Step 1 of the Big Error Shift: make os.Error an interface and replace *os.Errors with os.Errors.

lib/template updated to use new setup; its clients also updated.

Step 2 will make os's error support internally much cleaner.

R=rsc
OCL=27586
CL=27586

doc/progs/cat_rot13.go

@@ -24,7 +24,7 @@ func rot13(b byte) byte {
 }
 
 type reader interface {
-	Read(b []byte) (ret int, err *os.Error);
+	Read(b []byte) (ret int, err os.Error);
 	String() string;
 }
 
@@ -36,7 +36,7 @@ func newRotate13(source reader) *rotate13 {
 	return &rotate13{source}
 }
 
-func (r13 *rotate13) Read(b []byte) (ret int, err *os.Error) {
+func (r13 *rotate13) Read(b []byte) (ret int, err os.Error) {
 	r, e := r13.source.Read(b);
 	for i := 0; i < r; i++ {
 		b[i] = rot13(b[i])

doc/progs/file.go

@@ -27,12 +27,12 @@ var (
 	Stderr = newFile(2, "/dev/stderr");
 )
 
-func Open(name string, mode int64, perm int64) (file *File, err *os.Error) {
+func Open(name string, mode int64, perm int64) (file *File, err os.Error) {
 	r, e := syscall.Open(name, mode, perm);
 	return newFile(r, name), os.ErrnoToError(e)
 }
 
-func (file *File) Close() *os.Error {
+func (file *File) Close() os.Error {
 	if file == nil {
 		return os.EINVAL
 	}
@@ -41,7 +41,7 @@ func (file *File) Close() *os.Error {
 	return nil
 }
 
-func (file *File) Read(b []byte) (ret int, err *os.Error) {
+func (file *File) Read(b []byte) (ret int, err os.Error) {
 	if file == nil {
 		return -1, os.EINVAL
 	}
@@ -49,7 +49,7 @@ func (file *File) Read(b []byte) (ret int, err *os.Error) {
 	return int(r), os.ErrnoToError(e)
 }
 
-func (file *File) Write(b []byte) (ret int, err *os.Error) {
+func (file *File) Write(b []byte) (ret int, err os.Error) {
 	if file == nil {
 		return -1, os.EINVAL
 	}

src/cmd/gobuild/Makefile

@@ -5,7 +5,7 @@
 # sadly, not auto-generated
 
 O=6
-OS=568vq
+OS=568vqo
 GC=$(O)g
 CC=$(O)c -FVw
 AS=$(O)a

src/cmd/gobuild/gobuild.go

@@ -307,7 +307,7 @@ func Main() {
 
 	filenames := flag.Args();
 	if len(filenames) == 0 {
-		var err *os.Error;
+		var err os.Error;
 		filenames, err= SourceFiles(".");
 		if err != nil {
 			fatal("reading .: ", err.String());
@@ -317,7 +317,7 @@ func Main() {
 	state := ScanFiles(filenames);
 	state.Build();
 	if *writeMakefile {
-		t, err, line := template.Parse(makefileTemplate, makefileMap);
+		t, err := template.Parse(makefileTemplate, makefileMap);
 		if err != nil {
 			fatal("template.Parse: ", err.String());
 		}

src/cmd/gobuild/util.go

@@ -38,7 +38,7 @@ func fatal(args ...) {
 }
 
 func init() {
-	var err *os.Error;
+	var err os.Error;
 	goarch, err = os.Getenv("GOARCH");
 	goos, err = os.Getenv("GOOS");
 
@@ -183,7 +183,7 @@ func (s MakeString) String() string {
 var ParseError = os.NewError("parse errors");
 
 // TODO(rsc): Should this be in the AST library?
-func LitString(p []*ast.StringLit) (string, *os.Error) {
+func LitString(p []*ast.StringLit) (string, os.Error) {
 	s := "";
 	for i, lit := range p {
 		t, err := strconv.Unquote(string(lit.Value));
@@ -195,7 +195,7 @@ func LitString(p []*ast.StringLit) (string, *os.Error) {
 	return s, nil;
 }
 
-func PackageImports(file string) (pkg string, imports []string, err1 *os.Error) {
+func PackageImports(file string) (pkg string, imports []string, err1 os.Error) {
 	f, err := os.Open(file, os.O_RDONLY, 0);
 	if err != nil {
 		return "", nil, err
@@ -224,7 +224,7 @@ func PackageImports(file string) (pkg string, imports []string, err1 *os.Error)
 	return prog.Name.Value, imp, nil;
 }
 
-func SourceFiles(dir string) ([]string, *os.Error) {
+func SourceFiles(dir string) ([]string, os.Error) {
 	f, err := os.Open(dir, os.O_RDONLY, 0);
 	if err != nil {
 		return nil, err;

src/cmd/gotest/gotest

@@ -12,6 +12,7 @@ O=6
 GC=${GC:-${O}g}
 GL=${GL:-${O}l}
 export GC GL
+GC="$GC -I _obj"
 
 gofiles=""
 loop=true

src/lib/bufio.go

@@ -49,7 +49,7 @@ type BufRead struct {
 	buf []byte;
 	rd io.Read;
 	r, w int;
-	err *os.Error;
+	err os.Error;
 	lastbyte int;
 }
 
@@ -57,7 +57,7 @@ type BufRead struct {
 // which must be greater than zero.  If the argument io.Read is already a
 // BufRead with large enough size, it returns the underlying BufRead.
 // It returns the BufRead and any error.
-func NewBufReadSize(rd io.Read, size int) (*BufRead, *os.Error) {
+func NewBufReadSize(rd io.Read, size int) (*BufRead, os.Error) {
 	if size <= 0 {
 		return nil, BadBufSize
 	}
@@ -84,7 +84,7 @@ func NewBufRead(rd io.Read) *BufRead {
 }
 
 //.fill reads a new chunk into the buffer.
-func (b *BufRead) fill() *os.Error {
+func (b *BufRead) fill() os.Error {
 	if b.err != nil {
 		return b.err
 	}
@@ -113,7 +113,7 @@ func (b *BufRead) fill() *os.Error {
 // If nn < len(p), also returns an error explaining
 // why the read is short.  At EOF, the count will be
 // zero and err will be io.ErrEOF.
-func (b *BufRead) Read(p []byte) (nn int, err *os.Error) {
+func (b *BufRead) Read(p []byte) (nn int, err os.Error) {
 	nn = 0;
 	for len(p) > 0 {
 		n := len(p);
@@ -157,7 +157,7 @@ func (b *BufRead) Read(p []byte) (nn int, err *os.Error) {
 
 // ReadByte reads and returns a single byte.
 // If no byte is available, returns an error.
-func (b *BufRead) ReadByte() (c byte, err *os.Error) {
+func (b *BufRead) ReadByte() (c byte, err os.Error) {
 	if b.w == b.r {
 		b.fill();
 		if b.err != nil {
@@ -174,7 +174,7 @@ func (b *BufRead) ReadByte() (c byte, err *os.Error) {
 }
 
 // UnreadByte unreads the last byte.  Only one byte may be unread at a given time.
-func (b *BufRead) UnreadByte() *os.Error {
+func (b *BufRead) UnreadByte() os.Error {
 	if b.err != nil {
 		return b.err
 	}
@@ -195,7 +195,7 @@ func (b *BufRead) UnreadByte() *os.Error {
 
 // ReadRune reads a single UTF-8 encoded Unicode character and returns the
 // rune and its size in bytes.
-func (b *BufRead) ReadRune() (rune int, size int, err *os.Error) {
+func (b *BufRead) ReadRune() (rune int, size int, err os.Error) {
 	for b.r + utf8.UTFMax > b.w && !utf8.FullRune(b.buf[b.r:b.w]) {
 		n := b.w - b.r;
 		b.fill();
@@ -241,7 +241,7 @@ func (b *BufRead) Buffered() int {
 // Fails if the line doesn't fit in the buffer.
 // For internal or advanced use only; most uses should
 // call ReadLineString or ReadLineBytes instead.
-func (b *BufRead) ReadLineSlice(delim byte) (line []byte, err *os.Error) {
+func (b *BufRead) ReadLineSlice(delim byte) (line []byte, err os.Error) {
 	if b.err != nil {
 		return nil, b.err
 	}
@@ -288,7 +288,7 @@ func (b *BufRead) ReadLineSlice(delim byte) (line []byte, err *os.Error) {
 // If an error happens, returns the data (without a delimiter)
 // and the error.  (It can't leave the data in the buffer because
 // it might have read more than the buffer size.)
-func (b *BufRead) ReadLineBytes(delim byte) (line []byte, err *os.Error) {
+func (b *BufRead) ReadLineBytes(delim byte) (line []byte, err os.Error) {
 	if b.err != nil {
 		return nil, b.err
 	}
@@ -301,7 +301,7 @@ func (b *BufRead) ReadLineBytes(delim byte) (line []byte, err *os.Error) {
 	err = nil;
 
 	for {
-		var e *os.Error;
+		var e os.Error;
 		frag, e = b.ReadLineSlice(delim);
 		if e == nil {	// got final fragment
 			break
@@ -364,7 +364,7 @@ func (b *BufRead) ReadLineBytes(delim byte) (line []byte, err *os.Error) {
 // ReadLineString reads until the first occurrence of delim in the input,
 // returning a new string containing the line.
 // If savedelim, keep delim in the result; otherwise drop it.
-func (b *BufRead) ReadLineString(delim byte, savedelim bool) (line string, err *os.Error) {
+func (b *BufRead) ReadLineString(delim byte, savedelim bool) (line string, err os.Error) {
 	bytes, e := b.ReadLineBytes(delim);
 	if e != nil {
 		return string(bytes), e
@@ -380,7 +380,7 @@ func (b *BufRead) ReadLineString(delim byte, savedelim bool) (line string, err *
 
 // BufWrite implements buffering for an io.Write object.
 type BufWrite struct {
-	err *os.Error;
+	err os.Error;
 	buf []byte;
 	n int;
 	wr io.Write;
@@ -390,7 +390,7 @@ type BufWrite struct {
 // which must be greater than zero. If the argument io.Write is already a
 // BufWrite with large enough size, it returns the underlying BufWrite.
 // It returns the BufWrite and any error.
-func NewBufWriteSize(wr io.Write, size int) (*BufWrite, *os.Error) {
+func NewBufWriteSize(wr io.Write, size int) (*BufWrite, os.Error) {
 	if size <= 0 {
 		return nil, BadBufSize
 	}
@@ -416,7 +416,7 @@ func NewBufWrite(wr io.Write) *BufWrite {
 }
 
 // Flush writes any buffered data to the underlying io.Write.
-func (b *BufWrite) Flush() *os.Error {
+func (b *BufWrite) Flush() os.Error {
 	if b.err != nil {
 		return b.err
 	}
@@ -454,7 +454,7 @@ func (b *BufWrite) Buffered() int {
 // It returns the number of bytes written.
 // If nn < len(p), also returns an error explaining
 // why the write is short.
-func (b *BufWrite) Write(p []byte) (nn int, err *os.Error) {
+func (b *BufWrite) Write(p []byte) (nn int, err os.Error) {
 	if b.err != nil {
 		return 0, b.err
 	}
@@ -490,7 +490,7 @@ func (b *BufWrite) Write(p []byte) (nn int, err *os.Error) {
 }
 
 // WriteByte writes a single byte.
-func (b *BufWrite) WriteByte(c byte) *os.Error {
+func (b *BufWrite) WriteByte(c byte) os.Error {
 	if b.err != nil {
 		return b.err
 	}

src/lib/bufio_test.go

@@ -30,7 +30,7 @@ func newByteReader(p []byte) io.Read {
 	return b
 }
 
-func (b *byteReader) Read(p []byte) (int, *os.Error) {
+func (b *byteReader) Read(p []byte) (int, os.Error) {
 	n := len(p);
 	if n > len(b.p) {
 		n = len(b.p)
@@ -52,7 +52,7 @@ func newHalfByteReader(p []byte) io.Read {
 	return b
 }
 
-func (b *halfByteReader) Read(p []byte) (int, *os.Error) {
+func (b *halfByteReader) Read(p []byte) (int, os.Error) {
 	n := len(p)/2;
 	if n == 0 && len(p) > 0 {
 		n = 1
@@ -76,7 +76,7 @@ func newRot13Reader(r io.Read) *rot13Reader {
 	return r13
 }
 
-func (r13 *rot13Reader) Read(p []byte) (int, *os.Error) {
+func (r13 *rot13Reader) Read(p []byte) (int, os.Error) {
 	n, e := r13.r.Read(p);
 	if e != nil {
 		return n, e
@@ -218,7 +218,7 @@ func TestBufRead(t *testing.T) {
 }
 
 type writeBuffer interface {
-	Write(p []byte) (int, *os.Error);
+	Write(p []byte) (int, os.Error);
 	GetBytes() []byte
 }
 
@@ -232,7 +232,7 @@ func newByteWriter() writeBuffer {
 	return new(byteWriter)
 }
 
-func (w *byteWriter) Write(p []byte) (int, *os.Error) {
+func (w *byteWriter) Write(p []byte) (int, os.Error) {
 	if w.p == nil {
 		w.p = make([]byte, len(p)+100)
 	} else if w.n + len(p) >= len(w.p) {
@@ -262,7 +262,7 @@ func newHalfByteWriter() writeBuffer {
 	return w
 }
 
