此剪辑中共享指针的范围

Question

  void RecHouse::createRec( const std::string& SourceId,
                                           const std::string& Name,
                                           const std::string& Location,
                                           const std::string& Description,
                                           const std::string& Address,
                                           const std::string& Content,
                                           const std::string& MaxTime,
                                           std::string& RecToken,
                                           bool defRec )
    {
       std::shared_ptr<Recording> rec = std::make_shared<Recording>(
            Recording( SourceId, Name, Location,
                       Description, Address, Content,
                       MaxTime, m_EventList,
                       m_eventServiceResource ));

        LOG("finished: create rec object");

        m_eventServiceResource->GetEventProducerManager()->RegisterEventProducer( std::weak_ptr<Recording>(recording) );
        RecordingToken = recording->getToken();
        if ( m_RecordingList.count( RecordingToken ) )
        {
            throw onvif_exception( BadConfiguration );
        }
        m_RecordingList[ RecordingToken ] = recording;
        updateFindRecordings();
        m_serialize.serialize( this );
        LOG ("fn end : create rec object");
    }

共享指针 rec 的范围是什么？它是否在函数 createRec 结束时完成，因为它没有转移到另一个共享指针？它作为参数发送到 RegisterEventProducer，但仅作为弱指针。此弱指针进一步存储在弱指针列表中，不会放入共享指针以供其他地方使用。

Answer 1

是的，共享指针超出范围，弱指针正如预期的那样，不会延长生命周期。这是一种测试方法：

#include <iostream>
#include <memory>

int main() {
  std::weak_ptr<int> weak_rec;
  {
    std::shared_ptr<int> rec = std::make_shared<int>(200);
    weak_rec = rec;
  }
  std::cout << *weak_rec.lock() << "\n";
  return 0;
}

编译 & 运行 valgrind

#> g++ -g test.cc
#> valgrind ./a.out

输出

==767972== Invalid read of size 4
==767972==    at 0x401257: main (test.cc:10)
==767972==  Address 0x0 is not stack'd, malloc'd or (recently) free'd

此剪辑中共享指针的范围

Scope of shared pointer in this clippet

c++

smart-pointers

c++11