QLockFile: bypass QFile::remove() and go straight to the system call

This then avoids creating a QFilePrivate, QFSFileEngine, and
QFSFileEnginePrivate only to call QFileSystemEngine::removeFile(). We
are definitely using native files in this class, so we can skip all of
those classes.

We use the system call in removeStaleLock() anyway for Unix.

Pick-to: 6.10 6.9 6.8
Change-Id: I19ea637567ae38d31888fffd61ec79ae3eec50af
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/corelib/io/qlockfile_unix.cpp

@@ -154,8 +154,9 @@ QLockFile::LockError QLockFilePrivate::tryLock_sys()
     QByteArray fileData = lockFileContents();
     if (qt_write_loop(fd, fileData.constData(), fileData.size()) < fileData.size()) {
         qt_safe_close(fd);
-        if (!QFile::remove(fileName))
-            qWarning("QLockFile: Could not remove our own lock file %ls.", qUtf16Printable(fileName));
+        if (unlink(lockFileName) != 0)
+            qWarning("QLockFile: Could not remove our own lock file %s: %ls.",
+                     lockFileName.constBegin(), qUtf16Printable(qt_error_string()));
         return QLockFile::UnknownError; // partition full
     }
 
@@ -289,12 +290,16 @@ void QLockFile::unlock()
     Q_D(QLockFile);
     if (!d->isLocked)
         return;
-    close(d->fileHandle);
-    d->fileHandle = -1;
-    if (!QFile::remove(d->fileName)) {
-        qWarning() << "Could not remove our own lock file" << d->fileName << "maybe permissions changed meanwhile?";
+
+    const QByteArray lockFileName = QFile::encodeName(d->fileName);
+    if (unlink(lockFileName) != 0) {
+        qWarning("Could not remove our own lock file %s: %ls (maybe permissions changed meanwhile?)",
+                 lockFileName.constBegin(), qUtf16Printable(qt_error_string()));
         // This is bad because other users of this lock file will now have to wait for the stale-lock-timeout...
     }
+
+    close(d->fileHandle);
+    d->fileHandle = -1;
     d->lockError = QLockFile::NoError;
     d->isLocked = false;
 }

src/corelib/io/qlockfile_win.cpp

@@ -6,14 +6,17 @@
 
 #include "private/qlockfile_p.h"
 #include "private/qfilesystementry_p.h"
+#include "wcharhelpers_win_p.h"
+
+#include "QtCore/qdatetime.h"
+#include "QtCore/qdir.h"
+#include "QtCore/qdebug.h"
+#include "QtCore/qfileinfo.h"
+#include "QtCore/qthread.h"
+
 #include <qt_windows.h>
 #include <psapi.h>
 
-#include "QtCore/qfileinfo.h"
-#include "QtCore/qdatetime.h"
-#include "QtCore/qdebug.h"
-#include "QtCore/qthread.h"
-
 QT_BEGIN_NAMESPACE
 
 static inline bool fileExists(const wchar_t *fileName)
@@ -22,6 +25,11 @@ static inline bool fileExists(const wchar_t *fileName)
     return GetFileAttributesEx(fileName, GetFileExInfoStandard, &data);
 }
 
+static bool deleteFile(const QString &fileName)
+{
+    return DeleteFile(qt_castToWchar(QDir::toNativeSeparators(fileName)));
+}
+
 QLockFile::LockError QLockFilePrivate::tryLock_sys()
 {
     const QFileSystemEntry fileEntry(fileName);
@@ -70,8 +78,8 @@ QLockFile::LockError QLockFilePrivate::tryLock_sys()
 
 bool QLockFilePrivate::removeStaleLock()
 {
-    // QFile::remove fails on Windows if the other process is still using the file, so it's not stale.
-    return QFile::remove(fileName);
+    // DeleteFile fails if the other process is still using the file, so it's not stale.
+    return deleteFile(fileName);
 }
 
 bool QLockFilePrivate::isProcessRunning(qint64 pid, const QString &appname)
@@ -124,7 +132,7 @@ void QLockFile::unlock()
     CloseHandle(d->fileHandle);
     int attempts = 0;
     static const int maxAttempts = 500; // 500ms
-    while (!QFile::remove(d->fileName) && ++attempts < maxAttempts) {
+    while (!deleteFile(d->fileName) && ++attempts < maxAttempts) {
         // Someone is reading the lock file right now (on Windows this prevents deleting it).
         QThread::msleep(1);
     }