[postingatwork]

> What I expect it also means is that you'll get inconsistencies when doing inter-process communication, since they'll be using different libraries with potential mismatches. Is this correct?

At the first glance this is true, but you can guard against this in several ways. If your process only forks children then it already inherits the loaded libraries from the parent as part of the forked address space. Alternatively you can pass open file descriptors between processes. Another option is to use file-system snapshots, at least if the filesystem supports them.

Yet another option is to not replace individual files but complete directories and swap them out via RENAME_EXCHANGE (an atomic swap, available since kernel 3.15). As long as the process keeps a handle on its original working directory it can keep working with the old version even if it has been replaced with a new one.

Some of those approaches are tricky, but if you want to guard against such inconsistencies at least it is possible. And if your IPC interfaces provide a stable API it shouldn't be necessary.

> And then there's FILE_SHARE_DELETE which allows deletion

That has some issues when the file is mmaped. If I recall correctly you can't replace it as long as a mapping is open.