How to make my Qt application load dlls in a different folder?

[Roberrt]

How to set my qt project to search for the dependent DLLs in a different folder than the exe folder?

I can't compile it as static because I'm using the QWebEngine module which didn't support being built statically.

These are some things I already tried:

Creating a qt.conf file in the same folder of the exe and specifying a path.

[Paths]
Prefix = D:/Project/New folder

SetDllDirectory, addLibraryPath

    //SetDllDirectory(L"D:/Project/New folder"); 

    //QList<QString> list = {"D:/Project/New folder"};
    //QCoreApplication::setLibraryPaths(list);

    QCoreApplication::addLibraryPath("D:/Project/New folder");

    QApplication a(argc, argv);

I was not sure when to call these 3 options, I tried calling then before the QApplication line.

I have been able to deploy it using windeployqt, the project is being built using Qt 6.4 and Visual Studio 2019.

[jsulm]

@Roberrt On Windows you need to add the folder containing your libraries to environment variable PATH before starting your app.

[Roberrt]

@jsulm

I have put all dependencies in the folder D:\New folder and added it under the user Environment Variables, is it correctly?

I tested it, but it still complains about missing DLLs.

[jsulm]

@Roberrt I was talking about PATH variable. I can't see it in your screen shot. And keep in mind: if you do it this way you will need to log off and on again.

[Roberrt]

@jsulm said in How to make my Qt application load dlls in a different folder?:

PATH variable

To clarify, are you referring to System Variables > Path variables?

I've added the folder and rebooted, but now I'm getting this error:

This application failed to start because no Qt platform plugin could be initialized.

This is my dependencies folder:

[jsulm]

@Roberrt said in How to make my Qt application load dlls in a different folder?:

are you referring to System Variables > Path variables?

I'm referring to PATH environment variable.
You can set it in System Variables > Path variables. But as I already pointed out above: you need to log off and log in again after changing PATH. If it then still does not work then open a terminal and enter command "set" - check the value of the PATH variable there.
You should also consider that using paths with spaces can easily cause problems.

[Roberrt]

@jsulm said in How to make my Qt application load dlls in a different folder?:

You should also consider that using paths with spaces can easily cause problems.

I modified it to a path without spaces, and rebooted, continue getting the same error message.

If i execute the exe inside of the DLL folder it works correctly.

I think the problem is these folders dont?

I used windeployqt to copy the dependencies, is it possible to 'copy' everything without creating any folder?

[jsulm]

@Roberrt What about my suggestion from above: "If it then still does not work then open a terminal and enter command "set" - check the value of the PATH variable there.". If the PATH is set correctly try to start your app from a terminal - does that work?

[Roberrt]

@jsulm yes, when i enter "set" in the terminal i can see the path.

I tried launching the app using the terminal it gave the same error.

[jsulm]

@Roberrt Can you show your PATH?

[Roberrt]

@jsulm

[jsulm]

@Roberrt If c:\Users\Public\Qt is the folder with your libs it should work.
You also tried to use qt.conf: did you specify the folder with the libs using "Libraries = PAT_TO_LIBS_FOLDER"? Prefix is the app folder.

[Roberrt]

@jsulm
I got it working for a new project containing just a push button, I also needed to create a variable with the name QT_PLUGIN_PATH under the System variables environment, and set the folder which contains these plugins folders (platforms, etc), in my case C:\Users\Public\Qt.

But for my app using qwebengine its not working, when i run the exe i don't see any error message neither my gui, then it closes :(