QByteArrayList: fix narrowing in join() implementations [1/2]

We forgot to adjust the interface and implementation of join() to the
int → qsizetype change in Qt 6.

This part of the two-part patch fixes things in a forwards-BC way, to
allow picking into released versions. The forwards-BC break is in the
second patch of the series.

[ChangeLog][QtCore][QByteArrayList] Fixed a bug when calling join() on
lists with more than INTMAX elements.

Change-Id: I26976864e77169ff0db7c672d1d42d88dbfcc437
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
(cherry picked from commit c1c15abc8d0d4f0804dba49e95ffdde5f8591413)
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

2 files changed, 13 insertions, 8 deletions

diff --git a/src/corelib/text/qbytearraylist.cpp b/src/corelib/text/qbytearraylist.cpp
index c815e766ab..4a1df30216 100644
--- a/src/corelib/text/qbytearraylist.cpp
+++ b/src/corelib/text/qbytearraylist.cpp
@@ -122,12 +122,12 @@ QT_BEGIN_NAMESPACE
     element separated by the given \a separator.
 */
 
-static int QByteArrayList_joinedSize(const QByteArrayList *that, int seplen)
+static qsizetype QByteArrayList_joinedSize(const QByteArrayList *that, qsizetype seplen)
 {
-    int totalLength = 0;
-    const int size = that->size();
+    qsizetype totalLength = 0;
+    const qsizetype size = that->size();
 
-    for (int i = 0; i < size; ++i)
+    for (qsizetype i = 0; i < size; ++i)
         totalLength += that->at(i).size();
 
     if (size > 0)
@@ -139,10 +139,10 @@ static int QByteArrayList_joinedSize(const QByteArrayList *that, int seplen)
 QByteArray QtPrivate::QByteArrayList_join(const QByteArrayList *that, const char *sep, int seplen)
 {
     QByteArray res;
-    if (const int joinedSize = QByteArrayList_joinedSize(that, seplen))
+    if (const qsizetype joinedSize = QByteArrayList_joinedSize(that, seplen))
         res.reserve(joinedSize); // don't call reserve(0) - it allocates one byte for the NUL
-    const int size = that->size();
-    for (int i = 0; i < size; ++i) {
+    const qsizetype size = that->size();
+    for (qsizetype i = 0; i < size; ++i) {
         if (i)
             res.append(sep, seplen);
         res += that->at(i);
diff --git a/src/corelib/text/qbytearraylist.h b/src/corelib/text/qbytearraylist.h
index e00586291f..677161c21c 100644
--- a/src/corelib/text/qbytearraylist.h
+++ b/src/corelib/text/qbytearraylist.h
@@ -46,6 +46,8 @@
 
 #include <QtCore/qbytearray.h>
 
+#include <limits>
+
 QT_BEGIN_NAMESPACE
 
 #if !defined(QT_NO_JAVA_STYLE_ITERATORS)
@@ -78,7 +80,10 @@ public:
     inline QByteArray join() const
     { return QtPrivate::QByteArrayList_join(self(), nullptr, 0); }
     inline QByteArray join(const QByteArray &sep) const
-    { return QtPrivate::QByteArrayList_join(self(), sep.constData(), sep.size()); }
+    {
+        Q_ASSERT(sep.size() <= (std::numeric_limits<int>::max)());
+        return QtPrivate::QByteArrayList_join(self(), sep.data(), sep.size());
+    }
     inline QByteArray join(char sep) const
     { return QtPrivate::QByteArrayList_join(self(), &sep, 1); }
 };