-func (w *halfByteWriter) Write(p []byte) (int, *os.Error) {
+func (w *halfByteWriter) Write(p []byte) (int, os.Error) {
 	n := (len(p)+1) / 2;
 	// BUG return w.bw.Write(p[0:n])
 	r, e := w.bw.Write(p[0:n]);

src/lib/exec.go

@@ -32,7 +32,7 @@ type Cmd struct {
 
 // Given mode (DevNull, etc), return file for child
 // and file to record in Cmd structure.
-func modeToFiles(mode, fd int) (*os.File, *os.File, *os.Error) {
+func modeToFiles(mode, fd int) (*os.File, *os.File, os.Error) {
 	switch mode {
 	case DevNull:
 		rw := os.O_WRONLY;
@@ -78,7 +78,7 @@ func modeToFiles(mode, fd int) (*os.File, *os.File, *os.Error) {
 // If a parameter is Pipe, then the corresponding field (Stdin, Stdout, Stderr)
 // of the returned Cmd is the other end of the pipe.
 // Otherwise the field in Cmd is nil.
-func Run(argv0 string, argv, envv []string, stdin, stdout, stderr int) (p *Cmd, err *os.Error)
+func Run(argv0 string, argv, envv []string, stdin, stdout, stderr int) (p *Cmd, err os.Error)
 {
 	p = new(Cmd);
 	var fd [3]*os.File;
@@ -139,7 +139,7 @@ Error:
 // Setting options to 0 waits for p to exit;
 // other options cause Wait to return for other
 // process events; see package os for details.
-func (p *Cmd) Wait(options uint64) (*os.Waitmsg, *os.Error) {
+func (p *Cmd) Wait(options uint64) (*os.Waitmsg, os.Error) {
 	if p.Pid < 0 {
 		return nil, os.EINVAL;
 	}
@@ -153,7 +153,7 @@ func (p *Cmd) Wait(options uint64) (*os.Waitmsg, *os.Error) {
 // Close waits for the running command p to exit,
 // if it hasn't already, and then closes the non-nil file descriptors
 // p.Stdin, p.Stdout, and p.Stderr.
-func (p *Cmd) Close() *os.Error {
+func (p *Cmd) Close() os.Error {
 	if p.Pid >= 0 {
 		// Loop on interrupt, but
 		// ignore other errors -- maybe
@@ -165,7 +165,7 @@ func (p *Cmd) Close() *os.Error {
 	}
 
 	// Close the FDs that are still open.
-	var err *os.Error;
+	var err os.Error;
 	if p.Stdin != nil && p.Stdin.Fd() >= 0 {
 		if err1 := p.Stdin.Close(); err1 != nil {
 			err = err1;
@@ -197,7 +197,7 @@ func canExec(file string) bool{
 // If file contains a slash, it is tried directly and the PATH is not consulted.
 //
 // TODO(rsc): Does LookPath belong in os instead?
-func LookPath(file string) (string, *os.Error) {
+func LookPath(file string) (string, os.Error) {
 	// NOTE(rsc): I wish we could use the Plan 9 behavior here
 	// (only bypass the path if file begins with / or ./ or ../)
 	// but that would not match all the Unix shells.

src/lib/fmt/print.go

@@ -31,7 +31,7 @@ import (
 // the flags and options for the operand's format specifier.
 type Formatter interface {
 	// Write is the function to call to emit formatted output to be printed.
-	Write(b []byte) (ret int, err *os.Error);
+	Write(b []byte) (ret int, err os.Error);
 	// Width returns the value of the width option and whether it has been set.
 	Width()	(wid int, ok bool);
 	// Precision returns the value of the precision option and whether it has been set.
@@ -138,7 +138,7 @@ func (p *pp) add(c int) {
 
 // Implement Write so we can call fprintf on a P, for
 // recursive use in custom verbs.
-func (p *pp) Write(b []byte) (ret int, err *os.Error) {
+func (p *pp) Write(b []byte) (ret int, err os.Error) {
 	p.addbytes(b, 0, len(b));
 	return len(b), nil;
 }
@@ -149,7 +149,7 @@ func (p *pp) doprint(v reflect.StructValue, addspace, addnewline bool);
 // These routines end in 'f' and take a format string.
 
 // Fprintf formats according to a format specifier and writes to w.
-func Fprintf(w io.Write, format string, a ...) (n int, error *os.Error) {
+func Fprintf(w io.Write, format string, a ...) (n int, error os.Error) {
 	v := reflect.NewValue(a).(reflect.StructValue);
 	p := newPrinter();
 	p.doprintf(format, v);
@@ -158,7 +158,7 @@ func Fprintf(w io.Write, format string, a ...) (n int, error *os.Error) {
 }
 
 // Printf formats according to a format specifier and writes to standard output.
-func Printf(format string, v ...) (n int, errno *os.Error) {
+func Printf(format string, v ...) (n int, errno os.Error) {
 	n, errno = Fprintf(os.Stdout, format, v);
 	return n, errno;
 }
@@ -176,7 +176,7 @@ func Sprintf(format string, a ...) string {
 
 // Fprint formats using the default formats for its operands and writes to w.
 // Spaces are added between operands when neither is a string.
-func Fprint(w io.Write, a ...) (n int, error *os.Error) {
+func Fprint(w io.Write, a ...) (n int, error os.Error) {
 	v := reflect.NewValue(a).(reflect.StructValue);
 	p := newPrinter();
 	p.doprint(v, false, false);
@@ -186,7 +186,7 @@ func Fprint(w io.Write, a ...) (n int, error *os.Error) {
 
 // Print formats using the default formats for its operands and writes to standard output.
 // Spaces are added between operands when neither is a string.
-func Print(v ...) (n int, errno *os.Error) {
+func Print(v ...) (n int, errno os.Error) {
 	n, errno = Fprint(os.Stdout, v);
 	return n, errno;
 }
@@ -207,7 +207,7 @@ func Sprint(a ...) string {
 
 // Fprintln formats using the default formats for its operands and writes to w.
 // Spaces are always added between operands and a newline is appended.
-func Fprintln(w io.Write, a ...) (n int, error *os.Error) {
+func Fprintln(w io.Write, a ...) (n int, error os.Error) {
 	v := reflect.NewValue(a).(reflect.StructValue);
 	p := newPrinter();
 	p.doprint(v, true, true);
@@ -217,7 +217,7 @@ func Fprintln(w io.Write, a ...) (n int, error *os.Error) {
 
 // Println formats using the default formats for its operands and writes to standard output.
 // Spaces are always added between operands and a newline is appended.
-func Println(v ...) (n int, errno *os.Error) {
+func Println(v ...) (n int, errno os.Error) {
 	n, errno = Fprintln(os.Stdout, v);
 	return n, errno;
 }

src/lib/hash/adler32.go

@@ -31,7 +31,7 @@ func NewDigest() *Digest {
 
 // Write updates the Digest with the incremental checksum generated by p.
 // It returns the number of bytes written; err is always nil.
-func (d *Digest) Write(p []byte) (nn int, err *os.Error) {
+func (d *Digest) Write(p []byte) (nn int, err os.Error) {
 	a, b := d.a, d.b;
 	for i := 0; i < len(p); i++ {
 		a += uint32(p[i]);

src/lib/hash/crc32.go

@@ -69,7 +69,7 @@ func NewIEEEDigest() *Digest {
 
 // Write updates the Digest with the incremental checksum generated by p.
 // It returns the number of bytes written; err is always nil.
-func (d *Digest) Write(p []byte) (n int, err *os.Error) {
+func (d *Digest) Write(p []byte) (n int, err os.Error) {
 	crc := d.crc ^ 0xFFFFFFFF;
 	tab := d.tab;
 	for i := 0; i < len(p); i++ {

src/lib/hash/md5.go

@@ -38,7 +38,7 @@ func _Block(dig *Digest, p []byte) int
 
 // Write updates the Digest with the incremental checksum generated by p.
 // It returns the number of bytes written; err is always nil.
-func (d *Digest) Write(p []byte) (nn int, err *os.Error) {
+func (d *Digest) Write(p []byte) (nn int, err os.Error) {
 	nn = len(p);
 	d.len += uint64(nn);
 	if d.nx > 0 {

src/lib/hash/sha1.go

@@ -40,7 +40,7 @@ func _Block(dig *Digest, p []byte) int
 
 // Write updates the Digest with the incremental checksum generated by p.
 // It returns the number of bytes written; err is always nil.
-func (d *Digest) Write(p []byte) (nn int, err *os.Error) {
+func (d *Digest) Write(p []byte) (nn int, err os.Error) {
 	nn = len(p);
 	d.len += uint64(nn);
 	if d.nx > 0 {

src/lib/http/request.go

@@ -100,7 +100,7 @@ func (r *Request) ProtoAtLeast(major, minor int) bool {
 // Give up if the line exceeds maxLineLength.
 // The returned bytes are a pointer into storage in
 // the bufio, so they are only valid until the next bufio read.
-func readLineBytes(b *bufio.BufRead) (p []byte, err *os.Error) {
+func readLineBytes(b *bufio.BufRead) (p []byte, err os.Error) {
 	if p, err = b.ReadLineSlice('\n'); err != nil {
 		return nil, err
 	}
@@ -119,7 +119,7 @@ func readLineBytes(b *bufio.BufRead) (p []byte, err *os.Error) {
 }
 
 // readLineBytes, but convert the bytes into a string.
-func readLine(b *bufio.BufRead) (s string, err *os.Error) {
+func readLine(b *bufio.BufRead) (s string, err os.Error) {
 	p, e := readLineBytes(b);
 	if e != nil {
 		return "", e
@@ -131,7 +131,7 @@ func readLine(b *bufio.BufRead) (s string, err *os.Error) {
 // A key/value has the form Key: Value\r\n
 // and the Value can continue on multiple lines if each continuation line
 // starts with a space.
-func readKeyValue(b *bufio.BufRead) (key, value string, err *os.Error) {
+func readKeyValue(b *bufio.BufRead) (key, value string, err os.Error) {
 	line, e := readLineBytes(b);
 	if e != nil {
 		return "", "", e
@@ -266,7 +266,7 @@ func CanonicalHeaderKey(s string) string {
 }
 
 // ReadRequest reads and parses a request from b.
-func ReadRequest(b *bufio.BufRead) (req *Request, err *os.Error) {
+func ReadRequest(b *bufio.BufRead) (req *Request, err os.Error) {
 	req = new(Request);
 
 	// First line: GET /index.html HTTP/1.0

src/lib/http/server.go

@@ -56,7 +56,7 @@ type Conn struct {
 }
 
 // Create new connection from rwc.
-func newConn(rwc io.ReadWriteClose, raddr string, handler Handler) (c *Conn, err *os.Error) {
+func newConn(rwc io.ReadWriteClose, raddr string, handler Handler) (c *Conn, err os.Error) {
 	c = new(Conn);
 	c.RemoteAddr = raddr;
 	c.handler = handler;
@@ -70,7 +70,7 @@ func newConn(rwc io.ReadWriteClose, raddr string, handler Handler) (c *Conn, err
 func (c *Conn) SetHeader(hdr, val string)
 
 // Read next request from connection.
-func (c *Conn) readRequest() (req *Request, err *os.Error) {
+func (c *Conn) readRequest() (req *Request, err os.Error) {
 	if c.hijacked {
 		return nil, ErrHijacked
 	}
@@ -156,7 +156,7 @@ func (c *Conn) WriteHeader(code int) {
 // Write writes the data to the connection as part of an HTTP reply.
 // If WriteHeader has not yet been called, Write calls WriteHeader(http.StatusOK)
 // before writing the data.
-func (c *Conn) Write(data []byte) (n int, err *os.Error) {
+func (c *Conn) Write(data []byte) (n int, err os.Error) {
 	if c.hijacked {
 		log.Stderr("http: Conn.Write on hijacked connection");
 		return 0, ErrHijacked
@@ -228,7 +228,7 @@ func (c *Conn) serve() {
 // will not do anything else with the connection.
 // It becomes the caller's responsibility to manage
 // and close the connection.
-func (c *Conn) Hijack() (rwc io.ReadWriteClose, buf *bufio.BufReadWrite, err *os.Error) {
+func (c *Conn) Hijack() (rwc io.ReadWriteClose, buf *bufio.BufReadWrite, err os.Error) {
 	if c.hijacked {
 		return nil, nil, ErrHijacked;
 	}
@@ -448,7 +448,7 @@ func Handle(pattern string, handler Handler) {
 // creating a new service thread for each.  The service threads
 // read requests and then call handler to reply to them.
 // Handler is typically nil, in which case the DefaultServeMux is used.
-func Serve(l net.Listener, handler Handler) *os.Error {
+func Serve(l net.Listener, handler Handler) os.Error {
 	if handler == nil {
 		handler = DefaultServeMux;
 	}
@@ -492,7 +492,7 @@ func Serve(l net.Listener, handler Handler) *os.Error {
 //			panic("ListenAndServe: ", err.String())
 //		}
 //	}
-func ListenAndServe(addr string, handler Handler) *os.Error {
+func ListenAndServe(addr string, handler Handler) os.Error {
 	l, e := net.Listen("tcp", addr);
 	if e != nil {
 		return e

src/lib/http/url.go

@@ -45,7 +45,7 @@ func unhex(c byte) byte {
 // converting %AB into the byte 0xAB.
 // It returns a BadURL error if any % is not followed
 // by two hexadecimal digits.
-func URLUnescape(s string) (string, *os.Error) {
+func URLUnescape(s string) (string, os.Error) {
 	// Count %, check that they're well-formed.
 	n := 0;
 	for i := 0; i < len(s); {
@@ -98,7 +98,7 @@ type URL struct {
 // Maybe rawurl is of the form scheme:path.
 // (Scheme must be [a-zA-Z][a-zA-Z0-9+-.]*)
 // If so, return scheme, path; else return "", rawurl.
-func getscheme(rawurl string) (scheme, path string, err *os.Error) {
+func getscheme(rawurl string) (scheme, path string, err os.Error) {
 	for i := 0; i < len(rawurl); i++ {
 		c := rawurl[i];
 		switch {
@@ -139,7 +139,7 @@ func split(s string, c byte, cutc bool) (string, string) {
 // ParseURL parses rawurl into a URL structure.
 // The string rawurl is assumed not to have a #fragment suffix.
 // (Web browsers strip #fragment before sending the URL to a web server.)
-func ParseURL(rawurl string) (url *URL, err *os.Error) {
+func ParseURL(rawurl string) (url *URL, err os.Error) {
 	if rawurl == "" {
 		return nil, BadURL
 	}
@@ -184,7 +184,7 @@ func ParseURL(rawurl string) (url *URL, err *os.Error) {
 }
 
 // ParseURLReference is like ParseURL but allows a trailing #fragment.
-func ParseURLReference(rawurlref string) (url *URL, err *os.Error) {
+func ParseURLReference(rawurlref string) (url *URL, err os.Error) {
 	// Cut off #frag.
 	rawurl, frag := split(rawurlref, '#', true);
 	if url, err = ParseURL(rawurl); err != nil {

src/lib/http/url_test.go

@@ -126,7 +126,7 @@ func ufmt(u *URL) string {
 		u.Host, u.Path, u.Query, u.Fragment);
 }
 
