1 files changed, 14 insertions, 11 deletions

diff --git a/src/corelib/io/qurlidna.cpp b/src/corelib/io/qurlidna.cpp
index 9bb6b2a42d..fa0a229f4f 100644
--- a/src/corelib/io/qurlidna.cpp
+++ b/src/corelib/io/qurlidna.cpp
@@ -1502,18 +1502,20 @@ static bool isMappedToNothing(uint uc)
 }
 
 
-static void stripProhibitedOutput(QString *str, int from)
+static bool containsProhibitedOuptut(const QString *str, int from)
 {
-    ushort *out = (ushort *)str->data() + from;
-    const ushort *in = out;
+    const ushort *in = reinterpret_cast<const ushort *>(str->begin() + from);
     const ushort *end = (ushort *)str->data() + str->size();
-    while (in < end) {
+    for ( ; in < end; ++in) {
         uint uc = *in;
         if (QChar(uc).isHighSurrogate() && in < end - 1) {
             ushort low = *(in + 1);
             if (QChar(low).isLowSurrogate()) {
                 ++in;
                 uc = QChar::surrogateToUcs4(uc, low);
+            } else {
+                // unpaired surrogates are prohibited
+                return true;
             }
         }
         if (uc <= 0xFFFF) {
@@ -1538,7 +1540,7 @@ static void stripProhibitedOutput(QString *str, int from)
                 || (uc >= 0xFDD0 && uc <= 0xFDEF)
                 || uc == 0xFEFF
                 || (uc >= 0xFFF9 && uc <= 0xFFFF))) {
-                *out++ = *in;
+                continue;
             }
         } else {
             if (!((uc >= 0x1D173 && uc <= 0x1D17A)
@@ -1562,14 +1564,12 @@ static void stripProhibitedOutput(QString *str, int from)
                 || (uc >= 0xFFFFE && uc <= 0xFFFFF)
                 || (uc >= 0x100000 && uc <= 0x10FFFD)
                 || (uc >= 0x10FFFE && uc <= 0x10FFFF))) {
-                *out++ = QChar::highSurrogate(uc);
-                *out++ = QChar::lowSurrogate(uc);
+                continue;
             }
         }
-        ++in;
+        return true;
     }
-    if (in != out)
-        str->truncate(out - str->utf16());
+    return false;
 }
 
 static bool isBidirectionalRorAL(uint uc)
@@ -2084,7 +2084,10 @@ Q_AUTOTEST_EXPORT void qt_nameprep(QString *source, int from)
                         firstNonAscii > from ? firstNonAscii - 1 : from);
 
     // Strip prohibited output
-    stripProhibitedOutput(source, firstNonAscii);
+    if (containsProhibitedOuptut(source, firstNonAscii)) {
+        source->resize(from);
+        return;
+    }
 
     // Check for valid bidirectional characters
     bool containsLCat = false;