From ac608b7bd2fc3876d1a521cb3542b6b56133fd0f Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@kdab.com>
Date: Tue, 4 Jun 2019 12:43:16 +0200
Subject: QDebug: add nothrow move special member functions

This requires making QDebugStateSaver hold QDebug::Stream directly, not
QDebug by reference, as the referenced object will have been moved from
when ~QDebugStateSaver executes. The stream object, however, will still
be around.

Change-Id: I0ca2eb60cb9b68ea3835d9a9ff5e295d9b1c5fb5
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: David Faure <david.faure@kdab.com>
---
 src/corelib/io/qdebug.cpp | 36 +++++++++++++++++-------------------
 src/corelib/io/qdebug.h   |  9 +++++----
 2 files changed, 22 insertions(+), 23 deletions(-)

(limited to 'src/corelib/io')

diff --git a/src/corelib/io/qdebug.cpp b/src/corelib/io/qdebug.cpp
index 6dc12cd83f..d13e94e096 100644
--- a/src/corelib/io/qdebug.cpp
+++ b/src/corelib/io/qdebug.cpp
@@ -147,7 +147,7 @@ using QtMiscUtils::fromHex;
 // Has been defined in the header / inlined before Qt 5.4
 QDebug::~QDebug()
 {
-    if (!--stream->ref) {
+    if (stream && !--stream->ref) {
         if (stream->space && stream->buffer.endsWith(QLatin1Char(' ')))
             stream->buffer.chop(1);
         if (stream->message_output) {
@@ -843,36 +843,34 @@ QDebug &QDebug::resetFormat()
 class QDebugStateSaverPrivate
 {
 public:
-    QDebugStateSaverPrivate(QDebug &dbg)
-        : m_dbg(dbg),
-          m_spaces(dbg.autoInsertSpaces()),
-          m_flags(0),
-          m_streamParams(dbg.stream->ts.d_ptr->params)
+    QDebugStateSaverPrivate(QDebug::Stream *stream)
+        : m_stream(stream),
+          m_spaces(stream->space),
+          m_flags(stream->context.version > 1 ? stream->flags : 0),
+          m_streamParams(stream->ts.d_ptr->params)
     {
-        if (m_dbg.stream->context.version > 1)
-            m_flags = m_dbg.stream->flags;
     }
     void restoreState()
     {
-        const bool currentSpaces = m_dbg.autoInsertSpaces();
+        const bool currentSpaces = m_stream->space;
         if (currentSpaces && !m_spaces)
-            if (m_dbg.stream->buffer.endsWith(QLatin1Char(' ')))
-                m_dbg.stream->buffer.chop(1);
+            if (m_stream->buffer.endsWith(QLatin1Char(' ')))
+                m_stream->buffer.chop(1);
 
-        m_dbg.setAutoInsertSpaces(m_spaces);
-        m_dbg.stream->ts.d_ptr->params = m_streamParams;
-        if (m_dbg.stream->context.version > 1)
-            m_dbg.stream->flags = m_flags;
+        m_stream->space = m_spaces;
+        m_stream->ts.d_ptr->params = m_streamParams;
+        if (m_stream->context.version > 1)
+            m_stream->flags = m_flags;
 
         if (!currentSpaces && m_spaces)
-            m_dbg.stream->ts << ' ';
+            m_stream->ts << ' ';
     }
 
-    QDebug &m_dbg;
+    QDebug::Stream *m_stream;
 
     // QDebug state
     const bool m_spaces;
-    int m_flags;
+    const int m_flags;
 
     // QTextStream state
     const QTextStreamPrivate::Params m_streamParams;
@@ -886,7 +884,7 @@ public:
     \sa QDebug::setAutoInsertSpaces(), QDebug::autoInsertSpaces()
 */
 QDebugStateSaver::QDebugStateSaver(QDebug &dbg)
-    : d(new QDebugStateSaverPrivate(dbg))
+    : d(new QDebugStateSaverPrivate(dbg.stream))
 {
 }
 
diff --git a/src/corelib/io/qdebug.h b/src/corelib/io/qdebug.h
index 889fb6b571..421c5d933b 100644
--- a/src/corelib/io/qdebug.h
+++ b/src/corelib/io/qdebug.h
@@ -65,6 +65,7 @@ QT_BEGIN_NAMESPACE
 class Q_CORE_EXPORT QDebug
 {
     friend class QMessageLogger;
+    friend class QDebugStateSaver;
     friend class QDebugStateSaverPrivate;
     struct Stream {
         enum { VerbosityShift = 29, VerbosityMask = 0x7 };
@@ -114,7 +115,10 @@ public:
     inline QDebug(QString *string) : stream(new Stream(string)) {}
     inline QDebug(QtMsgType t) : stream(new Stream(t)) {}
     inline QDebug(const QDebug &o):stream(o.stream) { ++stream->ref; }
+    QDebug(QDebug &&other) noexcept : stream{qExchange(other.stream, nullptr)} {}
     inline QDebug &operator=(const QDebug &other);
+    QDebug &operator=(QDebug &&other) noexcept
+    { QDebug{std::move(other)}.swap(*this); return *this; }
     ~QDebug();
     inline void swap(QDebug &other) noexcept { qSwap(stream, other.stream); }
 
@@ -203,10 +207,7 @@ public:
 
 inline QDebug &QDebug::operator=(const QDebug &other)
 {
-    if (this != &other) {
-        QDebug copy(other);
-        qSwap(stream, copy.stream);
-    }
+    QDebug{other}.swap(*this);
     return *this;
 }
 
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