MySQL C++连接器中的内存泄漏

azpvetkf  于 2023-05-30  发布在  Mysql
关注(0)|答案(3)|浏览(210)

我正在使用MySQL C++连接器。Valgrind在每个连接上泄漏了192个字节。它只在线程环境中泄漏内存，而没有线程，它没有泄漏任何内存。我做错了什么？我是否需要调用其他函数进行清理？样本代码：

#include <pthread.h>
#include <iostream>
#include <cppconn/driver.h>
#include <cppconn/exception.h>
#include <cppconn/resultset.h>
#include <cppconn/statement.h>
#include <cppconn/prepared_statement.h>

using namespace std;

void* test(void* arg) {

  try {
    sql::Driver *driver;
    sql::Connection *con;
    /* Create a connection */
    driver = get_driver_instance();
    con = driver->connect("tcp://127.0.0.1:3306", "root", "root");
    /* Connect to the MySQL test database */
    con->setSchema("test");
    delete con;
  } catch (sql::SQLException &e) {
    cout << "# ERR: SQLException in " << __FILE__;
    cout << "(" << __FUNCTION__ << ") on line " << __LINE__ << endl;
    cout << "# ERR: " << e.what();
    cout << " (MySQL error code: " << e.getErrorCode();
    cout << ", SQLState: " << e.getSQLState() << " )" << endl;
  }
  return NULL;
}

int main() {
  pthread_t thread1, thread2, thread3, thread4;
  pthread_create(&thread1, NULL, test, NULL);
  pthread_create(&thread2, NULL, test, NULL);
  pthread_join(thread1, NULL);
  pthread_join(thread2, NULL);
  return 0;
}

Valgrind输出：

==10252== Memcheck, a memory error detector
==10252== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==10252== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==10252== Command: ./app/bin/app-test
==10252== Parent PID: 6312
==10252== 
==10252== 
==10252== HEAP SUMMARY:
==10252==     in use at exit: 384 bytes in 2 blocks
==10252==   total heap usage: 212 allocs, 210 frees, 208,400 bytes allocated
==10252== 
==10252== 192 bytes in 1 blocks are definitely lost in loss record 1 of 2
==10252==    at 0x4C29DB4: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10252==    by 0x5E1CB3E: my_thread_init (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18.0.0)
==10252==    by 0x5E1CE3C: my_thread_global_init (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18.0.0)
==10252==    by 0x5E1AA54: my_init (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18.0.0)
==10252==    by 0x5DF86CA: mysql_server_init (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18.0.0)
==10252==    by 0x4EA3C08: sql::mysql::NativeAPI::getCApiHandle(sql::SQLString const&) (in /usr/lib/libmysqlcppconn.so.5.1.1.0)
==10252==    by 0x4EA40EA: sql::mysql::NativeAPI::MySQL_NativeDriverWrapper::MySQL_NativeDriverWrapper(sql::SQLString const&) (in /usr/lib/libmysqlcppconn.so.5.1.1.0)
==10252==    by 0x4EA4138: sql::mysql::NativeAPI::createNativeDriverWrapper(sql::SQLString const&) (in /usr/lib/libmysqlcppconn.so.5.1.1.0)
==10252==    by 0x4E6F2F3: sql::mysql::MySQL_Driver::MySQL_Driver(sql::SQLString const&) (in /usr/lib/libmysqlcppconn.so.5.1.1.0)
==10252==    by 0x4E6F50B: sql::mysql::get_driver_instance_by_name(char const*) (in /usr/lib/libmysqlcppconn.so.5.1.1.0)
==10252==    by 0x40AB8C: test(void*) (main.cc:17)
==10252==    by 0x50D9E99: start_thread (pthread_create.c:308)
==10252== 
==10252== 192 bytes in 1 blocks are definitely lost in loss record 2 of 2
==10252==    at 0x4C29DB4: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10252==    by 0x5E1CB3E: my_thread_init (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18.0.0)
==10252==    by 0x5DF86DC: mysql_server_init (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18.0.0)
==10252==    by 0x5DFE85E: mysql_init (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18.0.0)
==10252==    by 0x4EA4A82: sql::mysql::NativeAPI::MySQL_NativeConnectionWrapper::MySQL_NativeConnectionWrapper(boost::shared_ptr<sql::mysql::NativeAPI::IMySQLCAPI>) (in /usr/lib/libmysqlcppconn.so.5.1.1.0)
==10252==    by 0x4EA4014: sql::mysql::NativeAPI::MySQL_NativeDriverWrapper::conn_init() (in /usr/lib/libmysqlcppconn.so.5.1.1.0)
==10252==    by 0x4E6F0DC: sql::mysql::MySQL_Driver::connect(sql::SQLString const&, sql::SQLString const&, sql::SQLString const&) (in /usr/lib/libmysqlcppconn.so.5.1.1.0)
==10252==    by 0x40ABE8: test(void*) (main.cc:18)
==10252==    by 0x50D9E99: start_thread (pthread_create.c:308)
==10252==    by 0x5AFCCBC: clone (clone.S:112)
==10252== 
==10252== LEAK SUMMARY:
==10252==    definitely lost: 384 bytes in 2 blocks
==10252==    indirectly lost: 0 bytes in 0 blocks
==10252==      possibly lost: 0 bytes in 0 blocks
==10252==    still reachable: 0 bytes in 0 blocks
==10252==         suppressed: 0 bytes in 0 blocks
==10252== 
==10252== For counts of detected and suppressed errors, rerun with: -v
==10252== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 2 from 2)
c++

