diff --git a/src/cmd/cgo/ast.go b/src/cmd/cgo/ast.go
index f5d884eafd..46e33686d2 100644
--- a/src/cmd/cgo/ast.go
+++ b/src/cmd/cgo/ast.go
@@ -30,7 +30,7 @@ func parse(name string, flags uint) *ast.File {
 			}
 			os.Exit(2)
 		}
-		fatal("parsing %s: %s", name, err)
+		fatalf("parsing %s: %s", name, err)
 	}
 	return ast1
 }
diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
index 11810db53f..ae5ca2c7da 100644
--- a/src/cmd/cgo/gcc.go
+++ b/src/cmd/cgo/gcc.go
@@ -79,7 +79,7 @@ NextLine:
 		l = strings.TrimSpace(l[4:])
 		fields := strings.Split(l, ":", 2)
 		if len(fields) != 2 {
-			fatal("%s: bad #cgo line: %s", srcfile, line)
+			fatalf("%s: bad #cgo line: %s", srcfile, line)
 		}
 
 		var k string
@@ -97,17 +97,17 @@ NextLine:
 				continue NextLine
 			}
 		default:
-			fatal("%s: bad #cgo option: %s", srcfile, fields[0])
+			fatalf("%s: bad #cgo option: %s", srcfile, fields[0])
 		}
 
 		if k != "CFLAGS" && k != "LDFLAGS" {
-			fatal("%s: unsupported #cgo option %s", srcfile, k)
+			fatalf("%s: unsupported #cgo option %s", srcfile, k)
 		}
 
 		v := strings.TrimSpace(fields[1])
 		args, err := splitQuoted(v)
 		if err != nil {
-			fatal("%s: bad #cgo option %s: %s", srcfile, k, err.String())
+			fatalf("%s: bad #cgo option %s: %s", srcfile, k, err.String())
 		}
 		if oldv, ok := p.CgoFlags[k]; ok {
 			p.CgoFlags[k] = oldv + " " + v
@@ -317,7 +317,7 @@ func (p *Package) guessKinds(f *File) []*Name {
 	b.WriteString("}\n")
 	stderr := p.gccErrors(b.Bytes())
 	if stderr == "" {
-		fatal("gcc produced no output\non input:\n%s", b.Bytes())
+		fatalf("gcc produced no output\non input:\n%s", b.Bytes())
 	}
 
 	names := make([]*Name, len(toSniff))
@@ -383,7 +383,7 @@ func (p *Package) guessKinds(f *File) []*Name {
 		error(token.NoPos, "could not determine kind of name for C.%s", n.Go)
 	}
 	if nerrors > 0 {
-		fatal("unresolved names")
+		fatalf("unresolved names")
 	}
 	return needType
 }
@@ -422,7 +422,7 @@ func (p *Package) loadDWARF(f *File, names []*Name) {
 	for {
 		e, err := r.Next()
 		if err != nil {
-			fatal("reading DWARF entry: %s", err)
+			fatalf("reading DWARF entry: %s", err)
 		}
 		if e == nil {
 			break
@@ -433,7 +433,7 @@ func (p *Package) loadDWARF(f *File, names []*Name) {
 			for {
 				e, err := r.Next()
 				if err != nil {
-					fatal("reading DWARF entry: %s", err)
+					fatalf("reading DWARF entry: %s", err)
 				}
 				if e.Tag == 0 {
 					break
@@ -452,27 +452,27 @@ func (p *Package) loadDWARF(f *File, names []*Name) {
 			name, _ := e.Val(dwarf.AttrName).(string)
 			typOff, _ := e.Val(dwarf.AttrType).(dwarf.Offset)
 			if name == "" || typOff == 0 {
-				fatal("malformed DWARF TagVariable entry")
+				fatalf("malformed DWARF TagVariable entry")
 			}
 			if !strings.HasPrefix(name, "__cgo__") {
 				break
 			}
 			typ, err := d.Type(typOff)
 			if err != nil {
-				fatal("loading DWARF type: %s", err)
+				fatalf("loading DWARF type: %s", err)
 			}
 			t, ok := typ.(*dwarf.PtrType)
 			if !ok || t == nil {
-				fatal("internal error: %s has non-pointer type", name)
+				fatalf("internal error: %s has non-pointer type", name)
 			}
 			i, err := strconv.Atoi(name[7:])
 			if err != nil {
-				fatal("malformed __cgo__ name: %s", name)
+				fatalf("malformed __cgo__ name: %s", name)
 			}
 			if enums[i] != 0 {
 				t, err := d.Type(enums[i])
 				if err != nil {
-					fatal("loading DWARF type: %s", err)
+					fatalf("loading DWARF type: %s", err)
 				}
 				types[i] = t
 			} else {
@@ -632,14 +632,14 @@ func (p *Package) gccDebug(stdin []byte) *dwarf.Data {
 	if f, err = elf.Open(gccTmp); err != nil {
 		if f, err = macho.Open(gccTmp); err != nil {
 			if f, err = pe.Open(gccTmp); err != nil {
-				fatal("cannot parse gcc output %s as ELF or Mach-O or PE object", gccTmp)
+				fatalf("cannot parse gcc output %s as ELF or Mach-O or PE object", gccTmp)
 			}
 		}
 	}
 
