1 files changed, 35 insertions, 21 deletions
diff --git a/src/corelib/io/qfsfileengine.cpp b/src/corelib/io/qfsfileengine.cpp
index 538fcb9a37..387990ed79 100644
--- a/src/corelib/io/qfsfileengine.cpp
+++ b/src/corelib/io/qfsfileengine.cpp
@@ -165,6 +165,35 @@ QFSFileEngine::QFSFileEngine(QFSFileEnginePrivate &dd)
 }
 
 /*!
+    \internal
+*/
+bool QFSFileEngine::processOpenModeFlags(QIODevice::OpenMode *mode)
+{
+    QIODevice::OpenMode &openMode = *mode;
+    if ((openMode & QFile::NewOnly) && (openMode & QFile::ExistingOnly)) {
+        qWarning("NewOnly and ExistingOnly are mutually exclusive");
+        setError(QFile::OpenError, QLatin1String("NewOnly and ExistingOnly are mutually exclusive"));
+        return false;
+    }
+
+    if ((openMode & QFile::ExistingOnly) && !(openMode & (QFile::ReadOnly | QFile::WriteOnly))) {
+        qWarning("ExistingOnly must be specified alongside ReadOnly, WriteOnly, or ReadWrite");
+        setError(QFile::OpenError, QLatin1String("ExistingOnly must be specified alongside ReadOnly, WriteOnly, or ReadWrite"));
+        return false;
+    }
+
+    // Either Append or NewOnly implies WriteOnly
+    if (openMode & (QFile::Append | QFile::NewOnly))
+        openMode |= QFile::WriteOnly;
+
+    // WriteOnly implies Truncate when ReadOnly, Append, and NewOnly are not set.
+    if ((openMode & QFile::WriteOnly) && !(openMode & (QFile::ReadOnly | QFile::Append | QFile::NewOnly)))
+        openMode |= QFile::Truncate;
+
+    return true;
+}
+
+/*!
     Destructs the QFSFileEngine.
 */
 QFSFileEngine::~QFSFileEngine()
@@ -205,13 +234,8 @@ bool QFSFileEngine::open(QIODevice::OpenMode openMode)
         return false;
     }
 
-    // Append implies WriteOnly.
-    if (openMode & QFile::Append)
-        openMode |= QFile::WriteOnly;
-
-    // WriteOnly implies Truncate if neither ReadOnly nor Append are sent.
-    if ((openMode & QFile::WriteOnly) && !(openMode & (QFile::ReadOnly | QFile::Append)))
-        openMode |= QFile::Truncate;
+    if (!processOpenModeFlags(&openMode))
+        return false;
 
     d->openMode = openMode;
     d->lastFlushFailed = false;
@@ -238,13 +262,8 @@ bool QFSFileEngine::open(QIODevice::OpenMode openMode, FILE *fh, QFile::FileHand
 
     Q_D(QFSFileEngine);
 
-    // Append implies WriteOnly.
-    if (openMode & QFile::Append)
-        openMode |= QFile::WriteOnly;
-
-    // WriteOnly implies Truncate if neither ReadOnly nor Append are sent.
-    if ((openMode & QFile::WriteOnly) && !(openMode & (QFile::ReadOnly | QFile::Append)))
-        openMode |= QFile::Truncate;
+    if (!processOpenModeFlags(&openMode))
+        return false;
 
     d->openMode = openMode;
     d->lastFlushFailed = false;
@@ -302,13 +321,8 @@ bool QFSFileEngine::open(QIODevice::OpenMode openMode, int fd, QFile::FileHandle
 {
     Q_D(QFSFileEngine);
 
-    // Append implies WriteOnly.
-    if (openMode & QFile::Append)
-        openMode |= QFile::WriteOnly;
-
-    // WriteOnly implies Truncate if neither ReadOnly nor Append are sent.
-    if ((openMode & QFile::WriteOnly) && !(openMode & (QFile::ReadOnly | QFile::Append)))
-        openMode |= QFile::Truncate;
+    if (!processOpenModeFlags(&openMode))
+        return false;
 
     d->openMode = openMode;
     d->lastFlushFailed = false;