I see the same problem on Mac OS. If the following appeared in a header somewhere CLOEXEC would work: #define SOCK_CLOEXEC FD_CLOEXEC It would work. Note the implementation in lib/accept4.c: #ifndef SOCK_CLOEXEC #define SOCK_CLOEXEC 0 #endif Then later the flags to accept4 have SOCK_CLOEXEC set, then the call to fcntl includes FD_CLOEXEC. So any system that defines FD_CLOEXEC should be able to use SOCK_CLOEXEC. But it needs to be defined.
I assume if a system supports O_NONBLOCK then something could be done with SOCK_NONBLOCK also. I was going to submit a patch that is the same, except that I removed the text “No ifdef as accept4 has a gnulib implementation.” Matt