 	d, err := f.DWARF()
 	if err != nil {
-		fatal("cannot load DWARF debug information from %s: %s", gccTmp, err)
+		fatalf("cannot load DWARF debug information from %s: %s", gccTmp, err)
 	}
 	return d
 }
@@ -807,7 +807,7 @@ func (tr *TypeRepr) Set(repr string, fargs ...interface{}) {
 func (c *typeConv) Type(dtype dwarf.Type) *Type {
 	if t, ok := c.m[dtype]; ok {
 		if t.Go == nil {
-			fatal("type conversion loop at %s", dtype)
+			fatalf("type conversion loop at %s", dtype)
 		}
 		return t
 	}
@@ -830,11 +830,11 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
 
 	switch dt := dtype.(type) {
 	default:
-		fatal("unexpected type: %s", dtype)
+		fatalf("unexpected type: %s", dtype)
 
 	case *dwarf.AddrType:
 		if t.Size != c.ptrSize {
-			fatal("unexpected: %d-byte address type - %s", t.Size, dtype)
+			fatalf("unexpected: %d-byte address type - %s", t.Size, dtype)
 		}
 		t.Go = c.uintptr
 		t.Align = t.Size
@@ -860,7 +860,7 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
 
 	case *dwarf.CharType:
 		if t.Size != 1 {
-			fatal("unexpected: %d-byte char type - %s", t.Size, dtype)
+			fatalf("unexpected: %d-byte char type - %s", t.Size, dtype)
 		}
 		t.Go = c.int8
 		t.Align = 1
@@ -880,7 +880,7 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
 		}
 		switch t.Size + int64(signed) {
 		default:
-			fatal("unexpected: %d-byte enum type - %s", t.Size, dtype)
+			fatalf("unexpected: %d-byte enum type - %s", t.Size, dtype)
 		case 1:
 			t.Go = c.uint8
 		case 2:
@@ -902,7 +902,7 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
 	case *dwarf.FloatType:
 		switch t.Size {
 		default:
-			fatal("unexpected: %d-byte float type - %s", t.Size, dtype)
+			fatalf("unexpected: %d-byte float type - %s", t.Size, dtype)
 		case 4:
 			t.Go = c.float32
 		case 8:
@@ -915,7 +915,7 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
 	case *dwarf.ComplexType:
 		switch t.Size {
 		default:
-			fatal("unexpected: %d-byte complex type - %s", t.Size, dtype)
+			fatalf("unexpected: %d-byte complex type - %s", t.Size, dtype)
 		case 8:
 			t.Go = c.complex64
 		case 16:
@@ -933,11 +933,11 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
 
