From 315ac36e5dce548fef1907e50271ed2412d445cc Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@kdab.com>
Date: Sat, 25 May 2019 13:32:48 +0200
Subject: QFile: hold engine by unique_ptr
MIME-Version: 1.0
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Unfortunately, we can't, yet, change QAbstractFileEngine::create() to
return a unique_ptr. But we should do it in Qt 6.

Change-Id: If18ff766bce73ecd4143274ac9f9a5a7b9d5912c
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
---
 src/corelib/io/qsavefile.cpp | 36 ++++++++++++++----------------------
 1 file changed, 14 insertions(+), 22 deletions(-)

(limited to 'src/corelib/io/qsavefile.cpp')

diff --git a/src/corelib/io/qsavefile.cpp b/src/corelib/io/qsavefile.cpp
index 04f440fea2..f41e6302a2 100644
--- a/src/corelib/io/qsavefile.cpp
+++ b/src/corelib/io/qsavefile.cpp
@@ -150,8 +150,7 @@ QSaveFile::~QSaveFile()
     QFileDevice::close();
     if (d->fileEngine) {
         d->fileEngine->remove();
-        delete d->fileEngine;
-        d->fileEngine = nullptr;
+        d->fileEngine.reset();
     }
 }
 
@@ -235,7 +234,7 @@ bool QSaveFile::open(OpenMode mode)
     }
 
     auto openDirectly = [&]() {
-        d->fileEngine = QAbstractFileEngine::create(d->finalFileName);
+        d->fileEngine.reset(QAbstractFileEngine::create(d->finalFileName));
         if (d->fileEngine->open(mode | QIODevice::Unbuffered)) {
             d->useTemporaryFile = false;
             QFileDevice::open(mode);
@@ -252,8 +251,7 @@ bool QSaveFile::open(OpenMode mode)
             if (openDirectly())
                 return true;
             d->setError(d->fileEngine->error(), d->fileEngine->errorString());
-            delete d->fileEngine;
-            d->fileEngine = nullptr;
+            d->fileEngine.reset();
         } else {
             QString msg =
                     QSaveFile::tr("QSaveFile cannot open '%1' without direct write fallback "
@@ -265,18 +263,17 @@ bool QSaveFile::open(OpenMode mode)
     }
 #endif
 
-    d->fileEngine = new QTemporaryFileEngine(&d->finalFileName, QTemporaryFileEngine::Win32NonShared);
+    d->fileEngine.reset(new QTemporaryFileEngine(&d->finalFileName, QTemporaryFileEngine::Win32NonShared));
     // if the target file exists, we'll copy its permissions below,
     // but until then, let's ensure the temporary file is not accessible
     // to a third party
     int perm = (existingFile.exists() ? 0600 : 0666);
-    static_cast<QTemporaryFileEngine *>(d->fileEngine)->initialize(d->finalFileName, perm);
+    static_cast<QTemporaryFileEngine *>(d->fileEngine.get())->initialize(d->finalFileName, perm);
     // Same as in QFile: QIODevice provides the buffering, so there's no need to request it from the file engine.
     if (!d->fileEngine->open(mode | QIODevice::Unbuffered)) {
         QFileDevice::FileError err = d->fileEngine->error();
 #ifdef Q_OS_UNIX
         if (d->directWriteFallback && err == QFileDevice::OpenError && errno == EACCES) {
-            delete d->fileEngine;
             if (openDirectly())
                 return true;
             err = d->fileEngine->error();
@@ -285,8 +282,7 @@ bool QSaveFile::open(OpenMode mode)
         if (err == QFileDevice::UnspecifiedError)
             err = QFileDevice::OpenError;
         d->setError(err, d->fileEngine->errorString());
-        delete d->fileEngine;
-        d->fileEngine = nullptr;
+        d->fileEngine.reset();
         return false;
     }
 
@@ -332,30 +328,26 @@ bool QSaveFile::commit()
     }
     QFileDevice::close(); // calls flush()
 
+    const auto fe = std::move(d->fileEngine);
+
     // Sync to disk if possible. Ignore errors (e.g. not supported).
-    d->fileEngine->syncToDisk();
+    fe->syncToDisk();
 
     if (d->useTemporaryFile) {
         if (d->writeError != QFileDevice::NoError) {
-            d->fileEngine->remove();
+            fe->remove();
             d->writeError = QFileDevice::NoError;
-            delete d->fileEngine;
-            d->fileEngine = nullptr;
             return false;
         }
         // atomically replace old file with new file
         // Can't use QFile::rename for that, must use the file engine directly
-        Q_ASSERT(d->fileEngine);
-        if (!d->fileEngine->renameOverwrite(d->finalFileName)) {
-            d->setError(d->fileEngine->error(), d->fileEngine->errorString());
-            d->fileEngine->remove();
-            delete d->fileEngine;
-            d->fileEngine = nullptr;
+        Q_ASSERT(fe);
+        if (!fe->renameOverwrite(d->finalFileName)) {
+            d->setError(fe->error(), fe->errorString());
+            fe->remove();
             return false;
         }
     }
-    delete d->fileEngine;
-    d->fileEngine = nullptr;
     return true;
 }
 
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