On Unix environments a subprocess is typically created with fork() + exec(). fork inherits all file descriptors of the parent process (fork(2) - Linux manual page) - unless the file/socket/pipe has the FD_CLOEXEC flag set. This can be done with fcntl (c - What does the FD_CLOEXEC fcntl() flag do? - Stack Overflow) or directly in open with O_CLOEXEC (open(2) - Linux manual page)
Is there anything different I can do so that it actually works properly?
a) don’t start and detach child processes from within sclang
b) open an issue on GitHub and ask to set the FD_CLOEXEC bit on all files and sockets
c) use Windows :-p