fix: avoid memory leak

[yixinshark]

as title

Log: as title
Pms: BUG-318023

Summary by Sourcery

Ensure proper Qt object ownership and cleanup to eliminate memory leaks in dde-session by parenting dynamically allocated objects and disposing of FIFO instances after use.

Bug Fixes:

• Prevent memory leaks by assigning QApplication as parent to QDBusServiceWatcher, Session, WMSwitcher, and Fifo objects and deleting FIFO instances after use.

Enhancements:

• Convert Fifo to a QObject subclass with parent support and integrate deleteLater on read completion.
• Simplify FIFO write logic by executing it synchronously instead of spawning a separate thread.
• Parent all dynamically allocated Qt objects to the application to leverage Qt’s automatic memory management.

[sourcery-ai]

Reviewer's Guide

This PR attaches heap-allocated Qt objects to the application’s parent, refactors the Fifo class for QObject ownership, and adds explicit cleanup to prevent leaks.

Class diagram for updated Fifo ownership and construction

classDiagram
    class Fifo {
        +Fifo(QObject *parent = nullptr)
        +virtual ~Fifo()
        +int Read(QString &data)
        +int Write(QString data)
        -int m_fd
        -QString m_fifoPath
    }
    Fifo --|> QObject

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Class diagram for updated Session and WMSwitcher construction

classDiagram
    class Session {
        +Session(QObject *parent = nullptr)
    }
    Session --|> QObject
    class WMSwitcher {
        +WMSwitcher(QObject *parent = nullptr)
    }
    WMSwitcher --|> QObject

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File-Level Changes

Change	Details	Files
Attach session-related objects to QCoreApplication for automatic deletion	Passed &app as parent to QDBusServiceWatcher Constructed Session and WMSwitcher with &app parent	src/dde-session/main.cpp
Scope and parent Fifo writer instance to avoid unmanaged allocation	Moved Fifo writer into a local block Passed &app as parent when instantiating Fifo for writing	src/dde-session/main.cpp
Ensure reader-side Fifo is deleted after use	Added fifo->deleteLater() at end of read thread	src/dde-session/main.cpp
Refactor Fifo class to support QObject ownership	Inherit Fifo from QObject and add Q_OBJECT macro Change constructor to accept QObject* parent and add virtual destructor	src/utils/fifo.h src/utils/fifo.cpp

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[sourcery-ai]

Hey @yixinshark - I've reviewed your changes - here's some feedback:

• You removed the background thread for the write‐FIFO and now invoke OpenWrite/Write on the main thread—this can block your UI, so consider keeping it in a worker thread or making it nonblocking.
• Calling deleteLater() on the FIFO inside a QThreadPool task won’t free it if there’s no running event loop—either give it a QObject parent or delete it explicitly when done.
• Make sure Fifo’s destructor properly closes m_fd and cleans up the FIFO file to avoid resource leaks at teardown.

Prompt for AI Agents

Please address the comments from this code review:
## Overall Comments
- You removed the background thread for the write‐FIFO and now invoke OpenWrite/Write on the main thread—this can block your UI, so consider keeping it in a worker thread or making it nonblocking.
- Calling deleteLater() on the FIFO inside a QThreadPool task won’t free it if there’s no running event loop—either give it a QObject parent or delete it explicitly when done.
- Make sure Fifo’s destructor properly closes m_fd and cleans up the FIFO file to avoid resource leaks at teardown.

## Individual Comments

### Comment 1
<location> `src/dde-session/main.cpp:103` </location>
<code_context>
-            qInfo()<<"leader pipe thread id: " << QThread::currentThreadId() << ", pid: " << curPid;
-            Fifo *fifo = new Fifo;
+
+        {   // none block
+            pid_t curPid = getpid();
+            Fifo *fifo = new Fifo(&app);
             fifo->OpenWrite();
             fifo->Write(QString::number(curPid));
-        });
-
+        }
         // We started the unit, open <dbus> and sleep forever.
         return app.exec();
</code_context>

<issue_to_address>
Switching from QThreadPool to direct execution for Fifo write may affect responsiveness.

Since Fifo writes are now synchronous, any delays or blocking in Fifo::OpenWrite or Fifo::Write could negatively impact startup or UI responsiveness. Please confirm this change is intentional and safe across all environments.
</issue_to_address>

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[sourcery-ai]

issue (performance): Switching from QThreadPool to direct execution for Fifo write may affect responsiveness.

Since Fifo writes are now synchronous, any delays or blocking in Fifo::OpenWrite or Fifo::Write could negatively impact startup or UI responsiveness. Please confirm this change is intentional and safe across all environments.

[deepin-ci-robot]

deepin pr auto review

关键摘要:

• 在main.cpp中，Fifo对象在多个线程中创建和销毁，可能会导致资源泄露或竞争条件。
• Fifo类的构造函数中缺少对m_fifoPath的初始化检查，可能导致后续操作失败。
• Fifo类缺少对文件描述符的异常处理，如果打开失败，应该有相应的错误处理机制。
• Fifo类应该使用QScopedPointer或std::unique_ptr来管理m_fd，以避免手动管理内存的问题。
• Fifo类应该提供异常安全的方法，例如在打开或读取/写入操作失败时抛出异常。
• main.cpp中的QDBusServiceWatcher和QThreadPool::globalInstance()->start的lambda表达式捕获了app对象，但没有检查app对象是否为空，可能会导致空指针解引用。

是否建议立即修改:
是

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: 18202781743, yixinshark

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• debian/deepin/OWNERS

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