Fix QSaveFile and QTemporaryFile issues with windows network shares

The commit amends commit 3966b571 to take UNC prefix into account as
well. Fixes the weird file name output as reported in QTBUG-74291 and
QTBUG-83365. Replace manual separator normalizing in qt_cleanPath(),
this is another spot where UNC prefix handling needs to be applied.

Also make QTemporaryFile operate on '/' as file separators to fix
creating both file types with native path separators on network shares.

Fixes: QTBUG-74291
Fixes: QTBUG-76228
Fixes: QTBUG-83365
Pick-to: 5.15 6.0 6.1
Change-Id: Iff8d26b994bf4194c074cd5c996cda3934297fa5
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

7 files changed, 45 insertions, 25 deletions

diff --git a/src/corelib/io/qdir.cpp b/src/corelib/io/qdir.cpp
index 4016c12f13..7f58569a28 100644
--- a/src/corelib/io/qdir.cpp
+++ b/src/corelib/io/qdir.cpp
@@ -953,22 +953,29 @@ QString QDir::toNativeSeparators(const QString &pathName)
 QString QDir::fromNativeSeparators(const QString &pathName)
 {
 #if defined(Q_OS_WIN)
-    int i = pathName.indexOf(QLatin1Char('\\'));
+    const QChar nativeSeparator = u'\\';
+    int i = pathName.indexOf(nativeSeparator);
     if (i != -1) {
         QString n(pathName);
-        if (n.startsWith(QLatin1String("\\\\?\\"))) {
-            n.remove(0, 4);
-            i = n.indexOf(QLatin1Char('\\'));
-            if (i == -1)
+        const QStringView uncPrefix(uR"(\\?\UNC\)");
+        const QStringView extendedLengthPathPrefix(uR"(\\?\)");
+        if (n.startsWith(uncPrefix)) {
+            // Keep the initial double-slash, chop out the rest of the prefix.
+            n = n.remove(2, uncPrefix.size() - 2);
+            if ((i = n.indexOf(nativeSeparator)) == -1)
+                return n;
+        } else if (n.startsWith(extendedLengthPathPrefix)) {
+            n = n.sliced(extendedLengthPathPrefix.size());
+            if ((i = n.indexOf(nativeSeparator)) == -1)
                 return n;
         }
 
         QChar * const data = n.data();
-        data[i++] = QLatin1Char('/');
+        data[i++] = u'/';
 
         for (; i < n.length(); ++i) {
-            if (data[i] == QLatin1Char('\\'))
-                data[i] = QLatin1Char('/');
+            if (data[i] == nativeSeparator)
+                data[i] = u'/';
         }
 
         return n;
@@ -2310,16 +2317,8 @@ static QString qt_cleanPath(const QString &path, bool *ok)
 {
     if (path.isEmpty())
         return path;
-    QString name = path;
-#if defined (Q_OS_WIN)
-    if (name.startsWith(QLatin1String("\\\\?\\")))
-        name.remove(0, 4);
-#endif
-
-    QChar dir_separator = QDir::separator();
-    if (dir_separator != QLatin1Char('/'))
-       name.replace(dir_separator, QLatin1Char('/'));
 
+    QString name = QDir::fromNativeSeparators(path);
     QString ret = qt_normalizePathSegments(name, OSSupportsUncPaths ? QDirPrivate::AllowUncPaths : QDirPrivate::DefaultNormalization, ok);
 
     // Strip away last slash except for root directories
diff --git a/src/corelib/io/qfilesystementry.cpp b/src/corelib/io/qfilesystementry.cpp
index 9b474b25b1..83f8a86439 100644
--- a/src/corelib/io/qfilesystementry.cpp
+++ b/src/corelib/io/qfilesystementry.cpp
@@ -142,12 +142,6 @@ void QFileSystemEntry::resolveFilePath() const
     if (m_filePath.isEmpty() && !m_nativeFilePath.isEmpty()) {
 #if defined(QFILESYSTEMENTRY_NATIVE_PATH_IS_UTF16)
         m_filePath = QDir::fromNativeSeparators(m_nativeFilePath);
-#ifdef Q_OS_WIN
-        if (m_filePath.startsWith(QLatin1String("//?/UNC/")))
-            m_filePath = m_filePath.remove(2,6);
-        if (m_filePath.startsWith(QLatin1String("//?/")))
-            m_filePath = m_filePath.remove(0,4);
-#endif
 #else
         m_filePath = QDir::fromNativeSeparators(QFile::decodeName(m_nativeFilePath));
 #endif
diff --git a/src/corelib/io/qtemporaryfile.cpp b/src/corelib/io/qtemporaryfile.cpp
index bdd128a88c..1e7e67b625 100644
--- a/src/corelib/io/qtemporaryfile.cpp
+++ b/src/corelib/io/qtemporaryfile.cpp
@@ -78,7 +78,7 @@ typedef int NativeFileHandle;
 QTemporaryFileName::QTemporaryFileName(const QString &templateName)
 {
     // Ensure there is a placeholder mask
-    QString qfilename = templateName;
+    QString qfilename = QDir::fromNativeSeparators(templateName);
     uint phPos = qfilename.length();
     uint phLength = 0;
 
