c++ - Valgrind C++ : Invalid Read Of Size 8

Question

我在尝试创建通用优先级队列时遇到了这个问题。

Valgrind 给我这些错误:

  HEAP SUMMARY:
==39639==     in use at exit: 0 bytes in 0 blocks
==39639==   total heap usage: 22 allocs, 22 frees, 1,811 bytes allocated
==39639== 
==39639== All heap blocks were freed -- no leaks are possible
==39639== 
==39639== ERROR SUMMARY: 4 errors from 2 contexts (suppressed: 6 from 6)
==39639== 
==39639== 2 errors in context 1 of 2:
==39639== Invalid read of size 8
==39639==    at 0x405FB5: mtm::PriorityQueue<int, Assignment>::Iterator::operator++() (priority_queue.h:505)
==39639==    by 0x405D2E: mtm::PriorityQueue<int, Assignment>::erase(mtm::PriorityQueue<int, Assignment>::Iterator, mtm::PriorityQueue<int, Assignment>::Iterator) (priority_queue.h:808)
==39639==    by 0x403BC0: eraseAndSizeTest() (priority_queue_test.cpp:119)
==39639==    by 0x404D6B: main (priority_queue_test.cpp:136)
==39639==  Address 0x5141c88 is 24 bytes inside a block of size 32 free'd
==39639==    at 0x4A05FD6: operator delete(void*) (vg_replace_malloc.c:480)
==39639==    by 0x405B1B: mtm::PriorityQueue<int, Assignment>::erase(mtm::PriorityQueue<int, Assignment>::Iterator) (priority_queue.h:768)
==39639==    by 0x405D04: mtm::PriorityQueue<int, Assignment>::erase(mtm::PriorityQueue<int, Assignment>::Iterator, mtm::PriorityQueue<int, Assignment>::Iterator) (priority_queue.h:809)
==39639==    by 0x403BC0: eraseAndSizeTest() (priority_queue_test.cpp:119)
==39639==    by 0x404D6B: main (priority_queue_test.cpp:136)
==39639== 
==39639== 
==39639== 2 errors in context 2 of 2:
==39639== Invalid read of size 8
==39639==    at 0x4CCB870: std::string::size() const (basic_string.h:713)
==39639==    by 0x4050E8: __gnu_cxx::__enable_if<std::__is_char<char>::__value, bool>::__type std::operator==<char>(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (in /u1/115/saoren/mtm/HW5/wet5/prog)
==39639==    by 0x405048: Assignment::operator==(Assignment const&) const (priority_queue_test.cpp:26)
==39639==    by 0x406337: mtm::PriorityQueue<int, Assignment>::Iterator::operator==(mtm::PriorityQueue<int, Assignment>::Iterator const&) const (priority_queue.h:553)
==39639==    by 0x406010: mtm::PriorityQueue<int, Assignment>::Iterator::operator=(mtm::PriorityQueue<int, Assignment>::Iterator const&) (priority_queue.h:451)
==39639==    by 0x405D1B: mtm::PriorityQueue<int, Assignment>::erase(mtm::PriorityQueue<int, Assignment>::Iterator, mtm::PriorityQueue<int, Assignment>::Iterator) (priority_queue.h:809)
==39639==    by 0x403BC0: eraseAndSizeTest() (priority_queue_test.cpp:119)
==39639==    by 0x404D6B: main (priority_queue_test.cpp:136)
==39639==  Address 0x5141c70 is 0 bytes inside a block of size 32 free'd
==39639==    at 0x4A05FD6: operator delete(void*) (vg_replace_malloc.c:480)
==39639==    by 0x405B1B: mtm::PriorityQueue<int, Assignment>::erase(mtm::PriorityQueue<int, Assignment>::Iterator) (priority_queue.h:768)
==39639==    by 0x405D04: mtm::PriorityQueue<int, Assignment>::erase(mtm::PriorityQueue<int, Assignment>::Iterator, mtm::PriorityQueue<int, Assignment>::Iterator) (priority_queue.h:809)
==39639==    by 0x403BC0: eraseAndSizeTest() (priority_queue_test.cpp:119)
==39639==    by 0x404D6B: main (priority_queue_test.cpp:136)
==39639== 
--39639-- 
--39639-- used_suppression:      4 U1004-ARM-_dl_relocate_object
--39639-- used_suppression:      2 glibc-2.5.x-on-SUSE-10.2-(PPC)-2a
==39639== 
==39639== ERROR SUMMARY: 4 errors from 2 contexts (suppressed: 6 from 6)

