@GregWilsonLindberg I think that the g++ version is what is doing it. The old version of rasbian is using g++ v4.9.2. The new version of rasbian is using g++ v6.3.0-18+. For the old compiler we had had to add an "INCLUDEPATH = /usr/include" line into the .pro file to get everything picked up properly. For the new compiler (and the change from #include to #include_next in cstdlib) that messes up. I'm removing the INCLUDEPATH, (which seems to have been included as -isystem instead of -I) and that is fixing the problem.

@shivaVMC you were already told: That's worthy of a new thread. so could you please start a thread on its own regarding Qwt and Windows? The issue you're now interested about has nothing to do with the original subject of post (which it was not even started by you by the way). Thanks