I have used fork as a stupid simple memory arena implementation. fork(); do work in the child; only malloc, never free; exit. It is much, much heavier than a normal memory arena would be, but also much simpler to use. Plus, if you can split the work in independent batches, you can run multiple children at a time in parallel.

As with all such stupid simple mechanisms, I would not advise its use if your program spans more than one .c file and more than a thousand lines.