If the tracing profiler compile option is enabled, but no MONGO_PROFILER_SPAN_ENTER() trace points are added to the code, mongod will consistently crash with a segfault. This appears to be due to the metrics generation code assuming _callMetrics.nodeMetrics() is non-empty, and always visiting node zero. This may also be an issue if trace points are only placed in obscure code locations that are never visited, but I don't know the implementation well enough to be sure of that.