man 3 malloc:

       The malloc(), calloc(), realloc(), and reallocarray() functions
       return a pointer to the allocated memory, which is suitably
       aligned for any type that fits into the requested size or less.
       On error, these functions return NULL and set errno.

Problem is that thanks to overcommit malloc sort of always succeeds, and then many (most?) code doesn't check that malloc successfully returned and proceeds to march on towards a later obscure failure, hence below:

> It's not an orderly 'abort: malloc failed' or process termination like I would've expected. Instead, you get weird intermittent failures that don't look like OOMs