3条答案

按热度按时间
cbjzeqam

cbjzeqam1#

正如WhozCraig建议的那样，你可以将delete Driver;添加到你的测试函数中，但是我建议你使用auto_ptr或C11 unique_ptr或shared_ptr来处理所有MYSQL，这样你就永远不必担心内存泄漏了。
就拿这个举例吧
C11

std::unique_ptr< sql::Connection > con( driver->connect("tcp://127.0.0.1:3306", "root", "root"));

或者C++

std::auto_ptr< sql::Connection > con( driver->connect("tcp://127.0.0.1:3306", "root", "root"));

编辑

你不能只是delete Driver，我会看看它更多的时候，我有时间

更新

我看了driver.h的源代码，确实是protected: virtual ~Driver() {}，所以你不能只使用删除，怎么在public:中有两个

virtual void threadInit() = 0;

    virtual void threadEnd() = 0;

这也许是你需要的
还有这个example可能是非常有用的，做这一点有点不同，然后你

赞(0）分享  回复(0）举报  2023-05-30
w1jd8yoj

w1jd8yoj2#

第一个问题是你的代码是错误的。如果在try块中出现任何异常，程序将永远不会到达delete con;语句，并且您将与MySQL服务器和内存泄漏保持开放连接。你必须在try块外声明并删除con，或者使用C++11智能指针：

错误：

try {
    sql::Connection *con = driver->connect("URL", "user", "password");

    // code

    delete con;
  }
  catch (const sql::SQLException &e) {
    // code
  }

正确，C++11之前：

sql::Connection *con = NULL;     
  try {
    con = driver->connect("URL", "user", "password");

    // code

  }
  catch (const sql::SQLException &e) {
    // code
  }
  delete con; // delete on NULL is harmless.
  con = NULL;

正确，C++11，推荐方式：

try {
    // unique_ptr will automatically call delete when it goes out of scope.
    // That will also happen in case of exception.
    std::unique_ptr<sql::Connection> con (driver->connect("URL", "user", "password"));     

    // code

  }
  catch (const sql::SQLException &e) {
    // code
  }

另外，driver = get_driver_instance();应该只在程序中调用一次，而不是在每个线程中。因此，您应该将sql::Driver *driver;设置为全局变量，并在创建任何线程之前在main()中调用driver = get_driver_instance();。

赞(0）分享  回复(0）举报  2023-05-30
8ljdwjyq

8ljdwjyq3#

我也收到了Valgrind的警告。您不能更改MySQL++，但可以将问题限制为0或1个泄漏。对我来说，我有一个带有1个线程的类，它使用一个线程安全队列处理所有同步/异步消息的SQL通信。
对于每一条消息，我都有一个包含信号量、回调函数、类型和消息id的类。ID用于日志记录。
而且，所有的重入问题都可以解决，因为不是所有的mysql实现都是线程安全的。
如果人们感兴趣，我会把这段代码放在sourceforge上。它被证明是有效的，因为它在许多荷兰餐馆的Linux POS软件中使用MySQL5.7。我也和Valgrind一起检查过了。

赞(0）分享  回复(0）举报  2023-05-30
我来回答

相关问题

    查看更多

    热门标签

    更多
    JavaquerypythonNode开发语言requestUtil数据库Table后端算法LoggerMessageElementParser

    最新问答

    更多
    • 蜀ICP备13028337号-1 大数据知识库 https://www.saoniuhuo.com © All rights reserved
    • 本站内容来源互联网,如果侵犯您的权益请联系我们删除, 联系方式：448109455@qq.com