+#ifdef SYS_dup2
+ if (old==new) return __syscall_ret(-EINVAL);
+ if (flags & O_CLOEXEC) {
+ while ((r=__syscall(SYS_dup3, old, new, flags))==-EBUSY);
+ if (r!=-ENOSYS) return __syscall_ret(r);
+ }
+ while ((r=__syscall(SYS_dup2, old, new))==-EBUSY);
+ if (flags & O_CLOEXEC) __syscall(SYS_fcntl, new, F_SETFD, FD_CLOEXEC);
+#else