I'm having an issue with having qt4/qt5 coexisting on the same box. For the most part, both qt4 and qt5 programs run fine on my systems that I've tested them on. The one issue that I'm having is that when compiling certain programs, the header files for both qt4 and qt5 get mixed up. For example, I have an issue compiling calibre when qt5 is installed.

After some testing it looks to be the environment variable $CPLUS_INCLUDE_PATH which is defined in /etc/profile.d/qt4.sh and /etc/profile.d/qt5.sh. The way that it is set up on my system is that the qt5 header files come before the qt4 header files in $CPLUS_INCLUDE_PATH.

This doesn't seem to be an issue with CMAKE or autotools but only seems to happen when compiling with python or calling qmake explicitly (possibly others). The reverse is true that if qt4 headers come before qt5 headers in $CPLUS_INCLUDE_PATH, then qt5 programs will fail to compile for the same issue.

My question is, would it be prudent to just exclude CPLUS_INCLUDE_PATH from the qt5.{sh,csh} profile.d files and avoid any qt4/qt5 header collisions? or is there something more obvious that I'm missing?

How exactly have you installed both?

We had a little discussion about this a while back :-

http://www.linuxquestions.org/questi...-a-4175468237/

I'm currently waiting on the full release of 5.2 for further testing.

Similar to how qt4 is installed in stock Slackware. Everything is located in /usr/lib{,64}/qt5, with proper symlinks.
Yes, I'm aware of that thread. I do see that in your slackbuild you don't use profile.d files.

I think I see exactly what has caused your setup to explode.

When you compile any large project these days the configure scripts use pkg-config to get information about installed libraries, how to compile against and how to link against them.

eg If I run the following :-
We get the include path used to compile against QtCore for Qt4

When you set the CPLUS include directory as you have you confuse the compiler as it now has the path to everything, even things you don't intend to use.

This is why I have gone away from a profile script for Qt 5 as it is no longer required when you install it as I have.

Qt 4 only needs it so far as setting the pkg-config path if you don't otherwise copy the pkg-config files into the existing /usr/lib{64}/pkgconfig directory.

Even the symlinks to the libs in the Qt 4 package are not used as things like KDE that use Qt have the full path to the library as that is what pkg-config gave it when it was compiled.

Well, I just removed CPLUS_INCLUDE_PATH from the profile.d files and all is well.

qt 5.2.0 just came out. Testing it now.