查找“未知地址上的 SEGV”的原因，由 READ 访问引起
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【中文标题】查找“未知地址上的 SEGV”的原因，由 READ 访问引起【英文标题】：Find the cause of 'SEGV on unknown address', cause by READ access 【发布时间】：2019-10-28 19:01:04 【问题描述】：我正在编写一个 Splay Tree 实现。代码在 VS 中编译得很好，但测试系统因 DEADLYSIGNAL 而失败。 测试的具体输入是：
search 66
min
max
set 1 20
print
这里是完整的代码：
#include <iostream>
#include <sstream>
#include <stack>
#include <queue>
#include <cmath>
struct Node
int64_t key;
std::string value;
Node* left, * right, * parent;
Node(const int64_t& k) : key(k), left(nullptr), right(nullptr), parent(nullptr)
Node(const int64_t& k, const std::string& v, Node* p) : key(k), value(v),
left(nullptr), right(nullptr), parent(p)
;
class SplayTree
Node* root;
size_t size;
bool isRight(Node* node)
if (node && node->parent)
if (node->parent->right == node)
return true;
else
return false;
std::pair<int, Node*> Find(const int64_t& key)
Node* node = root;
while (node)
if (node->key == key)
return 2, node ;
else if (node->key > key)
if (node->left)
node = node->left;
else
return 0, node ;
else if (node->key < key)
if (node->right)
node = node->right;
else
return 1, node ;
void Merge(Node* left, Node* right)
if (!left && !right)
root = nullptr;
else if (!left)
root = right;
right->parent = nullptr;
else if (!right)
root = left;
left->parent = nullptr;
else
left = Max(left);
left->parent = nullptr;
left->right = right;
right->parent = left;
void rotateL(Node* node)
Node* p = node->parent;
Node* r = node->right;
if (p != nullptr)
if (p->left == node)
p->left = r;
else
p->right = r;
Node* temp = r->left;
r->left = node;
node->right = temp;
node->parent = r;
r->parent = p;
if (temp != nullptr)
temp->parent = node;
void rotateR(Node* node)
Node* p = node->parent;
Node* l = node->left;
if (p != nullptr)
if (p->left == node)
p->left = l;
else
p->right = l;
Node* temp = l->right;
l->right = node;
node->left = temp;
node->parent = l;
l->parent = p;
if (temp != nullptr)
temp->parent = node;
void Zig(Node* node)
!isRight(node) ?
rotateR(node->parent) : rotateL(node->parent);
void ZigZig(Node* node, bool side)
if (side)
rotateL(node->parent->parent);
rotateL(node->parent);
else
rotateR(node->parent->parent);
rotateR(node->parent);
void ZigZag(Node* node, bool side)
if (side)
rotateL(node->parent);
rotateR(node->parent);
else
rotateR(node->parent);
rotateL(node->parent);
void Splay(Node* node)
while (node->parent != nullptr)
if (node->parent == root)
Zig(node);
else if (!isRight(node) && !isRight(node->parent))
ZigZig(node, 0);
else if (isRight(node) && isRight(node->parent))
ZigZig(node, 1);
else if (!isRight(node) && isRight(node->parent))
ZigZag(node, 0);
else
ZigZag(node, 1);
root = node;
std::string printNode(Node* node)
std::string result;
result += '[' + std::to_string(node->key) + ' ' + node->value;
if (node->parent)
result += ' ' + std::to_string(node->parent->key);
result += ']';
return result;
Node* Max(Node* node)
Node* temp = node;
if (temp)
while (temp->right)
temp = temp->right;
Splay(temp);
return temp;
else
return nullptr;
Node* Min(Node* node)
Node* temp = node;
if (temp)
while (temp->left)
temp = temp->left;
Splay(temp);
return temp;
else
return nullptr;
public:
Node* getRoot() return root;
SplayTree() : root(nullptr), size(0)
SplayTree(uint64_t key)
root = new Node(key);
size = 1;
~SplayTree()
if (root)
std::stack<Node*> toDelete;
toDelete.push(root);
while (!toDelete.empty())
Node* node = toDelete.top();
if (node->left)
toDelete.push(node->left);
node->left = nullptr;
else if (node->right)
toDelete.push(node->right);
node->right = nullptr;
else
toDelete.pop();
delete node;
bool Add(const int64_t& key, const std::string& value)
if (!root)
root = new Node(key, value, nullptr);
size++;
return true;
else
std::pair<int, Node*> result = Find(key);
if (result.first == 2)
return false;
else if (result.first == 0)
result.second->left = new Node(key, value, result.second);
Splay(result.second->left);
size++;
return true;
else
result.second->right = new Node(key, value, result.second);
Splay(result.second->right);
size++;
return true;
std::string Search(const int64_t& key)
if (root)
std::pair<int, Node*> result = Find(key);
if (result.first == 2)
Splay(result.second);
return "1 " + result.second->value;
Splay(result.second);
return "0";
Node* Min() return Min(root);
Node* Max() return Max(root);
bool Set(const int64_t& key, const std::string& value)
std::pair<int, Node*> result = Find(key);
if (result.first == 2)
result.second->value = value;
Splay(result.second);
return true;
else
return false;
bool Delete(const int64_t& key)
if (!root)
return false;
std::pair<int, Node*> result = Find(key);
if (result.first == 2)
Splay(result.second);
Node* subL = result.second->left;
Node* subR = result.second->right;
Merge(subL, subR);
delete result.second;
size--;
return true;
return false;
std::string Print()
std::string result;
std::queue<Node*> toPrint;
toPrint.push(root);
size_t counter = size;
size_t space = 0;
size_t i = 0;
while (!toPrint.empty())
Node* node = toPrint.front();
toPrint.pop();
space++;
if (node)
result += printNode(node);
toPrint.push(node->left);
toPrint.push(node->right);
counter--;
else
result += "_";
toPrint.push(nullptr);
toPrint.push(nullptr);
if (space == pow(2, i))
result += "\n";
if (counter != 0)
i++;
space = 0;
else
result += " ";
if (counter == 0 && space == pow(2, i))
break;
return result;
;
int main()
std::string data;
std::getline(std::cin, data, '\0');
data += '\n';
std::istringstream is(data);
std::ostringstream os;
SplayTree tree;
int64_t key;
std::string command, value;
bool empty = false;
while (is >> command)
if (command.empty())
empty = true;
if (command == "add" && is.peek() != '\n'
&& is >> key && is.peek() != '\n' && is >> value && is.peek() == '\n')
if (!tree.Add(key, value))
os << "error" << std::endl;
else if (command == "set" && is.peek() != '\n'
&& is >> key && is.peek() != '\n' && is >> value && is.peek() == '\n')
if (!tree.Set(key, value))
os << "error" << std::endl;
else if (command == "delete" && is.peek() != '\n'
&& is >> key && is.peek() == '\n')
if (!tree.Delete(key))
os << "error" << std::endl;
else if (command == "search" && is.peek() != '\n'
&& is >> key && is.peek() == '\n')
os << tree.Search(key) << std::endl;
else if (command == "min" && is.peek() == '\n')
Node* temp = tree.Min();
if (temp)
os << temp->key << " "
<< temp->value << std::endl;
else
os << "error" << std::endl;
else if (command == "max" && is.peek() == '\n')
Node* temp = tree.Max();
if (temp)
os << temp->key << " "
<< temp->value << std::endl;
else
os << "error" << std::endl;
else if (command == "print" && is.peek() == '\n')
os << tree.Print();
else
if (!empty)
os << "error" << std::endl;
std::cout << os.str();
return 0;
VS 调试器没有告诉我导致此错误的原因。 Sanitazier 将其描述为读取错误，但我无法弄清楚它到底发生在哪个函数中。 此外，完整的消毒剂输出：
AddressSanitizer:DEADLYSIGNAL
=================================================================
==26100==ERROR: AddressSanitizer: SEGV on unknown address 0x00000004 (pc 0x08164c7a bp 0xbff0f8d8 sp 0xbff0f420 T0)
==26100==The signal is caused by a READ memory access.
==26100==Hint: address points to the zero page.
希望有人帮忙。提前谢谢你。
【问题讨论】：
VS 调试器没有告诉我导致此错误的原因。 -- 调试器的作用是让您使用收集到的信息，以便您确定错误是什么.调试器不知道你的程序试图做什么——它只是在出现问题时报告，然后你的工作就是将信息更进一步。 代码在 VS 中编译得很好 -- 这仅意味着您的代码没有语法错误，并且链接器已找到您正在调用的所有函数。它与您的代码是否存在逻辑错误无关。其次，我强烈建议您编写main 程序来获取和处理连贯的简单输入，即带有指令（“search”、“max”等）的简单getline。所有这些ispeek 的东西都不重要——它只会把水搅浑，无缘无故地混淆问题。
isRight 有一个错误。打开你的编译器警告，这样编译器可以帮助你注意到这些由“当你的缩进对你说谎”引起的疏忽。
不仅isRight，Find也有同样的错误。由于您使用的是 Visual C++，请将您的警告转至 /W4。
You have multiple warnings you need to fix.
【参考方案1】：
因为它出现在搜索结果中：
您的代码的某些部分（当您看到完整的 ASan 错误时会发现）正在创建一个无效的地址 0x4 ASan 想要查看其内存。
可能会说 int 意外地转换为指针或像 say 这样的故意转换
auto p = (int*)4;
查看完整错误和其中的堆栈跟踪。
Derived class offset calculation in boost::serialization. Is it valid?【讨论】：
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