OCCI getColumnListMetaData，terminateEnvironment 踩坑

项目中发现一个问题，用一个简单的例子描述下：

使用OCCI 的getColumnListMetaData 获取一张表的内容，执行完报错：

int main(int argc, char* argv[])
{
    string program = argv[0];
    glogInit();
    Environment *env = NULL;
    Connection *conn = NULL;
    Statement *stmt = NULL;
    ResultSet *rs = NULL;
    int errNum;
    string errMsg;



    string username = "usr1";                        
    string password = "usr1";                        
    string connstring = "192.168.0.1:1521/orcl";    
    env = Environment::createEnvironment();

    assert(env != NULL);
    conn = env->createConnection(username,password,connstring); 
    if(!conn)
    {
        return -1;
    }
    
   
    Statement *pStmt = NULL;   
    string sqlStmt="select * from USER_TABLES";
    pStmt = conn->createStatement(sqlStmt);
    ResultSet *pRs = pStmt->executeQuery(sqlStmt);

    vector<MetaData> metafield = pRs->getColumnListMetaData();

    while(pRs->next()) {  
        for(int col =0;col <metafield.size();col++)
        {
            string reStr = pRs->getString(col + 1).empty() ? "" : pRs->getString(col + 1).c_str();
            cout<<" "<<reStr<<" ";
        }
        cout<<endl;
    }

    pStmt->closeResultSet(pRs);       
    env->terminateConnection(conn);
    Environment::terminateEnvironment(env); 

    return 0;
}

程序执行完显示如下错误：

E0827 17:32:38.492885 30841 oracleconnector.cpp:40] *** Aborted at 1566898358 (unix time) try "date -d @1566898358" if you are using GNU date ***
E0827 17:32:38.494403 30841 oracleconnector.cpp:40] PC: @                0x0 (unknown)
E0827 17:32:38.494635 30841 oracleconnector.cpp:40] *** SIGSEGV (@0x10) received by PID 30841 (TID 0x7feef115ae80) from PID 16; stack trace: ***
E0827 17:32:38.495303 30841 oracleconnector.cpp:40]     @     0x7feef0d605d0 (unknown)
E0827 17:32:38.504227 30841 oracleconnector.cpp:40]     @     0x7feeefc45cd2 kpuhhfre
E0827 17:32:38.511675 30841 oracleconnector.cpp:40]     @     0x7feeeedce5df OCIPHeapFree
E0827 17:32:38.512270 30841 oracleconnector.cpp:40]     @     0x7feef05b2974 oracle::occi::HeapAlloc<>::operator delete()
E0827 17:32:38.512823 30841 oracleconnector.cpp:40]     @     0x7feef05e024f _ZN6oracle4occi12MetaDataImplD9Ev
E0827 17:32:38.513456 30841 oracleconnector.cpp:40]     @     0x7feef05e027a oracle::occi::MetaDataImpl::~MetaDataImpl()
E0827 17:32:38.514011 30841 oracleconnector.cpp:40]     @     0x7feef05e011a oracle::occi::RefCounted::onZeroReferences()
E0827 17:32:38.514832 30841 oracleconnector.cpp:40]     @     0x7feef05e0137 oracle::occi::RefCounted::deleteRef()
E0827 17:32:38.515621 30841 oracleconnector.cpp:40]     @     0x7feef05b8079 _ZN6oracle4occi8ConstPtrINS0_12MetaDataImplEED9Ev
E0827 17:32:38.516194 30841 oracleconnector.cpp:40]     @     0x7feef05b8062 oracle::occi::ConstPtr<>::~ConstPtr()
E0827 17:32:38.516757 30841 oracleconnector.cpp:40]     @     0x7feef05b804d _ZN6oracle4occi3PtrINS0_12MetaDataImplEED9Ev
E0827 17:32:38.517264 30841 oracleconnector.cpp:40]     @     0x7feef05b803e oracle::occi::Ptr<>::~Ptr()
E0827 17:32:38.517736 30841 oracleconnector.cpp:40]     @     0x7feef05e06eb _ZN6oracle4occi8MetaDataD9Ev
E0827 17:32:38.518162 30841 oracleconnector.cpp:40]     @     0x7feef05e06dc oracle::occi::MetaData::~MetaData()
E0827 17:32:38.518338 30841 oracleconnector.cpp:40]     @           0x4128c2 std::_Destroy<>()
E0827 17:32:38.518527 30841 oracleconnector.cpp:40]     @           0x4127aa std::_Destroy_aux<>::__destroy<>()
E0827 17:32:38.518707 30841 oracleconnector.cpp:40]     @           0x41265d std::_Destroy<>()
E0827 17:32:38.518891 30841 oracleconnector.cpp:40]     @           0x4124f1 std::_Destroy<>()
E0827 17:32:38.519076 30841 oracleconnector.cpp:40]     @           0x412239 std::vector<>::~vector()
E0827 17:32:38.519229 30841 oracleconnector.cpp:40]     @           0x411d99 main
E0827 17:32:38.519829 30841 oracleconnector.cpp:40]     @     0x7feeecfe8495 __libc_start_main
E0827 17:32:38.520076 30841 oracleconnector.cpp:40]     @           0x40f5b9 (unknown)
E0827 17:32:38.520521 30841 oracleconnector.cpp:40]     @                0x0 (unknown)

排查代码发现，只要执行 Environment::terminateEnvironment(env); 该测试程序就出错

根据错误提示，是程序执行完，MetaData在析构时出错。 如果注释掉45行的Environment::terminateEnvironment(env); 该测试程序不会出错。

猜测是因为执行完main函数时，该函数开始释放函数栈，vector<MetaData> metafield 会销毁它所有的实例，此时Oracle 所有链接资源都已经被释放，metafield 应该是使用了Oracle 创建的指针，此时指针已经失效，因此发生段错误。

根据猜测，将31至43行加一对大括号，让其先释放vector 没有再报错。

有知道详情的大佬麻烦解释下！