用C ++连接MySQL

Question

我正在尝试学习C ++，我在做一个连接到MySQL数据库的测试时遇到了一些噩梦。

我有MySQL连接器没有正确链接的问题然后得到与relocation truncated to fitr_x86_64_32 against symbol相关的问题relocation truncated to fitr_x86_64_32 against symbol 。

我想我已经通过添加编译器标志来修复它，现在应用程序成功构建和链接。

当我运行应用程序时，它会调用get_driver_instance但它会退出。 没有异常被抛出，没有任何错误只是退出代码0。

下面是我的DBManager类

#include "DBConnectionManager.h"

using namespace std;

DBConnectionManager::DBConnectionManager() {
    cout << "Starting DBConnectionManager - Updated" << endl;
    try {
        cout << "Getting driver instance" << endl;
        driver = get_driver_instance();
        cout << "Got driver instance" << endl;
        conn = driver->connect("tcp://127.0.0.1:3306", "root", "password");
        conn->setSchema("bugs");
        cout << "Connected to database" << endl;
    }
    catch (SQLException ex) {
        cout << "Error connecting to DB: " << ex.what() << endl;
    }
    catch (...) {
        cout << "Something has gone wrong" << endl;
    }
}

下面是头文件

#ifndef MYSQLTEST_DBCONNECTIONMANAGER_H
#define MYSQLTEST_DBCONNECTIONMANAGER_H
#include <driver.h>
#include <exception.h>
#include <resultset.h>
#include <statement.h>

using namespace sql;

class DBConnectionManager
{
private:
    sql::Driver *driver;
    sql::Connection *conn;
    sql::Statement *statement;
    sql::ResultSet *res;
public:
    DBConnectionManager();
    void performSql();
};
#endif //MYSQLTEST_DBCONNECTIONMANAGER_H

以下是我的主要方法

#include "DBConnectionManager.h"

int main() {
    DBConnectionManager dbConnectionManager;
    dbConnectionManager.performSql();
    return 0;
}

下面是我的CMakeLists.txt文件

cmake_minimum_required(VERSION 3.6)
project(MySQLTest)

include_directories("C:\\Program Files\\MySQL\\MySQL Connector C++ 1.1.7\\include\\cppconn" "C:\\Program Files\\MySQL\\MySQL Connector C++ 1.1.7\\lib\\opt")

SET(GCC_COVERAGE_LINK_FLAGS    "-m64 -Wl,--image-base -Wl,0x10000000 -lpthread -pthread")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -m64 -Wl,--image-base -Wl,0x10000000 -lpthread -pthread ")

set(SOURCE_FILES main.cpp DBConnectionManager.cpp)
add_executable(MySQLTest ${SOURCE_FILES})
add_library(mysqlcppconn.lib)

set_target_properties(MySQLTest PROPERTIES LINKER_LANGUAGE CXX)
set_target_properties(mysqlcppconn.lib PROPERTIES LINKER_LANGUAGE CXX)

target_link_libraries(MySQLTest "C:\\Program Files\\MySQL\\MySQL Connector C++ 1.1.7\\lib\\opt\\mysqlcppconn.lib")

当我创建我的DBConnectionManager类的实例时，它成功调用了查询并打印了Starting DBConnectionManager - Updated后跟Getting Driver Instance但是它退出时Process finished with exit code 0 ，没有关于出错的线索。

更新

我终于到了某个地方。 我发现Cygwin中有一些MySQL客户端库，所以我下载它们并在cmake文件中引用它们。

我的cmake文件现在看起来像这样：

cmake_minimum_required(VERSION 3.6)
project(MySQLTest)

SET(CPPCONN_PUBLIC_FUNC=)

SET(GCC_COVERAGE_LINK_FLAGS    "-g -m64 -DCPPCONN_PUBLIC_FUNC= -Dmysqlcppconn_EXPORTS -lpthread -pthread -Wl,--image-base -Wl,0x10000000  -lz")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DCPPCONN_PUBLIC_FUNC= -Dmysqlcppconn_EXPORTS -std=c++11 -g -m64 -Wl,--image-base -Wl,0x10000000  -lpthread -pthread  -lz")

include_directories("C:/mysql_connector/include")
include_directories("C:/boost_1_61_0")

set(BOOST_INCLUDE_DIR C:/boost_1_61_0)
set(BOOST_LIBRARY_DIR C:/boost_1_61_0/libs)
set(SOURCE_FILES main.cpp DBConnectionManager.cpp)

add_executable(MySQLTest ${SOURCE_FILES})

find_package(Boost COMPONENTS REQUIRED)

link_directories(C:/mysql_connector/lib)

target_link_libraries(MySQLTest "C:/mysql_connector/lib/mysqlcppconn.dll"  "C:/Program Files/MySQL/MySQL Server 5.7/lib/libmysql.dll" "C:/mysql_connector/lib/libmysqlclient.dll.a" "C:/mysql_connector/lib/libmysqlclient_r.dll.a" ${Boost_LIBRARY_DIR})

请注意我是如何链接库libmysqlclient.dll.a和libmysqlclient_r.dll.a的，这是我从Cygwin获得的。

当我现在运行应用程序时，它成功获取驱动程序实例并输出到控制台

Starting DBConnectionManaged - Updated
Getting driver instance
Got driver instance

