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qtqsqldatabase

QSqlDatabase: QTDS driver not loaded

I have a program which uses QTDS driver.

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

  1. -rwxr-xr-x 1 foxprd foxprd 47880 Jan 29 17:33 libqsqltds.so*
  2. -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.

  1. MyappDir/sqldrivers/libqsqltds.so
  2. MyappDir/sqldrivers/libsybdb.so
  3. 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()
Solution

  • 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