Windows/QSaveFile: Fix locking issues on Dropbox drives

Add a flag to QTemporaryFileEngine causing the file to be opened in
non-shared mode, preventing renaming failures caused by the Dropbox
driver accessing it.

Task-number: QTBUG-57299
Change-Id: Id7afc3559fd15784d4166efbbd057d592b5e0ab2
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/src/corelib/io/qtemporaryfile.cpp b/src/corelib/io/qtemporaryfile.cpp
index 73249d7df8..1983a22c65 100644
--- a/src/corelib/io/qtemporaryfile.cpp
+++ b/src/corelib/io/qtemporaryfile.cpp
@@ -207,7 +207,7 @@ QFileSystemEntry::NativePath QTemporaryFileName::generateNext()
     changed and contain the generated path name.
 */
 static bool createFileFromTemplate(NativeFileHandle &file, QTemporaryFileName &templ,
-                                   quint32 mode, QSystemError &error)
+                                   quint32 mode, int flags, QSystemError &error)
 {
     const int maxAttempts = 16;
     for (int attempt = 0; attempt < maxAttempts; ++attempt) {
@@ -216,16 +216,18 @@ static bool createFileFromTemplate(NativeFileHandle &file, QTemporaryFileName &t
 
 #if defined(Q_OS_WIN)
         Q_UNUSED(mode);
+        const DWORD shareMode = (flags & QTemporaryFileEngine::Win32NonShared)
+                                ? 0u : (FILE_SHARE_READ | FILE_SHARE_WRITE);
 
 #  ifndef Q_OS_WINRT
         file = CreateFile((const wchar_t *)path.constData(),
                 GENERIC_READ | GENERIC_WRITE,
-                FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, CREATE_NEW,
+                shareMode, NULL, CREATE_NEW,
                 FILE_ATTRIBUTE_NORMAL, NULL);
 #  else // !Q_OS_WINRT
         file = CreateFile2((const wchar_t *)path.constData(),
                 GENERIC_READ | GENERIC_WRITE,
-                FILE_SHARE_READ | FILE_SHARE_WRITE, CREATE_NEW,
+                shareMode, CREATE_NEW,
                 NULL);
 #  endif // Q_OS_WINRT
 
@@ -247,6 +249,7 @@ static bool createFileFromTemplate(NativeFileHandle &file, QTemporaryFileName &t
             return false;
         }
 #else // POSIX
+        Q_UNUSED(flags)
         file = QT_OPEN(path.constData(),
                 QT_OPEN_CREAT | QT_OPEN_EXCL | QT_OPEN_RDWR | QT_OPEN_LARGEFILE,
                 static_cast<mode_t>(mode));
@@ -366,7 +369,7 @@ bool QTemporaryFileEngine::open(QIODevice::OpenMode openMode)
         unnamedFile = true;
         d->fileEntry.clear();
     } else if (st == CreateUnnamedFileStatus::NotSupported &&
-               createFileFromTemplate(file, tfn, fileMode, error)) {
+               createFileFromTemplate(file, tfn, fileMode, flags, error)) {
         filePathIsTemplate = false;
         unnamedFile = false;
         d->fileEntry = QFileSystemEntry(tfn.path, QFileSystemEntry::FromNativePath());