The segfault only occurs if that malloc feature is enabled. The mallopt manpage says that there should be a backtrace. (cf M_CHECK_ACTION) I'm a bit out of my depth, but the lack of output might indicate that the feature itself is encountering a problem. If you need more details I'll be happy to provide them. I'm just not familiar with debugging this beyond what I provided, so might need some pointer or example commands to run.