Question

由指示的线引起的内存泄漏。 “pendingSendReqs.push_back（安培; F）;”在sendreq（）方法中。我是c ++的新手所以我似乎无法弄清楚为什么会发生内存泄漏。泄漏的内存大小为16个字节。

class Station {
    struct Frame {
        enum { Token, Data, Ack } type;                  // type of frame
        unsigned int src;                                // source id
        unsigned int dst;                                // destination id
        unsigned int prio;                               // priority
    } frame;

    unsigned int stnId;
    static unsigned int requests;                        // total send requests (if needed)
    void data( Frame frame );                            // pass frame
    void main();                                         // coroutine main
    Station *nextStation;
    vector<Frame*> pendingSendReqs;
  public:
    Station( unsigned int id ) : stnId(id) { }
    ~Station() {
        for (int i = 0; i < pendingSendReqs.size(); i++) {
            delete pendingSendReqs.at(i);
            cout << "~: " << pendingSendReqs.at(i) << endl;
        }
    }
    //unsigned int getId() { return stnId; }
    void setup( Station *nexthop ) {                     // supply next hop
        //*nexthop is the object
        nextStation = nexthop;
        //cout << "size: " << sizeof(*nexthop) << endl;
    }
    void sendreq( unsigned int round, unsigned int dst, unsigned int prio ) { // store send request
        Frame f;
        f.type = Frame::Data;
        f.src = stnId;
        f.dst = dst;
        f.prio = prio;


        pendingSendReqs.push_back(&f); //MEMORY LEAK CAUSED BY THIS LINE
    }
    void start();                                        // inject token and start
};

Answer 1

这不是内存泄漏

pendingSendReqs.push_back(&f);

这是未来未定义的行为。您正在存储本地变量的地址。任何尝试在函数范围之外取消引用其中一个指针的尝试都是未定义的行为。

你必须问问自己是否真的需要一个指针向量。如果你不知道答案，很可能你没有。

Answer 2

您正在向量中存储指向局部变量的指针，这些变量将自动被销毁。这是非法的。

 vector<Frame*> pendingSendReqs;
 // this is a vector of pointers to struct and not a vector of structs

void sendreq( unsigned int round, unsigned int dst, unsigned int prio ) {
    Frame f;     // this automatic variable will get destroyed when sendreq returns
    f.type = Frame::Data;
    f.src = stnId;
    f.dst = dst;
    f.prio = prio;


    pendingSendReqs.push_back(&f); //MEMORY LEAK CAUSED BY THIS LINE
    // because you're going to hold on to this address which will mean
    // nothing when this function returns
}

您打算这样做的方式是：

vector<Frame> pendingSendReqs;

和sendreq内部：

pendingSendReqs.push_back(f); // store the object's copy instead of it's address so that it outlives the life of this local

Answer 3

当

void sendreq（unsigned int round，unsigned int dst，unsigned int prio）

端部，

你的vector pendingSendReqs将包含已被删除的变量的指针（因为是局部变量），并且将包含垃圾，并且会让你崩溃。

由结构向量引起的c ++内存泄漏

3 个答案: