[英]Segmentation fault after returning unique_ptr inside of pair from function
I have a factory that creates class instances from strings.我有一个从字符串创建类实例的工厂。 KeyValueType is an abstract class, which will be passed to Map/Reduce functions.
KeyValueType 是一个抽象类,它将传递给 Map/Reduce 函数。
class KeyValueType {
public:
virtual void parse(const std::string &) = 0;
virtual std::string to_string() const = 0;
};
Factories in code are getting from the shared library (to be able to config map/reduce functions from a remote computer).代码工厂从共享库中获取(以便能够从远程计算机配置映射/减少功能)。
std::unique_ptr<KeyValueType> KeyValueTypeFactory::create() override {
return std::make_unique<KeyValueType<T>>();
};
std::unique_ptr<KeyValueType> KeyValueTypeFactory::create(const std::string &str) override {
std::unique_ptr<KeyValueType> ptr = this->create();
ptr->parse(str);
return ptr;
};
So, I have the next code, where I'm creating two objects key/value and returning them, as a pair of unique_ptr所以,我有下一个代码,我在其中创建两个对象键/值并将它们作为一对 unique_ptr 返回
std::pair<std::unique_ptr<KeyValueType>, std::unique_ptr<KeyValueType>>
get_key_value_from_json(const std::string &data, std::unique_ptr<KeyValueTypeFactory> &key_factory, std::unique_ptr<KeyValueTypeFactory> &value_factory) {
boost::property_tree::ptree pt{};
boost::property_tree::json_parser::read_json(dynamic_cast<std::stringstream &>(std::stringstream{} << data), pt);
return { std::move(key_factory->create(pt.get("key", ""))),
std::move(value_factory->create(pt.get("value", ""))) };
}
std::pair<std::unique_ptr<KeyValueType>, std::unique_ptr<KeyValueType>> blocking_get_result() {
... // Get json and config
auto[key, value] = get_key_value_from_json(json, cfg->key_out_factory, cfg->value_res_factory);
std::cout << "The result of Map/Reduce is " << value->to_string() << std::endl;
return { std::move(key), std::move(value) };
}
int main() {
auto[key, value] = blocking_get_result();
std::cout << (value.get() == nullptr) << std::endl;
std::cout << "The result of Map/Reduce is " << value->to_string() << std::endl;
return 0;
}
The actual problem is, that in blocking_get_result()
function key and value are valid and virtual function to_string()
is working correctly, but after returning pair from function to main unique_ptr
is not null, but to_string
throws Segmentation Fault.实际问题是,
blocking_get_result()
函数中的key 和value 是有效的,并且虚函数to_string()
工作正常,但是从函数返回pair 到main 后unique_ptr
不为空,但是to_string
抛出Segmentation Fault。 Also, dynamic_cast
to a derived class is causing Segfault.此外,对派生类的
dynamic_cast
会导致段错误。
The actual problem was, that getting config fulfilled by using dlopen
and dlsym
and wrapping result into shared_ptr.实际的问题是,通过使用
dlopen
和dlsym
并将结果包装到 shared_ptr 来实现配置。 So shared library was freed in blocking_get_result.所以共享库在blocking_get_result 中被释放。 So in the main pointer in the vtable became invalid.
所以在vtable中的main指针就失效了。
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