syscall, os: use pipe2 syscall on DragonflyBSD instead of pipe

Follow the implementation used by the other BSDs ith os.Pipe and
syscall.forkExecPipe consisting of a single syscall instead of three.

Change-Id: I602187672f244cbd8faaa3397904d71d15452d9f
Reviewed-on: https://go-review.googlesource.com/130996
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/os/pipe2_bsd.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build freebsd netbsd openbsd
+// +build dragonfly freebsd netbsd openbsd
 
 package os
 

src/os/pipe_bsd.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly js,wasm nacl solaris
+// +build darwin js,wasm nacl solaris
 
 package os
 

src/syscall/forkpipe.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly solaris
+// +build darwin solaris
 
 package syscall
 

src/syscall/forkpipe2.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build freebsd netbsd openbsd
+// +build dragonfly freebsd netbsd openbsd
 
 package syscall
 

src/syscall/syscall_dragonfly.go

@@ -72,13 +72,17 @@ func direntNamlen(buf []byte) (uint64, bool) {
 	return readInt(buf, unsafe.Offsetof(Dirent{}.Namlen), unsafe.Sizeof(Dirent{}.Namlen))
 }
 
-//sysnb pipe() (r int, w int, err error)
+func Pipe(p []int) error {
+	return Pipe2(p, 0)
+}
+
+//sysnb pipe2(flags int) (r int, w int, err error)
 
-func Pipe(p []int) (err error) {
+func Pipe2(p []int, flags int) (err error) {
 	if len(p) != 2 {
 		return EINVAL
 	}
-	p[0], p[1], err = pipe()
+	p[0], p[1], err = pipe2(flags)
 	return
 }
 

src/syscall/zsyscall_dragonfly_amd64.go

@@ -261,8 +261,8 @@ func fcntl(fd int, cmd int, arg int) (val int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func pipe() (r int, w int, err error) {
-	r0, r1, e1 := RawSyscall(SYS_PIPE, 0, 0, 0)
+func pipe2(flags int) (r int, w int, err error) {
+	r0, r1, e1 := RawSyscall(SYS_PIPE2, uintptr(flags), 0, 0)
 	r = int(r0)
 	w = int(r1)
 	if e1 != 0 {

src/syscall/zsysnum_dragonfly_amd64.go

@@ -301,6 +301,7 @@ const (
 	SYS_LPATHCONF              = 533 // { int lpathconf(char *path, int name); }
 	SYS_VMM_GUEST_CTL          = 534 // { int vmm_guest_ctl(int op, struct vmm_guest_options *options); }
 	SYS_VMM_GUEST_SYNC_ADDR    = 535 // { int vmm_guest_sync_addr(long *dstaddr, long *srcaddr); }
+	SYS_PIPE2                  = 538 // { int pipe2(int *fildes, int flags); }
 	SYS_UTIMENSAT              = 539 // { int utimensat(int fd, const char *path, const struct timespec *ts, int flags); }
 	SYS_ACCEPT4                = 541 // { int accept4(int s, caddr_t name, int *anamelen, int flags); }
 )