c++ - mysqlcppconn 程序中的内存泄漏

Question

我有一个运行的程序占用越来越多的内存。这一直持续到整个程序崩溃。我已经将它缩小到这个部分——如果我把它注释掉，正在使用的内存就不会再增加了。

为什么这段代码会导致内存泄漏？指针是否由于某种原因没有被删除？我是否使用了错误的 executeUpdate 函数？

#include <cppconn/prepared_statement.h> // preparedStatement
sql::PreparedStatement* pstatement; 
try{
for(const auto& bar : m_bars) {

    std::string sql = "INSERT INTO " 
                    + m_table_name 
                    + " VALUES (' "
                    + trade_platform::datetime::toString(datetime) + "', '"
                    + bar.first + "', "
                    + "'IB', "
                    + std::to_string(bar.second.getOpen()) + ", "
                    + std::to_string(bar.second.getHigh()) + ", "
                    + std::to_string(bar.second.getLow())  + ", "
                    + std::to_string(bar.second.getClose()) + ", "
                    + std::to_string(bar.second.getVolume()) + ");";

    pstatement = m_conn->prepareStatement(sql);
    // prepare our statement and execute query
    pstatement->executeUpdate();
}
}catch(const std::exception& e){
    std::cerr << "flushToDB problem: " << e.what() << "\n"; 
}catch(...){
    std::cerr << "unspecified flushToDB problem\n";
}

// free
delete pstatement;

Answer 1

您正在创建 sql 语句 N 次，但只有最后一个被删除。

删除每条语句会更好:

#include <memory>
...

try{
for(const auto& bar : m_bars) {

    std::string sql = "INSERT INTO " 
                    + m_table_name 
                    + " VALUES (' "
                    + trade_platform::datetime::toString(datetime) + "', '"
                    + bar.first + "', "
                    + "'IB', "
                    + std::to_string(bar.second.getOpen()) + ", "
                    + std::to_string(bar.second.getHigh()) + ", "
                    + std::to_string(bar.second.getLow())  + ", "
                    + std::to_string(bar.second.getClose()) + ", "
                    + std::to_string(bar.second.getVolume()) + ");";

    std::unique_ptr<sql::PreparedStatement> pstatement(m_conn->prepareStatement(sql)); // enabling RAII
    // prepare our statement and execute query
    pstatement->executeUpdate();

    // unique_ptr wil automatically call delete on sql statement
    // after pstatement leaves the scope, and c++ guarantees that 
    // the destructor of pstatement will be called always even in case of exception thrown
}
}catch(const std::exception& e){
    std::cerr << "flushToDB problem: " << e.what() << "\n"; 
}catch(...){
    std::cerr << "unspecified flushToDB problem\n";
}