9 files changed, 127 insertions, 28 deletions
diff --git a/src/pkg/text/scanner/scanner.go b/src/pkg/text/scanner/scanner.go
index e0d86e343..db7ca73c6 100644
--- a/src/pkg/text/scanner/scanner.go
+++ b/src/pkg/text/scanner/scanner.go
@@ -240,6 +240,9 @@ func (s *Scanner) next() rune {
 			s.srcEnd = i + n
 			s.srcBuf[s.srcEnd] = utf8.RuneSelf // sentinel
 			if err != nil {
+				if err != io.EOF {
+					s.error(err.Error())
+				}
 				if s.srcEnd == 0 {
 					if s.lastCharLen > 0 {
 						// previous character was not EOF
@@ -248,9 +251,6 @@ func (s *Scanner) next() rune {
 					s.lastCharLen = 0
 					return EOF
 				}
-				if err != io.EOF {
-					s.error(err.Error())
-				}
 				// If err == EOF, we won't be getting more
 				// bytes; break to avoid infinite loop. If
 				// err is something else, we don't know if
diff --git a/src/pkg/text/scanner/scanner_test.go b/src/pkg/text/scanner/scanner_test.go
index 496eed4a3..7d3f597eb 100644
--- a/src/pkg/text/scanner/scanner_test.go
+++ b/src/pkg/text/scanner/scanner_test.go
@@ -360,7 +360,7 @@ func TestScanSelectedMask(t *testing.T) {
 func TestScanNext(t *testing.T) {
 	const BOM = '\uFEFF'
 	BOMs := string(BOM)
-	s := new(Scanner).Init(bytes.NewBufferString(BOMs + "if a == bcd /* com" + BOMs + "ment */ {\n\ta += c\n}" + BOMs + "// line comment ending in eof"))
+	s := new(Scanner).Init(strings.NewReader(BOMs + "if a == bcd /* com" + BOMs + "ment */ {\n\ta += c\n}" + BOMs + "// line comment ending in eof"))
 	checkTok(t, s, 1, s.Scan(), Ident, "if") // the first BOM is ignored
 	checkTok(t, s, 1, s.Scan(), Ident, "a")
 	checkTok(t, s, 1, s.Scan(), '=', "=")
@@ -402,7 +402,7 @@ func TestScanWhitespace(t *testing.T) {
 }
 
 func testError(t *testing.T, src, pos, msg string, tok rune) {
-	s := new(Scanner).Init(bytes.NewBufferString(src))
+	s := new(Scanner).Init(strings.NewReader(src))
 	errorCalled := false
 	s.Error = func(s *Scanner, m string) {
 		if !errorCalled {
@@ -462,6 +462,33 @@ func TestError(t *testing.T) {
 	testError(t, `/*/`, "1:4", "comment not terminated", EOF)
 }
 
+// An errReader returns (0, err) where err is not io.EOF.
+type errReader struct{}
+
+func (errReader) Read(b []byte) (int, error) {
+	return 0, io.ErrNoProgress // some error that is not io.EOF
+}
+
+func TestIOError(t *testing.T) {
+	s := new(Scanner).Init(errReader{})
+	errorCalled := false
+	s.Error = func(s *Scanner, msg string) {
+		if !errorCalled {
+			if want := io.ErrNoProgress.Error(); msg != want {
+				t.Errorf("msg = %q, want %q", msg, want)
+			}
+			errorCalled = true
+		}
+	}
+	tok := s.Scan()
+	if tok != EOF {
+		t.Errorf("tok = %s, want EOF", TokenString(tok))
+	}
+	if !errorCalled {
+		t.Errorf("error handler not called")
+	}
+}
+
 func checkPos(t *testing.T, got, want Position) {
 	if got.Offset != want.Offset || got.Line != want.Line || got.Column != want.Column {
 		t.Errorf("got offset, line, column = %d, %d, %d; want %d, %d, %d",
@@ -491,13 +518,13 @@ func checkScanPos(t *testing.T, s *Scanner, offset, line, column int, char rune)
 
 func TestPos(t *testing.T) {
 	// corner case: empty source
-	s := new(Scanner).Init(bytes.NewBufferString(""))
+	s := new(Scanner).Init(strings.NewReader(""))
 	checkPos(t, s.Pos(), Position{Offset: 0, Line: 1, Column: 1})
 	s.Peek() // peek doesn't affect the position
 	checkPos(t, s.Pos(), Position{Offset: 0, Line: 1, Column: 1})
 
