C++ 内存泄漏 (valgrind)

Question

Valgrind 声称我正在间接失去记忆；让我烦恼的是，我不知道为什么会这样。

不确定这是误报还是我只是不理解某些指针赋值之类的东西。

我是不是失忆了？如果是，为什么？

Valgrind 报告：

==24392== 21 bytes in 2 blocks are indirectly lost in loss record 1 of 3
==24392==    at 0x4028699: operator new[](unsigned int) (in        /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==24392==    by 0x804B41D: Perishable::load(std::basic_fstream<char,        std::char_traits<char> >&) (Perishable.cpp:42)
==24392==    by 0x804C504: sict::PosApp::loadRecs() (PosApp.cpp:139)
==24392==    by 0x804D58E: sict::PosApp::run() (PosApp.cpp:393)
==24392==    by 0x8049337: main (milestone4.cpp:8)

这是第 42 行：

std::fstream& Perishable::load(std::fstream& stream) {
    char    mysku[MAX_SKU_LEN + 1];
    char    mynam[100];
    bool    mytax;
    double  myprice;
    int     myqty;
    int     date[5]; 

    stream.getline(mysku, 100, ',');
    sku(mysku);
    stream.getline(mynam, 100, ',');

    name(mynam);//bytes indirectly lost

这是 name() [完全评论]

void Item::name(char *name){
    delete[] _name; //..............Just in case it points to something.
                    //..............Note: How could I possibly be losing memory with this line here??
    int x = strlen(name); //........Grab the length of the new input

    if (_name == '[=12=]') {//..........If it was empty, ie. its the first assignment
        _name = new char[x + 1];//..Allocate the space, +1 for null char
    }

    for (int i = 0; i < x; i++) {//.Copy
        _name[i] = name[i];
    }

    _name[x]   = '[=12=]';//............Yeah, its manual termination. I should maybe use strcpy
}

编辑>>>这里是析构函数

Item::~Item() {
    std::cout << "called destructor";
    delete[] _name;
    _name = '[=13=]';
}

编辑>>复制构造函数和赋值运算符

//Copy Constructor
Item::Item(const Item& copyfrom){
    (*this) = copyfrom;

}

//Member operators
Item& Item::operator=(const Item &myitem) {
    if (!myitem.isEmpty()){
        init((*this), myitem._sku, myitem._name, myitem._price, myitem._taxed);
        this->_quantity = myitem._quantity;

    }
    return (*this);
}

void Item::init(Item &obj, char const sku[], char const name[], double priced, bool taxed) {

    int length = strlen(name);
    int skulength = strlen(sku);

    obj._price = priced;
    obj._taxed = taxed;
    obj._quantity = 0;
    obj._name = new char[length+1]; //+1 for the null which wasn't counted. Huge pain debugging that.


    for (int i = 0; i < length; i++) {

        obj._name[i] = name[i];

        if (i < skulength) {//redundanc


            obj._sku[i] = sku[i];
        }
    }

    obj._name[length]   = '[=14=]';
    obj._sku[skulength] = '[=14=]';

}

Answer 1

如果你真的必须使用 new 和裸指针（提示：几乎没有人这样做），那么你需要确保 _name 的所有者在不再需要它时释放它。

正确的位置可能 ~Item() 析构函数，但如果没有其余代码，很难确定。

Answer 2

我只看到：

Item::~Item() {
    std::cout << "called destructor";
    delete[] _name;
    // Don't reassign
}

和

void Item::init(Item &obj, char const sku[], char const name[], double priced, bool taxed) {
    // ...
    if (obj._name == nullptr /* 0 */) {
        obj._name = new char[length+1]; 
        // What if it's not null?
    } else {
        // Do you want to delete and new up a char?
    }
}

此外，使用非常量引用对我来说很可怕。我看到 init 中 obj._name 的 new-ing 是最大的问题，没有任何先发制人的检查。

C++ 内存泄漏 (valgrind)

C++ memory leak (valgrind)

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valgrind

memory-leaks

dynamic-memory-allocation

delete-operator