Ensure QTextStream doesn't modify the Text flag on the underlying iodevice

An empty read or a failed write on the underlying QIODevice of the text
stream would lead to an early return where we wouldn't correctly restore
the QIODevice::Text flag of the io device.

Change-Id: I5b632f45dea6ede3f408113556c3dad1b96574e2
Task-number: QTBUG-47176
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

1 files changed, 10 insertions, 9 deletions

diff --git a/src/corelib/io/qtextstream.cpp b/src/corelib/io/qtextstream.cpp
index a8fd2dd7ab..78dcbfe0e7 100644
--- a/src/corelib/io/qtextstream.cpp
+++ b/src/corelib/io/qtextstream.cpp
@@ -449,6 +449,10 @@ bool QTextStreamPrivate::fillReadBuffer(qint64 maxBytes)
             bytesRead = device->read(buf, sizeof(buf));
     }
 
+    // reset the Text flag.
+    if (textModeEnabled)
+        device->setTextModeEnabled(true);
+
     if (bytesRead <= 0)
         return false;
 
@@ -484,10 +488,6 @@ bool QTextStreamPrivate::fillReadBuffer(qint64 maxBytes)
     readBuffer += QString::fromLatin1(buf, bytesRead);
 #endif
 
-    // reset the Text flag.
-    if (textModeEnabled)
-        device->setTextModeEnabled(true);
-
     // remove all '\r\n' in the string.
     if (readBuffer.size() > oldReadBufferSize && textModeEnabled) {
         QChar CR = QLatin1Char('\r');
@@ -586,17 +586,18 @@ void QTextStreamPrivate::flushWriteBuffer()
     qDebug("QTextStreamPrivate::flushWriteBuffer(), device->write(\"%s\") == %d",
            qt_prettyDebug(data.constData(), qMin(data.size(),32), data.size()).constData(), int(bytesWritten));
 #endif
-    if (bytesWritten <= 0) {
-        status = QTextStream::WriteFailed;
-        return;
-    }
 
 #if defined (Q_OS_WIN)
-    // replace the text flag
+    // reset the text flag
     if (textModeEnabled)
         device->setTextModeEnabled(true);
 #endif
 
+    if (bytesWritten <= 0) {
+        status = QTextStream::WriteFailed;
+        return;
+    }
+
     // flush the file
 #ifndef QT_NO_QOBJECT
     QFileDevice *file = qobject_cast<QFileDevice *>(device);