QLogging: fix potential missing NUL-terminator when calling OutputDebugString

The string returned from QStringView::utf16() is, in general, not
NUL-terminated, as OutputDebugString() requires. Though we only ever
call win_outputDebugString_helper() with an actual QString, it's not
100% clear said QString doesn't originate from, say, a QStringLiteral,
in which case QString::utf16() would have to (an does) detach() to
ensure the NUL-termination.

So, take by const QString&, but use QStringView::mid() to avoid
copying the substring content twice.

Amends a049325cc708b483ed1aadc6589419f4d74b19f3.

Pick-to: 6.3 6.2 5.15
Change-Id: Ie42a6000c75c6a55d629621d89e0cf498b174d29
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/corelib/global/qlogging.cpp b/src/corelib/global/qlogging.cpp
index f2d4a50a2c..6e4da27d5e 100644
--- a/src/corelib/global/qlogging.cpp
+++ b/src/corelib/global/qlogging.cpp
@@ -1671,7 +1671,7 @@ static bool android_default_message_handler(QtMsgType type,
 #endif //Q_OS_ANDROID
 
 #ifdef Q_OS_WIN
-static void win_outputDebugString_helper(QStringView message)
+static void win_outputDebugString_helper(const QString &message)
 {
     const qsizetype maxOutputStringLength = 32766;
     static QBasicMutex m;
@@ -1683,7 +1683,7 @@ static void win_outputDebugString_helper(QStringView message)
         wchar_t *messagePart = new wchar_t[maxOutputStringLength + 1];
         for (qsizetype i = 0; i < message.length(); i += maxOutputStringLength) {
             const qsizetype length = qMin(message.length() - i, maxOutputStringLength);
-            const qsizetype len = message.mid(i, length).toWCharArray(messagePart);
+            const qsizetype len = QStringView{message}.mid(i, length).toWCharArray(messagePart);
             Q_ASSERT(len == length);
             messagePart[len] = 0;
             OutputDebugString(messagePart);