Do I have to include all these Qt dlls with my application?

Question

I'm totally new in using Qt and I don't know a lot of stuff.

As a test I created a simple application using Visual Studio 2012 and Qt-VS-Add-in based on the newest Qt5.1

After I compiled the application it didn't work for me (gave errors), I searched all over the internet and found a lot of people saying that I have to copy those dlls mentioned below from the directory:

C:\Qt\Qt5.1.0\5.1.0\msvc2012\bin\ 

DLL's I had to copy to make my application work:

icudt51.dll icuin51.dll icuuc51.dll libEGL.dll libGLESv2.dll Qt5Core.dll Qt5Gui.dll Qt5Widgets.dll 

My problem is the size of these dlls, they're about "37 MB" and my application itself is only "30 KB"! So, those Qt libraries will add at least 37 MB to my application [ Which I don't see it happens with other Qt-based applications I download ]. Is there any solution can make me end up with a single small .exe file?!

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And I heard some people saying that I have to also include a dll for Microsoft C++ Compiler, can you explain this for me?

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Note: I've come across a lot of questions here on StackOverFlow but I couldn't find anything can help me, so please do not flag this as a duplication because if I found a clear answer I wouldn't post this question!

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Any help would be appreciated.

Answer 1

UPDATE: Use windeployqt.exe! It works really well.

http://doc.qt.io/qt-5/windows-deployment.html#the-windows-deployment-tool

The simplest way to use windeployqt is to add the bin directory of your Qt installation (e.g. ) to the PATH variable and then run:

windeployqt <path-to-app-binary> 

UPDATE: Upon Further testing, windeployqt did not copy over all the MingW dlls for me. (Tested with Qt 5.4 on Windows 10 with MingW 4.9.1). So you need to manually get the last 3 dlls before deploying:

libgcc_s_dw2-1.dll libstdc++-6.dll libwinpthread-1.dll 

From

C:\Qt\5.4\mingw491_32\bin 

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I think you may have a few extras in your list... I would double check the docs in the links below...

Here is the definitive documentation on it:

http://doc.qt.io/qt-5/windows-deployment.html

http://doc.qt.io/qt-5/windows-deployment.html#application-dependencies

Size of Qt DLLs

The amazing Qt Libraries can do a lot, but they are kind of big. Some of the older versions of Qt might be a little smaller.

For Qt 4.8 msvc QtCore4.dll is 2.5 MB, and QtGui4.dll is 8.4 MB.

How Windows Resolves Shared Libraries/Dynamic Link Libraries (DLL)

Here is how Windows tracks down a library at runtime:

http://msdn.microsoft.com/en-us/library/windows/desktop/ms682586(v=vs.85).aspx

Single Small EXE

If you statically link, then your EXE should grab the libraries it needs and gets built into a stand alone exe. It still may be dependent on msvc redistributables. See the next section for more info on it. But it now compiles down the .libs that you reference into your EXE and your exe no longer is pointing at other dynamically linked libraries. It does take more time to get your statically linked exe environment setup.

Your exe will certainly get bigger as it now includes the binary information for the libraries that you referenced before.

https://www.google.com/search?q=qt+static+linking

EDIT: Statically building the exe, means that you aren't using the LGPL version. means that you have to have your object files easy to access to end users if you are using LGPL.

I think @peppe described it well (see comment below):

Technically, you are allowed to statically link when using Qt under LGPL, even if your application is not using LGPL. The only tricky requirement is keeping the ability for a third party to relink your application against a different Qt version. But you can comply with that easily, f.i. by providing a huge object file (.o) of your application, that only needs to be linked against any Qt version.

http://blog.qt.io/blog/2009/11/30/qt-making-the-right-licensing-decision/

Look at the chart near the bottom. If you are doing the commercial version, then you can statically link, without worrying about the object files.

MSVC Redistributables

Redistributable dependencies have to do with the run-time library linker options.

http://msdn.microsoft.com/en-us/library/aa278396(v=vs.60).aspx

/MD, /ML, /MT, /LD (Use Run-Time Library)

To find these options in the development environment, click Settings on the Project menu. Then click the C/C++ tab, and click Code Generation in the Category box. See the Use Run-Time Library drop-down box.

These two links below talk about some older versions of visual studio, but the reasoning should still stand.

http://www.davidlenihan.com/2008/01/choosing_the_correct_cc_runtim.html

How do I make a fully statically linked .exe with Visual Studio Express 2005?

Hope that helps.

Answer 2

Just open your terminal execute your_qt_installpath/version/compiler/bin/windeployqt.exe YourApplication.exe. It will automatically copy all the required libs and stuff into the folder, where your exe is located and you can just distribute it.