diff --git a/tests/auto/corelib/io/qdir/tst_qdir.cpp b/tests/auto/corelib/io/qdir/tst_qdir.cpp
index f71bc7e7eb..cfb25d7acb 100644
--- a/tests/auto/corelib/io/qdir/tst_qdir.cpp
+++ b/tests/auto/corelib/io/qdir/tst_qdir.cpp
@@ -1269,6 +1269,8 @@ tst_QDir::cleanPath_data()
     QTest::newRow("unc-server-up") << "//server/path/.." << "//server";
     QTest::newRow("unc-server-above-root") << "//server/.." << "//server/..";
     QTest::newRow("longpath") << "\\\\?\\d:\\" << "d:/";
+    QTest::newRow("unc-network-share") << uR"(\\?\UNC\localhost\c$\tmp.txt)"_qs
+        << u"//localhost/c$/tmp.txt"_qs;
 #else
     QTest::newRow("data15") << "//c:/foo" << "/c:/foo";
 #endif // non-windows
@@ -1744,6 +1746,8 @@ void tst_QDir::nativeSeparators()
     QCOMPARE(QDir::fromNativeSeparators(QLatin1String("/")), QString("/"));
     QCOMPARE(QDir::fromNativeSeparators(QLatin1String("\\")), QString("/"));
     QCOMPARE(QDir::fromNativeSeparators(QLatin1String("\\\\?\\C:\\")), QString("C:/"));
+    QCOMPARE(QDir::fromNativeSeparators(uR"(\\?\UNC\localhost\c$\tmp.txt)"_qs),
+             u"//localhost/c$/tmp.txt"_qs);
 #else
     QCOMPARE(QDir::toNativeSeparators(QLatin1String("/")), QString("/"));
     QCOMPARE(QDir::toNativeSeparators(QLatin1String("\\")), QString("\\"));
diff --git a/tests/auto/corelib/io/qfilesystementry/tst_qfilesystementry.cpp b/tests/auto/corelib/io/qfilesystementry/tst_qfilesystementry.cpp
index 30c38b20f9..a9ae848251 100644
--- a/tests/auto/corelib/io/qfilesystementry/tst_qfilesystementry.cpp
+++ b/tests/auto/corelib/io/qfilesystementry/tst_qfilesystementry.cpp
@@ -104,6 +104,17 @@ void tst_QFileSystemEntry::getSetCheck_data()
             << QString("A:dir\\without\\leading\\backslash.bat")
             << absPrefix + QString("A:\\dir\\without\\leading\\backslash.bat")
             << "A:dir/without/leading/backslash.bat" << "backslash.bat" << "backslash" << "backslash" << "bat" << "bat" << false << false;
+
+    QTest::newRow("longpath")
+            << uR"(\\?\D:\)"_qs
+            << absPrefix + QLatin1String(R"(D:\)")
+            << "D:/" << "" << "" << "" << "" << "" << true << false;
+
+    QTest::newRow("uncprefix")
+            << uR"(\\?\UNC\localhost\C$\tmp.txt)"_qs
+            << absPrefix + QLatin1String(R"(UNC\localhost\C$\tmp.txt)")
+            << "//localhost/C$/tmp.txt" << "tmp.txt" << "tmp" << "tmp" << "txt" << "txt" << true
+            << false;
 }
 
 void tst_QFileSystemEntry::getSetCheck()
@@ -137,7 +148,7 @@ void tst_QFileSystemEntry::getSetCheck()
     QCOMPARE(entry2.isRelative(), relative);
     QCOMPARE(entry2.filePath(), filepath);
     // Since this entry was created using the native path,
-    // the object shouldnot change nativeFilePath.
+    // the object shouldn't change nativeFilePath.
     QCOMPARE(entry2.nativeFilePath(), nativeFilePath);
     QCOMPARE(entry2.fileName(), filename);
     QCOMPARE(entry2.baseName(), baseName);
diff --git a/tests/auto/corelib/io/qtemporarydir/tst_qtemporarydir.cpp b/tests/auto/corelib/io/qtemporarydir/tst_qtemporarydir.cpp
index 4969c0e6e3..db07f80495 100644
--- a/tests/auto/corelib/io/qtemporarydir/tst_qtemporarydir.cpp
+++ b/tests/auto/corelib/io/qtemporarydir/tst_qtemporarydir.cpp
@@ -157,6 +157,12 @@ void tst_QTemporaryDir::fileTemplate_data()
         prefix = "qt_" + hanTestText();
         QTest::newRow("Chinese") << (prefix + "XXXXXX" + umlautTestText()) << prefix << umlautTestText();
     }
+
+#ifdef Q_OS_WIN
+    const auto tmp = QDir::toNativeSeparators(QDir::tempPath()).sliced(QDir::rootPath().size());
+    QTest::newRow("UNC") << uR"(\\localhost\C$\)"_qs + tmp + uR"(\UNC.XXXXXX.tmpDir)"_qs
+                         << "UNC." << ".tmpDir";
+#endif
 }
 
 void tst_QTemporaryDir::fileTemplate()
diff --git a/tests/auto/corelib/io/qtemporaryfile/tst_qtemporaryfile.cpp b/tests/auto/corelib/io/qtemporaryfile/tst_qtemporaryfile.cpp
index 331558255f..bb938e9695 100644
--- a/tests/auto/corelib/io/qtemporaryfile/tst_qtemporaryfile.cpp
+++ b/tests/auto/corelib/io/qtemporaryfile/tst_qtemporaryfile.cpp
@@ -206,6 +206,12 @@ void tst_QTemporaryFile::fileTemplate_data()
         prefix = "qt_" + hanTestText();
         QTest::newRow("Chinese characters") << (prefix + "XXXXXX") << prefix << QString() << QString();
     }
+
+#ifdef Q_OS_WIN
+    const auto tmp = QDir::toNativeSeparators(QDir::tempPath()).sliced(QDir::rootPath().size());
+    QTest::newRow("UNC") << uR"(\\localhost\C$\)"_qs + tmp + uR"(\QTBUG-74291.XXXXXX.tmpFile)"_qs
+                         << "QTBUG-74291." << ".tmpFile" << "";
+#endif
 }
 
 void tst_QTemporaryFile::fileTemplate()