但是当我尝试连接driver-> connect时，我得到以下错误

0 [main] MySQLTest 2976 C:\Users\Chris\.CLion2016.2\system\cmake\generated\MySQLTest-8702ae13\8702ae13\Debug\MySQLTest.exe: *** fatal error - Internal error: TP_NUM_C_BUFS too small: 50

当我通过调试器时，它在驱动程序 - > connect with上失败

gdb: unknown target exception 0xe06d7363 at 0x7fff11347788

Program received signal ?, Unknown signal.
0x00007fff11347788 in RaiseException () from /cygdrive/c/WINDOWS/System32/KERNELBASE.dll

更新2

我读过的所有内容都指出mysql连接器二进制文件应该可以正常工作，所以我再次开始。 下面是我的cmake文件的内容

cmake_minimum_required(VERSION 3.6)
project(MySQLTest)


#add_compile_options("-v")

SET(GCC_COVERAGE_LINK_FLAGS )
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")

set(BOOST_INCLUDE_DIR C:/boost_1_61_0)
set(BOOST_LIBRARY_DIR C:/boost_1_61_0/libs)

include_directories("C:/Program\ Files/MySQL/MySQL\ Connector\ C++\ 1.1.7/include" "C:/Program\ Files/MySQL/MySQL\ Connector\ C++\ 1.1.7/include/cppconn" ${BOOST_INCLUDE_DIR})


set(SOURCE_FILES main.cpp DBConnectionManager.cpp)

add_executable(MySQLTest ${SOURCE_FILES})

find_package(Boost COMPONENTS REQUIRED)

link_directories(C:/Program\ Files/MySQL/MySQL\ Connector\ C++\ 1.1.7/lib/opt)

target_link_libraries(MySQLTest C:/Program\ Files/MySQL/MySQL\ Connector\ C++\ 1.1.7/lib/opt/mysqlcppconn.lib ${Boost_LIBRARY_DIR})

现在，当我编译时，我得到原始错误

C:/Program Files/MySQL/MySQL Connector C++ 1.1.7/lib/opt/mysqlcppconn.lib(mysqlcppconn.dll.b):(.text+0x2): relocation truncated to fit: R_X86_64_32 against symbol `__imp_get_driver_instance' defined in .idata$5 section in C:/Program Files/MySQL/MySQL Connector C++ 1.1.7/lib/opt/mysqlcppconn.lib(mysqlcppconn.dll.b)

听起来像我的应用程序正在编译为32位而不是64位。 作为测试，我运行了以下代码：

cout << "Int size is: " << sizeof(int) << endl;

上面的代码打印4（如果它被编译为64位，则不应该是8）。

如果我的想法是正确的，为什么不将它编译为64位，我已经尝试设置编译器标志-m64但没有区别。 我已经安装了Cion正在使用的Cygwinx64。

Answer 1

您可以使用MySQL Connector C ++

这是使用Cmake进行配置的方法

cmake_minimum_required(VERSION 3.7)

project(projectname)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")

包括你解压缩mysql-connector-cpp的目录 - 下载

include_directories(/usr/local/include/mysql-connector-cpp/include)

创建包含项目源文件的cmake变量

set(SOURCE_FILES main.cpp)

创建可执行文件

add_executable(projectname ${SOURCE_FILES})

创建可执行文件后链接

target_link_libraries(projectname mysqlcppconn)

您的CMakeList至少应该按此顺序显示或看起来像这样

cmake_minimum_required(VERSION 3.7)
project(projectname)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
include_directories(/usr/local/include/mysql-connector-cpp/include)
set(SOURCE_FILES main.cpp)
add_executable(projectname ${SOURCE_FILES})
target_link_libraries(projectname mysqlcppconn)

Answer 2

您可以使用mysql ++库从c ++连接到mysql。
为了安装mysql ++，
（ Ubuntu ）

sudo apt-get install mysql-server mysql-client
sudo apt-get install libmysqlclient-dev libmysql++-dev libmysqlcppconn-dev

（ Mac ）

brew install mysql++

包括库添加，

/usr/include/mysql++
/usr/include/mysql

并添加连接器，

-lmysqlpp -lmysqlclient

示例代码 ，

#include <iostream>
#include <string>
#include <mysql++.h>
#include <mysql.h>

#define dbname "dbname"
#define server "localhost"
#define user "username"
#define pass "password"

using namespace std;
using namespace mysqlpp;

int main() {
    Connection con(true);
    try {
        con.connect(dbname, server, user, pass);
        cout << "Connected to database\n";
        string s = "SELECT * FROM mirrors_mee WHERE id=1";
        Query q = con.query(s);
        StoreQueryResult sq = q.store();
        StoreQueryResult::iterator it;
        it = sq.begin();
        while (it != sq.end()) {
            Row row = *it;
            cout << row[5] << " " << row[6] << " " << row[7] << endl;
            it++;
        }
    } catch (Exception &e) {
        cout << e.what() << endl;
    }
    return 0;
}

您将在此处获得该库的完整文档。