-func DoTest(t *testing.T, parse func(string) (*URL, *os.Error), name string, tests []URLTest) {
+func DoTest(t *testing.T, parse func(string) (*URL, os.Error), name string, tests []URLTest) {
 	for i, tt := range tests {
 		u, err := parse(tt.in);
 		if err != nil {
@@ -150,7 +150,7 @@ func TestParseURLReference(t *testing.T) {
 	DoTest(t, ParseURLReference, "ParseURLReference", urlfragtests);
 }
 
-func DoTestString(t *testing.T, parse func(string) (*URL, *os.Error), name string, tests []URLTest) {
+func DoTestString(t *testing.T, parse func(string) (*URL, os.Error), name string, tests []URLTest) {
 	for i, tt := range tests {
 		u, err := parse(tt.in);
 		if err != nil {

src/lib/io/bytebuffer.go

@@ -40,7 +40,7 @@ func (b *ByteBuffer) Reset() {
 
 // Write appends the contents of p to the buffer.  The return
 // value is the length of p; err is always nil.
-func (b *ByteBuffer) Write(p []byte) (n int, err *os.Error) {
+func (b *ByteBuffer) Write(p []byte) (n int, err os.Error) {
 	plen := len(p);
 	if len(b.buf) == 0 {
 		b.cap = plen + 1024;
@@ -60,7 +60,7 @@ func (b *ByteBuffer) Write(p []byte) (n int, err *os.Error) {
 
 // Read reads the next len(p) bytes from the buffer or until the buffer
 // is drained.  The return value is the number of bytes read; err is always nil.
-func (b *ByteBuffer) Read(p []byte) (n int, err *os.Error) {
+func (b *ByteBuffer) Read(p []byte) (n int, err os.Error) {
 	plen := len(p);
 	if len(b.buf) == 0 {
 		return 0, nil

src/lib/io/io.go

@@ -18,17 +18,17 @@ var ErrEOF = os.NewError("EOF")
 
 // Read is the interface that wraps the basic Read method.
 type Read interface {
-	Read(p []byte) (n int, err *os.Error);
+	Read(p []byte) (n int, err os.Error);
 }
 
 // Write is the interface that wraps the basic Write method.
 type Write interface {
-	Write(p []byte) (n int, err *os.Error);
+	Write(p []byte) (n int, err os.Error);
 }
 
 // Close is the interface that wraps the basic Close method.
 type Close interface {
-	Close() *os.Error;
+	Close() os.Error;
 }
 
 // ReadWrite is the interface that groups the basic Read and Write methods.
@@ -66,12 +66,12 @@ func StringBytes(s string) []byte {
 }
 
 // WriteString writes the contents of the string s to w, which accepts an array of bytes.
-func WriteString(w Write, s string) (n int, err *os.Error) {
+func WriteString(w Write, s string) (n int, err os.Error) {
 	return w.Write(StringBytes(s))
 }
 
 // Readn reads r until the buffer buf is full, or until EOF or error.
-func Readn(r Read, buf []byte) (n int, err *os.Error) {
+func Readn(r Read, buf []byte) (n int, err os.Error) {
 	n = 0;
 	for n < len(buf) {
 		nn, e := r.Read(buf[n:len(buf)]);
@@ -94,7 +94,7 @@ type fullRead struct {
 	r	Read;
 }
 
-func (fr *fullRead) Read(p []byte) (n int, err *os.Error) {
+func (fr *fullRead) Read(p []byte) (n int, err os.Error) {
 	n, err = Readn(fr.r, p);
 	return n, err
 }
@@ -111,7 +111,7 @@ func MakeFullReader(r Read) Read {
 
 // Copy n copies n bytes (or until EOF is reached) from src to dst.
 // It returns the number of bytes copied and the error, if any.
-func Copyn(src Read, dst Write, n int64) (written int64, err *os.Error) {
+func Copyn(src Read, dst Write, n int64) (written int64, err os.Error) {
 	buf := make([]byte, 32*1024);
 	for written < n {
 		l := len(buf);
@@ -147,7 +147,7 @@ func Copyn(src Read, dst Write, n int64) (written int64, err *os.Error) {
 
 // Copy copies from src to dst until EOF is reached.
 // It returns the number of bytes copied and the error, if any.
-func Copy(src Read, dst Write) (written int64, err *os.Error) {
+func Copy(src Read, dst Write) (written int64, err os.Error) {
 	buf := make([]byte, 32*1024);
 	for {
 		nr, er := src.Read(buf);

src/lib/io/pipe.go

@@ -15,7 +15,7 @@ import (
 
 type pipeReturn struct {
 	n int;
-	err *os.Error;
+	err os.Error;
 }
 
 // Shared pipe structure.
@@ -28,7 +28,7 @@ type pipe struct {
 	cw chan pipeReturn;	// ... and reads the n, err back from here.
 }
 
-func (p *pipe) Read(data []byte) (n int, err *os.Error) {
+func (p *pipe) Read(data []byte) (n int, err os.Error) {
 	if p == nil || p.rclosed {
 		return 0, os.EINVAL;
 	}
@@ -65,7 +65,7 @@ func (p *pipe) Read(data []byte) (n int, err *os.Error) {
 	return n, nil;
 }
 
-func (p *pipe) Write(data []byte) (n int, err *os.Error) {
+func (p *pipe) Write(data []byte) (n int, err os.Error) {
 	if p == nil || p.wclosed {
 		return 0, os.EINVAL;
 	}
@@ -81,7 +81,7 @@ func (p *pipe) Write(data []byte) (n int, err *os.Error) {
 	return res.n, res.err;
 }
 
-func (p *pipe) CloseReader() *os.Error {
+func (p *pipe) CloseReader() os.Error {
 	if p == nil || p.rclosed {
 		return os.EINVAL;
 	}
@@ -97,7 +97,7 @@ func (p *pipe) CloseReader() *os.Error {
 	return nil;
 }
 
-func (p *pipe) CloseWriter() *os.Error {
+func (p *pipe) CloseWriter() os.Error {
 	if p == nil || p.wclosed {
 		return os.EINVAL;
 	}
@@ -127,14 +127,14 @@ type pipeRead struct {
 	p *pipe;
 }
 
-func (r *pipeRead) Read(data []byte) (n int, err *os.Error) {
+func (r *pipeRead) Read(data []byte) (n int, err os.Error) {
 	r.lock.Lock();
 	defer r.lock.Unlock();
 
 	return r.p.Read(data);
 }
 
-func (r *pipeRead) Close() *os.Error {
+func (r *pipeRead) Close() os.Error {
 	r.lock.Lock();
 	defer r.lock.Unlock();
 
@@ -151,14 +151,14 @@ type pipeWrite struct {
 	p *pipe;
 }
 
-func (w *pipeWrite) Write(data []byte) (n int, err *os.Error) {
+func (w *pipeWrite) Write(data []byte) (n int, err os.Error) {
 	w.lock.Lock();
 	defer w.lock.Unlock();
 
 	return w.p.Write(data);
 }
 
-func (w *pipeWrite) Close() *os.Error {
+func (w *pipeWrite) Close() os.Error {
 	w.lock.Lock();
 	defer w.lock.Unlock();
 

src/lib/json/generic.go

@@ -327,4 +327,4 @@ func StringToJson(s string) (json Json, ok bool, errtok string) {
 	return j, true, ""
 }
 
-// BUG(rsc): StringToJson should return an *os.Error instead of a bool.
+// BUG(rsc): StringToJson should return an os.Error instead of a bool.

src/lib/net/dnsclient.go

@@ -41,7 +41,7 @@ var (
 
 // Send a request on the connection and hope for a reply.
 // Up to cfg.attempts attempts.
-func _Exchange(cfg *_DNS_Config, c Conn, name string) (m *_DNS_Msg, err *os.Error) {
+func _Exchange(cfg *_DNS_Config, c Conn, name string) (m *_DNS_Msg, err os.Error) {
 	if len(name) >= 256 {
 		return nil, DNS_NameTooLong
 	}
@@ -86,7 +86,7 @@ func _Exchange(cfg *_DNS_Config, c Conn, name string) (m *_DNS_Msg, err *os.Erro
 // Find answer for name in dns message.
 // On return, if err == nil, addrs != nil.
 // TODO(rsc): Maybe return []IP instead?
-func answer(name string, dns *_DNS_Msg) (addrs []string, err *os.Error) {
+func answer(name string, dns *_DNS_Msg) (addrs []string, err os.Error) {
 	addrs = make([]string, 0, len(dns.answer));
 
 	if dns.rcode == _DNS_RcodeNameError && dns.authoritative {
@@ -137,7 +137,7 @@ Cname:
 
 // Do a lookup for a single name, which must be rooted
 // (otherwise answer will not find the answers).
-func tryOneName(cfg *_DNS_Config, name string) (addrs []string, err *os.Error) {
+func tryOneName(cfg *_DNS_Config, name string) (addrs []string, err os.Error) {
 	err = DNS_NoServers;
 	for i := 0; i < len(cfg.servers); i++ {
 		// Calling Dial here is scary -- we have to be sure
@@ -168,7 +168,7 @@ func tryOneName(cfg *_DNS_Config, name string) (addrs []string, err *os.Error) {
 }
 
 var cfg *_DNS_Config
-var dnserr *os.Error
+var dnserr os.Error
 
 func loadConfig() {
 	cfg, dnserr = _DNS_ReadConfig();
@@ -177,7 +177,7 @@ func loadConfig() {
 // LookupHost looks up the host name using the local DNS resolver.
 // It returns the canonical name for the host and an array of that
 // host's addresses.
-func LookupHost(name string) (cname string, addrs []string, err *os.Error)
+func LookupHost(name string) (cname string, addrs []string, err os.Error)
 {
 	// TODO(rsc): Pick out obvious non-DNS names to avoid
 	// sending stupid requests to the server?

src/lib/net/dnsconfig.go

@@ -22,16 +22,16 @@ type _DNS_Config struct {
 	rotate bool;	// round robin among servers
 }
 
-var _DNS_configError *os.Error;
+var _DNS_configError os.Error;
 
 // See resolv.conf(5) on a Linux machine.
 // TODO(rsc): Supposed to call uname() and chop the beginning
 // of the host name to get the default search domain.
 // We assume it's in resolv.conf anyway.
-func _DNS_ReadConfig() (*_DNS_Config, *os.Error) {
+func _DNS_ReadConfig() (*_DNS_Config, os.Error) {
 	// TODO(rsc): 6g won't let me say file, err :=
 	var file *file;
-	var err *os.Error;
+	var err os.Error;
 	file, err = open("/etc/resolv.conf");
 	if err != nil {
 		return nil, err

src/lib/net/fd.go

@@ -38,7 +38,7 @@ type netFD struct {
 }
 
 // Make reads and writes on fd return EAGAIN instead of blocking.
-func setNonblock(fd int64) *os.Error {
+func setNonblock(fd int64) os.Error {
 	flags, e := syscall.Fcntl(fd, syscall.F_GETFL, 0);
 	if e != 0 {
 		return os.ErrnoToError(e)
@@ -97,7 +97,7 @@ type pollServer struct {
 }
 func (s *pollServer) Run();
 
-func newPollServer() (s *pollServer, err *os.Error) {
+func newPollServer() (s *pollServer, err os.Error) {
 	s = new(pollServer);
 	s.cr = make(chan *netFD, 1);
 	s.cw = make(chan *netFD, 1);
@@ -318,7 +318,7 @@ func _StartServer() {
 	pollserver = p
 }
 
-func newFD(fd int64, net, laddr, raddr string) (f *netFD, err *os.Error) {
+func newFD(fd int64, net, laddr, raddr string) (f *netFD, err os.Error) {
 	if pollserver == nil {
 		once.Do(_StartServer);
 	}
@@ -336,7 +336,7 @@ func newFD(fd int64, net, laddr, raddr string) (f *netFD, err *os.Error) {
 	return f, nil
 }
 
-func (fd *netFD) Close() *os.Error {
+func (fd *netFD) Close() os.Error {
 	if fd == nil || fd.file == nil {
 		return os.EINVAL
 	}
@@ -355,7 +355,7 @@ func (fd *netFD) Close() *os.Error {
 	return e
 }
 
-func (fd *netFD) Read(p []byte) (n int, err *os.Error) {
+func (fd *netFD) Read(p []byte) (n int, err os.Error) {
 	if fd == nil || fd.file == nil {
 		return -1, os.EINVAL
 	}
@@ -374,7 +374,7 @@ func (fd *netFD) Read(p []byte) (n int, err *os.Error) {
 	return n, err
 }
 
-func (fd *netFD) Write(p []byte) (n int, err *os.Error) {
+func (fd *netFD) Write(p []byte) (n int, err os.Error) {
 	if fd == nil || fd.file == nil {
 		return -1, os.EINVAL
 	}
@@ -406,9 +406,9 @@ func (fd *netFD) Write(p []byte) (n int, err *os.Error) {
 	return nn, err
 }
 
-func sockaddrToHostPort(sa *syscall.Sockaddr) (hostport string, err *os.Error)
+func sockaddrToHostPort(sa *syscall.Sockaddr) (hostport string, err os.Error)
 
-func (fd *netFD) Accept(sa *syscall.Sockaddr) (nfd *netFD, err *os.Error) {
+func (fd *netFD) Accept(sa *syscall.Sockaddr) (nfd *netFD, err os.Error) {
 	if fd == nil || fd.file == nil {
 		return nil, os.EINVAL
 	}

src/lib/net/fd_darwin.go

@@ -18,7 +18,7 @@ type pollster struct {
 	events []syscall.Kevent_t;
 }
 
-func newpollster() (p *pollster, err *os.Error) {
+func newpollster() (p *pollster, err os.Error) {
 	p = new(pollster);
 	var e int64;
 	if p.kq, e = syscall.Kqueue(); e != 0 {
@@ -28,7 +28,7 @@ func newpollster() (p *pollster, err *os.Error) {
 	return p, nil
 }
 
-func (p *pollster) AddFD(fd int64, mode int, repeat bool) *os.Error {
+func (p *pollster) AddFD(fd int64, mode int, repeat bool) os.Error {
 	var kmode int16;
 	if mode == 'r' {
 		kmode = syscall.EVFILT_READ
@@ -81,7 +81,7 @@ func (p *pollster) DelFD(fd int64, mode int) {
 	syscall.Kevent(p.kq, &events, &events, nil);
 }
 
