From 576c8126ab569020b6396134570190525567e36f Mon Sep 17 00:00:00 2001
From: Simon Hausmann <simon.hausmann@qt.io>
Date: Wed, 23 Oct 2019 16:58:26 +0200
Subject: [PATCH] Avoid erroneous creation of QScopedValueRollback objects
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Mark the class as [[nodiscard]] to ensure that instances are given names
and do not destruct (roll back) immediately. This avoids accidental code
like this:

    QScopedValueRollback<Foo>(bar, baz);

which rolls back instantly, when it should be

    QScopedValueRollback<Foo> blah(bar, baz);

which rolls back at the end of the scope.

Change-Id: I00269fe325b804078bd0a9d5058c941af7ba5597
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
---
 src/corelib/tools/qscopedvaluerollback.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/corelib/tools/qscopedvaluerollback.h b/src/corelib/tools/qscopedvaluerollback.h
index f904b8dfcb..b8ceff6665 100644
--- a/src/corelib/tools/qscopedvaluerollback.h
+++ b/src/corelib/tools/qscopedvaluerollback.h
@@ -45,7 +45,11 @@
 QT_BEGIN_NAMESPACE
 
 template <typename T>
-class QScopedValueRollback
+class
+#if QT_HAS_CPP_ATTRIBUTE(nodiscard) && __cplusplus >= 201703L
+[[nodiscard]]
+#endif
+QScopedValueRollback
 {
 public:
     explicit QScopedValueRollback(T &var)