 	case *dwarf.IntType:
 		if dt.BitSize > 0 {
-			fatal("unexpected: %d-bit int type - %s", dt.BitSize, dtype)
+			fatalf("unexpected: %d-bit int type - %s", dt.BitSize, dtype)
 		}
 		switch t.Size {
 		default:
-			fatal("unexpected: %d-byte int type - %s", t.Size, dtype)
+			fatalf("unexpected: %d-byte int type - %s", t.Size, dtype)
 		case 1:
 			t.Go = c.int8
 		case 2:
@@ -1022,18 +1022,18 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
 
 	case *dwarf.UcharType:
 		if t.Size != 1 {
-			fatal("unexpected: %d-byte uchar type - %s", t.Size, dtype)
+			fatalf("unexpected: %d-byte uchar type - %s", t.Size, dtype)
 		}
 		t.Go = c.uint8
 		t.Align = 1
 
 	case *dwarf.UintType:
 		if dt.BitSize > 0 {
-			fatal("unexpected: %d-bit uint type - %s", dt.BitSize, dtype)
+			fatalf("unexpected: %d-bit uint type - %s", dt.BitSize, dtype)
 		}
 		switch t.Size {
 		default:
-			fatal("unexpected: %d-byte uint type - %s", t.Size, dtype)
+			fatalf("unexpected: %d-byte uint type - %s", t.Size, dtype)
 		case 1:
 			t.Go = c.uint8
 		case 2:
@@ -1067,7 +1067,7 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
 	}
 
 	if t.C.Empty() {
-		fatal("internal error: did not create C name for %s", dtype)
+		fatalf("internal error: did not create C name for %s", dtype)
 	}
 
 	return t
@@ -1229,7 +1229,7 @@ func (c *typeConv) Struct(dt *dwarf.StructType) (expr *ast.StructType, csyntax s
 		off = dt.ByteSize
 	}
 	if off != dt.ByteSize {
-		fatal("struct size calculation error")
+		fatalf("struct size calculation error")
 	}
 	buf.WriteString("}")
 	csyntax = buf.String()
diff --git a/src/cmd/cgo/main.go b/src/cmd/cgo/main.go
index 584e547087..00ffc45063 100644
--- a/src/cmd/cgo/main.go
+++ b/src/cmd/cgo/main.go
@@ -177,11 +177,11 @@ func main() {
 
 	arch := os.Getenv("GOARCH")
 	if arch == "" {
-		fatal("$GOARCH is not set")
+		fatalf("$GOARCH is not set")
 	}
 	ptrSize := ptrSizeMap[arch]
 	if ptrSize == 0 {
-		fatal("unknown $GOARCH %q", arch)
+		fatalf("unknown $GOARCH %q", arch)
 	}
 
 	// Clear locale variables so gcc emits English errors [sic].
@@ -205,7 +205,7 @@ func main() {
 	for _, input := range goFiles {
 		f, err := os.Open(input)
 		if err != nil {
-			fatal("%s", err)
+			fatalf("%s", err)
 		}
 		io.Copy(h, f)
 		f.Close()
diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go
index 4a5fa6a73f..abf8c8bc20 100644
--- a/src/cmd/cgo/out.go
+++ b/src/cmd/cgo/out.go
@@ -105,7 +105,7 @@ func dynimport(obj string) (syms, imports []string) {
 	if f, err1 = elf.Open(obj); err1 != nil {
 		if f, err2 = pe.Open(obj); err2 != nil {
 			if f, err3 = macho.Open(obj); err3 != nil {
-				fatal("cannot parse %s as ELF (%v) or PE (%v) or Mach-O (%v)", obj, err1, err2, err3)
+				fatalf("cannot parse %s as ELF (%v) or PE (%v) or Mach-O (%v)", obj, err1, err2, err3)
 			}
 			isMacho = true
 		}
@@ -114,7 +114,7 @@ func dynimport(obj string) (syms, imports []string) {
 	var err os.Error
 	syms, err = f.ImportedSymbols()
 	if err != nil {
-		fatal("cannot load dynamic symbols: %v", err)
+		fatalf("cannot load dynamic symbols: %v", err)
 	}
 	if isMacho {
 		// remove leading _ that OS X insists on
@@ -127,7 +127,7 @@ func dynimport(obj string) (syms, imports []string) {
 
