hermann@qt.io>
Date: Wed, 1 Jun 2022 07:50:46 +0200
Subject: [PATCH] Endian: Allow special bitfield union fields to cover the
 whole storage

This requires a different computation of the mask since we can't shift
out of the storage type.

Change-Id: Ife85ca3e0c5ca47f06988a397cc2f8a7e28ad0fe
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 src/corelib/global/qendian_p.h                      |  7 ++++++-
 tests/auto/corelib/global/qtendian/tst_qtendian.cpp | 12 +++++++++++-
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/corelib/global/qendian_p.h b/src/corelib/global/qendian_p.h
index fd5a9dd992..9e31f7940a 100644
--- a/src/corelib/global/qendian_p.h
+++ b/src/corelib/global/qendian_p.h
@@ -139,7 +139,12 @@ public:
 
     static constexpr UnsignedType mask() noexcept
     {
-        return ((UnsignedType(1) << width) - 1) << pos;
+        if constexpr (width == sizeof(UnsignedType) * 8) {
+            static_assert(pos == 0);
+            return ~UnsignedType(0);
+        } else {
+            return ((UnsignedType(1) << width) - 1) << pos;
+        }
     }
 
 private:
diff --git a/tests/auto/corelib/global/qtendian/tst_qtendian.cpp b/tests/auto/corelib/global/qtendian/tst_qtendian.cpp
index 7f13559067..e688768b74 100644
--- a/tests/auto/corelib/global/qtendian/tst_qtendian.cpp
+++ b/tests/auto/corelib/global/qtendian/tst_qtendian.cpp
@@ -377,8 +377,9 @@ void testBitfieldUnion()
     using upper = Member<21, 11, uint>;
     using lower = Member<10, 11, uint>;
     using bottom = Member<0, 10, int>;
+    using all = Member<0, 32, uint>;
 
-    using UnionType = Union<upper, lower, bottom>;
+    using UnionType = Union<upper, lower, bottom, all>;
     UnionType u;
 
     u.template set<upper>(200);
@@ -402,6 +403,15 @@ void testBitfieldUnion()
     UnionType u2(QSpecialIntegerBitfieldZero);
     QCOMPARE(u2.data(), 0U);
 
+    u2.template set<all>(std::numeric_limits<uint>::max());
+    QCOMPARE(u2.template get<all>(), std::numeric_limits<uint>::max());
+
+    u2.template set<all>(453);
+    QCOMPARE(u2.template get<all>(), 453U);
+
+    u2.template set<all>(0);
+    QCOMPARE(u2.template get<all>(), 0U);
+
     UnionType u3(42U);
     QCOMPARE(u3.data(), 42U);