QFile::rename: avoid two stat(2)/CreateFile in a row

QFileSystemEngine::id() will stat(2)/CreateFile in order to get the ID
of the file anyway, so we don't need to use QFile::exists() to check if
the destination exists. Instead, rely on id() returning a null value to
indicate error. On Windows, it's possible that the calls to either
GetFileInformationByHandle or GetFileInformationByHandleEx might fail,
but we ignore those.

Change-Id: I1eba2b016de74620bfc8fffd14ccaebcbed64419
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@qt.io>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/corelib/io/qfilesystemengine_unix.cpp b/src/corelib/io/qfilesystemengine_unix.cpp
index 90e4faaf50..c3906c3207 100644
--- a/src/corelib/io/qfilesystemengine_unix.cpp
+++ b/src/corelib/io/qfilesystemengine_unix.cpp
@@ -338,7 +338,8 @@ QByteArray QFileSystemEngine::id(const QFileSystemEntry &entry)
 {
     QT_STATBUF statResult;
     if (QT_STAT(entry.nativeFilePath().constData(), &statResult)) {
-        qErrnoWarning("stat() failed for '%s'", entry.nativeFilePath().constData());
+        if (errno != ENOENT)
+            qErrnoWarning("stat() failed for '%s'", entry.nativeFilePath().constData());
         return QByteArray();
     }
     QByteArray result = QByteArray::number(quint64(statResult.st_dev), 16);