-func (p *pollster) WaitFD(nsec int64) (fd int64, mode int, err *os.Error) {
+func (p *pollster) WaitFD(nsec int64) (fd int64, mode int, err os.Error) {
 	var t *syscall.Timespec;
 	for len(p.events) == 0 {
 		if nsec > 0 {
@@ -114,7 +114,7 @@ func (p *pollster) WaitFD(nsec int64) (fd int64, mode int, err *os.Error) {
 	return fd, mode, nil
 }
 
-func (p *pollster) Close() *os.Error {
+func (p *pollster) Close() os.Error {
 	r, e := syscall.Close(p.kq);
 	return os.ErrnoToError(e)
 }

src/lib/net/fd_linux.go

@@ -24,7 +24,7 @@ type pollster struct {
 	events map[int64] uint32;
 }
 
-func newpollster() (p *pollster, err *os.Error) {
+func newpollster() (p *pollster, err os.Error) {
 	p = new(pollster);
 	var e int64;
 
@@ -38,7 +38,7 @@ func newpollster() (p *pollster, err *os.Error) {
 	return p, nil
 }
 
-func (p *pollster) AddFD(fd int64, mode int, repeat bool) *os.Error {
+func (p *pollster) AddFD(fd int64, mode int, repeat bool) os.Error {
 	var ev syscall.EpollEvent;
 	var already bool;
 	ev.Fd = int32(fd);
@@ -106,7 +106,7 @@ func (p *pollster) DelFD(fd int64, mode int) {
 	}
 }
 
-func (p *pollster) WaitFD(nsec int64) (fd int64, mode int, err *os.Error) {
+func (p *pollster) WaitFD(nsec int64) (fd int64, mode int, err os.Error) {
 	// Get an event.
 	var evarray [1]syscall.EpollEvent;
 	ev := &evarray[0];
@@ -145,7 +145,7 @@ func (p *pollster) WaitFD(nsec int64) (fd int64, mode int, err *os.Error) {
 	return fd, 'r', nil;
 }
 
-func (p *pollster) Close() *os.Error {
+func (p *pollster) Close() os.Error {
 	r, e := syscall.Close(p.epfd);
 	return os.ErrnoToError(e);
 }

src/lib/net/net.go

@@ -19,11 +19,11 @@ var (
 	UnknownSocketFamily = os.NewError("unknown socket family");
 )
 
-func LookupHost(name string) (cname string, addrs []string, err *os.Error)
+func LookupHost(name string) (cname string, addrs []string, err os.Error)
 
 // Split "host:port" into "host" and "port".
 // Host cannot contain colons unless it is bracketed.
-func splitHostPort(hostport string) (host, port string, err *os.Error) {
+func splitHostPort(hostport string) (host, port string, err os.Error) {
 	// The port starts after the last colon.
 	var i int;
 	for i = len(hostport)-1; i >= 0; i-- {
@@ -63,7 +63,7 @@ func joinHostPort(host, port string) string {
 // Convert "host:port" into IP address and port.
 // For now, host and port must be numeric literals.
 // Eventually, we'll have name resolution.
-func hostPortToIP(net, hostport, mode string) (ip []byte, iport int, err *os.Error) {
+func hostPortToIP(net, hostport, mode string) (ip []byte, iport int, err os.Error) {
 	var host, port string;
 	host, port, err = splitHostPort(hostport);
 	if err != nil {
@@ -114,7 +114,7 @@ func hostPortToIP(net, hostport, mode string) (ip []byte, iport int, err *os.Err
 }
 
 // Convert socket address into "host:port".
-func sockaddrToHostPort(sa *syscall.Sockaddr) (hostport string, err *os.Error) {
+func sockaddrToHostPort(sa *syscall.Sockaddr) (hostport string, err os.Error) {
 	switch sa.Family {
 	case syscall.AF_INET, syscall.AF_INET6:
 		addr, port, e := sockaddrToIP(sa);
@@ -139,7 +139,7 @@ func boolint(b bool) int {
 
 // Generic socket creation.
 func socket(net, laddr, raddr string, f, p, t int64, la, ra *syscall.Sockaddr)
-	(fd *netFD, err *os.Error)
+	(fd *netFD, err os.Error)
 {
 	// See ../syscall/exec.go for description of ForkLock.
 	syscall.ForkLock.RLock();
@@ -201,17 +201,17 @@ func (c *connBase) sysFD() int64 {
 	return c.fd.fd;
 }
 
-func (c *connBase) Read(b []byte) (n int, err *os.Error) {
+func (c *connBase) Read(b []byte) (n int, err os.Error) {
 	n, err = c.fd.Read(b);
 	return n, err
 }
 
-func (c *connBase) Write(b []byte) (n int, err *os.Error) {
+func (c *connBase) Write(b []byte) (n int, err os.Error) {
 	n, err = c.fd.Write(b);
 	return n, err
 }
 
-func (c *connBase) ReadFrom(b []byte) (n int, raddr string, err *os.Error) {
+func (c *connBase) ReadFrom(b []byte) (n int, raddr string, err os.Error) {
 	if c == nil {
 		return -1, "", os.EINVAL
 	}
@@ -219,7 +219,7 @@ func (c *connBase) ReadFrom(b []byte) (n int, raddr string, err *os.Error) {
 	return n, c.raddr, err
 }
 
-func (c *connBase) WriteTo(raddr string, b []byte) (n int, err *os.Error) {
+func (c *connBase) WriteTo(raddr string, b []byte) (n int, err os.Error) {
 	if c == nil {
 		return -1, os.EINVAL
 	}
@@ -230,7 +230,7 @@ func (c *connBase) WriteTo(raddr string, b []byte) (n int, err *os.Error) {
 	return n, err
 }
 
-func (c *connBase) Close() *os.Error {
+func (c *connBase) Close() os.Error {
 	if c == nil {
 		return os.EINVAL
 	}
@@ -238,57 +238,57 @@ func (c *connBase) Close() *os.Error {
 }
 
 
-func setsockopt_int(fd, level, opt int64, value int) *os.Error {
+func setsockopt_int(fd, level, opt int64, value int) os.Error {
 	return os.ErrnoToError(syscall.Setsockopt_int(fd, level, opt, value));
 }
 
-func setsockopt_tv(fd, level, opt int64, nsec int64) *os.Error {
+func setsockopt_tv(fd, level, opt int64, nsec int64) os.Error {
 	return os.ErrnoToError(syscall.Setsockopt_tv(fd, level, opt, nsec));
 }
 
-func (c *connBase) SetReadBuffer(bytes int) *os.Error {
+func (c *connBase) SetReadBuffer(bytes int) os.Error {
 	return setsockopt_int(c.sysFD(), syscall.SOL_SOCKET, syscall.SO_RCVBUF, bytes);
 }
 
-func (c *connBase) SetWriteBuffer(bytes int) *os.Error {
+func (c *connBase) SetWriteBuffer(bytes int) os.Error {
 	return setsockopt_int(c.sysFD(), syscall.SOL_SOCKET, syscall.SO_SNDBUF, bytes);
 }
 
-func (c *connBase) SetReadTimeout(nsec int64) *os.Error {
+func (c *connBase) SetReadTimeout(nsec int64) os.Error {
 	c.fd.rdeadline_delta = nsec;
 	return nil;
 }
 
-func (c *connBase) SetWriteTimeout(nsec int64) *os.Error {
+func (c *connBase) SetWriteTimeout(nsec int64) os.Error {
 	c.fd.wdeadline_delta = nsec;
 	return nil;
 }
 
-func (c *connBase) SetTimeout(nsec int64) *os.Error {
+func (c *connBase) SetTimeout(nsec int64) os.Error {
 	if e := c.SetReadTimeout(nsec); e != nil {
 		return e
 	}
 	return c.SetWriteTimeout(nsec)
 }
 
-func (c *connBase) SetReuseAddr(reuse bool) *os.Error {
+func (c *connBase) SetReuseAddr(reuse bool) os.Error {
 	return setsockopt_int(c.sysFD(), syscall.SOL_SOCKET, syscall.SO_REUSEADDR, boolint(reuse));
 }
 
-func (c *connBase) BindToDevice(dev string) *os.Error {
+func (c *connBase) BindToDevice(dev string) os.Error {
 	// TODO(rsc): call setsockopt with null-terminated string pointer
 	return os.EINVAL
 }
 
-func (c *connBase) SetDontRoute(dontroute bool) *os.Error {
+func (c *connBase) SetDontRoute(dontroute bool) os.Error {
 	return setsockopt_int(c.sysFD(), syscall.SOL_SOCKET, syscall.SO_DONTROUTE, boolint(dontroute));
 }
 
-func (c *connBase) SetKeepAlive(keepalive bool) *os.Error {
+func (c *connBase) SetKeepAlive(keepalive bool) os.Error {
 	return setsockopt_int(c.sysFD(), syscall.SOL_SOCKET, syscall.SO_KEEPALIVE, boolint(keepalive));
 }
 
-func (c *connBase) SetLinger(sec int) *os.Error {
+func (c *connBase) SetLinger(sec int) os.Error {
 	e := syscall.Setsockopt_linger(c.sysFD(), syscall.SOL_SOCKET, syscall.SO_LINGER, sec);
 	return os.ErrnoToError(e);
 }
@@ -305,12 +305,12 @@ func (c *connBase) SetLinger(sec int) *os.Error {
 const preferIPv4 = false
 
 func internetSocket(net, laddr, raddr string, proto int64, mode string)
-	(fd *netFD, err *os.Error)
+	(fd *netFD, err os.Error)
 {
 	// Parse addresses (unless they are empty).
 	var lip, rip IP;
 	var lport, rport int;
-	var lerr, rerr *os.Error;
+	var lerr, rerr os.Error;
 
 	if laddr != "" {
 		lip, lport, lerr = hostPortToIP(net, laddr, mode);
@@ -343,7 +343,7 @@ func internetSocket(net, laddr, raddr string, proto int64, mode string)
 		}
 	}
 
-	var cvt func(addr []byte, port int) (sa *syscall.Sockaddr, err *os.Error);
+	var cvt func(addr []byte, port int) (sa *syscall.Sockaddr, err os.Error);
 	var family int64;
 	if vers == 4 {
 		cvt = v4ToSockaddr;
@@ -378,7 +378,7 @@ type ConnTCP struct {
 	connBase
 }
 
-func (c *ConnTCP) SetNoDelay(nodelay bool) *os.Error {
+func (c *ConnTCP) SetNoDelay(nodelay bool) os.Error {
 	if c == nil {
 		return os.EINVAL
 	}
@@ -393,7 +393,7 @@ func newConnTCP(fd *netFD, raddr string) *ConnTCP {
 	return c
 }
 
-func DialTCP(net, laddr, raddr string) (c *ConnTCP, err *os.Error) {
+func DialTCP(net, laddr, raddr string) (c *ConnTCP, err os.Error) {
 	if raddr == "" {
 		return nil, MissingAddress
 	}
@@ -420,7 +420,7 @@ func newConnUDP(fd *netFD, raddr string) *ConnUDP {
 	return c
 }
 
-func DialUDP(net, laddr, raddr string) (c *ConnUDP, err *os.Error) {
+func DialUDP(net, laddr, raddr string) (c *ConnUDP, err os.Error) {
 	if raddr == "" {
 		return nil, MissingAddress
 	}
@@ -441,48 +441,48 @@ type Conn interface {
 	// Read blocks until data is ready from the connection
 	// and then reads into b.  It returns the number
 	// of bytes read, or 0 if the connection has been closed.
-	Read(b []byte) (n int, err *os.Error);
+	Read(b []byte) (n int, err os.Error);
 
 	// Write writes the data in b to the connection.
-	Write(b []byte) (n int, err *os.Error);
+	Write(b []byte) (n int, err os.Error);
 
 	// Close closes the connection.
-	Close() *os.Error;
+	Close() os.Error;
 
 	// For packet-based protocols such as UDP,
 	// ReadFrom reads the next packet from the network,
 	// returning the number of bytes read and the remote
 	// address that sent them.
-	ReadFrom(b []byte) (n int, addr string, err *os.Error);
+	ReadFrom(b []byte) (n int, addr string, err os.Error);
 
 	// For packet-based protocols such as UDP,
 	// WriteTo writes the byte buffer b to the network
 	// as a single payload, sending it to the target address.
-	WriteTo(addr string, b []byte) (n int, err *os.Error);
+	WriteTo(addr string, b []byte) (n int, err os.Error);
 
 	// SetReadBuffer sets the size of the operating system's
 	// receive buffer associated with the connection.
-	SetReadBuffer(bytes int) *os.Error;
+	SetReadBuffer(bytes int) os.Error;
 
 	// SetReadBuffer sets the size of the operating system's
 	// transmit buffer associated with the connection.
-	SetWriteBuffer(bytes int) *os.Error;
+	SetWriteBuffer(bytes int) os.Error;
 
 	// SetTimeout sets the read and write deadlines associated
 	// with the connection.
-	SetTimeout(nsec int64) *os.Error;
+	SetTimeout(nsec int64) os.Error;
 
 	// SetReadTimeout sets the time (in nanoseconds) that
 	// Read will wait for data before returning os.EAGAIN.
 	// Setting nsec == 0 (the default) disables the deadline.
-	SetReadTimeout(nsec int64) *os.Error;
+	SetReadTimeout(nsec int64) os.Error;
 
 	// SetWriteTimeout sets the time (in nanoseconds) that
 	// Write will wait to send its data before returning os.EAGAIN.
 	// Setting nsec == 0 (the default) disables the deadline.
 	// Even if write times out, it may return n > 0, indicating that
 	// some of the data was successfully written.
-	SetWriteTimeout(nsec int64) *os.Error;
+	SetWriteTimeout(nsec int64) os.Error;
 
 	// SetLinger sets the behavior of Close() on a connection
 	// which still has data waiting to be sent or to be acknowledged.
@@ -495,22 +495,22 @@ type Conn interface {
 	//
 	// If sec > 0, Close blocks for at most sec seconds waiting for
 	// data to be sent and acknowledged.
-	SetLinger(sec int) *os.Error;
+	SetLinger(sec int) os.Error;
 