 	imports, err = f.ImportedLibraries()
 	if err != nil {
-		fatal("cannot load dynamic imports: %v", err)
+		fatalf("cannot load dynamic imports: %v", err)
 	}
 
 	return
diff --git a/src/cmd/cgo/util.go b/src/cmd/cgo/util.go
index b4f56e31e0..1ca24103e3 100644
--- a/src/cmd/cgo/util.go
+++ b/src/cmd/cgo/util.go
@@ -18,23 +18,23 @@ import (
 func run(stdin []byte, argv []string) (stdout, stderr []byte, ok bool) {
 	cmd, err := exec.LookPath(argv[0])
 	if err != nil {
-		fatal("exec %s: %s", argv[0], err)
+		fatalf("exec %s: %s", argv[0], err)
 	}
 	r0, w0, err := os.Pipe()
 	if err != nil {
-		fatal("%s", err)
+		fatalf("%s", err)
 	}
 	r1, w1, err := os.Pipe()
 	if err != nil {
-		fatal("%s", err)
+		fatalf("%s", err)
 	}
 	r2, w2, err := os.Pipe()
 	if err != nil {
-		fatal("%s", err)
+		fatalf("%s", err)
 	}
 	p, err := os.StartProcess(cmd, argv, &os.ProcAttr{Files: []*os.File{r0, w1, w2}})
 	if err != nil {
-		fatal("%s", err)
+		fatalf("%s", err)
 	}
 	defer p.Release()
 	r0.Close()
@@ -58,14 +58,14 @@ func run(stdin []byte, argv []string) (stdout, stderr []byte, ok bool) {
 
 	w, err := p.Wait(0)
 	if err != nil {
-		fatal("%s", err)
+		fatalf("%s", err)
 	}
 	ok = w.Exited() && w.ExitStatus() == 0
 	return
 }
 
 // Die with an error message.
-func fatal(msg string, args ...interface{}) {
+func fatalf(msg string, args ...interface{}) {
 	fmt.Fprintf(os.Stderr, msg+"\n", args...)
 	os.Exit(2)
 }
@@ -97,7 +97,7 @@ func isName(s string) bool {
 func creat(name string) *os.File {
 	f, err := os.Create(name)
 	if err != nil {
-		fatal("%s", err)
+		fatalf("%s", err)
 	}
 	return f
 }
diff --git a/src/cmd/govet/govet.go b/src/cmd/govet/govet.go
index c112844162..b811c61a2d 100644
--- a/src/cmd/govet/govet.go
+++ b/src/cmd/govet/govet.go
@@ -63,6 +63,7 @@ func main() {
 				}
 				name = name[:colon]
 			}
+			name = strings.ToLower(name)
 			if name[len(name)-1] == 'f' {
 				printfList[name] = skip
 			} else {
@@ -205,35 +206,38 @@ func (f *File) checkCallExpr(call *ast.CallExpr) {
 }
 
 // printfList records the formatted-print functions. The value is the location
-// of the format parameter.
+// of the format parameter. Names are lower-cased so the lookup is
+// case insensitive.
 var printfList = map[string]int{
-	"Errorf":  0,
-	"Fatalf":  0,
-	"Fprintf": 1,
-	"Panicf":  0,
-	"Printf":  0,
-	"Sprintf": 0,
+	"errorf":  0,
+	"fatalf":  0,
+	"fprintf": 1,
+	"panicf":  0,
+	"printf":  0,
+	"sprintf": 0,
 }
 