这是我的代码(我相信是相关部分):

template<typename Priority, typename T>
typename PriorityQueue<Priority, T>::Iterator PriorityQueue<Priority, T>::Iterator::operator+(
        int offset) {

    if (offset == 0) {
        return *this;
    }

    Iterator it = *this;

    for (int i = 0; i < offset; i++) {
        it++;
    }

    //TODO: SHOULD WE ALLOCATE NEWITERATOR WITH NEW ??

    return it;
}`

`template<typename Priority, typename T>
typename PriorityQueue<Priority, T>::Iterator PriorityQueue<Priority, T>::Iterator::operator++() {
    //TODO: CHECK IF NOT NULL

    if (this->data != nullptr) {

        data = data->next;
        index++;
    }

    return *this;
}

    template<typename Priority, typename T>
    typename PriorityQueue<Priority, T>::Iterator PriorityQueue<Priority, T>::Iterator::operator++(
            int) {

        Iterator it = *this;

        if (this->data != nullptr) {

            if (this->data->next == nullptr) {
                data = nullptr;
                index++;
                return *this;
            }

            data = data->next;
            index++;
        }

        return it;
    }

template<typename Priority, typename T>
typename PriorityQueue<Priority, T>::Iterator PriorityQueue<Priority, T>::erase(
        Iterator exactPosition) {

    if (elementsNo == 0) {
        return end();
    }

    bool lastOne = false;
    bool firstOne = false;
    lastOne = exactPosition + 1 == end();
    firstOne = exactPosition == begin();
    if (firstOne) {
        elementsNo--;
        head = head->next;
        delete (exactPosition.data);
        exactPosition.data = nullptr;
        return begin();
    }

    Iterator previousPosition = begin();

    while (previousPosition.data->next != exactPosition.data) {
        previousPosition++;
    }

    if (lastOne) {
        elementsNo--;
        delete exactPosition.data;
        previousPosition.data->next = nullptr;
        return end();
    }

    Node* next = exactPosition.data->next;
    previousPosition.data->next = next;

    delete exactPosition.data;
    exactPosition.data = nullptr;
    this->elementsNo--;

    return Iterator(next, exactPosition.index + 1);

}

template<typename Priority, typename T>
typename PriorityQueue<Priority, T>::Iterator PriorityQueue<Priority, T>::erase(
        Iterator start, Iterator end) {

    if (!size()) {
        return end;
    }
    //TODO: CHECK BOUNDRIES (START AFTER END)
    Iterator iterator = start;

    //FOREACH(iterator,start,end)
    for (Iterator i = start; i != end; ++i) {
        iterator = erase(iterator);
    }

    return ++iterator;


template<typename Priority, typename T>
bool PriorityQueue<Priority, T>::Iterator::operator==(
        const Iterator& original) const {

    if (data == nullptr && original.data == nullptr) {
        return true;
    }
    if (data == nullptr || original.data == nullptr) {
        return false;
    }

    return data->element.data == original.data->element.data;
}

如果有人能发现错误并告诉我，我将不胜感激尽管有很多功能和很多错误，但都被删除了。

Answer 1

在erase( Iterator start, Iterator end)函数你在函数的末尾执行以下操作:

    return ++iterator;

如果传入函数的结束迭代器实际上是容器的 end迭代器，那么您将返回一个超过容器末尾的迭代器。

自 erase( Iterator exactPosition)返回被删除后的迭代器，你应该简单地返回 iterator来自 erase( Iterator start, Iterator end) .