> Which reminds me: what is a good tool for analyzing / viewing a C++ programs call tree?

As already mentioned, perf can capture call stacks, but those are statistical samples, so not necessarily complete.

callgrind (https://www.valgrind.org/docs/manual/cl-manual.html) by contrast can capture all call-stacks.

kCacheGrind/qCacheGrind (https://kcachegrind.github.io/html/Home.html) can be used to view the output from either perf or callgrind. Sources for kcachegrind, including converters from perf, oprofile, etc., can be found at https://github.com/KDE/kcachegrind