 // printList records the unformatted-print functions. The value is the location
-// of the first parameter to be printed.
+// of the first parameter to be printed.  Names are lower-cased so the lookup is
+// case insensitive.
 var printList = map[string]int{
-	"Error":  0,
-	"Fatal":  0,
-	"Fprint": 1, "Fprintln": 1,
-	"Panic": 0, "Panicln": 0,
-	"Print": 0, "Println": 0,
-	"Sprint": 0, "Sprintln": 0,
+	"error":  0,
+	"fatal":  0,
+	"fprint": 1, "fprintln": 1,
+	"panic": 0, "panicln": 0,
+	"print": 0, "println": 0,
+	"sprint": 0, "sprintln": 0,
 }
 
 // checkCall triggers the print-specific checks if the call invokes a print function.
-func (f *File) checkCall(call *ast.CallExpr, name string) {
+func (f *File) checkCall(call *ast.CallExpr, Name string) {
+	name := strings.ToLower(Name)
 	if skip, ok := printfList[name]; ok {
-		f.checkPrintf(call, name, skip)
+		f.checkPrintf(call, Name, skip)
 		return
 	}
 	if skip, ok := printList[name]; ok {
-		f.checkPrint(call, name, skip)
+		f.checkPrint(call, Name, skip)
 		return
 	}
 }
@@ -362,8 +366,14 @@ func BadFunctionUsedInTests() {
 	fmt.Printf("%s%%%d", "hi", 3)      // right # percents
 	fmt.Printf("%.*d", 3, 3)           // right # percents, with a *
 	fmt.Printf("%.*d", 3, 3, 3)        // wrong # percents, with a *
+	printf("now is the time", "buddy") // no %s
 	Printf("now is the time", "buddy") // no %s
 	f := new(File)
 	f.Warn(0, "%s", "hello", 3)  // % in call to added function
 	f.Warnf(0, "%s", "hello", 3) // wrong # %s in call to added function
 }
+
+// printf is used by the test.
+func printf(format string, args ...interface{}) {
+	panic("don't call - testing only")
+}
diff --git a/src/cmd/goyacc/goyacc.go b/src/cmd/goyacc/goyacc.go
index 2a1ed46fc7..220c994920 100644
--- a/src/cmd/goyacc/goyacc.go
+++ b/src/cmd/goyacc/goyacc.go
@@ -382,7 +382,7 @@ outer:
 	for {
 		switch t {
 		default:
-			error("syntax error tok=%v", t-PRIVATE)
+			errorf("syntax error tok=%v", t-PRIVATE)
 
 		case MARK, ENDFILE:
 			break outer
@@ -392,14 +392,14 @@ outer:
 		case START:
 			t = gettok()
 			if t != IDENTIFIER {
-				error("bad %%start construction")
+				errorf("bad %%start construction")
 			}
 			start = chfind(1, tokname)
 
 		case TYPEDEF:
 			t = gettok()
 			if t != TYPENAME {
-				error("bad syntax in %%type")
+				errorf("bad syntax in %%type")
 			}
 			ty = numbval
 			for {
@@ -410,7 +410,7 @@ outer:
 					if t < NTBASE {
 						j = TYPE(toklev[t])
 						if j != 0 && j != ty {
-							error("type redeclaration of token ",
+							errorf("type redeclaration of token ",
 								tokset[t].name)
 						} else {
 							toklev[t] = SETTYPE(toklev[t], ty)
@@ -418,7 +418,7 @@ outer:
 					} else {
 						j = nontrst[t-NTBASE].value
 						if j != 0 && j != ty {
-							error("type redeclaration of nonterminal %v",
+							errorf("type redeclaration of nonterminal %v",
 								nontrst[t-NTBASE].name)
 						} else {
 							nontrst[t-NTBASE].value = ty
@@ -464,18 +464,18 @@ outer:
 				case IDENTIFIER:
 					j = chfind(0, tokname)
 					if j >= NTBASE {
-						error("%v defined earlier as nonterminal", tokname)
+						errorf("%v defined earlier as nonterminal", tokname)
 					}
 					if lev != 0 {
 						if ASSOC(toklev[j]) != 0 {
-							error("redeclaration of precedence of %v", tokname)
+							errorf("redeclaration of precedence of %v", tokname)
 						}
 						toklev[j] = SETASC(toklev[j], lev)
 						toklev[j] = SETPLEV(toklev[j], i)
 					}
 					if ty != 0 {
 						if TYPE(toklev[j]) != 0 {
-							error("redeclaration of type of %v", tokname)
+							errorf("redeclaration of type of %v", tokname)
 						}
 						toklev[j] = SETTYPE(toklev[j], ty)
 					}
@@ -498,7 +498,7 @@ outer:
 	}
 
 	if t == ENDFILE {
-		error("unexpected EOF before %%")
+		errorf("unexpected EOF before %%")
 	}
 
