c++ - C++ 程序的内存使用量增长，(在 Debian 的 "top"中显示)，直到它崩溃

Question

我正在开发一个C++程序，应该可以运行几天，所以它的内存消耗似乎增长得非常快，这有点麻烦。

程序的完整代码有点长，所以我只贴相关的东西。结构如下:

int main (void){
//initialization of the global variables
error = 0;
state = 0;
cycle = 0;
exportcycle = 0;
status = 0;
counter_temp_ctrl = 0;
start = 0;
stop = 0;


inittimer();
mysql_del ("TempMeas");
mysql_del ("TempMeasHist");
mysql_del ("MyControl");
mysql_del ("MyStatus");
initmysql();



while(1){

    statemachine();

    pause();

    }

}

上面初始化的定时器函数如下:

void catch_alarm (int sig)
{
//Set the statemachine to state 1 (reading in new values)

    start = readmysql("MyStatus", "Start", 0);
    stop = readmysql("MyStatus", "Stop", 0);

       if (start == 1){
            state = 1;
      }
      if (stop == 1){
            state = 5;
      }


  //printf("Alarm event\n");
  signal (sig, catch_alarm);

  return void();
}

所以基本上，由于我没有在修改 MyStatus 选项卡的 Web 界面中设置起始位，程序只是每秒调用 readmysql 函数两次(计时器的间隔)。 readmysql 函数如下:

float readmysql(string table, string row, int lastvalue){
float readdata = 0;

// Initialize a connection to MySQL
MYSQL_RES *mysql_res;
MYSQL_ROW mysqlrow;
MYSQL *con = mysql_init(NULL);
if(con == NULL)
{
error_exit(con);
}


if (mysql_real_connect(con, "localhost", "user1", "user1", "TempDB", 0, NULL, 0) == NULL)
{
error_exit(con);
}

if (lastvalue == 1){
    string qu = "Select "+ row +" from "+ table +" AS a where MeasTime=(select MAX(MeasTime) from "+ table;
    error = mysql_query(con, qu.c_str());
}
else{
    string qu = "Select "+ row +" from "+ table;
    error = mysql_query(con, qu.c_str());
}


mysql_res = mysql_store_result(con);

while((mysqlrow = mysql_fetch_row(mysql_res)) != NULL)
{
    readdata = atoi(mysqlrow[0]);
}

//cout << "readdata "+table+ " "+row+" = " << readdata << endl;

// Close the MySQL connection
mysql_close(con);

//delete mysql_res;
//delete mysqlrow;


return readdata;
}

我认为这个函数中的变量存储在堆栈中，并在离开函数时自动释放。然而，似乎有一部分内存没有被释放，因为它毕竟只是在增长。如您所见，我已尝试对其中两个变量使用删除函数。好像没有效果。我在内存管理等方面做错了什么？

感谢您的帮助!

问候奥利弗。

Answer 1

至少 mysql_store_result 正在泄漏。来自 documentation :

After invoking mysql_query() or mysql_real_query(), you must call mysql_store_result() or mysql_use_result() for every statement that successfully produces a result set (SELECT, SHOW, DESCRIBE, EXPLAIN, CHECK TABLE, and so forth). You must also call mysql_free_result() after you are done with the result set.