How to set a relative path for Qt dlls when releasing a Qt project?

Question

When I release my Qt project, I want to redistribute the QtCore4.dll and QtGui4.dll files with my project, but not in the same directory as my .exe (in some other relative path).

How can I make my .exe find them automatically?

I also don't want to set the %PATH% or any other environment variable in my customer's environment.

Answer 1

Probably the safest way is to launch your application using a script that does change the PATH (but only for that session) before launching your application. Here is a script I use to launch a custom version of Qt Creator:

set PATH=%PATH%;C:\Qt\qt474_custom_msvc2008_x64\lib;C:\Qt\jom
start C:\Qt\qtcreator231__custom_msvc2008_x64\bin\qtcreator.exe

I think there are alternatives, like SetDllDirectory, but (just like rpath on *nix), they introduce other problems. Either side-by-side dlls or a change in the PATH seems to be the most stable solution.

Also, did you mean that you want to deploy the debug versions (QtCore*d*4.dll, etc.) of those dlls? That would be pretty unusual--make sure you use the release versions. (Unless, of course, you have a valid reason for using the debug versions.)

Answer 2

First, you should reconsider not changing the PATH in your customer's environment: many projects/applications do that, so you should consider that as a real option.

Second, the best way of doing this seems to be by editing a qt.conf file placed in the same folder as your executable. See this link for more information about editing an qt.conf file.