 	// put out non-literal terminals
@@ -533,7 +533,7 @@ outer:
 	curprod := make([]int, RULEINC)
 	t = gettok()
 	if t != IDENTCOLON {
-		error("bad syntax on first rule")
+		errorf("bad syntax on first rule")
 	}
 
 	if start == 0 {
@@ -557,11 +557,11 @@ outer:
 		} else if t == IDENTCOLON {
 			curprod[mem] = chfind(1, tokname)
 			if curprod[mem] < NTBASE {
-				error("token illegal on LHS of grammar rule")
+				errorf("token illegal on LHS of grammar rule")
 			}
 			mem++
 		} else {
-			error("illegal rule: missing semicolon or | ?")
+			errorf("illegal rule: missing semicolon or | ?")
 		}
 
 		// read rule body
@@ -582,11 +582,11 @@ outer:
 			}
 			if t == PREC {
 				if gettok() != IDENTIFIER {
-					error("illegal %%prec syntax")
+					errorf("illegal %%prec syntax")
 				}
 				j = chfind(2, tokname)
 				if j >= NTBASE {
-					error("nonterminal " + nontrst[j-NTBASE].name + " illegal after %%prec")
+					errorf("nonterminal " + nontrst[j-NTBASE].name + " illegal after %%prec")
 				}
 				levprd[nprod] = toklev[j]
 				t = gettok()
@@ -642,7 +642,7 @@ outer:
 			// no explicit action, LHS has value
 			tempty := curprod[1]
 			if tempty < 0 {
-				error("must return a value, since LHS has a type")
+				errorf("must return a value, since LHS has a type")
 			}
 			if tempty >= NTBASE {
 				tempty = nontrst[tempty-NTBASE].value
@@ -650,7 +650,7 @@ outer:
 				tempty = TYPE(toklev[tempty])
 			}
 			if tempty != nontrst[curprod[0]-NTBASE].value {
-				error("default action causes potential type clash")
+				errorf("default action causes potential type clash")
 			}
 			fmt.Fprintf(fcode, "\ncase %v:", nprod)
 			fmt.Fprintf(fcode, "\n\t%sVAL.%v = %sS[%spt-0].%v;",
@@ -773,7 +773,7 @@ func defin(nt int, s string) int {
 			case 'v':
 				val = '\v'
 			default:
-				error("invalid escape %v", s[1:3])
+				errorf("invalid escape %v", s[1:3])
 			}
 		} else if s[2] == 'u' && len(s) == 2+1+4 { // \unnnn sequence
 			val = 0
@@ -788,16 +788,16 @@ func defin(nt int, s string) int {
 				case c >= 'A' && c <= 'F':
 					c -= 'A' - 10
 				default:
-					error("illegal \\unnnn construction")
+					errorf("illegal \\unnnn construction")
 				}
 				val = val*16 + c
 				s = s[1:]
 			}
 			if val == 0 {
-				error("'\\u0000' is illegal")
+				errorf("'\\u0000' is illegal")
 			}
 		} else {
-			error("unknown escape")
+			errorf("unknown escape")
 		}
 	} else {
 		val = extval
@@ -855,7 +855,7 @@ func gettok() int {
 		}
 
 		if c != '>' {
-			error("unterminated < ... > clause")
+			errorf("unterminated < ... > clause")
 		}
 