 	// SetReuseAddr sets whether it is okay to reuse addresses
 	// from recent connections that were not properly closed.
-	SetReuseAddr(reuseaddr bool) *os.Error;
+	SetReuseAddr(reuseaddr bool) os.Error;
 
 	// SetDontRoute sets whether outgoing messages should
 	// bypass the system routing tables.
-	SetDontRoute(dontroute bool) *os.Error;
+	SetDontRoute(dontroute bool) os.Error;
 
 	// SetKeepAlive sets whether the operating system should send
 	// keepalive messages on the connection.
-	SetKeepAlive(keepalive bool) *os.Error;
+	SetKeepAlive(keepalive bool) os.Error;
 
 	// BindToDevice binds a connection to a particular network device.
-	BindToDevice(dev string) *os.Error;
+	BindToDevice(dev string) os.Error;
 }
 
 // Dial connects to the remote address raddr on the network net.
@@ -528,7 +528,7 @@ type Conn interface {
 //	Dial("tcp", "", "google.com:80")
 //	Dial("tcp", "", "[de:ad:be:ef::ca:fe]:80")
 //	Dial("tcp", "127.0.0.1:123", "127.0.0.1:88")
-func Dial(net, laddr, raddr string) (c Conn, err *os.Error) {
+func Dial(net, laddr, raddr string) (c Conn, err os.Error) {
 	switch net {
 	case "tcp", "tcp4", "tcp6":
 		c, err := DialTCP(net, laddr, raddr);
@@ -557,8 +557,8 @@ func Dial(net, laddr, raddr string) (c Conn, err *os.Error) {
 // A Listener is a generic network listener.
 // Accept waits for the next connection and Close closes the connection.
 type Listener interface {
-	Accept() (c Conn, raddr string, err *os.Error);
-	Close() *os.Error;
+	Accept() (c Conn, raddr string, err os.Error);
+	Close() os.Error;
 }
 
 // ListenerTCP is a TCP network listener.
@@ -571,7 +571,7 @@ type ListenerTCP struct {
 
 // ListenTCP announces on the TCP address laddr and returns a TCP listener.
 // Net must be "tcp", "tcp4", or "tcp6".
-func ListenTCP(net, laddr string) (l *ListenerTCP, err *os.Error) {
+func ListenTCP(net, laddr string) (l *ListenerTCP, err os.Error) {
 	fd, e := internetSocket(net, laddr, "", syscall.SOCK_STREAM, "listen");
 	if e != nil {
 		return nil, e
@@ -588,7 +588,7 @@ func ListenTCP(net, laddr string) (l *ListenerTCP, err *os.Error) {
 
 // AcceptTCP accepts the next incoming call and returns the new connection
 // and the remote address.
-func (l *ListenerTCP) AcceptTCP() (c *ConnTCP, raddr string, err *os.Error) {
+func (l *ListenerTCP) AcceptTCP() (c *ConnTCP, raddr string, err os.Error) {
 	if l == nil || l.fd == nil || l.fd.fd < 0 {
 		return nil, "", os.EINVAL
 	}
@@ -607,7 +607,7 @@ func (l *ListenerTCP) AcceptTCP() (c *ConnTCP, raddr string, err *os.Error) {
 
 // Accept implements the accept method in the Listener interface;
 // it waits for the next call and returns a generic Conn.
-func (l *ListenerTCP) Accept() (c Conn, raddr string, err *os.Error) {
+func (l *ListenerTCP) Accept() (c Conn, raddr string, err os.Error) {
 	c1, r1, e1 := l.AcceptTCP();
 	if e1 != nil {
 		return nil, "", e1
@@ -617,7 +617,7 @@ func (l *ListenerTCP) Accept() (c Conn, raddr string, err *os.Error) {
 
 // Close stops listening on the TCP address.
 // Already Accepted connections are not closed.
-func (l *ListenerTCP) Close() *os.Error {
+func (l *ListenerTCP) Close() os.Error {
 	if l == nil || l.fd == nil {
 		return os.EINVAL
 	}
@@ -626,7 +626,7 @@ func (l *ListenerTCP) Close() *os.Error {
 
 // Listen announces on the local network address laddr.
 // The network string net must be "tcp", "tcp4", or "tcp6".
-func Listen(net, laddr string) (l Listener, err *os.Error) {
+func Listen(net, laddr string) (l Listener, err os.Error) {
 	switch net {
 	case "tcp", "tcp4", "tcp6":
 		l, err := ListenTCP(net, laddr);

src/lib/net/net_darwin.go

@@ -11,7 +11,7 @@ import (
 	"unsafe";
 )
 
-func v4ToSockaddr(p IP, port int) (sa1 *syscall.Sockaddr, err *os.Error) {
+func v4ToSockaddr(p IP, port int) (sa1 *syscall.Sockaddr, err os.Error) {
 	p = p.To4();
 	if p == nil || port < 0 || port > 0xFFFF {
 		return nil, os.EINVAL
@@ -27,7 +27,7 @@ func v4ToSockaddr(p IP, port int) (sa1 *syscall.Sockaddr, err *os.Error) {
 	return (*syscall.Sockaddr)(unsafe.Pointer(sa)), nil
 }
 
-func v6ToSockaddr(p IP, port int) (sa1 *syscall.Sockaddr, err *os.Error) {
+func v6ToSockaddr(p IP, port int) (sa1 *syscall.Sockaddr, err os.Error) {
 	p = p.To16();
 	if p == nil || port < 0 || port > 0xFFFF {
 		return nil, os.EINVAL
@@ -44,7 +44,7 @@ func v6ToSockaddr(p IP, port int) (sa1 *syscall.Sockaddr, err *os.Error) {
 }
 
 
-func sockaddrToIP(sa1 *syscall.Sockaddr) (p IP, port int, err *os.Error) {
+func sockaddrToIP(sa1 *syscall.Sockaddr) (p IP, port int, err os.Error) {
 	switch sa1.Family {
 	case syscall.AF_INET:
 		sa := (*syscall.SockaddrInet4)(unsafe.Pointer(sa1));

src/lib/net/net_linux.go

@@ -11,7 +11,7 @@ import (
 	"unsafe";
 )
 
-func v4ToSockaddr(p IP, port int) (sa1 *syscall.Sockaddr, err *os.Error) {
+func v4ToSockaddr(p IP, port int) (sa1 *syscall.Sockaddr, err os.Error) {
 	p = p.To4();
 	if p == nil || port < 0 || port > 0xFFFF {
 		return nil, os.EINVAL
@@ -26,7 +26,7 @@ func v4ToSockaddr(p IP, port int) (sa1 *syscall.Sockaddr, err *os.Error) {
 	return (*syscall.Sockaddr)(unsafe.Pointer(sa)), nil
 }
 
-func v6ToSockaddr(p IP, port int) (sa1 *syscall.Sockaddr, err *os.Error) {
+func v6ToSockaddr(p IP, port int) (sa1 *syscall.Sockaddr, err os.Error) {
 	p = p.To16();
 	if p == nil || port < 0 || port > 0xFFFF {
 		return nil, os.EINVAL
@@ -49,7 +49,7 @@ func v6ToSockaddr(p IP, port int) (sa1 *syscall.Sockaddr, err *os.Error) {
 	return (*syscall.Sockaddr)(unsafe.Pointer(sa)), nil
 }
 
-func sockaddrToIP(sa1 *syscall.Sockaddr) (p IP, port int, err *os.Error) {
+func sockaddrToIP(sa1 *syscall.Sockaddr) (p IP, port int, err os.Error) {
 	switch sa1.Family {
 	case syscall.AF_INET:
 		sa := (*syscall.SockaddrInet4)(unsafe.Pointer(sa1));

src/lib/net/parse.go

@@ -55,7 +55,7 @@ func (f *file) readLine() (s string, ok bool) {
 	return
 }
 
-func open(name string) (*file, *os.Error) {
+func open(name string) (*file, os.Error) {
 	fd, err := os.Open(name, os.O_RDONLY, 0);
 	if err != nil {
 		return nil, err;

src/lib/net/port.go

@@ -19,7 +19,7 @@ import (
 var ErrNoService = os.NewError("unknown network service");
 
 var services map[string] map[string] int
-var servicesError *os.Error
+var servicesError os.Error
 
 func readServices() {
 	services = make(map[string] map[string] int);
@@ -55,7 +55,7 @@ func readServices() {
 }
 
 // LookupPort looks up the port for the given network and service.
-func LookupPort(network, service string) (port int, err *os.Error) {
+func LookupPort(network, service string) (port int, err os.Error) {
 	once.Do(readServices);
 
 	switch network {

src/lib/os/dir_amd64_darwin.go

@@ -15,7 +15,7 @@ const (
 )
 
 // Negative count means read until EOF.
-func readdirnames(file *File, count int) (names []string, err *os.Error) {
+func readdirnames(file *File, count int) (names []string, err Error) {
 	// If this file has no dirinfo, create one.
 	if file.dirinfo == nil {
 		file.dirinfo = new(dirInfo);
@@ -36,7 +36,7 @@ func readdirnames(file *File, count int) (names []string, err *os.Error) {
 			// Final argument is (basep *int64) and the syscall doesn't take nil.
 			d.nbuf, errno = syscall.Getdirentries(file.fd, &d.buf[0], int64(len(d.buf)), new(int64));
 			if d.nbuf < 0 {
-				return names, os.ErrnoToError(errno)
+				return names, ErrnoToError(errno)
 			}
 			if d.nbuf == 0 {
 				break	// EOF

src/lib/os/dir_amd64_linux.go

@@ -24,7 +24,7 @@ func clen(n []byte) int {
 }
 
 // Negative count means read until EOF.
-func readdirnames(file *File, count int) (names []string, err *os.Error) {
+func readdirnames(file *File, count int) (names []string, err Error) {
 	// If this file has no dirinfo, create one.
 	if file.dirinfo == nil {
 		file.dirinfo = new(dirInfo);
@@ -45,7 +45,7 @@ func readdirnames(file *File, count int) (names []string, err *os.Error) {
 			dbuf := (*syscall.Dirent)(unsafe.Pointer(&d.buf[0]));
 			d.nbuf, errno = syscall.Getdents(file.fd, dbuf, int64(len(d.buf)));
 			if d.nbuf < 0 {
-				return names, os.ErrnoToError(errno)
+				return names, ErrnoToError(errno)
 			}
 			if d.nbuf == 0 {
 				break	// EOF

src/lib/os/env.go

@@ -31,7 +31,7 @@ func copyenv() {
 
 // Getenv retrieves the value of the environment variable named by the key.
 // It returns the value and an error, if any.
-func Getenv(key string) (value string, err *Error) {
+func Getenv(key string) (value string, err Error) {
 	once.Do(copyenv);
 
 	if len(key) == 0 {
@@ -46,7 +46,7 @@ func Getenv(key string) (value string, err *Error) {
 
 // Setenv sets the value of the environment variable named by the key.
 // It returns an Error, if any.
-func Setenv(key, value string) *Error {
+func Setenv(key, value string) Error {
 	once.Do(copyenv);
 
 	if len(key) == 0 {

src/lib/os/error.go

@@ -6,31 +6,43 @@ package os
 
 import syscall "syscall"
 
-// Error is a structure wrapping a string describing an error.
+// An Error can represent any printable error condition.
+type Error interface {
+	String() string
+}
+
+// A helper type that can be embedded or wrapped to simplify satisfying
+// Error.
+type ErrorString string
+func (e *ErrorString) String() string {
+	return *e
+}
+
+// _Error is a structure wrapping a string describing an error.
 // Errors are singleton structures, created by NewError, so their addresses can
 // be compared to test for equality. A nil Error pointer means ``no error''.
 // Use the String() method to get the contents; it handles the nil case.
 // The Error type is intended for use by any package that wishes to define
 // error strings.
-type Error struct {
+type _Error struct {
 	s string
 }
 
 // Indexed by errno.
 // If we worry about syscall speed (only relevant on failure), we could
 // make it an array, but it's probably not important.
-var errorTab = make(map[int64] *Error);
+var errorTab = make(map[int64] Error);
 
 // Table of all known errors in system.  Use the same error string twice,
-// get the same *os.Error.
-var errorStringTab = make(map[string] *Error);
+// get the same *os._Error.
+var errorStringTab = make(map[string] Error);
 
 // These functions contain a race if two goroutines add identical
 // errors simultaneously but the consequences are unimportant.
 
