我正在创建一个链表,但我不断收到内存泄漏。有时它说问题出在at()函数中,有时出在remove()函数中,但是对我来说,这一切似乎都非常紧密。是什么导致内存泄漏?
这是我的链表代码:
void LinkedList::insertHead(int value)
{
if (value < 0) {
return;
}
iterator pos(this, head);
for (int i = 0; i < num_items; i++) {
if (pos.current->data == value)
return;
else
pos++;
}
head = new Node(value, NULL, head);
if (head->next != NULL)
head->next->prev = head;
if (tail == NULL)
tail = head;
num_items++;
}
void LinkedList::insertTail(int value)
{
if (value < 0) {
return;
}
iterator pos(this, head);
for (int i = 0; i < num_items; i++) {
if (pos.current->data == value)
return;
else
pos++;
}
if (tail != NULL) {
tail->next = new Node(value, tail, NULL);
tail = tail->next;
num_items++;
} else
insertHead(value);
}
void LinkedList::insertAfter(int value, int insertionNode)
{
if (value < 0) {
return;
}
iterator pos(this, head);
for (int i = 0; i < num_items; i++) {
if (pos.current->data == value)
return;
else
pos++;
}
pos = iterator(this, head);
for (int i = 0; i < num_items; i++) {
if (pos.current->data == insertionNode)
break;
else
pos++;
}
if (pos.current == NULL || pos.current->data != insertionNode) {
return;
} /*else if(pos.current==NULL)
insertTail(value);*/
else {
Node *new_node = new Node(value, pos.current, pos.current->next);
if (pos.current->next != NULL)
pos.current->next->prev = new_node;
pos.current->next = new_node;
num_items++;
}
}
void LinkedList::remove(int value)
{
if (value < 0) {
return;
}
iterator pos(this, head);
for (int i = 0; i < num_items; i++) {
if (pos.current->data == value)
break;
else
pos++;
}
if (pos.current->data != value) {
return;
}
if (pos.current == head) {
Node *removed_node = head;
head = head->next;
delete removed_node;
if (head != NULL)
head->prev = NULL;
else
tail = NULL;
num_items--;
} else if (pos.current == tail) {
Node *removed_node = tail;
tail = tail->prev;
delete removed_node;
if (tail != NULL)
tail->next = NULL;
else
head = NULL;
num_items--;
} else {
Node *removed_node = pos.current;
removed_node->prev->next = removed_node->next;
removed_node->next->prev = removed_node->prev;
delete removed_node;
num_items--;
}
}
void LinkedList::clear()
{
if (num_items == 0)
return;
if (head != NULL)
remove(head->data);
num_items = 0;
}
int LinkedList::at(int index)
{
if (index < 0 || index >= num_items)
return -1;
iterator pos(this, head);
for (int i = 0; i < index; i++)
pos++;
return pos.current->data;
}
int LinkedList::size()
{
return num_items;
}
这是迭代器的代码:
class iterator {
friend class LinkedList;
private:
LinkedList * parent;
Node *current;
iterator(LinkedList * my_parent, Node * position):parent(my_parent),
current(position) {
}
public:
int &operator*() const {
if (current == NULL)
throw "Attempt to dereference end()";
return current->data;
}
int *operator->() const {
if (current == NULL)
throw "attempt to dereference end()";
return &(current->data);
}
iterator & operator++() {
if (current == NULL)
throw "Attempt to advance past end()";
current = current->next;
return *this;
}
iterator & operator--() {
if (current == parent->head)
throw "Attempt to move before begin()";
if (current == NULL)
current = parent->tail;
else
current = current->prev;
return *this;
}
iterator operator++(int) {
iterator return_value = *this;
++(*this);
return return_value;
}
iterator operator--(int) {
iterator return_value = *this;
--(*this);
return return_value;
}
bool operator==(const iterator & other) {
return current == other.current;
}
bool operator!=(const iterator & other) {
return !operator==(other);
}
};
根据要求输出:
==18072== Invalid read of size 4
==18072== at 0x402556: LinkedList::remove(int) (LinkedList.cpp:115)
==18072== by 0x405946: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== Address 0x0 is not stack'd, malloc'd or (recently) free'd
==18072==
segmentation fault
This segmentation fault was most likely caused by insertHead(), insertTail(), insertAfter(), or remove()
==18072==
==18072== HEAP SUMMARY:
==18072== in use at exit: 4,074 bytes in 118 blocks
==18072== total heap usage: 981 allocs, 863 frees, 158,945 bytes allocated
==18072==
==18072== 16 bytes in 1 blocks are still reachable in loss record 1 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x405888: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 32 bytes in 1 blocks are still reachable in loss record 2 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x4020B2: Factory::getLinkedList() (Factory.cpp:21)
