Improve pagination (#105)

vendor/golang.org/x/sys/unix/syscall_dragonfly.go

@@ -12,9 +12,25 @@
 
 package unix
 
-import "unsafe"
+import (
+	"sync"
+	"unsafe"
+)
 
-//sys	sysctl(mib []_C_int, old *byte, oldlen *uintptr, new *byte, newlen uintptr) (err error) = SYS___SYSCTL
+// See version list in https://github.com/DragonFlyBSD/DragonFlyBSD/blob/master/sys/sys/param.h
+var (
+	osreldateOnce sync.Once
+	osreldate     uint32
+)
+
+// First __DragonFly_version after September 2019 ABI changes
+// http://lists.dragonflybsd.org/pipermail/users/2019-September/358280.html
+const _dragonflyABIChangeVersion = 500705
+
+func supportsABI(ver uint32) bool {
+	osreldateOnce.Do(func() { osreldate, _ = SysctlUint32("kern.osreldate") })
+	return osreldate >= ver
+}
 
 // SockaddrDatalink implements the Sockaddr interface for AF_LINK type sockets.
 type SockaddrDatalink struct {
@@ -152,6 +168,8 @@ func setattrlistTimes(path string, times []Timespec, flags int) error {
 
 //sys	ioctl(fd int, req uint, arg uintptr) (err error)
 
+//sys   sysctl(mib []_C_int, old *byte, oldlen *uintptr, new *byte, newlen uintptr) (err error) = SYS___SYSCTL
+
 func sysctlUname(mib []_C_int, old *byte, oldlen *uintptr) error {
 	err := sysctl(mib, old, oldlen, nil, 0)
 	if err != nil {