QFSFileEngine: make rename() on Unix not overwrite

The rename(2) system call overwrites, so instead of using it, we try to
use the link/unlink pair. This works for regular cases, but can fail if
trying to change case in case-insensitive filesystems, if we're
operating on a non-Unix filesystem (FAT) or, on Linux, if the file
doesn't belong to the calling user (BSDs permit this). For those cases,
we fall back to rename(2).

That means there's a race condition if a new file is created there. But
we at least reduce the likelihood of that happening for regular files.

Change-Id: I1eba2b016de74620bfc8fffd14ccb38fd929e5aa
Reviewed-by: David Faure <david.faure@kdab.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/corelib/io/qfilesystemengine_win.cpp b/src/corelib/io/qfilesystemengine_win.cpp
index 5a9864edb2..74c6b52a66 100644
--- a/src/corelib/io/qfilesystemengine_win.cpp
+++ b/src/corelib/io/qfilesystemengine_win.cpp
@@ -1247,6 +1247,17 @@ bool QFileSystemEngine::renameFile(const QFileSystemEntry &source, const QFileSy
 }
 
 //static
+bool QFileSystemEngine::renameOverwriteFile(const QFileSystemEntry &source, const QFileSystemEntry &target, QSystemError &error)
+{
+    bool ret = ::MoveFileEx(reinterpret_cast<const wchar_t *>(source.nativeFilePath().utf16()),
+                            reinterpret_cast<const wchar_t *>(target.nativeFilePath().utf16()),
+                            MOVEFILE_REPLACE_EXISTING) != 0;
+    if (!ret)
+        error = QSystemError(::GetLastError(), QSystemError::NativeError);
+    return ret;
+}
+
+//static
 bool QFileSystemEngine::removeFile(const QFileSystemEntry &entry, QSystemError &error)
 {
     bool ret = ::DeleteFile((wchar_t*)entry.nativeFilePath().utf16()) != 0;