==18072== by 0x40587B: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 32 bytes in 2 blocks are still reachable in loss record 3 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x407AC5: TADuck::insertHead(int) (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x405D91: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 48 bytes in 2 blocks are still reachable in loss record 4 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x4021F1: LinkedList::insertHead(int) (LinkedList.cpp:20)
==18072== by 0x405D84: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 48 bytes in 2 blocks are indirectly lost in loss record 5 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x40247A: LinkedList::insertAfter(int, int) (LinkedList.cpp:88)
==18072== by 0x405137: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 192 bytes in 8 blocks are indirectly lost in loss record 6 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x402308: LinkedList::insertTail(int) (LinkedList.cpp:47)
==18072== by 0x404D9F: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 216 bytes in 9 blocks are indirectly lost in loss record 7 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x4021F1: LinkedList::insertHead(int) (LinkedList.cpp:20)
==18072== by 0x404341: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 216 bytes in 9 blocks are indirectly lost in loss record 8 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x4021F1: LinkedList::insertHead(int) (LinkedList.cpp:20)
==18072== by 0x404BAD: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 240 bytes in 10 blocks are indirectly lost in loss record 9 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x402308: LinkedList::insertTail(int) (LinkedList.cpp:47)
==18072== by 0x4046B1: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 240 bytes in 10 blocks are indirectly lost in loss record 10 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x40247A: LinkedList::insertAfter(int, int) (LinkedList.cpp:88)
==18072== by 0x404897: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 256 bytes in 1 blocks are still reachable in loss record 11 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x4074AD: std::vector<int, std::allocator<int> >::_M_insert_aux(__gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, int const&) (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x402B7C: fillMasterList(std::vector<int, std::allocator<int> >&, int) (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x404B82: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 432 bytes in 18 blocks are indirectly lost in loss record 12 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x4021F1: LinkedList::insertHead(int) (LinkedList.cpp:20)
==18072== by 0x402BFD: initList(LinkedListInterface*, LinkedListInterface*) (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x403F78: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 456 bytes in 19 blocks are indirectly lost in loss record 13 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x4021F1: LinkedList::insertHead(int) (LinkedList.cpp:20)
==18072== by 0x4039E9: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 480 bytes in 20 blocks are indirectly lost in loss record 14 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x4021F1: LinkedList::insertHead(int) (LinkedList.cpp:20)
==18072== by 0x402BFD: initList(LinkedListInterface*, LinkedListInterface*) (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x4040DF: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 480 (24 direct, 456 indirect) bytes in 1 blocks are definitely lost in loss record 15 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x4021F1: LinkedList::insertHead(int) (LinkedList.cpp:20)
==18072== by 0x4039E9: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 480 (24 direct, 456 indirect) bytes in 1 blocks are definitely lost in loss record 16 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x4021F1: LinkedList::insertHead(int) (LinkedList.cpp:20)
==18072== by 0x402374: LinkedList::insertTail(int) (LinkedList.cpp:52)
==18072== by 0x404D9F: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 537 bytes in 1 blocks are possibly lost in loss record 17 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x38C88B9F48: std::string::_Rep::_S_create(unsigned long, unsigned long, std::allocator<char> const&) (in /usr/lib64/libstdc++.so.6.0.18)
==18072== by 0x38C88BAB1A: std::string::_Rep::_M_clone(std::allocator<char> const&, unsigned long) (in /usr/lib64/libstdc++.so.6.0.18)
==18072== by 0x38C88BABB3: std::string::reserve(unsigned long) (in /usr/lib64/libstdc++.so.6.0.18)
