Using unsafePerformIO safely?

[atravers]

Unfortunately, there’s no reliable way to tell if the SMT solver (or any other foreign entity) is going to be “well-behaved” or not when it’s used:

Using unsafePerformIO safely?

Here’s a concrete example of why I don’t like pretending that anything that interacts with the OS is “pure”: At work we have a Nix-based build system. It “should be” pure, since Nix is reproducible. However, it sometimes calls out to external hardware which is transiently broken, caching “hardware did not respond” into our build results, and with no way of purging it. There’s no direct analogue of that in Haskell, but it really makes me cautious of “pure” APIs that call out to the OS, and I wou…