C++ Poco MySQL Data wrapper segmentation fault error - c++

Question

I am using Poco 1.8 Data library. I want to build a database wrapper to run multiple SQL queries concurrently.
I build a dbconn.h with the following.
std::string _dbConnString = "host=" + host + ";user=" + user + ";password=" + password + ";db="+db
+";compress=true;auto-reconnect=true";
std::string getkey(int userID, int exchangeID) {
Poco::Data::MySQL::Connector::registerConnector();
std::string key;
{
// 0. connect & create table
Session session(Poco::Data::MySQL::Connector::KEY,_dbConnString);
Statement selectn(session);
selectn << "SELECT key FROM API WHERE user_id=? ", into(key), use(userID), now;
}
catch (const Poco::Data::ConnectionFailedException &ce)
{
std::cout << ce.displayText() << std::endl;
}
catch (const Poco::Data::MySQL::StatementException &se)
{
std::cout << se.displayText() << std::endl;
}
Poco::Data::MySQL::Connector::unregisterConnector();
return key;
}
std::string getuser(int userID, int exchangeID) {
Poco::Data::MySQL::Connector::registerConnector();
std::string user;
try
{
// 0. connect & create table
Session session(Poco::Data::MySQL::Connector::KEY, _dbConnString);
Statement selectn(session);
selectn << "SELECT user FROM API WHERE user_id=? ", into(user), use(userID), now;
}
catch (const Poco::Data::ConnectionFailedException &ce)
{
std::cout << ce.displayText() << std::endl;
}
catch (const Poco::Data::MySQL::StatementException &se)
{
std::cout << se.displayText() << std::endl;
}
Poco::Data::MySQL::Connector::unregisterConnector();
return user;
}
The following will throw out segmental fault.
teset.cpp
int user_id = 100;
int exchange_id = 1;
std::string key = getkey(user_id,exchange_id); //no error
std::string user = getuser(user_id,exchange_id); //segmentation fault
If you reverse the order of the function call, same error:
std::string user = getuser(user_id,exchange_id); //no error
std::string key = getkey(user_id,exchange_id); //segmentation fault
I think something to do with the the part of creating the session. But there is not so many Poco data examples available on internet, any advice is appreciated.
Valgrind error:
==3316== Thread 2:
==3316== Invalid read of size 4
==3316== at 0x4E45FA0: pthread_mutex_lock (pthread_mutex_lock.c:65)
==3316== by 0x76332D9: ??? (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20.3.12)
==3316== by 0x760AB40: ??? (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20.3.12)
==3316== by 0x75DEB2A: mysql_real_connect (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20.3.12)
==3316== by 0x5B43736: Poco::Data::MySQL::SessionHandle::connect(char const*, char const*, char const*, char const*, unsigned int) (in /usr/lib/libPocoDataMySQL.so.50)
==3316== by 0x5B4795A: Poco::Data::MySQL::SessionImpl::open(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (in /usr/lib/libPocoDataMySQL.so.50)
==3316== by 0x5B48D86: Poco::Data::MySQL::SessionImpl::SessionImpl(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned long) (in /usr/lib/libPocoDataMySQL.so.50)
==3316== by 0x5B3E51D: Poco::Data::MySQL::Connector::createSession(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned long) (in /usr/lib/libPocoDataMySQL.so.50)
==3316== by 0x5498B83: Poco::Data::SessionFactory::create(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned long) (in /usr/lib/libPocoData.so.50)
==3316== by 0x115048: getAPIsecret[abi:cxx11](int, int) (dbconnector.h:85)
==3316== by 0x11561A: Trading::Binance::BUY::process(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (binance.cpp:36)
==3316== by 0x110F95: Trading::ExchangeRequest::run() (exchangeRequest.cpp:58)
==3316== Address 0x30 is not stack'd, malloc'd or (recently) free'd
==3316==
==3316==
==3316== Process terminating with default action of signal 11 (SIGSEGV)
==3316== Access not within mapped region at address 0x30
==3316== at 0x4E45FA0: pthread_mutex_lock (pthread_mutex_lock.c:65)
==3316== by 0x76332D9: ??? (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20.3.12)
==3316== by 0x760AB40: ??? (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20.3.12)
==3316== by 0x75DEB2A: mysql_real_connect (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20.3.12)
==3316== by 0x5B43736: Poco::Data::MySQL::SessionHandle::connect(char const*, char const*, char const*, char const*, unsigned int) (in /usr/lib/libPocoDataMySQL.so.50)
==3316== by 0x5B4795A: Poco::Data::MySQL::SessionImpl::open(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (in /usr/lib/libPocoDataMySQL.so.50)
==3316== by 0x5B48D86: Poco::Data::MySQL::SessionImpl::SessionImpl(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned long) (in /usr/lib/libPocoDataMySQL.so.50)
==3316== by 0x5B3E51D: Poco::Data::MySQL::Connector::createSession(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned long) (in /usr/lib/libPocoDataMySQL.so.50)
==3316== by 0x5498B83: Poco::Data::SessionFactory::create(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned long) (in /usr/lib/libPocoData.so.50)
==3316== by 0x115048: getAPIsecret[abi:cxx11](int, int) (dbconnector.h:85)
==3316== by 0x11561A: Trading::Binance::BUY::process(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (binance.cpp:36)
==3316== by 0x110F95: Trading::ExchangeRequest::run() (exchangeRequest.cpp:58)
==3316== If you believe this happened as a result of a stack
==3316== overflow in your program's main thread (unlikely but
==3316== possible), you can try to increase the size of the
==3316== main thread stack using the --main-stacksize= flag.
==3316== The main thread stack size used in this run was 8388608.
==3316==
==3316== HEAP SUMMARY:
==3316== in use at exit: 266,548 bytes in 966 blocks
==3316== total heap usage: 2,241 allocs, 1,275 frees, 790,945 bytes allocated
==3316==
==3316== LEAK SUMMARY:
==3316== definitely lost: 0 bytes in 0 blocks
==3316== indirectly lost: 0 bytes in 0 blocks
==3316== possibly lost: 62,545 bytes in 63 blocks
==3316== still reachable: 204,003 bytes in 903 blocks
==3316== suppressed: 0 bytes in 0 blocks
==3316== Rerun with --leak-check=full to see details of leaked memory
==3316==
==3316== For counts of detected and suppressed errors, rerun with: -v
==3316== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

Answer 1

The Poco::Data::MySQL::Connector::registerConnector(); and Poco::Data::MySQL::Connector::unregisterConnector(); have non-local effects, you should move them out of the concurrently-called bits into some global setup/teardown. And it should be enough to call them once, you don't have to repeat them for every query.