==18072== by 0x38C8898F75: std::basic_stringbuf<char, std::char_traits<char>, std::allocator<char> >::overflow(int) (in /usr/lib64/libstdc++.so.6.0.18)
==18072== by 0x38C889D195: std::basic_streambuf<char, std::char_traits<char> >::xsputn(char const*, long) (in /usr/lib64/libstdc++.so.6.0.18)
==18072== by 0x38C88949A4: std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long) (in /usr/lib64/libstdc++.so.6.0.18)
==18072== by 0x4036B6: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 537 bytes in 1 blocks are possibly lost in loss record 18 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x38C88B9F48: std::string::_Rep::_S_create(unsigned long, unsigned long, std::allocator<char> const&) (in /usr/lib64/libstdc++.so.6.0.18)
==18072== by 0x38C88BAB1A: std::string::_Rep::_M_clone(std::allocator<char> const&, unsigned long) (in /usr/lib64/libstdc++.so.6.0.18)
==18072== by 0x38C88BABB3: std::string::reserve(unsigned long) (in /usr/lib64/libstdc++.so.6.0.18)
==18072== by 0x38C8898F75: std::basic_stringbuf<char, std::char_traits<char>, std::allocator<char> >::overflow(int) (in /usr/lib64/libstdc++.so.6.0.18)
==18072== by 0x38C889D195: std::basic_streambuf<char, std::char_traits<char> >::xsputn(char const*, long) (in /usr/lib64/libstdc++.so.6.0.18)
==18072== by 0x38C88949A4: std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long) (in /usr/lib64/libstdc++.so.6.0.18)
==18072== by 0x403A7C: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 720 (24 direct, 696 indirect) bytes in 1 blocks are definitely lost in loss record 19 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x4021F1: LinkedList::insertHead(int) (LinkedList.cpp:20)
==18072== by 0x404341: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== 936 (24 direct, 912 indirect) bytes in 1 blocks are definitely lost in loss record 20 of 20
==18072== at 0x4A068F3: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==18072== by 0x4021F1: LinkedList::insertHead(int) (LinkedList.cpp:20)
==18072== by 0x402BFD: initList(LinkedListInterface*, LinkedListInterface*) (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x403F78: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072==
==18072== LEAK SUMMARY:
==18072== definitely lost: 96 bytes in 4 blocks
==18072== indirectly lost: 2,520 bytes in 105 blocks
==18072== possibly lost: 1,074 bytes in 2 blocks
==18072== still reachable: 384 bytes in 7 blocks
==18072== suppressed: 0 bytes in 0 blocks
==18072==
==18072== For counts of detected and suppressed errors, rerun with: -v
==18072== ERROR SUMMARY: 7 errors from 7 contexts (suppressed: 2 from 2)
最佳答案
您的valgrind
输出报告内存泄漏。但是,由于您的程序由于对内存位置0x0
的无效读取而导致了分段错误,因此现在可以忽略它们:
==18072== Invalid read of size 4
==18072== at 0x402556: LinkedList::remove(int) (LinkedList.cpp:115)
==18072== by 0x405946: testAll() (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== by 0x401E81: main (in /users/guest/s/scalen/Desktop/To Students/dont_run_me)
==18072== Address 0x0 is not stack'd, malloc'd or (recently) free'd
segmentation fault
您需要找到行
115
的位置,并弄清楚为什么代码试图引用无效的内存位置。作为示例,我将用发现的第一个示例进行说明(我不知道这是否是valgrind
抱怨的示例,因为我不知道代码的行号是什么): for (int i = 0; i < num_items; i++) {
if (pos.current->data == value)
break;
else
pos++;
}
if (pos.current->data != value) {
return;
}
如果
value
没有匹配项,则pos.current
似乎不太可能指向有意义的条目。因此,取消引用以检查它是否与早期return
不匹配可能是错误的事情。相反,请检查for
循环是否确实使它遍历了整个列表: int i;
for (i = 0; i < num_items; i++) {
//...
}
if (i == num_items) {
return;
}
当您遇到
valgrind
中报告的错误时,请先解决segmentation
故障,然后再解决Invalid read
或Invalid write
,然后内存泄漏。根据您的评论,您似乎对调试过程有些困惑。这个问题是关于内存泄漏的,但事实证明这是崩溃的征兆。希望这个答案可以帮助您更好地理解如何理解
valgrind
报告的输出,但是您应该花一些时间浏览其documentation,以便能够从中提取最大的信息量。您可以。为此,您的问题已得到解决。但是,让我稍微扩展一下此答案,以讨论有关调试的一些知识。调试只是解决问题的一种练习,而擅长调试是一项技能。这个过程可以比作解决犯罪或谜团的过程,因此调试是在程序员成为侦探时开始的。与大多数人类努力一样,有些人的调试能力要比其他人好得多。但是任何人都可以成为熟练的调试器,因为通过实践,您可以更好地进行调试,这也是事实。
我在高中和大学期间学过很多数学,因此我对调试与解决数学问题非常相似的看法有偏见。随着时间的流逝,您对如何更快地找到解决方案有了直觉,但总的来说,我所遵循的过程很大程度上遵循了乔治·波利亚(George Polya)在其《 How to Solve It》中提出的步骤。
第一:了解问题。输入什么?输出是什么?该程序预期产生什么输出?您的程序需要哪些假设和前提条件?是否满足所有这些条件?
第二:制定计划。这个问题是新的还是与您过去遇到的问题类似?异常结果与程序的特定部分之间是否存在关系?要使程序的该部分正确运行,需要哪些假设和前提条件?您能够测试这些条件吗?
第三:执行计划。如果问题不是新问题,请尽可能应用与以前相同的修复程序来解决问题。否则,请逐步检查程序的状态,以确保满足所有假设和前提条件。确定程序行为在什么时候偏离了应该做的事情。在偏差点,了解偏差的原因,并采取适当的纠正措施。
第四:回头。程序更正后,请采取必要的步骤使自己确信此修复程序是正确的。过去通过的任何测试都应该仍然通过。不管导致失败的任何测试,现在都应该通过。确定可能暴露出代码那部分其他弱点的新测试。了解导致问题的原因,并考虑将来可以更改程序编写方式的方式,这些方式可以减少产生相同错误的可能性,也可以使问题的原因更容易识别。
关于c++ - Valgrind报告在运行之间发生变化的许多地方出现内存泄漏,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/19106277/