不确定分段错误在哪里

Question

我在尝试编译 C++ 程序时遇到分段错误问题，但不确定问题出在哪里。我怀疑问题出在 .find() ..... 可能是迭代器运算符 < 和 == 是 find() 的比较器吗？我希望有人能指出我认为问题出在哪里。

以下是test01.cpp的一部分，这里我运行测试代码，用print语句找出问题所在：

bool confirmEverythingMatches(const btree<long>& testContainer, const set<long>& stableContainer) {
  cout << "Confirms the btree and the set " 
          "contain exactly the same values..." << endl;


  for (long i = kMinInteger; i <= kMaxInteger; i++) {
    cout << "Start of for-loop to find iterator for comparisons..." << endl;

    if (stableContainer.find(i) != stableContainer.end()) {
      cout << "can find i (" << i << ") in stableContainer!" << endl;
    } else {
      cout << "cannot find i (" << i << ") in stableContainer!" << endl;
    }

    cout << "In between finding i in stable and testContainers..." << endl;

    if (testContainer.find(i) != testContainer.end()) {
      cout << "can find i (" << i << ") in testContainer!" << endl;
    } else {
      cout << "cannot find i (" << i << ") in testContainer!" << endl;
    }

    cout << "Before assigning the find to boolean variables..." << endl;

    bool foundInTree = (testContainer.find(i) != testContainer.end());
    cout << "testContainer.find(i) != testContainer.end()" << endl;


    bool foundInSet = (stableContainer.find(i) != stableContainer.end());
    cout << "stableContainer.find(i) != stableContainer.end()" << endl;

    if (foundInTree != foundInSet) {
      cout << "- btree and set don't contain the same data!" << endl; 
      cout << "Mismatch at element: " << i << endl;
      return false;
    } else {cout << "foundInTree == foundInSet!!!" << i << endl;}
  }
  cout << "- btree checks out just fine." << endl;

  return true;
}

}  // namespace close


/**
 * Codes for testing various bits and pieces. Most of the code is commented out
 * you should uncomment it as appropriate.
 **/
int main(void) {

  // initialise random number generator with 'random' seed
  initRandom();

  cout << "after initRandom().." << endl;

  // insert lots of random numbers and compare with a known correct container
  btree<long> testContainer(99);

  cout << "after specifying max node elements in testContainer.." << endl;

  set<long> stableContainer;

  cout << "after constructing stableContainer.." << endl;

  insertRandomNumbers(testContainer, stableContainer, 1000000);

  cout << "after inserting random numbers into testContainer and for success inserts, also into stableContainer.." << endl;

  btree<long> btcpy = testContainer;

  cout << "after copy assigning a copy of testContainer to btcopy.." << endl;

  confirmEverythingMatches(btcpy, stableContainer);

  cout << "after confirming everything internally matches between testContainer and stableContainer.." << endl;

  return 0; 
}

我在运行编译程序时得到的输出（编译时没有问题）是这样的：

Confirms the btree and the set contain exactly the same values...
Start of for-loop to find iterator for comparisons...
cannot find i (1000000) in stableContainer!
In between finding i in stable and testContainers...
ASAN:DEADLYSIGNAL
=================================================================
==7345==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000018 (pc 0x000108d132a8 bp 0x000000000000 sp 0x7fff56eee6f0 T0)
    #0 0x108d132a7 in btree<long>::find(long const&) const (test01+0x1000022a7)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV (test01+0x1000022a7) in btree<long>::find(long const&) const
==7345==ABORTING
Abort trap: 6

我在另一台机器上尝试运行时也遇到了这个错误：

==29936==ERROR: AddressSanitizer failed to allocate 0x200000 (2097152) bytes of SizeClassAllocator32: 12

我发现进入find()的时候会出现segmentation fault:

/**
 * Identical in functionality to the non-const version of find,
 * save the fact that what's pointed to by the returned iterator
 * is deemed as const and immutable.
 *
 * @param elem the client element we are trying to match.
 * @return an iterator to the matching element, or whatever the
 *         const end() returns if no such match was ever found.
 */
template<typename T> typename btree<T>::const_iterator
btree<T>::find(const T& elem) const {
    std::cout << "CONST ITERATOR'S FIND" << std::endl;

Node *tmp_ = root_;
std::cout << "1" << std::endl;

while(true) {
std::cout << "2" << std::endl;
size_t i;

std::cout << "3" << std::endl;
// go through all elements from root to tail
for (i = 0; i < tmp_->__occupied_size_; ++i) {

    std::cout << "4" << std::endl;

    if (tmp_->__elem_[i] == elem) {

        std::cout << "5" << std::endl;

        // find the elem, return an iterator
        return const_iterator(tmp_, i, this);

        std::cout << "6" << std::endl;

    } else if (tmp_->__elem_[i] > elem) {

        std::cout << "7" << std::endl;

        // elem is not in current Node, go to descendants
        // for the elem.
        if (tmp_->__descendants_ == nullptr) {

            std::cout << "8" << std::endl;
            return cend();
            std::cout << "9" << std::endl;

        } else {

            std::cout << "10" << std::endl;
            tmp_ = tmp_->__descendants_[i];
            std::cout << "11" << std::endl;
            break;
                }
            }
        }
        // handling boundaries cases
        if (i == tmp_->__occupied_size_) {
            std::cout << "12" << std::endl;
            if (tmp_->__descendants_[i] == nullptr) {
                std::cout << "13" << std::endl;
                return cend();
                std::cout << "14" << std::endl;
            } else {
                std::cout << "15" << std::endl;
                tmp_ = tmp_->__descendants_[i];
            }
        }
    }
}

此查找的打印语句是：

CONST ITERATOR'S FIND
1
2
3
4
4
7
10
11
2
3
4
7
10
11
ASAN:DEADLYSIGNAL

Answer 1

好的，所以根据这个find函数的实现，我觉得问题可能出在

if (tmp_->__descendants_ == nullptr) {
    std::cout << "8" << std::endl;
    return cend();
    std::cout << "9" << std::endl;
} else {
    std::cout << "10" << std::endl;
    tmp_ = tmp_->__descendants_[i];
    std::cout << "11" << std::endl;
    break;
}

然后是

// handling boundaries cases
if (i == tmp_->__occupied_size_) {
    std::cout << "12" << std::endl;
    if (tmp_->__descendants_[i] == nullptr) {
        std::cout << "13" << std::endl;
        return cend();
        std::cout << "14" << std::endl;
    } else {
        std::cout << "15" << std::endl;
        tmp_ = tmp_->__descendants_[i];
    }
}

因此，您正在检查 tmp->__descendants_ 是否不为空。如果不是，则设置 tmp_ = tmp_->descendants_[i];

注意：您只是在检查 __descendants_ 指针是否为空，而不是在检查 __descendants_ [i] 是否为空！

如果 tmp->__descendants_[i] 为 null（或超出后代数组）怎么办？

如果该值为空，则 tmp_->occupied_size_ 可能会出现段错误。

注 2：出于某种原因，您使用相同的索引 "i" 遍历 __elem_ 和 __descendants_。我不确定后代是如何创建的，但这可能也是一个问题。

Answer 2

这就是调试器存在的原因。运行你的程序在调试器中，让程序失败，然后调试器会告诉你哪里出错，为什么出错。

看起来你可能有很多代码需要浏览，这里没有人真的想这样做，因为这不是一个简洁的问题。

祝你好运！

不确定分段错误在哪里

Not sure where the segmentation fault is

c++

iterator

b-tree

find

segmentation-fault