 // NewError allocates an Error object, but if s has been seen before,
-// shares the Error associated with that message.
-func NewError(s string) *Error {
+// shares the _Error associated with that message.
+func NewError(s string) Error {
 	if s == "" {
 		return nil
 	}
@@ -38,14 +50,14 @@ func NewError(s string) *Error {
 	if ok {
 		return err
 	}
-	err = &Error{s};
+	err = &_Error{s};
 	errorStringTab[s] = err;
 	return err;
 }
 
-// ErrnoToError calls NewError to create an Error object for the string
+// ErrnoToError calls NewError to create an _Error object for the string
 // associated with Unix error code errno.
-func ErrnoToError(errno int64) *Error {
+func ErrnoToError(errno int64) Error {
 	if errno == 0 {
 		return nil
 	}
@@ -61,6 +73,11 @@ func ErrnoToError(errno int64) *Error {
 
 // Commonly known Unix errors.
 var (
+	// TODO(r):
+	// 1. these become type ENONE struct { ErrorString }
+	// 2. create private instances of each type: var eNONE ENONE(ErrnoToString(syscall.ENONE));
+	// 3. put them in a table
+	// 4. ErrnoToError uses the table. its error case ECATCHALL("%d")
 	ENONE = ErrnoToError(syscall.ENONE);
 	EPERM = ErrnoToError(syscall.EPERM);
 	ENOENT = ErrnoToError(syscall.ENOENT);
@@ -99,10 +116,10 @@ var (
 	EAGAIN = ErrnoToError(syscall.EAGAIN);
 )
 
-// String returns the string associated with the Error.
-func (e *Error) String() string {
+// String returns the string associated with the _Error.
+func (e *_Error) String() string {
 	if e == nil {
-		return "No Error"
+		return "No _Error"
 	}
 	return e.s
 }

src/lib/os/exec.go

@@ -16,7 +16,7 @@ import (
 // descriptor 0 (standard input), fd[1] descriptor 1, and so on.  A nil entry
 // will cause the child to have no open file descriptor with that index.
 func ForkExec(argv0 string, argv []string, envv []string, fd []*File)
-	(pid int, err *Error)
+	(pid int, err Error)
 {
 	// Create array of integer (system) fds.
 	intfd := make([]int64, len(fd));
@@ -36,7 +36,7 @@ func ForkExec(argv0 string, argv []string, envv []string, fd []*File)
 // named by argv0, with arguments argv and environment envv.
 // If successful, Exec never returns.  If it fails, it returns an Error.
 // ForkExec is almost always a better way to execute a program.
-func Exec(argv0 string, argv []string, envv []string) *Error {
+func Exec(argv0 string, argv []string, envv []string) Error {
 	if envv == nil {
 		envv = Environ();
 	}
@@ -69,7 +69,7 @@ const (
 // Wait waits for process pid to exit or stop, and then returns a
 // Waitmsg describing its status and an Error, if any. The options
 // (WNOHANG etc.) affect the behavior of the Wait call.
-func Wait(pid int, options uint64) (w *Waitmsg, err *Error) {
+func Wait(pid int, options uint64) (w *Waitmsg, err Error) {
 	var status syscall.WaitStatus;
 	var rusage *syscall.Rusage;
 	if options & WRUSAGE != 0 {

src/lib/os/file.go

@@ -70,7 +70,7 @@ const (
 // Open opens the named file with specified flag (O_RDONLY etc.) and perm, (0666 etc.)
 // if applicable.  If successful, methods on the returned File can be used for I/O.
 // It returns the File and an Error, if any.
-func Open(name string, flag int, perm int) (file *File, err *Error) {
+func Open(name string, flag int, perm int) (file *File, err Error) {
 	r, e := syscall.Open(name, int64(flag | syscall.O_CLOEXEC), int64(perm));
 	if e != 0 {
 		return nil, ErrnoToError(e);
@@ -87,7 +87,7 @@ func Open(name string, flag int, perm int) (file *File, err *Error) {
 
 // Close closes the File, rendering it unusable for I/O.
 // It returns an Error, if any.
-func (file *File) Close() *Error {
+func (file *File) Close() Error {
 	if file == nil {
 		return EINVAL
 	}
@@ -100,7 +100,7 @@ func (file *File) Close() *Error {
 // It returns the number of bytes read and an Error, if any.
 // EOF is signaled by a zero count with a nil Error.
 // TODO(r): Add Pread, Pwrite (maybe ReadAt, WriteAt).
-func (file *File) Read(b []byte) (ret int, err *Error) {
+func (file *File) Read(b []byte) (ret int, err Error) {
 	if file == nil {
 		return 0, EINVAL
 	}
@@ -117,7 +117,7 @@ func (file *File) Read(b []byte) (ret int, err *Error) {
 // Write writes len(b) bytes to the File.
 // It returns the number of bytes written and an Error, if any.
 // If the byte count differs from len(b), it usually implies an error occurred.
-func (file *File) Write(b []byte) (ret int, err *Error) {
+func (file *File) Write(b []byte) (ret int, err Error) {
 	if file == nil {
 		return 0, EINVAL
 	}
@@ -135,7 +135,7 @@ func (file *File) Write(b []byte) (ret int, err *Error) {
 // according to whence: 0 means relative to the origin of the file, 1 means
 // relative to the current offset, and 2 means relative to the end.
 // It returns the new offset and an Error, if any.
-func (file *File) Seek(offset int64, whence int) (ret int64, err *Error) {
+func (file *File) Seek(offset int64, whence int) (ret int64, err Error) {
 	r, e := syscall.Seek(file.fd, offset, int64(whence));
 	if e != 0 {
 		return -1, ErrnoToError(e)
@@ -148,7 +148,7 @@ func (file *File) Seek(offset int64, whence int) (ret int64, err *Error) {
 
 // WriteString is like Write, but writes the contents of string s rather than
 // an array of bytes.
-func (file *File) WriteString(s string) (ret int, err *Error) {
+func (file *File) WriteString(s string) (ret int, err Error) {
 	if file == nil {
 		return 0, EINVAL
 	}
@@ -161,7 +161,7 @@ func (file *File) WriteString(s string) (ret int, err *Error) {
 
 // Pipe returns a connected pair of Files; reads from r return bytes written to w.
 // It returns the files and an Error, if any.
-func Pipe() (r *File, w *File, err *Error) {
+func Pipe() (r *File, w *File, err Error) {
 	var p [2]int64;
 
 	// See ../syscall/exec.go for description of lock.
@@ -180,7 +180,7 @@ func Pipe() (r *File, w *File, err *Error) {
 
 // Mkdir creates a new directory with the specified name and permission bits.
 // It returns an error, if any.
-func Mkdir(name string, perm int) *Error {
+func Mkdir(name string, perm int) Error {
 	r, e := syscall.Mkdir(name, int64(perm));
 	return ErrnoToError(e)
 }
@@ -189,7 +189,7 @@ func Mkdir(name string, perm int) *Error {
 // is a symbolic link, it returns information about the file the link
 // references.
 // It returns the Dir and an error, if any.
-func Stat(name string) (dir *Dir, err *Error) {
+func Stat(name string) (dir *Dir, err Error) {
 	stat := new(syscall.Stat_t);
 	r, e := syscall.Stat(name, stat);
 	if e != 0 {
@@ -200,7 +200,7 @@ func Stat(name string) (dir *Dir, err *Error) {
 
 // Stat returns the Dir structure describing file.
 // It returns the Dir and an error, if any.
-func (file *File) Stat() (dir *Dir, err *Error) {
+func (file *File) Stat() (dir *Dir, err Error) {
 	stat := new(syscall.Stat_t);
 	r, e := syscall.Fstat(file.fd, stat);
 	if e != 0 {
@@ -212,7 +212,7 @@ func (file *File) Stat() (dir *Dir, err *Error) {
 // Lstat returns the Dir structure describing the named file. If the file
 // is a symbolic link, it returns information about the link itself.
 // It returns the Dir and an error, if any.
-func Lstat(name string) (dir *Dir, err *Error) {
+func Lstat(name string) (dir *Dir, err Error) {
 	stat := new(syscall.Stat_t);
 	r, e := syscall.Lstat(name, stat);
 	if e != 0 {
@@ -223,14 +223,14 @@ func Lstat(name string) (dir *Dir, err *Error) {
 
 // Readdirnames has a non-portable implemenation so its code is separated into an
 // operating-system-dependent file.
-func readdirnames(file *File, count int) (names []string, err *os.Error)
+func readdirnames(file *File, count int) (names []string, err Error)
 
 // Readdirnames reads the contents of the directory associated with file and
 // returns an array of up to count names, in directory order.  Subsequent
 // calls on the same file will yield further names.
 // A negative count means to read until EOF.
 // It returns the array and an Error, if any.
-func (file *File) Readdirnames(count int) (names []string, err *os.Error) {
+func (file *File) Readdirnames(count int) (names []string, err Error) {
 	return readdirnames(file, count);
 }
 
@@ -239,7 +239,7 @@ func (file *File) Readdirnames(count int) (names []string, err *os.Error) {
 // calls on the same file will yield further Dirs.
 // A negative count means to read until EOF.
 // It returns the array and an Error, if any.
-func (file *File) Readdir(count int) (dirs []Dir, err *os.Error) {
+func (file *File) Readdir(count int) (dirs []Dir, err Error) {
 	dirname := file.name;
 	if dirname == "" {
 		dirname = ".";
@@ -262,13 +262,13 @@ func (file *File) Readdir(count int) (dirs []Dir, err *os.Error) {
 }
 
 // Chdir changes the current working directory to the named directory.
-func Chdir(dir string) *os.Error {
+func Chdir(dir string) Error {
 	r, e := syscall.Chdir(dir);
 	return ErrnoToError(e);
 }
 
 // Remove removes the named file or directory.
-func Remove(name string) *os.Error {
+func Remove(name string) Error {
 	// System call interface forces us to know
 	// whether name is a file or directory.
 	// Try both: it is cheaper on average than

src/lib/os/time.go

@@ -14,7 +14,7 @@ import (
 // fractional nanoseconds, plus an Error if any. The current
 // time is thus 1e9*sec+nsec, in nanoseconds.  The zero of
 // time is the Unix epoch.
-func Time() (sec int64, nsec int64, err *Error) {
+func Time() (sec int64, nsec int64, err Error) {
 	var errno int64;
 	sec, nsec, errno = syscall.Gettimeofday();
 	if errno != 0 {

src/lib/regexp/all_test.go

@@ -32,7 +32,7 @@ var good_re = []string{
 // TODO: nice to do this with a map
 type stringError struct {
 	re	string;
-	err	*os.Error;
+	err	os.Error;
 }
 var bad_re = []stringError{
 	stringError{ `*`,	 	regexp.ErrBareClosure },
@@ -85,7 +85,7 @@ var matches = []tester {
 	tester{ `a*(|(b))c*`,	"aacc",	vec{0,4, 2,2, -1,-1} },
 }
 
-func compileTest(t *testing.T, expr string, error *os.Error) *regexp.Regexp {
+func compileTest(t *testing.T, expr string, error os.Error) *regexp.Regexp {
 	re, err := regexp.Compile(expr);
 	if err != error {
 		t.Error("compiling `", expr, "`; unexpected error: ", err.String());

src/lib/regexp/regexp.go

@@ -70,7 +70,7 @@ func (c *common) setIndex(i int) { c._index = i }
 type Regexp struct {
 	expr	string;	// the original expression
 	ch	chan<- *Regexp;	// reply channel when we're done
-	error	*os.Error;	// compile- or run-time error; nil if OK
+	error	os.Error;	// compile- or run-time error; nil if OK
 	inst	*vector.Vector;
 	start	instr;
 	nbra	int;	// number of brackets in expression, for subexpressions
@@ -233,7 +233,7 @@ func (nop *_Nop) kind() int { return _NOP }
 func (nop *_Nop) print() { print("nop") }
 
 // report error and exit compiling/executing goroutine
-func (re *Regexp) setError(err *os.Error) {
+func (re *Regexp) setError(err os.Error) {
 	re.error = err;
 	re.ch <- re;
 	sys.Goexit();
@@ -586,7 +586,7 @@ func compiler(str string, ch chan *Regexp) {
 
 // Compile parses a regular expression and returns, if successful, a Regexp
 // object that can be used to match against text.
-func Compile(str string) (regexp *Regexp, error *os.Error) {
+func Compile(str string) (regexp *Regexp, error os.Error) {
 	// Compile in a separate goroutine and wait for the result.
 	ch := make(chan *Regexp);
 	go compiler(str, ch);
@@ -754,7 +754,7 @@ func (re *Regexp) MatchStrings(s string) (a []string) {
 // Match checks whether a textual regular expression
 // matches a substring.  More complicated queries need
 // to use Compile and the full Regexp interface.
-func Match(pattern string, s string) (matched bool, error *os.Error) {
+func Match(pattern string, s string) (matched bool, error os.Error) {
 	re, err := Compile(pattern);
 	if err != nil {
 		return false, err

src/lib/strconv/atof.go

@@ -321,7 +321,7 @@ func decimalAtof32(neg bool, d *decimal, trunc bool) (f float32, ok bool) {
 // If s is syntactically well-formed but is more than 1/2 ULP
 // away from the largest floating point number of the given size,
 // Atof32 returns f = ±Inf, err = os.ERANGE.
-func Atof32(s string) (f float32, err *os.Error) {
+func Atof32(s string) (f float32, err os.Error) {
 	neg, d, trunc, ok := stringToDecimal(s);
 	if !ok {
 		return 0, os.EINVAL;
@@ -342,7 +342,7 @@ func Atof32(s string) (f float32, err *os.Error) {
 // Atof64 converts the string s to a 64-bit floating-point number.
 // Except for the type of its result, its definition is the same as that
 // of Atof32.
-func Atof64(s string) (f float64, err *os.Error) {
+func Atof64(s string) (f float64, err os.Error) {
 	neg, d, trunc, ok := stringToDecimal(s);
 	if !ok {
 		return 0, os.EINVAL;
@@ -361,7 +361,7 @@ func Atof64(s string) (f float64, err *os.Error) {
 }
 
 // Atof is like Atof32 or Atof64, depending on the size of float.
-func Atof(s string) (f float, err *os.Error) {
+func Atof(s string) (f float, err os.Error) {
 	if FloatSize == 32 {
 		f1, err1 := Atof32(s);
 		return float(f1), err1;

src/lib/strconv/atof_test.go

@@ -13,7 +13,7 @@ import (
 type atofTest struct {
 	in string;
 	out string;
-	err *os.Error;
+	err os.Error;
 }
 
 var atoftests = []atofTest {

src/lib/strconv/atoi.go

@@ -29,7 +29,7 @@ func cutoff64(base int) uint64 {
 // range or s is empty or contains invalid digits.
 // It returns err == os.ERANGE if the value corresponding
 // to s cannot be represented by a uint64.
-func Btoui64(s string, b int) (n uint64, err *os.Error) {
+func Btoui64(s string, b int) (n uint64, err os.Error) {
 	if b < 2 || b > 36 || len(s) < 1 {
 		return 0, os.EINVAL;
 	}
@@ -77,7 +77,7 @@ func Btoui64(s string, b int) (n uint64, err *os.Error) {
 //
 // Atoui64 returns err == os.EINVAL if s is empty or contains invalid digits.
 // It returns err == os.ERANGE if s cannot be represented by a uint64.
-func Atoui64(s string) (n uint64, err *os.Error) {
+func Atoui64(s string) (n uint64, err os.Error) {
 	// Empty string bad.
 	if len(s) == 0 {
 		return 0, os.EINVAL
@@ -99,7 +99,7 @@ func Atoui64(s string) (n uint64, err *os.Error) {
 
 // Atoi64 is like Atoui64 but allows signed numbers and
 // returns its result in an int64.
-func Atoi64(s string) (i int64, err *os.Error) {
+func Atoi64(s string) (i int64, err os.Error) {
 	// Empty string bad.
 	if len(s) == 0 {
 		return 0, os.EINVAL
@@ -134,7 +134,7 @@ func Atoi64(s string) (i int64, err *os.Error) {
 }
 
