syscall: add fcntl test

Also updates documentation.

LGTM=minux.ma
R=iant, bradfitz, nightlyone, minux.ma
CC=golang-codereviews
https://golang.org/cl/58660044

diff --git a/src/pkg/syscall/syscall_unix_test.go b/src/pkg/syscall/syscall_unix_test.go
index 818dda839de9b34310a185bb5dc6d1a9f4aea12a..cff44de6a154cdea7e0935e4256dc91c83ce92f6 100644 (file)
--- a/src/pkg/syscall/syscall_unix_test.go
+++ b/src/pkg/syscall/syscall_unix_test.go
@@ -4,9 +4,6 @@
 
 // +build freebsd dragonfly darwin linux netbsd openbsd
 
-// This file tests that some basic syscalls are consistent across
-// all Unixes.
-
 package syscall_test
 
 import (
@@ -16,14 +13,17 @@ import (
        "net"
        "os"
        "os/exec"
+       "path/filepath"
        "runtime"
        "syscall"
        "testing"
        "time"
 )
 
-// {Set,Get}priority and needed constants for them
+// Tests that below functions, structures and constants are consistent
+// on all Unix-like systems.
 func _() {
+       // program scheduling priority functions and constants
        var (
                _ func(int, int, int) error   = syscall.Setpriority
                _ func(int, int) (int, error) = syscall.Getpriority
@@ -33,24 +33,47 @@ func _() {
                _ int = syscall.PRIO_PROCESS
                _ int = syscall.PRIO_PGRP
        )
-}
 
-// termios functions and constants
-func _() {
+       // termios constants
        const (
                _ int = syscall.TCIFLUSH
                _ int = syscall.TCIOFLUSH
                _ int = syscall.TCOFLUSH
        )
+
+       // fcntl file locking structure and constants
+       var (
+               _ = syscall.Flock_t{
+                       Type:   int16(0),
+                       Whence: int16(0),
+                       Start:  int64(0),
+                       Len:    int64(0),
+                       Pid:    int32(0),
+               }
+       )
+       const (
+               _ = syscall.F_GETLK
+               _ = syscall.F_SETLK
+               _ = syscall.F_SETLKW
+       )
 }
 
-func _() {
-       _ = syscall.Flock_t{
-               Type:   int16(0),
-               Whence: int16(0),
-               Start:  int64(0),
-               Len:    int64(0),
-               Pid:    int32(0),
+// TestFcntlFlock tests whether the file locking structure matches
+// the calling convention of each kernel.
+func TestFcntlFlock(t *testing.T) {
+       name := filepath.Join(os.TempDir(), "TestFcntlFlock")
+       fd, err := syscall.Open(name, syscall.O_CREAT|syscall.O_RDWR|syscall.O_CLOEXEC, 0)
+       if err != nil {
+               t.Fatalf("Open failed: %v", err)
+       }
+       defer syscall.Unlink(name)
+       defer syscall.Close(fd)
+       flock := syscall.Flock_t{
+               Type:  syscall.F_RDLCK,
+               Start: 0, Len: 0, Whence: 1,
+       }
+       if err := syscall.FcntlFlock(uintptr(fd), syscall.F_GETLK, &flock); err != nil {
+               t.Fatalf("FcntlFlock failed: %v", err)
        }
 }