Looking at compile options for various things. Stuff like "sanity check - detect buffer overflows. Used for debugging. Slight overhead. Disable for production". IMO it's "disable for production" idiocy despite the minuscule perf. penalty that's responsible for a lot of breakage.

Brings to mind again C.A.R. Hoare's remarks about having lifejackets on in harbor but removing them on the open sea. Real world systems can have data that doesn't conform to the programmer's assumptions and break things, as shown by fuzzing. Leave the sanity checks in FFS. A little humility on the part of some programmers also wouldn't go amiss.