 		for i = 1; i <= ntypes; i++ {
@@ -881,7 +881,7 @@ func gettok() int {
 		for {
 			c = getrune(finput)
 			if c == '\n' || c == EOF {
-				error("illegal or missing ' or \"")
+				errorf("illegal or missing ' or \"")
 			}
 			if c == '\\' {
 				tokname += string('\\')
@@ -926,7 +926,7 @@ func gettok() int {
 				return resrv[c].value
 			}
 		}
-		error("invalid escape, or illegal reserved word: %v", tokname)
+		errorf("invalid escape, or illegal reserved word: %v", tokname)
 
 	case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
 		numbval = c - '0'
@@ -1004,7 +1004,7 @@ func fdtype(t int) int {
 		s = tokset[t].name
 	}
 	if v <= 0 {
-		error("must specify type for %v", s)
+		errorf("must specify type for %v", s)
 	}
 	return v
 }
@@ -1026,7 +1026,7 @@ func chfind(t int, s string) int {
 
 	// cannot find name
 	if t > 1 {
-		error("%v should have been defined earlier", s)
+		errorf("%v should have been defined earlier", s)
 	}
 	return defin(t, s)
 }
@@ -1047,7 +1047,7 @@ out:
 	for {
 		c := getrune(finput)
 		if c == EOF {
-			error("EOF encountered while processing %%union")
+			errorf("EOF encountered while processing %%union")
 		}
 		ftable.WriteRune(c)
 		switch c {
@@ -1097,7 +1097,7 @@ func cpycode() {
 		c = getrune(finput)
 	}
 	lineno = lno
-	error("eof before %%}")
+	errorf("eof before %%}")
 }
 
 //
@@ -1115,11 +1115,11 @@ func skipcom() int {
 			}
 			c = getrune(finput)
 		}
-		error("EOF inside comment")
+		errorf("EOF inside comment")
 		return 0
 	}
 	if c != '*' {
-		error("illegal comment")
+		errorf("illegal comment")
 	}
 
 	nl := 0 // lines skipped
@@ -1196,7 +1196,7 @@ loop:
 			if c == '<' {
 				ungetrune(finput, c)
 				if gettok() != TYPENAME {
-					error("bad syntax on $<ident> clause")
+					errorf("bad syntax on $<ident> clause")
 				}
 				tok = numbval
 				c = getrune(finput)
@@ -1226,13 +1226,13 @@ loop:
 				ungetrune(finput, c)
 				j = j * s
 				if j >= max {
-					error("Illegal use of $%v", j)
+					errorf("Illegal use of $%v", j)
 				}
 			} else if isword(c) || c == '_' || c == '.' {
 				// look for $name
 				ungetrune(finput, c)
 				if gettok() != IDENTIFIER {
-					error("$ must be followed by an identifier")
+					errorf("$ must be followed by an identifier")
 				}
 				tokn := chfind(2, tokname)
 				fnd := -1
@@ -1240,7 +1240,7 @@ loop:
 				if c != '@' {
 					ungetrune(finput, c)
 				} else if gettok() != NUMBER {
-					error("@ must be followed by number")
+					errorf("@ must be followed by number")
 				} else {
 					fnd = numbval
 				}
@@ -1253,7 +1253,7 @@ loop:
 					}
 				}
 				if j >= max {
-					error("$name or $name@number not found")
+					errorf("$name or $name@number not found")
 				}
 			} else {
 				fcode.WriteRune('$')
@@ -1268,7 +1268,7 @@ loop:
 			// put out the proper tag
 			if ntypes != 0 {
 				if j <= 0 && tok < 0 {
-					error("must specify type of $%v", j)
+					errorf("must specify type of $%v", j)
 				}
 				if tok < 0 {
 					tok = fdtype(curprod[j])
@@ -1315,7 +1315,7 @@ loop:
 				fcode.WriteRune(c)
 				c = getrune(finput)
 			}
-			error("EOF inside comment")
+			errorf("EOF inside comment")
 
