See https://gitlab.gnome.org/GNOME/epiphany/merge_requests/438 Ideally we would have WebKit clean up after itself. The best option would be to not need using named temporary files during compilation; that way the kernel would clean up automatically when the file descriptor is closed during the process exit.
In Linux we can use “open("/path/to/dir", mode | O_TMPFILE)” to get a file descriptor which is not linked to a directory entry in the file system. If the process exits or drops the file handle cleanup is automatic. Such a file descriptor can be directly linked into its final location using “linkat()” passing “/proc/self/fd/<num>” as the first path. While the above is very neat, we still need some other mechanism for other systems (the BSDs come to mind). In that case, I think a reasonable fallback is to unlink the temporary file immediately after its creation, then once compilation ended create a *new* file into the final location, truncate it to the right size, and copy the data. Note that in the current implementation a data copy is already being performed if “/tmp” and the storage location for a WebKitUserContentFilterStore aren't inside the same mount point (not uncommon with “/tmp” very often being an on-RAM file system and “/home” often being a separate volume). If somebody is aware of something similar to Linux's “O_TMPFILE” which would work on other common systems we support, I would love to hear about it =)