 	// corner case: source with only a newline
-	s = new(Scanner).Init(bytes.NewBufferString("\n"))
+	s = new(Scanner).Init(strings.NewReader("\n"))
 	checkPos(t, s.Pos(), Position{Offset: 0, Line: 1, Column: 1})
 	checkNextPos(t, s, 1, 2, 1, '\n')
 	// after EOF position doesn't change
@@ -509,7 +536,7 @@ func TestPos(t *testing.T) {
 	}
 
 	// corner case: source with only a single character
-	s = new(Scanner).Init(bytes.NewBufferString("本"))
+	s = new(Scanner).Init(strings.NewReader("本"))
 	checkPos(t, s.Pos(), Position{Offset: 0, Line: 1, Column: 1})
 	checkNextPos(t, s, 3, 1, 2, '本')
 	// after EOF position doesn't change
@@ -521,7 +548,7 @@ func TestPos(t *testing.T) {
 	}
 
 	// positions after calling Next
-	s = new(Scanner).Init(bytes.NewBufferString("  foo६४  \n\n本語\n"))
+	s = new(Scanner).Init(strings.NewReader("  foo६४  \n\n本語\n"))
 	checkNextPos(t, s, 1, 1, 2, ' ')
 	s.Peek() // peek doesn't affect the position
 	checkNextPos(t, s, 2, 1, 3, ' ')
@@ -546,7 +573,7 @@ func TestPos(t *testing.T) {
 	}
 
 	// positions after calling Scan
-	s = new(Scanner).Init(bytes.NewBufferString("abc\n本語\n\nx"))
+	s = new(Scanner).Init(strings.NewReader("abc\n本語\n\nx"))
 	s.Mode = 0
 	s.Whitespace = 0
 	checkScanPos(t, s, 0, 1, 1, 'a')
diff --git a/src/pkg/text/tabwriter/tabwriter.go b/src/pkg/text/tabwriter/tabwriter.go
index 722ac8d87..c0c32d5de 100644
--- a/src/pkg/text/tabwriter/tabwriter.go
+++ b/src/pkg/text/tabwriter/tabwriter.go
@@ -434,9 +434,13 @@ func (b *Writer) terminateCell(htab bool) int {
 	return len(*line)
 }
 
-func handlePanic(err *error) {
+func handlePanic(err *error, op string) {
 	if e := recover(); e != nil {
-		*err = e.(osError).err // re-panics if it's not a local osError
+		if nerr, ok := e.(osError); ok {
+			*err = nerr.err
+			return
+		}
+		panic("tabwriter: panic during " + op)
 	}
 }
 
@@ -447,7 +451,7 @@ func handlePanic(err *error) {
 //
 func (b *Writer) Flush() (err error) {
 	defer b.reset() // even in the presence of errors
-	defer handlePanic(&err)
+	defer handlePanic(&err, "Flush")
 
 	// add current cell if not empty
 	if b.cell.size > 0 {
@@ -471,7 +475,7 @@ var hbar = []byte("---\n")
 // while writing to the underlying output stream.
 //
 func (b *Writer) Write(buf []byte) (n int, err error) {
-	defer handlePanic(&err)
+	defer handlePanic(&err, "Write")
 
 	// split text into cells
 	n = 0
diff --git a/src/pkg/text/tabwriter/tabwriter_test.go b/src/pkg/text/tabwriter/tabwriter_test.go
index ace535647..9d3111e2c 100644
--- a/src/pkg/text/tabwriter/tabwriter_test.go
+++ b/src/pkg/text/tabwriter/tabwriter_test.go
@@ -14,7 +14,7 @@ type buffer struct {
 	a []byte
 }
 
