Connecting c++ to mysql using mysql-c++-connector 8

user_8343075 0
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I want to connect to mysql 8 using mysql-c++-connector8 (xdevapi) and I use .so file for linking but I get errors here is my main.cpp file

#include <iostream>
#include <mysqlx/xdevapi.h>

using namespace ::mysqlx;
using std::cout;
using std::cin;
using std::endl;

int main(){

 Session sess("localhost",3306,"root","mypass");
 Schema db = sess.getSchema("university");

 Collection myColl = db.getCollection("student");
 DocResult myDocs = myColl.find("name like :param").execute();

 cout<<myDocs.fetchOne();
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.10)
project(1)
set(CMAKE_CXX_STANDARD 17)

include_directories(~/mysql-connector-c++/include)
link_directories(~/mysql-connector-c++/lib64)

set(PROJECT_LINK_LIBS libmysqlcppconn8.so)
add_executable(myExe main.cpp)
target_link_libraries(myExe ${PROJECT_LINK_LIBS})

Errors: 

[ 50%] Linking CXX executable myExe
/usr/bin/ld: CMakeFiles/myExe.dir/main.cpp.o: in function `mysqlx::string::string(char const*)':
/home/amir/mysql-connector-c++/include/mysqlx/devapi/common.h:100: undefined reference to `mysqlx::string::Impl::from_utf8(mysqlx::string&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
/usr/bin/ld: CMakeFiles/myExe.dir/main.cpp.o: in function `mysqlx::string::string(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
/home/amir/mysql-connector-c++/include/mysqlx/devapi/common.h:105: undefined reference to `mysqlx::string::Impl::from_utf8(mysqlx::string&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
/usr/bin/ld: CMakeFiles/myExe.dir/main.cpp.o: in function `mysqlx::string::operator std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >() const':
/home/amir/mysql-connector-c++/include/mysqlx/devapi/common.h:115: undefined reference to `mysqlx::string::Impl::to_utf8[abi:cxx11](mysqlx::string const&)'
/usr/bin/ld: CMakeFiles/myExe.dir/main.cpp.o: in function `void mysqlx::internal::Settings_detail<mysqlx::internal::Settings_traits>::set<true, mysqlx::SessionOption, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, mysqlx::SessionOption, unsigned int&, mysqlx::SessionOption, mysqlx::string const&>(mysqlx::SessionOption, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, mysqlx::SessionOption&&, unsigned int&, mysqlx::SessionOption&&, mysqlx::string const&)':
/home/amir/mysql-connector-c++/include/mysqlx/devapi/detail/settings.h:67: undefined reference to `mysqlx::internal::Settings_detail<mysqlx::internal::Settings_traits>::do_set(std::__cxx11::list<std::pair<int, mysqlx::common::Value>, std::allocator<std::pair<int, mysqlx::common::Value> > >&&)'
/usr/bin/ld: CMakeFiles/myExe.dir/main.cpp.o: in function `void mysqlx::internal::Settings_detail<mysqlx::internal::Settings_traits>::set<true, mysqlx::SessionOption, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >(mysqlx::SessionOption, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&&)':
/home/amir/mysql-connector-c++/include/mysqlx/devapi/detail/settings.h:67: undefined reference to `mysqlx::internal::Settings_detail<mysqlx::internal::Settings_traits>::do_set(std::__cxx11::list<std::pair<int, mysqlx::common::Value>, std::allocator<std::pair<int, mysqlx::common::Value> > >&&)'
/usr/bin/ld: CMakeFiles/myExe.dir/main.cpp.o: in function `void mysqlx::internal::Settings_detail<mysqlx::internal::Settings_traits>::set<true, mysqlx::SessionOption, mysqlx::string const&>(mysqlx::SessionOption, mysqlx::string const&)':
/home/amir/mysql-connector-c++/include/mysqlx/devapi/detail/settings.h:67: undefined reference to `mysqlx::internal::Settings_detail<mysqlx::internal::Settings_traits>::do_set(std::__cxx11::list<std::pair<int, mysqlx::common::Value>, std::allocator<std::pair<int, mysqlx::common::Value> > >&&)'
collect2: error: ld returned 1 exit status
make[3]: *** [CMakeFiles/myExe.dir/build.make:95: myExe] Error 1
make[2]: *** [CMakeFiles/Makefile2:68: CMakeFiles/myExe.dir/all] Error 2
make[1]: *** [CMakeFiles/Makefile2:80: CMakeFiles/myExe.dir/rule] Error 2
make: *** [Makefile:118: myExe] Error 2

I don't want to use legacy connectors as it is not recommended .

mysql c++
2 Answers

TL;DR; You need to use the old GCC ABI by setting the _GLIBCXX_USE_CXX11_ABI to 0. This can be done with cmake by adding the following to your CMakeLists.txt:

add_definitions(-D_GLIBCXX_USE_CXX11_ABI=0)

The issue comes from the "Linux - Generic" of the MySQL connector which have likely been built without the new CXX11 ABI of GCC (introduced in gcc 5.1).

Since your compiler is recent, the default is to use the new ABI, so when you include <mysqlx/xdevapi.h>, you create declarations such as:

mysqlx::string::Impl::from_utf8(
    mysqlx::string&, 
    std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)

...that use the new ABI (see the __cxx11 namespace).

But since the connectors have been built with the old ABI, the libmysqlcppconn8.so contains symbols for functions matching this kind of declaration:

mysqlx::string::Impl::from_utf8(
    mysqlx::string&, 
    std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)

You can check this by running readelf -Ws libmysqlcppconn8.so, for the "Linux - Generic" version I get (with a grep from_utf8)1:

1428: 00000000000a0a86 193 FUNC  GLOBAL DEFAULT   12 _ZN6mysqlx6string4Impl9from_utf8ERS0_RKSs
9437: 00000000000a0a86 193 FUNC  GLOBAL DEFAULT   12 _ZN6mysqlx6string4Impl9from_utf8ERS0_RKSs

But for the Ubuntu 18.10 version I get:

  725: 00000000000a23e0 183 FUNC GLOBAL DEFAULT   12 _ZN6mysqlx6string4Impl9from_utf8ERS0_RKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE
10141: 00000000000a23e0 183 FUNC GLOBAL DEFAULT   12 _ZN6mysqlx6string4Impl9from_utf8ERS0_RKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE

The easiest fix is to tell your compiler to use the old ABI, so that the symbol will match. This can be done by setting the _GLIBCXX_USE_CXX11_ABI macro to 0 when compiling:

g++ -D_GLIBCXX_USE_CXX11_ABI=0 main.cpp

...or by adding the following to CMakeLists.txt:

add_definitions(-D_GLIBCXX_USE_CXX11_ABI=0)

If you use multiple external libraries, you have to be careful that those also use the old ABI, otherwise you will likely face the opposite issue, i.e., a library built with the new ABI cannot be used directly to build a program with the old ABI.

1 The "Linux - Generic" version contains reference to the CXX11 ABI, so I do not really know what is going on here. It looks like some parts of the library has been compile with the new ABI.

user_26662890

You may need to download the specific version for current OS instead generic-linux version.

for example rhel8 x86_64 platform, the mysql-connector-c++-8.0.23-1.el8.x86_64.rpm and mysql-connector-c++-devel-8.0.23-1.el8.x86_64.rpm should be downloaded. (https://dev.mysql.com/downloads/connector/cpp/)

Then unarchive that into same folder. (note if you have windows system, please unarchive it in linux since there's some soft link in it) Then just using it without old CXX11ABI (need NOT to define _GLIBCXX_USE_CXX11_ABI=0)

user_125298850
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