QSqlDatabase: QTDS driver not loaded



  • I have a program which uses QTDS driver.

    in development environment everything works fine. in production i have both the TDS plugin and sybdb available with appropriate rights.

    rwxr-xr-x 1 foxprd foxprd 47880 Jan 29 17:33 libqsqltds.so

    rwxr-xr-x 1 foxprd foxprd 472579 Jan 29 17:33 libsybdb.so*

    they are both inside a directory which has been added to the LD_LIBRARY_PATH

    and yet i got

    @QSqlDatabase: QTDS driver not loaded@

    EDIT
    I aslo can tell that:

    @app.libraryPaths()@

    points to a directory in which there is an sqldrivers/ directory containing all the libs
    If i rename this direcotry in dev I get the same error, if I put it back it works again.

    MyappDir/sqldrivers/libqsqltds.so
    MyappDir/sqldrivers/libsybdb.so
    MyappDir/sqldrivers/libsybdb.so.5

    In dev it works if and only if this directory is here. In Prod it does not work in either case. While "MyappDir/" is always listed in the

    @app.libraryPaths()@



  • self answer:

    When a linux app loads it need to be able to access all the libXXX.so it needs. "ld" will look for them in any directory declared in the "LD_LIBRARY_PATH" variable

    However Qt seems to load its plugins dynamically from some paths which can be found there:

    @QCoreApplication app(argc,argv);
    qDebug() << app.libraryPaths();@

    which printed

    @("/my/App/Path","/Qt/Dir/Path" )@

    And from one of this path it should load the plugins. So if in qtDir you have

    @/Qt/Dir/Path/plugins/sqldrivers/libqsqltds.so@

    You want to make sure to deploy something like:

    @/my/App/Path/sqldrivers/libqsqltds.so@

    this worked fine because the app path is always in "app.libraryPaths()". However, where things get complicated it that libqsqltds.so requires "libsybdb.so.5" to work properly. Which I knew so there also was a

    @/my/App/Path/sqldrivers/libsybdb.so.5 @

    which was wrong because Qt loads dynamically libqsqltds.so but not its dependency, which it seems ld expects to find the usual way ( e.g. in the LD_LIBRARY_PATH )

    The fact is that in my dev/integration environments I had libsybdb.so.5 in my path, but not in my production environment.

    So whatever Qt plugins you need make sure to copy the plugin directory ( with only the .so inside ) to your production environment. And Also make sure that performing:

    @ldd /my/App/Path/sqldrivers/libsybdb.so.5@

    will not print any "not found" as these dependency will not appear with:

    @ldd /my/App/Path/myAppBin@


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