-func (b *buffer) init(n int) { b.a = make([]byte, n)[0:0] }
+func (b *buffer) init(n int) { b.a = make([]byte, 0, n) }
 
 func (b *buffer) clear() { b.a = b.a[0:0] }
 
@@ -613,3 +613,40 @@ func Test(t *testing.T) {
 		check(t, e.testname, e.minwidth, e.tabwidth, e.padding, e.padchar, e.flags, e.src, e.expected)
 	}
 }
+
+type panicWriter struct{}
+
+func (panicWriter) Write([]byte) (int, error) {
+	panic("cannot write")
+}
+
+func wantPanicString(t *testing.T, want string) {
+	if e := recover(); e != nil {
+		got, ok := e.(string)
+		switch {
+		case !ok:
+			t.Errorf("got %v (%T), want panic string", e, e)
+		case got != want:
+			t.Errorf("wrong panic message: got %q, want %q", got, want)
+		}
+	}
+}
+
+func TestPanicDuringFlush(t *testing.T) {
+	defer wantPanicString(t, "tabwriter: panic during Flush")
+	var p panicWriter
+	w := new(Writer)
+	w.Init(p, 0, 0, 5, ' ', 0)
+	io.WriteString(w, "a")
+	w.Flush()
+	t.Errorf("failed to panic during Flush")
+}
+
+func TestPanicDuringWrite(t *testing.T) {
+	defer wantPanicString(t, "tabwriter: panic during Write")
+	var p panicWriter
+	w := new(Writer)
+	w.Init(p, 0, 0, 5, ' ', 0)
+	io.WriteString(w, "a\n\n") // the second \n triggers a call to w.Write and thus a panic
+	t.Errorf("failed to panic during Write")
+}
diff --git a/src/pkg/text/template/doc.go b/src/pkg/text/template/doc.go
index f622ac7dc..7c6efd59c 100644
--- a/src/pkg/text/template/doc.go
+++ b/src/pkg/text/template/doc.go
@@ -20,7 +20,7 @@ The input text for a template is UTF-8-encoded text in any format.
 "{{" and "}}"; all text outside actions is copied to the output unchanged.
 Actions may not span newlines, although comments can.
 
-Once constructed, a template may be executed safely in parallel.
+Once parsed, a template may be executed safely in parallel.
 
 Here is a trivial example that prints "17 items are made of wool".
 
diff --git a/src/pkg/text/template/exec.go b/src/pkg/text/template/exec.go
index 43b0b266e..2f3231264 100644
--- a/src/pkg/text/template/exec.go
+++ b/src/pkg/text/template/exec.go
@@ -108,6 +108,10 @@ func errRecover(errp *error) {
 
 // ExecuteTemplate applies the template associated with t that has the given name
 // to the specified data object and writes the output to wr.
+// If an error occurs executing the template or writing its output,
+// execution stops, but partial results may already have been written to
+// the output writer.
+// A template may be executed safely in parallel.
 func (t *Template) ExecuteTemplate(wr io.Writer, name string, data interface{}) error {
 	tmpl := t.tmpl[name]
 	if tmpl == nil {
@@ -118,6 +122,10 @@ func (t *Template) ExecuteTemplate(wr io.Writer, name string, data interface{})
 
