--- a/src/gui/painting/qfixed_p.h
+++ b/src/gui/painting/qfixed_p.h
@@ -18,6 +18,7 @@
 #include <QtGui/private/qtguiglobal_p.h>
 #include "QtCore/qdebug.h"
 #include "QtCore/qpoint.h"
+#include "QtCore/qnumeric.h"
 #include "QtCore/qsize.h"

 QT_BEGIN_NAMESPACE
@@ -136,6 +137,22 @@ constexpr inline QFixed operator+(uint i, QFixed d) { return d+i; }
 constexpr inline QFixed operator-(uint i, QFixed d) { return -(d-i); }
 // constexpr inline QFixed operator*(qreal d, QFixed d2) { return d2*d; }

+inline bool qAddOverflow(QFixed v1, QFixed v2, QFixed *r)
+{
+    int val;
+    bool result = qAddOverflow(v1.value(), v2.value(), &val);
+    r->setValue(val);
+    return result;
+}
+
+inline bool qMulOverflow(QFixed v1, QFixed v2, QFixed *r)
+{
+    int val;
+    bool result = qMulOverflow(v1.value(), v2.value(), &val);
+    r->setValue(val);
+    return result;
+}
+
 #ifndef QT_NO_DEBUG_STREAM
 inline QDebug &operator<<(QDebug &dbg, QFixed f)
 { return dbg << f.toReal(); }


--- a/src/gui/text/qtextlayout.cpp
+++ b/src/gui/text/qtextlayout.cpp
@@ -2164,9 +2164,12 @@ found:
         eng->maxWidth = qMax(eng->maxWidth, line.textWidth);
     } else {
         eng->minWidth = qMax(eng->minWidth, lbh.minw);
-        eng->layoutData->currentMaxWidth += line.textWidth;
-        if (!manuallyWrapped)
-            eng->layoutData->currentMaxWidth += lbh.spaceData.textWidth;
+        if (qAddOverflow(eng->layoutData->currentMaxWidth, line.textWidth, &eng->layoutData->currentMaxWidth))
+            eng->layoutData->currentMaxWidth = QFIXED_MAX;
+        if (!manuallyWrapped) {
+            if (qAddOverflow(eng->layoutData->currentMaxWidth, lbh.spaceData.textWidth, &eng->layoutData->currentMaxWidth))
+                eng->layoutData->currentMaxWidth = QFIXED_MAX;
+        }
         eng->maxWidth = qMax(eng->maxWidth, eng->layoutData->currentMaxWidth);
         if (manuallyWrapped)
             eng->layoutData->currentMaxWidth = 0;