Every couple of years, I revisit my PL dev hobby and this time I decided to create a language/runtime with pre-emptive scheduling using instruction fuel. While I always do freestanding builds, this time I decided that I also wanted to support native FFI.
That is when I realized the true horror of (g)libc. It wants to inject itself at the root of the library/program and everything from threading to dlopen/dlsym is impacted. I tried a lot of workarounds including trying to implement a loader myself, but the complexity (and fragility) grew so much that I felt it was not worth it.
Finally, I retreated into the safe world of a freestanding runtime + syscalls. FFI, if it has to happen, will occur via IPC of some kind. A second process linked against glibc that will manage calls on behalf of the clean first one.