`puts` is an "stdio" function, not a system call. It won't EINTR, it correctly resumes if the underlying write() EINTRs. If it does get an error, it will return EOF, then you'll have to call `ferror()` to find out which error.

But the point stands; there's no error handling in the OpenBSD version. But that could be considered a design decision; the OpenBSD version never gives up on writing data until you kill it; the GNU version bails at the first error.