QCborValue: fix the move-assignment operatorv5.15.0-beta4

The double-swap technique I used was flawed and broke on
self-assignment. What I had meant to use was the move-and-swap
technique. Thanks to Peppe for pointing it out.

This also fixes a compiler bug in the Green Hills compiler. It was
finding the wrong "swap" function in qSwap:

    using std::swap;
    swap(value1, value2);

It's supposed to find swap(QCborValue &, QCborValue &) due to argument-
dependent lookup. It's instead finding std::swap<QCborValue>, which
recurses.

Fixes: QTBUG-83390
Change-Id: Ibdc95e9af7bd456a94ecfffd1603e1bee90cd107
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>

1 files changed, 2 insertions, 3 deletions

diff --git a/src/corelib/serialization/qcborvalue.h b/src/corelib/serialization/qcborvalue.h
index f7064ac6e1..aa51e5da81 100644
--- a/src/corelib/serialization/qcborvalue.h
+++ b/src/corelib/serialization/qcborvalue.h
@@ -188,9 +188,8 @@ public:
     QCborValue &operator=(const QCborValue &other);
     QCborValue &operator=(QCborValue &&other) noexcept
     {
-        QCborValue tmp;
-        qSwap(*this, tmp);
-        qSwap(other, *this);
+        QCborValue tmp(std::move(other));
+        swap(tmp);
         return *this;
     }