[SOLVED] problems with QT5.4 x64, mingw w64 an MySql 64bit on Win7

  • I am running a third-party sjlj build from http://www.tver-soft.org/qt64. and attempting to connect to Mysql server.
    System environment: Windows 7, 64bit
    -Qt Creator 3.4
    -MySQL 64bit (tried 5.5, 5.6, 5.7) all with same result.
    Initially used included qsqlmysql files from third-party build. While in Debug, it fails with SIGSEGV (Segmentation fault) while attempting to open the connection to the server.

    • QSqlDatabase::db
    • db.Open

    Then I build my own driver, everything builds great. While in debug, it fails again with SIGSEGV (Segmentation fault). But this time it fails inside qsql_mysql.cpp line 1265

    if ((d->mysql = mysql_init((MYSQL*) 0)) &&
                                   host.isNull() ? static_cast<const char *>(0)
                                                 : host.toLocal8Bit().constData(),
                                   user.isNull() ? static_cast<const char *>(0)
                                                 : user.toLocal8Bit().constData(),
                                   password.isNull() ? static_cast<const char *>(0)
                                                     : password.toLocal8Bit().constData(),
                                   db.isNull() ? static_cast<const char *>(0)
                                               : db.toLocal8Bit().constData(),
                                   (port > -1) ? port : 0,
                                   unixSocket.isNull() ? static_cast<const char *>(0)
                                               : unixSocket.toLocal8Bit().constData(),
            if (!db.isEmpty() && mysql_select_db(d->mysql, db.toLocal8Bit().constData())) {
                setLastError(qMakeError(tr("Unable to open database '%1'").arg(db), QSqlError::ConnectionError, d));
                return false;
    #if MYSQL_VERSION_ID >= 50000
                mysql_options(d->mysql, MYSQL_OPT_RECONNECT, &reconnect);
        } else {
            setLastError(qMakeError(tr("Unable to connect"),
                         QSqlError::ConnectionError, d));
            d->mysql = NULL;
            return false;

    I am not receiving the else notice of "Unable to connect"

    I believe my driver is working, but am unsure where to look from here.
    If we build on QT4.5 32bit, wingw32, things work fine. We can even run on a Mysql 64bit install using a libmysql.dll from a 32 bit mysql install. not a desired condition.
    We have been fighting this for a few days now.
    Thank you in advance for any help or direction.

    [edit: Added missing coding tags ```before and after SGaist]

  • @swankster
    Solution was, finding this gem https://github.com/kivy/kivy/wiki/Creating-a-64-bit-development-environment-with-MinGW-on-Windows then making a few modifications. Basically rebuilding MySQL Connector.C 6.1\lib\libmysql.dll with gendef.exe
    will need to Install Ruby x64, I used (rubyinstaller-2.2.2-x64.exe)
    set Ruby...\bin to System Variables.
    copy C:\Program Files\MySQL\MySQL Connector.C 6.1 to C: and rename as \mysql-connector
    open cmd window
    > gendef.exe libmysql.dll
    > dlltool -v --dllname libmysql.dll --def libmysql.def --output-lib libmysql.lib
    > gem install mysql2 --no-rdoc --no-ri -- '--with-mysql-lib="C:\mysql-connector\lib" --with-mysql-include="C:\mysql-connector\include"'

    copy c:\mysql-connector\lib\libmysql.lib
    to c:\Program Files\MySQL\MySQL Server 5.6\lib

    copy c:\Ruby22-x64\lib\ruby\gems\2.2.0\gems\mysql2-0.3.18-x64-mingw32\vendor\libmysql.dll
    to c:\Program Files\MySQL\MySQL Server 5.6\lib

    Now build MySql Driver for QT. I used third party QT 64 from http://www.tver-soft.org/qt64
    put in System Variables
    Create QT cmd window (needs custom qtenv.bat file, copied from other QT version and modified for x64)
    from QT cmd x64

    set mysql=C:\PROGRA~1\MySQL\MYSQLS~1.6 (must be short names)
    cd c:\Qt\qt-5.4.1-src\qtbase\src\plugins\sqldrivers\mysql
    qmake "INCLUDEPATH+=%mysql%\include" "LIBS+=%mysql%\lib\libmysql.lib" -o Makefile mysql.pro

    copy qsqlmysql.dll and qsqlmysqld.dll from C:\Qt\qt-5.4.1-src\qtbase\plugins\sqldrivers to c:\Qt\5.4.1-x64\mingw492r1-sjlj-rev1\qt-5.4.1-x64-mingw492r1-sjlj-rev1\plugins\sqldrivers

    copy %mysql%\lib\libmysql.dll c:\windows

    Hope this helps someone else save a few days worth of time and aggravation.