Qt 5 linux deployment - using qt.conf for dynamic linking

te777

I have a Qt 5 app that I don't want to opensource (so I don't want to do a static build of Qt 5 from source). I'm trying to dynamic link the required dependencies using the ldd command, and a qt.conf file in the same folder as the executable. Is this possible? I really would rather not do a static build of Qt 5 and opensource my app. I would like to offer my app as a tar.gz (with dependencies). Here's what I have in my qt.conf:

[Paths]
PrefixPath = data
LibrariesPath = libs_32
TranslationsPath = translations

And my folder looks like this:

Executable
qt.conf
data/libs_32/
data/translations/
platforms/

libs_32 contains the dependencies listed by the ldd command. Also, do I need translations?

The above configuration doesn't work. It only works with Qt 5 installed, which means it's looking for some hard-coded paths I'm missing or configuring incorrectly. Am I missing something or doing something wrong? Any input would greatly be appreciated. Thanks in advance.

mrdebug

With my experience qt.conf works only on Linux. On Windows is necessary to store the qt libraries in the executable folder-. In Mac you have to run macedeployqt.

te777

I am in Linux. But despite pointing the executable to the dependencies, it's still looking for some hard-coded paths. It runs with Qt 5 installed. When I temporarily move the Qt 5 installation to Trash, the application will not run.

mrdebug

Sorry. With linux I use qt.conf only for plugins.
Please insert in your .pro file the rows below:

unix:!mac {
LIBS += -Wl,-rpath=\$$ORIGIN/libs
}

and then please store your required libraries in libs subfolder.

te777

I tried it. It didn't work. In my app folder I have:

myapp
libs/
platforms/

Any ideas?

te777

The Qt libraries needed (libicuxxx, libQt5Corexxx, libQt5Guixxx, libQt5WidgetsXXX) are listed in the Qt 5 library as links to other versions of those files. Maybe resolving the dependencies is having a problem with that.

mrdebug

Can you try to download and compile that?
http://kde-apps.org/content/show.php?content=149622
I'm sure that works correctly with Qt 4.8.4

te777

I did a build in Qt 4.8.2 (installed from the software manager in Linux Mint 14 32 bit) and everything works perfectly. I tried it with a shell wrapper also, and also a qt.conf and everything works. There's definitely a problem with dynamic linking with Qt 5.

mrdebug

This means that for now I can't use Qt 5. When you will find the solution please post here.

te777

If I find a solution I will post it. Maybe when Qt 5.1.0 comes out it will be solved (scheduled for some time in April if no delays). Note that I didn't have any problems with dynamic linking in Qt 5 with a Windows build. Just Linux.

te777

I was missing libQt5DBus in my dependencies. It was not listed by the ldd command. I found that out on another forum. Dynamic linking in Qt 5 works for me now, both using your addition to the .pro file, and a wrapper shell script. But I can't get a qt.conf to work. I saw somewhere where it doesn't for Windows builds. Maybe not Linux either. It works for Qt 4.8.2. I'll check the bug reports to see if it is already reported. Qt 5 dynamic linking works.

mrdebug

Yes, you're right. qt.conf works only with plugins for me.

te777

I filed a bug report. Here's the answer I got:

Quote: "

qt.conf can not make the linker look for libraries in a different location, it's simply technically not possible. The "Libraries" entry (and all other entries) are only fixing up the paths that the QLibraryInfo API returns.

From the qt.conf documentation:

The qt.conf file overrides the hard-coded paths that are compiled into the Qt library. These paths are accessible using the QLibraryInfo class.

If you want to make your application/libraries look for Qt at a different location, your only choice are the options that the linker offers you, i.e. on Linux basically LD_LIBRARY_PATH or rpath (e.g. with $ORIGIN to make it independent from absolute paths)." UnQuote. FYI.

mrdebug

Ok. Thanks for the investigation and the explanation.