 // Atoui is like Atoui64 but returns its result as a uint.
-func Atoui(s string) (i uint, err *os.Error) {
+func Atoui(s string) (i uint, err os.Error) {
 	i1, e1 := Atoui64(s);
 	if e1 != nil && e1 != os.ERANGE {
 		return 0, e1
@@ -149,7 +149,7 @@ func Atoui(s string) (i uint, err *os.Error) {
 }
 
 // Atoi is like Atoi64 but returns its result as an int.
-func Atoi(s string) (i int, err *os.Error) {
+func Atoi(s string) (i int, err os.Error) {
 	i1, e1 := Atoi64(s);
 	if e1 != nil && e1 != os.ERANGE {
 		return 0, e1

src/lib/strconv/atoi_test.go

@@ -14,7 +14,7 @@ import (
 type atoui64Test struct {
 	in string;
 	out uint64;
-	err *os.Error;
+	err os.Error;
 }
 
 var atoui64tests = []atoui64Test {
@@ -41,7 +41,7 @@ var atoui64tests = []atoui64Test {
 type atoi64Test struct {
 	in string;
 	out int64;
-	err *os.Error;
+	err os.Error;
 }
 
 var atoi64test = []atoi64Test {
@@ -71,7 +71,7 @@ var atoi64test = []atoi64Test {
 type atoui32Test struct {
 	in string;
 	out uint32;
-	err *os.Error;
+	err os.Error;
 }
 
 var atoui32tests = []atoui32Test {
@@ -91,7 +91,7 @@ var atoui32tests = []atoui32Test {
 type atoi32Test struct {
 	in string;
 	out int32;
-	err *os.Error;
+	err os.Error;
 }
 
 var atoi32tests = []atoi32Test {

src/lib/strconv/quote.go

@@ -97,7 +97,7 @@ func unhex(b byte) (v int, ok bool) {
 	return;
 }
 
-func unquoteChar(s string, i int, q byte) (t string, ii int, err *os.Error) {
+func unquoteChar(s string, i int, q byte) (t string, ii int, err os.Error) {
 	err = os.EINVAL;  // assume error for easy return
 
 	// easy cases
@@ -190,7 +190,7 @@ func unquoteChar(s string, i int, q byte) (t string, ii int, err *os.Error) {
 // that s quotes.  (If s is single-quoted, it would be a Go
 // character literal; Unquote returns the corresponding
 // one-character string.)
-func Unquote(s string) (t string, err *os.Error) {
+func Unquote(s string) (t string, err os.Error) {
 	err = os.EINVAL;  // assume error for easy return
 	n := len(s);
 	if n < 2 || s[0] != s[n-1] {
@@ -207,7 +207,7 @@ func Unquote(s string) (t string, err *os.Error) {
 		t := "";
 		q := s[0];
 		var c string;
-		var err *os.Error;
+		var err os.Error;
 		for i := 1; i < n-1; {
 			c, i, err = unquoteChar(s, i, q);
 			if err != nil {

src/lib/tabwriter/tabwriter.go

@@ -222,7 +222,7 @@ func (b *Writer) dump() {
 }
 
 
-func (b *Writer) write0(buf []byte) *os.Error {
+func (b *Writer) write0(buf []byte) os.Error {
 	n, err := b.output.Write(buf);
 	if n != len(buf) && err == nil {
 		err = os.EIO;
@@ -233,7 +233,7 @@ func (b *Writer) write0(buf []byte) *os.Error {
 
 var newline = []byte{'\n'}
 
-func (b *Writer) writePadding(textw, cellw int) (err *os.Error) {
+func (b *Writer) writePadding(textw, cellw int) (err os.Error) {
 	if b.padbytes[0] == '\t' {
 		// make cell width a multiple of cellwidth
 		cellw = ((cellw + b.cellwidth - 1) / b.cellwidth) * b.cellwidth;
@@ -262,7 +262,7 @@ exit:
 }
 
 
-func (b *Writer) writeLines(pos0 int, line0, line1 int) (pos int, err *os.Error) {
+func (b *Writer) writeLines(pos0 int, line0, line1 int) (pos int, err os.Error) {
 	pos = pos0;
 	for i := line0; i < line1; i++ {
 		line_size, line_width := b.line(i);
@@ -319,7 +319,7 @@ exit:
 }
 
 
-func (b *Writer) format(pos0 int, line0, line1 int) (pos int, err *os.Error) {
+func (b *Writer) format(pos0 int, line0, line1 int) (pos int, err os.Error) {
 	pos = pos0;
 	column := b.widths.Len();
 	last := line0;
@@ -373,7 +373,7 @@ exit:
 // Flush should be called after the last call to Write to ensure
 // that any data buffered in the Writer is written to output.
 //
-func (b *Writer) Flush() *os.Error {
+func (b *Writer) Flush() os.Error {
 	dummy, err := b.format(0, 0, b.lines_size.Len());
 	// reset (even in the presence of errors)
 	b.buf.clear();
@@ -411,7 +411,7 @@ func (b *Writer) append(buf []byte) {
 // The only errors returned are ones encountered
 // while writing to the underlying output stream.
 //
-func (b *Writer) Write(buf []byte) (written int, err *os.Error) {
+func (b *Writer) Write(buf []byte) (written int, err os.Error) {
 	i0, n := 0, len(buf);
 
 	// split text into cells

src/lib/tabwriter/tabwriter_test.go

@@ -27,7 +27,7 @@ func (b *buffer) clear() {
 }
 
 
-func (b *buffer) Write(buf []byte) (written int, err *os.Error) {
+func (b *buffer) Write(buf []byte) (written int, err os.Error) {
 	n := len(b.a);
 	m := len(buf);
 	if n + m <= cap(b.a) {

src/lib/template/template.go

@@ -66,19 +66,9 @@ import (
 	"template";
 )
 
-// Errors returned during parsing and execution.
-var ErrUnmatchedRDelim = os.NewError("unmatched closing delimiter")
-var ErrUnmatchedLDelim = os.NewError("unmatched opening delimiter")
-var ErrBadDirective = os.NewError("unrecognized directive name")
-var ErrEmptyDirective = os.NewError("empty directive")
-var ErrFields = os.NewError("incorrect fields for directive")
-var ErrSyntax = os.NewError("directive out of place")
-var ErrNoEnd = os.NewError("section does not have .end")
-var ErrNoVar = os.NewError("variable name not in struct");
-var ErrBadType = os.NewError("unsupported type for variable");
-var ErrNotStruct = os.NewError("driver must be a struct")
-var ErrNoFormatter = os.NewError("unknown formatter")
-var ErrBadDelims = os.NewError("invalid delimiter strings")
+// Errors returned during parsing. TODO: different error model for execution?
+
+type ParseError struct { os.ErrorString }
 
 // All the literals are aces.
 var lbrace = []byte{ '{' }
@@ -112,15 +102,14 @@ var builtins = FormatterMap {
 // State for executing a Template
 type state struct {
 	parent	*state;	// parent in hierarchy
-	errorchan	chan *os.Error;	// for erroring out
+	errorchan	chan os.Error;	// for erroring out
 	data	reflect.Value;	// the driver data for this section etc.
 	wr	io.Write;	// where to send output
 }
 
 // Report error and stop generation.
-func (st *state) error(err *os.Error, args ...) {
-	fmt.Fprintf(os.Stderr, "template: %v%s\n", err, fmt.Sprint(args));
-	st.errorchan <- err;
+func (st *state) parseError(line int, err string, args ...) {
+	st.errorchan <- ParseError{fmt.Sprintf("line %d: %s", line, fmt.Sprintf(err, args))};
 	sys.Goexit();
 }
 
@@ -217,7 +206,7 @@ Loop:
 			i = j - 1;
 		case equal(t.buf, i, t.rdelim):
 			if !sawLeft {
-				st.error(ErrUnmatchedRDelim)
+				st.parseError(*t.linenum, "unmatched closing delimiter")
 			}
 			sawLeft = false;
 			i += len(t.rdelim);
@@ -227,7 +216,7 @@ Loop:
 		}
 	}
 	if sawLeft {
-		st.error(ErrUnmatchedLDelim)
+		st.parseError(*t.linenum, "unmatched opening delimiter")
 	}
 	item := t.buf[start:i];
 	if special && trim_white {
@@ -281,10 +270,10 @@ func (t *Template) analyze(item []byte, st *state) (tok int, w []string) {
 		return
 	}
 	if !equal(item, len(item)-len(t.rdelim), t.rdelim) {	// doesn't end with right delimiter
-		st.error(ErrUnmatchedLDelim)  // should not happen anyway
+		st.parseError(*t.linenum, "unmatched opening delimiter")  // should not happen anyway
 	}
 	if len(item) <= len(t.ldelim)+len(t.rdelim) {	// no contents
-		st.error(ErrEmptyDirective)
+		st.parseError(*t.linenum, "empty directive")
 	}
 	// Comment
 	if item[len(t.ldelim)] == '#' {
@@ -294,10 +283,7 @@ func (t *Template) analyze(item []byte, st *state) (tok int, w []string) {
 	// Split into words
 	w = words(item[len(t.ldelim): len(item)-len(t.rdelim)]);  // drop final delimiter
 	if len(w) == 0 {
-		st.error(ErrBadDirective)
-	}
-	if len(w[0]) == 0 {
-		st.error(ErrEmptyDirective)
+		st.parseError(*t.linenum, "empty directive")
 	}
 	if len(w) == 1 && w[0][0] != '.' {
 		tok = Variable;
@@ -315,24 +301,24 @@ func (t *Template) analyze(item []byte, st *state) (tok int, w []string) {
 		return;
 	case ".section":
 		if len(w) != 2 {
-			st.error(ErrFields, ": ", string(item))
+			st.parseError(*t.linenum, "incorrect fields for .section: %s", item)
 		}
 		tok = Section;
 		return;
 	case ".repeated":
 		if len(w) != 3 || w[1] != "section" {
-			st.error(ErrFields, ": ", string(item))
+			st.parseError(*t.linenum, "incorrect fields for .repeated: %s", item)
 		}
 		tok = Repeated;
 		return;
 	case ".alternates":
 		if len(w) != 2 || w[1] != "with" {
-			st.error(ErrFields, ": ", string(item))
+			st.parseError(*t.linenum, "incorrect fields for .alternates: %s", item)
 		}
 		tok = Alternates;
 		return;
 	}
-	st.error(ErrBadDirective, ": ", string(item));
+	st.parseError(*t.linenum, "bad directive: %s", item);
 	return
 }
 
@@ -375,18 +361,19 @@ func empty(v reflect.Value, indirect_ok bool) bool {
 // Execute a ".repeated" section
 func (t *Template) executeRepeated(w []string, st *state) {
 	if w[1] != "section" {
-		st.error(ErrSyntax, `: .repeated must have "section"`)
+		st.parseError(*t.linenum, `.repeated must have "section"`)
 	}
 
 	// Find driver array/struct for this section.  It must be in the current struct.
 	field := st.findVar(w[2]);
 	if field == nil {
-		st.error(ErrNoVar, ": .repeated ", w[2], " in ", reflect.Indirect(st.data).Type());
+		st.parseError(*t.linenum, ".repeated: cannot find %s in %s", w[2], reflect.Indirect(st.data).Type());
 	}
+	field = reflect.Indirect(field);
 
 	// Must be an array/slice
 	if field != nil && field.Kind() != reflect.ArrayKind {
-		st.error(ErrBadType, " in .repeated: ", w[2], " ", field.Type().String());
+		st.parseError(*t.linenum, ".repeated: %s has bad type %s", w[2], field.Type());
 	}
 	// Scan repeated section, remembering slice of text we must execute.
 	nesting := 0;
@@ -396,7 +383,7 @@ Loop:
 	for {
 		item := t.nextItem(st);
 		if len(item) ==  0 {
-			st.error(ErrNoEnd)
+			st.parseError(*t.linenum, "missing .end")
 		}
 		tok, s := t.analyze(item, st);
 		switch tok {
@@ -430,7 +417,7 @@ func (t *Template) executeSection(w []string, st *state) {
 	// Find driver data for this section.  It must be in the current struct.
 	field := st.findVar(w[1]);
 	if field == nil {
-		st.error(ErrNoVar, ": .section ", w[1], " in ", reflect.Indirect(st.data).Type());
+		st.parseError(*t.linenum, ".section: cannot find %s in %s", w[1], reflect.Indirect(st.data).Type());
 	}
 	// Scan section, remembering slice of text we must execute.
 	orFound := false;
@@ -442,7 +429,7 @@ Loop:
 	for {
 		item := t.nextItem(st);
 		if len(item) ==  0 {
-			st.error(ErrNoEnd)
+			st.parseError(*t.linenum, "missing .end")
 		}
 		tok, s := t.analyze(item, st);
 		switch tok {
@@ -458,7 +445,7 @@ Loop:
 				break
 			}
 			if orFound {
-				st.error(ErrSyntax, ": .or");
+				st.parseError(*t.linenum, "unexpected .or");
 			}
 			orFound = true;
 			if !accumulate {
@@ -491,7 +478,7 @@ func (t *Template) varValue(name string, st *state) reflect.Value {
 	field := st.findVar(name);
 	if field == nil {
 		if st.parent == nil {
-			st.error(ErrNoVar, ": ", name)
+			st.parseError(*t.linenum, "name not found: %s", name)
 		}
 		return t.varValue(name, st.parent);
 	}
@@ -521,7 +508,7 @@ func (t *Template) writeVariable(st *state, name_formatter string) {
 		fn(st.wr, val, formatter);
 		return;
 	}
-	st.error(ErrNoFormatter, ": ", formatter);
+	st.parseError(*t.linenum, "unknown formatter: %s", formatter);
 	panic("notreached");
 }
 
@@ -553,7 +540,7 @@ func (t *Template) execute(st *state) {
 		case Variable:
 			t.writeVariable(st, w[0]);
 		case Or, End, Alternates:
-			st.error(ErrSyntax, ": ", string(item));
+			st.parseError(*t.linenum, "unexpected %s", w[0]);
 		case Section:
 			t.executeSection(w, st);
 		case Repeated:
@@ -568,7 +555,7 @@ func (t *Template) doParse() {
 	// stub for now
 }
 
-// A valid delimeter must contain no white space and be non-empty.
+// A valid delimiter must contain no white space and be non-empty.
 func validDelim(d []byte) bool {
 	if len(d) == 0 {
 		return false
@@ -581,32 +568,29 @@ func validDelim(d []byte) bool {
 	return true;
 }
 
