Effective C++ 8. Prevent exceptions from leaving destructors

最新推荐文章于 2024-12-10 15:36:55 发布

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本文探讨了C++中数据库连接的管理方法，通过示例代码展示了如何正确地关闭数据库连接并处理潜在的异常情况，确保程序稳定运行。

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class DBConnection {
public:
    ...
    static DBConnection create();

    void close();
};

// class to manage DBConnection
class DBConn {
public:
    ...
    ~DBConn() {
        db.close();
    }
private:
    DBConnection db;
};

Terminate the program if close throws, typically by calling abort:

DBConn::~DBConn() {
    try { db.close(); }
    catch (...) {
        std::abort();
    }
}

Swallow the exception arising from the call to close

DBCoon::~DBCoon () {
    try { db.close(); }
    catch (...) {

    }
}

because destructors that emit exceptions are dangerous, always running the risk of permature program terminate or undefined behavior. Telling clients to call close themselves does not impose a burden on them; it give them an opportunity to deal with errors they would otherwise have no chance to react to.

class DBCoon {
public:
    ...
    void close() {
        db.close();
        closed = true;
    }
    ~DBConn() {
        if (!closed) {
            try {
                db.close();
            }
        }
        catch(...) {
        }
    }
    private:
        DBConnection db;
        bool closed;
};