 // Execute applies a parsed template to the specified data object,
 // and writes the output to wr.
+// If an error occurs executing the template or writing its output,
+// execution stops, but partial results may already have been written to
+// the output writer.
+// A template may be executed safely in parallel.
 func (t *Template) Execute(wr io.Writer, data interface{}) (err error) {
 	defer errRecover(&err)
 	value := reflect.ValueOf(data)
@@ -594,6 +602,9 @@ func (s *state) validateType(value reflect.Value, typ reflect.Type) reflect.Valu
 		switch {
 		case value.Kind() == reflect.Ptr && value.Type().Elem().AssignableTo(typ):
 			value = value.Elem()
+			if !value.IsValid() {
+				s.errorf("dereference of nil pointer of type %s", typ)
+			}
 		case reflect.PtrTo(value.Type()).AssignableTo(typ) && value.CanAddr():
 			value = value.Addr()
 		default:
diff --git a/src/pkg/text/template/exec_test.go b/src/pkg/text/template/exec_test.go
index f60702de8..868f2cb94 100644
--- a/src/pkg/text/template/exec_test.go
+++ b/src/pkg/text/template/exec_test.go
@@ -512,6 +512,8 @@ var execTests = []execTest{
 	{"bug9", "{{.cause}}", "neglect", map[string]string{"cause": "neglect"}, true},
 	// Field chain starting with function did not work.
 	{"bug10", "{{mapOfThree.three}}-{{(mapOfThree).three}}", "3-3", 0, true},
+	// Dereferencing nil pointer while evaluating function arguments should not panic. Issue 7333.
+	{"bug11", "{{valueString .PS}}", "", T{}, false},
 }
 
 func zeroArgs() string {
@@ -546,6 +548,11 @@ func vfunc(V, *V) string {
 	return "vfunc"
 }
 
+// valueString takes a string, not a pointer.
+func valueString(v string) string {
+	return "value is ignored"
+}
+
 func add(args ...int) int {
 	sum := 0
 	for _, x := range args {
@@ -580,17 +587,18 @@ func mapOfThree() interface{} {
 func testExecute(execTests []execTest, template *Template, t *testing.T) {
 	b := new(bytes.Buffer)
 	funcs := FuncMap{
-		"add":        add,
-		"count":      count,
-		"dddArg":     dddArg,
-		"echo":       echo,
-		"makemap":    makemap,
-		"mapOfThree": mapOfThree,
-		"oneArg":     oneArg,
-		"stringer":   stringer,
-		"typeOf":     typeOf,
-		"vfunc":      vfunc,
-		"zeroArgs":   zeroArgs,
+		"add":         add,
+		"count":       count,
+		"dddArg":      dddArg,
+		"echo":        echo,
+		"makemap":     makemap,
+		"mapOfThree":  mapOfThree,
+		"oneArg":      oneArg,
+		"stringer":    stringer,
+		"typeOf":      typeOf,
+		"valueString": valueString,
+		"vfunc":       vfunc,
+		"zeroArgs":    zeroArgs,
 	}
 	for _, test := range execTests {
 		var tmpl *Template
diff --git a/src/pkg/text/template/multi_test.go b/src/pkg/text/template/multi_test.go
index 1f6ed5d8e..e4e804880 100644
--- a/src/pkg/text/template/multi_test.go
+++ b/src/pkg/text/template/multi_test.go
@@ -259,6 +259,18 @@ func TestAddParseTree(t *testing.T) {
 	}
 }
 
+// Issue 7032
+func TestAddParseTreeToUnparsedTemplate(t *testing.T) {
+	master := "{{define \"master\"}}{{end}}"
+	tmpl := New("master")
+	tree, err := parse.Parse("master", master, "", "", nil)
+	if err != nil {
+		t.Fatalf("unexpected parse err: %v", err)
+	}
+	masterTree := tree["master"]
+	tmpl.AddParseTree("master", masterTree) // used to panic
+}
+
 func TestRedefinition(t *testing.T) {
 	var tmpl *Template
 	var err error
diff --git a/src/pkg/text/template/template.go b/src/pkg/text/template/template.go
index a2b9062ad..249d0cbfb 100644
--- a/src/pkg/text/template/template.go
+++ b/src/pkg/text/template/template.go
@@ -105,7 +105,7 @@ func (t *Template) copy(c *common) *Template {
 // AddParseTree creates a new template with the name and parse tree
 // and associates it with t.
 func (t *Template) AddParseTree(name string, tree *parse.Tree) (*Template, error) {
-	if t.tmpl[name] != nil {
+	if t.common != nil && t.tmpl[name] != nil {
 		return nil, fmt.Errorf("template: redefinition of template %q", name)
 	}
 	nt := t.New(name)