-// Parse initializes a Template by parsing its definition.  The string s contains
-// the template text.  If any errors occur, it returns the error and line number
-// in the text of the erroneous construct.
-func (t *Template) Parse(s string) (err *os.Error, eline int) {
+// Parse initializes a Template by parsing its definition.  The string
+// s contains the template text.  If any errors occur, Parse returns
+// the error.
+func (t *Template) Parse(s string) (err os.Error) {
 	if !validDelim(t.ldelim) || !validDelim(t.rdelim) {
-		return ErrBadDelims, 0
+		return ParseError{fmt.Sprintf("bad delimiter strings %q %q", t.ldelim, t.rdelim)}
 	}
 	t.init(io.StringBytes(s));
-	ch := make(chan *os.Error);
+	ch := make(chan os.Error);
 	go func() {
 		t.doParse();
 		ch <- nil;	// clean return;
 	}();
 	err = <-ch;
-	if err != nil {
-		return err, *t.linenum
-	}
 	return
 }
 
 // Execute executes a parsed template on the specified data object,
 // generating output to wr.
-func (t *Template) Execute(data interface{}, wr io.Write) *os.Error {
+func (t *Template) Execute(data interface{}, wr io.Write) os.Error {
 	// Extract the driver data.
 	val := reflect.NewValue(data);
-	ch := make(chan *os.Error);
+	ch := make(chan os.Error);
 	go func() {
 		t.p = 0;
 		t.execute(&state{nil, ch, val, wr});
@@ -625,23 +609,23 @@ func New(fmap FormatterMap) *Template {
 	return t;
 }
 
-// SetDelims sets the left and right delimiters for operations in the template.
-// They are validated during parsing.  They could be validated here but it's
-// better to keep the routine simple.  The delimiters are very rarely invalid
-// and Parse has the necessary error-handling interface already.
+// SetDelims sets the left and right delimiters for operations in the
+// template.  They are validated during parsing.  They could be
+// validated here but it's better to keep the routine simple.  The
+// delimiters are very rarely invalid and Parse has the necessary
+// error-handling interface already.
 func (t *Template) SetDelims(left, right string) {
 	t.ldelim = io.StringBytes(left);
 	t.rdelim = io.StringBytes(right);
 }
 
 // Parse creates a Template with default parameters (such as {} for
-// metacharacters).  The string s contains the template text while the
-// formatter map fmap, which may be nil, defines auxiliary functions
+// metacharacters).  The string s contains the template text while
+// the formatter map fmap, which may be nil, defines auxiliary functions
 // for formatting variables.  The template is returned. If any errors
-// occur, err will be non-nil and eline will be  the line number in the
-// text of the erroneous construct.
-func Parse(s string, fmap FormatterMap) (t *Template, err *os.Error, eline int) {
+// occur, err will be non-nil.
+func Parse(s string, fmap FormatterMap) (t *Template, err os.Error) {
 	t = New(fmap);
-	err, eline = t.Parse(s);
+	err = t.Parse(s);
 	return
 }

src/lib/template/template_test.go

@@ -194,9 +194,9 @@ func TestAll(t *testing.T) {
 	var buf io.ByteBuffer;
 	for i, test := range tests {
 		buf.Reset();
-		tmpl, err, line := Parse(test.in, formatters);
+		tmpl, err := Parse(test.in, formatters);
 		if err != nil {
-			t.Error("unexpected parse error:", err, "line", line);
+			t.Error("unexpected parse error:", err);
 			continue;
 		}
 		err = tmpl.Execute(s, &buf);
@@ -210,7 +210,7 @@ func TestAll(t *testing.T) {
 }
 
 func TestStringDriverType(t *testing.T) {
-	tmpl, err, line := Parse("template: {@}", nil);
+	tmpl, err := Parse("template: {@}", nil);
 	if err != nil {
 		t.Error("unexpected parse error:", err)
 	}
@@ -226,7 +226,7 @@ func TestStringDriverType(t *testing.T) {
 }
 
 func TestTwice(t *testing.T) {
-	tmpl, err, line := Parse("template: {@}", nil);
+	tmpl, err := Parse("template: {@}", nil);
 	if err != nil {
 		t.Error("unexpected parse error:", err)
 	}
@@ -265,7 +265,7 @@ func TestCustomDelims(t *testing.T) {
 				ldelim + "@" + rdelim +
 				ldelim + ".meta-left" + rdelim +
 				ldelim + ".meta-right" + rdelim;
-			err, line := tmpl.Parse(text);
+			err := tmpl.Parse(text);
 			if err != nil {
 				if i == 0 || j == 0 {	// expected
 					continue

src/lib/time/sleep.go

@@ -12,7 +12,7 @@ import (
 
 // Sleep pauses the current goroutine for ns nanoseconds.
 // It returns os.EINTR if interrupted.
-func Sleep(ns int64) *os.Error {
+func Sleep(ns int64) os.Error {
 	var tv syscall.Timeval;
 	syscall.Nstotimeval(ns, &tv);
 	r1, r2, err := syscall.Syscall6(syscall.SYS_SELECT, 0, 0, 0, 0,

src/lib/time/zoneinfo.go

@@ -88,7 +88,7 @@ type zonetime struct {
 	isstd, isutc bool;	// ignored - no idea what these mean
 }
 
-func parseinfo(bytes []byte) (zt []zonetime, err *os.Error) {
+func parseinfo(bytes []byte) (zt []zonetime, err os.Error) {
 	d := data{bytes, false};
 
 	// 4-byte magic "TZif"
@@ -203,7 +203,7 @@ func parseinfo(bytes []byte) (zt []zonetime, err *os.Error) {
 	return zt, nil
 }
 
-func readfile(name string, max int) (p []byte, err *os.Error) {
+func readfile(name string, max int) (p []byte, err os.Error) {
 	f, e := os.Open(name, os.O_RDONLY, 0);
 	if e != nil {
 		return nil, e;
@@ -220,7 +220,7 @@ func readfile(name string, max int) (p []byte, err *os.Error) {
 	return p[0:n], nil;
 }
 
-func readinfofile(name string) (tx []zonetime, err *os.Error) {
+func readinfofile(name string) (tx []zonetime, err os.Error) {
 	buf, e := readfile(name, maxFileSize);
 	if e != nil {
 		return nil, e
@@ -230,7 +230,7 @@ func readinfofile(name string) (tx []zonetime, err *os.Error) {
 }
 
 var zones []zonetime
-var zoneerr *os.Error
+var zoneerr os.Error
 
 func setupZone() {
 	// consult $TZ to find the time zone to use.
@@ -252,7 +252,7 @@ func setupZone() {
 	}
 }
 
-func lookupTimezone(sec int64) (zone string, offset int, err *os.Error) {
+func lookupTimezone(sec int64) (zone string, offset int, err os.Error) {
 	once.Do(setupZone);
 	if zoneerr != nil || len(zones) == 0 {
 		return "UTC", 0, zoneerr

src/lib/xml.go

@@ -175,26 +175,26 @@ type Builder interface {
 	//	<name attr.name=attr.value attr1.name=attr1.value ... />
 	// xmlns and xmlns:foo attributes are handled internally
 	// and not passed through to StartElement.
-	StartElement(name Name, attr []Attr) *os.Error;
+	StartElement(name Name, attr []Attr) os.Error;
 
 	// Called when an element ends.
 	//	</name>
 	//	<name ... />
-	EndElement(name Name) *os.Error;
+	EndElement(name Name) os.Error;
 
 	// Called for non-empty character data string inside element.
 	// Can be called multiple times between elements.
 	//	text
 	//	<![CDATA[text]]>
-	Text(text []byte) *os.Error;
+	Text(text []byte) os.Error;
 
 	// Called when a comment is found in the XML.
 	//	<!-- text -->
-	Comment(text []byte) *os.Error;
+	Comment(text []byte) os.Error;
 
 	// Called for a processing instruction
 	// <?target text?>
-	ProcInst(target string, text []byte) *os.Error;
+	ProcInst(target string, text []byte) os.Error;
 }
 
 // Default builder.  Implements no-op Builder methods.
@@ -203,28 +203,28 @@ type Builder interface {
 type BaseBuilder struct {
 }
 
-func (b *BaseBuilder) StartElement(name Name, attr []Attr) *os.Error {
+func (b *BaseBuilder) StartElement(name Name, attr []Attr) os.Error {
 	return nil;
 }
 
-func (b *BaseBuilder) EndElement(name Name) *os.Error {
+func (b *BaseBuilder) EndElement(name Name) os.Error {
 	return nil;
 }
 
-func (b *BaseBuilder) Text(text []byte) *os.Error {
+func (b *BaseBuilder) Text(text []byte) os.Error {
 	return nil;
 }
 
-func (b *BaseBuilder) Comment(text []byte) *os.Error {
+func (b *BaseBuilder) Comment(text []byte) os.Error {
 	return nil;
 }
 
-func (b *BaseBuilder) ProcInst(target string, text []byte) *os.Error {
+func (b *BaseBuilder) ProcInst(target string, text []byte) os.Error {
 	return nil;
 }
 
 // XML Parser.  Calls Builder methods as it parses.
-func Parse(r io.Read, b Builder) *os.Error {
+func Parse(r io.Read, b Builder) os.Error {
 	return os.NewError("unimplemented");
 }
 
@@ -252,12 +252,12 @@ type Token struct {
 	Attr []Attr;		// attributes (TokenStartElement)
 	Target string;		// target (TokenProcessingInstruction)
 	Text []byte;		// text (TokenCharData, TokenComment, etc.)
-	Err *os.Error;		// error (TokenEnd)
+	Err os.Error;		// error (TokenEnd)
 }
 
 type ChanBuilder chan Token;
 
-func (c ChanBuilder) StartElement(name Name, attr []Attr) *os.Error {
+func (c ChanBuilder) StartElement(name Name, attr []Attr) os.Error {
 	var t Token;
 	t.Kind = TokenStartElement;
 	t.Name = name;
@@ -266,7 +266,7 @@ func (c ChanBuilder) StartElement(name Name, attr []Attr) *os.Error {
 	return nil;
 }
 
-func (c ChanBuilder) EndElement(name Name) *os.Error {
+func (c ChanBuilder) EndElement(name Name) os.Error {
 	var t Token;
 	t.Kind = TokenEndElement;
 	t.Name = name;
@@ -274,7 +274,7 @@ func (c ChanBuilder) EndElement(name Name) *os.Error {
 	return nil;
 }
 
-func (c ChanBuilder) Text(text []byte) *os.Error {
+func (c ChanBuilder) Text(text []byte) os.Error {
 	var t Token;
 	t.Kind = TokenText;
 	t.Text = text;
@@ -282,7 +282,7 @@ func (c ChanBuilder) Text(text []byte) *os.Error {
 	return nil;
 }
 
-func (c ChanBuilder) Comment(text []byte) *os.Error {
+func (c ChanBuilder) Comment(text []byte) os.Error {
 	var t Token;
 	t.Kind = TokenComment;
 	t.Text = text;
@@ -290,7 +290,7 @@ func (c ChanBuilder) Comment(text []byte) *os.Error {
 	return nil;
 }
 
-func (c ChanBuilder) ProcInst(target string, text []byte) *os.Error {
+func (c ChanBuilder) ProcInst(target string, text []byte) os.Error {
 	var t Token;
 	t.Kind = TokenProcInst;
 	t.Target = target;

test/chan/goroutines.go

@@ -21,7 +21,7 @@ func f(left, right chan int) {
 func main() {
 	var n = 10000;
 	if len(sys.Args) > 1 {
-		var err *os.Error;
+		var err os.Error;
 		n, err = strconv.Atoi(sys.Args[1]);
 		if err != nil {
 			print("bad arg\n");

usr/gri/pretty/astprinter.go

@@ -450,7 +450,7 @@ func (P *Printer) Error(pos token.Position, tok token.Token, msg string) {
 
 // An astPrinter implements io.Write.
 // TODO this is not yet used.
-func (P *Printer) Write(p []byte) (n int, err *os.Error) {
+func (P *Printer) Write(p []byte) (n int, err os.Error) {
 	// TODO
 	// - no string conversion every time
 	// - return proper results

usr/gri/pretty/godoc.go

@@ -85,7 +85,7 @@ const (
 )
 
 func init() {
-	var err *os.Error;
+	var err os.Error;
 	goroot, err = os.Getenv("GOROOT");
 	if err != nil {
 		goroot = "/home/r/go-build/go";
@@ -118,7 +118,7 @@ func makeTabwriter(writer io.Write) *tabwriter.Writer {
 
 
 // TODO(rsc): this belongs in a library somewhere, maybe os
-func ReadFile(name string) ([]byte, *os.Error) {
+func ReadFile(name string) ([]byte, os.Error) {
 	f, err := os.Open(name, os.O_RDONLY, 0);
 	if err != nil {
 		return nil, err;
@@ -321,9 +321,9 @@ func ReadTemplate(name string) *template.Template {
 	if err != nil {
 		log.Exitf("ReadFile %s: %v", name, err);
 	}
-	t, err1, line := template.Parse(string(data), fmap);
+	t, err1 := template.Parse(string(data), fmap);
 	if err1 != nil {
-		log.Exitf("%s:%d: %v", name, line, err);
+		log.Exitf("%s: %v", name, err);
 	}
 	return t;
 }

usr/gri/pretty/platform.go

@@ -19,7 +19,7 @@ var
 	USER string;
 
 func init() {
-	var e *OS.Error;
+	var e OS.Error;
 
 	GOARCH, e = OS.Getenv("GOARCH");
 	GOOS, e = OS.Getenv("GOOS");
@@ -37,7 +37,7 @@ const (
 	Obj_file_ext = ".7";
 )
 
-func readfile(filename string) ([]byte, *OS.Error) {
+func readfile(filename string) ([]byte, OS.Error) {
 	f, err := OS.Open(filename, OS.O_RDONLY, 0);
 	if err != nil {
 		return []byte{}, err;
@@ -51,7 +51,7 @@ func readfile(filename string) ([]byte, *OS.Error) {
 	return buf[0:n], err1;
 }
 
-func writefile(name, data string) *OS.Error {
+func writefile(name, data string) OS.Error {
 	fd, err := OS.Open(name, OS.O_WRONLY, 0);
 	if err != nil {
 		return err;