Allow QSettings to synchronize non-atomically

This is required so that one can use QSettings in situations that
temporary files or renaming may not work.

[ChangeLog][QtCore][QSettings] Added setAtomicSyncRequired(), which
allows one to use QSettings with config files in unwriteable directories
or in Alternate Data Streams on NTFS on Windows. This used to work
before Qt 5.4, but remains a non-default behavior due to the potential
of data corruption.

Task-number: QTBUG-47379
Change-Id: I81480fdb578d4d43b3fcfffd14d4f77112f0402f
Reviewed-by: Jesus Fernandez <Jesus.Fernandez@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Kai Koehne <kai.koehne@qt.io>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/corelib/io/qsettings_p.h b/src/corelib/io/qsettings_p.h
index d8e91e48ce..7923c24770 100644
--- a/src/corelib/io/qsettings_p.h
+++ b/src/corelib/io/qsettings_p.h
@@ -249,6 +249,7 @@ protected:
     QString groupPrefix;
     bool fallbacks;
     bool pendingChanges;
+    bool atomicSyncOnly = true;
     mutable QSettings::Status status;
 };