Changing Qt Lib Paths

[bob2oneil]

I performed the standard Qt SDK install, and my binaries produced show
paths to the Qt libraries as /home/QtSDK/etc as revealed by entering the
ldd command under Linux. I am building within Qt Creator using a .pro
file.

As a result, check paths under Linux when building an RPM detects this
absolute path as an error.

For my distribution, I intend to use an RPM to copy two Qt libraries
to /usr/lib64 on a target machine that will not have Qt installed on
it.

While I have changed the LD_LIBRARY_PATH within the QtCreator IDE,
the binaries produced continue to reference my local home SDK install.

I would like this to be the /usr/lib64 pathname where the libraries
are also stored.

Is there a easy way to do this?

[ChrisW67]

The easy way to do it is to build using the system Qt4 (i.e. use its qmake) rather than the one you are using so that the RPATH/RUNPATH are "correct".

Alternatively, you can force the RPATH using your PRO file:

QMAKE_LFLAGS_RPATH="-Wl,-rpath,/some/other/location"
# or remove it completely
QMAKE_LFLAGS_RPATH=

QMAKE_LFLAGS_RPATH="-Wl,-rpath,/some/other/location"
# or remove it completely
QMAKE_LFLAGS_RPATH=

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You can also remove the RPATH/RUNPATH from your executable after it is built using a utility "chrpath".

The rules for locating libraries can can be found in:

$ man ld-linux.so

$ man ld-linux.so

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but you have to temper that with some "What actually happens" information: http://labs.qt.nokia.com/2011/10/28/rpath-and-runpath/

Qt builds executable with both DT_RPATH and DT_RUNPATH set by default. You can see that in the output of:

readelf -d programexe
...

readelf -d programexe
...

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With both set, RPATH is ignored and the dynamic linker will use LD_LIBRARY_PATH, the RUNPATH embedded locations, and the system locations in that order. This is why the Creating the Application Package instructions use a script to ensure that a set of Qt libraries bundled in the application directory are found first. If you don't use LD_LIBRARY_PATH and the RUNPATH does not exist on the target then the system locations will be searched for needed libraries.

You should be aware to writing your application Qt libraries into system location may cripple any system Qt installed on that machine. If you want a system Qt on the machine I suggest you use the system's package manager to install a compatible version.