From 76226f19f52515c12480f4c36f15d4edf7120d0e Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Wed, 18 Mar 2015 16:16:24 +1100
Subject: [PATCH] Updated PosixTest.WriteStartsPastEndOfFile_AppendMode for
 Linux.

---
 samples/memfs/posix_test.go | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/samples/memfs/posix_test.go b/samples/memfs/posix_test.go
index e11dc84..48fe75e 100644
--- a/samples/memfs/posix_test.go
+++ b/samples/memfs/posix_test.go
@@ -22,6 +22,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path"
+	"runtime"
 	"testing"
 
 	. "github.com/jacobsa/oglematchers"
@@ -183,9 +184,22 @@ func (t *PosixTest) WriteStartsPastEndOfFile_AppendMode() {
 	AssertEq(3, n)
 
 	// Read the full contents of the file.
+	//
+	// Linux's support for pwrite is buggy; the pwrite(2) man page says this:
+	//
+	//     POSIX requires that opening a file with the O_APPEND flag should have
+	//     no affect on the location at which pwrite() writes data.  However, on
+	//     Linux,  if  a  file  is opened with O_APPEND, pwrite() appends data to
+	//     the end of the file, regardless of the value of offset.
+	//
 	contents, err := ioutil.ReadFile(f.Name())
 	AssertEq(nil, err)
-	ExpectEq("111\x00\x00\x00222", string(contents))
+
+	if runtime.GOOS == "linux" {
+		ExpectEq("111222", string(contents))
+	} else {
+		ExpectEq("111\x00\x00\x00222", string(contents))
+	}
 }
 
 func (t *PosixTest) WriteAtDoesntChangeOffset_NotAppendMode() {
@@ -300,7 +314,12 @@ func (t *PosixTest) AppendMode() {
 	// So we allow either the POSIX result or the Linux result.
 	n, err = f.ReadAt(buf, 0)
 	AssertEq(io.EOF, err)
-	ExpectThat(string(buf[:n]), AnyOf("Hello, world!", "Jello, world!H"))
+
+	if runtime.GOOS == "linux" {
+		ExpectEq("Jello, world!H", string(buf[:n]))
+	} else {
+		ExpectEq("Hello, world!", string(buf[:n]))
+	}
 }
 
 func (t *PosixTest) ReadsPastEndOfFile() {