Comment by jlokier

It's really unfortunate that the sanctioned way to call Linux syscalls directly is via the syscall() function (previously the _syscallN macros), and both of those methods set errno on error, which fails in a clone() thread.

If only Glibc provided a syscall_r() or something that returns the raw return value whether it's an error or not.

It is possible to make syscall() (and regular libc syscalls like read()) work in a clone() thread. I use this in performance-optimised I/O code in a database engine, so I know it works, but it requires some ugly Glibc-and-architecture-specific things. Doing it portably doesn't seem to be an option.