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My OS (Ubuntu 12.04) comes with a pre-packaged Qt4 libraries and other relevant stuffs. But I wanted to use the latest vanilla Qt 5.2.1, I have installed it and it's working fine, suppose I have compiled this framework which depends on Qt.

What I had to do is to add the Qt 5.2.1 libraries to the $LD_LIBRARY_PATH. My Qt 5.2.1 home path is /opt/Qt5.2.1/5.2.1/gcc_64, and thus my $LD_LIBRARY_PATH contains /opt/Qt5.2.1/5.2.1/gcc_64/lib (and /opt/Qt5.2.1/Tools/QtCreator/lib for qtcreator related stuffs)

However, recently I am trying to compile the latest gnu octave. It's configure script looks for the Qt cflags (i.e. -l/-I/-L flags) by invoking the pkg-config.

What I came to know that pkg-config looks for the appropriate .pc files to get the exact information related to all compilation/linking flags. My system (Ubuntu) maintains a list of all required .pc file locations in /var/lib/dpkg/info/pkg-config.list. But I do not have any $PKG_CONFIG_PATH environment variable on Ubuntu 12.04 (I am not sure why).

My newly installed Qt5 has a set of .pc files in /opt/Qt5.2.1/5.2.1/gcc_64/lib/pkgconfig/.

So, how do I make pkg-config to recognize the development libraries in the newly installed Qt 5.2.1 ?

I know that this could be solved by just installing the Qt4 -dev packages from the Ubuntu repo, but I do not want to do that. I need the vanilla Qt 5.2.1 for other purposes.

NOTE:

  • I have added the the path /opt/Qt5.2.1/5.2.1/gcc_64/lib/pkgconfig/ to the pkg-config.list but the pkg-config does not update the compilation flags accordingly.
  • Adding the path (/opt/Qt5.2.1/5.2.1/gcc_64/lib/pkgconfig/) to $PKG_CONFIG_PATH does not work as well.

Here is the octave configure script output.

ramgorur
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  • what does the following command returns in your system? `pkg-config --exists --print-errors "QtCore"` ? And does it return when you have `QtGui` and `QtNetwork` instead? Does any of them cause an error? – carandraug Apr 18 '14 at 23:48
  • `Package QtCore was not found in the pkg-config search path.` `Perhaps you should add the directory containing 'QtCore.pc'` `to the PKG_CONFIG_PATH environment variable` `No package 'QtCore' found` -- same for `QtGui` and `QtNetwork` – ramgorur Apr 19 '14 at 00:08
  • my bad, what I have in my machine are `Qt5Core.pc`, `Qt5Gui.pc` etc. Let me test by adding them to `PKG_CONFIG_PATH`, and I will let you know. – ramgorur Apr 19 '14 at 00:11
  • did my answer below fixed your problem? Does octave build fine now? Someone upvoted it but I don't know if it was you. – carandraug Apr 19 '14 at 18:38
  • There is no need to prefix every one of your question titles with a tag - that's precisely what the "tags" field is for. If you want to mention the subject matter in the title, that's fine, but there is no need for a dedicated tag prefix. – BoltClock May 06 '14 at 03:33
  • @BoltClock, well, I was just wondering how did you know I am doing that ?? – ramgorur May 09 '14 at 23:18

2 Answers2

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This problem is because Octave is searching for QtCore.pc, QtGUI.pc, and QtNetwork.pc but Qt5 seems to have renamed them as Qt5Core.pc, Qt5GUI.pc, and Qt5Network.pc. One solution is to create symlinks for them:

cd /opt/Qt5.2.1/5.2.1/gcc_64/lib/pkgconfig/
ln -s ./Qt5Core.pc ./QtCore.pc
ln -s ./Qt5GUI.pc ./QtGUI.pc
ln -s ./Qt5Network.pc ./QtNetwork.pc
cd octave_build_dir
export $PKG_CONFIG_PATH="/opt/Qt5.2.1/5.2.1/gcc_64/lib/pkgconfig/"
./configure # with fingers crossed

I am unsure of the why the reason of name change. I wonder if there should be some sort of mechanism in place where the unversion versions would be in the $PKG_CONFIG_PATH, and changing your preferences would change the link to correct version.

Finally, your config.log and config.status would have been more useful than just the output of configure. The mentioned files will have the actual commands and output of your configure.

carandraug
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  • yes, configure works now, at least your hack gives compilation flags. But the bad news is it is giving this `error configure: WARNING: QAbstractItemModel::beginResetModel() not found -- disabling GUI` – ramgorur Apr 22 '14 at 01:34
  • @ramgorur I just checked and Qt 5.2 does have [that method](http://qt-project.org/doc/qt-5/qabstractitemmodel.html#beginResetModel). Look into your `config.log` for the exact test that is failing causing configure to say that the method does not exist. – carandraug Apr 22 '14 at 01:55
  • looks like the current version of octave does not support compilation with Qt5+. http://savannah.gnu.org/bugs/?func=detailitem&item_id=40252#comment0 – ramgorur Jul 23 '14 at 23:26
3

The carandraug's answer is correct, but I didn't need to symlink .pc files(Qt 5.9.5). To prevent removing other pkg-config addresses, export PKG_CONFIG_PATH like below:

PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/opt/Qt5.2.1/5.2.1/gcc_64/lib/pkgconfig/

And to execute it at startup and systemwide(no need to export in every terminal session), put these lines at the bottom line in ".bashrc":

PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/opt/Qt5.2.1/5.2.1/gcc_64/lib/pkgconfig/
export PKG_CONFIG_PATH
mohammads
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