A better version (which tcberner has prepared) checks for the existence of the header file and for the existence of the symbol.

Reason for this is that clang is not sufficient .. clang 3.4 (base compiler in FreeBSD 10) for instance doesn't have it at all, and later clangs do not implement this for non-Linux platforms. You can see k3b in the KDE CI for FreeBSD here: https://build-sandbox.kde.org/job/Applications k3b kf5-qt5 FreeBSDQt5.7/lastFailedBuild/

.. reconsidering. This is internal debugging / memory profiling that is dumped to stdout when some secret(-ish) extra arguments are given to k3b. The interface used was added to clang on march 15th 2017, so it's only available on very-very recent clangs .. I think the right thing to do is just remove this, as "accidentally committed debugging code".