 		case '\'', '"':
 			// character string or constant
@@ -1333,16 +1333,16 @@ loop:
 					break swt
 				}
 				if c == '\n' {
-					error("newline in string or char const")
+					errorf("newline in string or char const")
 				}
 				fcode.WriteRune(c)
 				c = getrune(finput)
 			}
-			error("EOF in string or character constant")
+			errorf("EOF in string or character constant")
 
 		case EOF:
 			lineno = lno
-			error("action does not terminate")
+			errorf("action does not terminate")
 
 		case '\n':
 			lineno++
@@ -1356,14 +1356,14 @@ func openup() {
 	infile = flag.Arg(0)
 	finput = open(infile)
 	if finput == nil {
-		error("cannot open %v", infile)
+		errorf("cannot open %v", infile)
 	}
 
 	foutput = nil
 	if vflag != "" {
 		foutput = create(vflag)
 		if foutput == nil {
-			error("can't create file %v", vflag)
+			errorf("can't create file %v", vflag)
 		}
 	}
 
@@ -1373,7 +1373,7 @@ func openup() {
 	}
 	ftable = create(oflag)
 	if ftable == nil {
-		error("can't create file %v", oflag)
+		errorf("can't create file %v", oflag)
 	}
 
 }
@@ -1433,7 +1433,7 @@ func cpres() {
 			}
 		}
 		if n == 0 {
-			error("nonterminal %v not defined", nontrst[i].name)
+			errorf("nonterminal %v not defined", nontrst[i].name)
 			continue
 		}
 		pres[i] = make([][]int, n)
@@ -1506,7 +1506,7 @@ more:
 		}
 		if pempty[i] != OK {
 			fatfl = 0
-			error("nonterminal " + nontrst[i].name + " never derives any token string")
+			errorf("nonterminal " + nontrst[i].name + " never derives any token string")
 		}
 	}
 
@@ -1921,11 +1921,11 @@ look:
 	// state is new
 	zznewstate++
 	if nolook != 0 {
-		error("yacc state/nolook error")
+		errorf("yacc state/nolook error")
 	}
 	pstate[nstate+2] = p2
 	if nstate+1 >= NSTATES {
-		error("too many states")
+		errorf("too many states")
 	}
 	if c >= NTBASE {
 		mstates[nstate] = ntstates[c-NTBASE]
@@ -2061,7 +2061,7 @@ nextk:
 		}
 		return off + rr
 	}
-	error("no space in action table")
+	errorf("no space in action table")
 	return 0
 }
 
@@ -2623,7 +2623,7 @@ nextgp:
 			if s > maxa {
 				maxa = s
 				if maxa >= ACTSIZE {
-					error("a array overflow")
+					errorf("a array overflow")
 				}
 			}
 			if amem[s] != 0 {
@@ -2646,7 +2646,7 @@ nextgp:
 		}
 		return
 	}
-	error("cannot place goto %v\n", i)
+	errorf("cannot place goto %v\n", i)
 }
 
 func stin(i int) {
@@ -2705,7 +2705,7 @@ nextn:
 				maxa = s
 			}
 			if amem[s] != 0 && amem[s] != q[r+1] {
-				error("clobber of a array, pos'n %v, by %v", s, q[r+1])
+				errorf("clobber of a array, pos'n %v, by %v", s, q[r+1])
 			}
 			amem[s] = q[r+1]
 		}
@@ -2715,7 +2715,7 @@ nextn:
 		}
 		return
 	}
-	error("Error; failure to place state %v", i)
+	errorf("Error; failure to place state %v", i)
 }
 
 //
@@ -3014,7 +3014,7 @@ func getrune(f *bufio.Reader) int {
 		return EOF
 	}
 	if err != nil {
-		error("read error: %v", err)
+		errorf("read error: %v", err)
 	}
 	//fmt.Printf("rune = %v n=%v\n", string(c), n);
 	return c
@@ -3038,7 +3038,7 @@ func write(f *bufio.Writer, b []byte, n int) int {
 func open(s string) *bufio.Reader {
 	fi, err := os.Open(s)
 	if err != nil {
-		error("error opening %v: %v", s, err)
+		errorf("error opening %v: %v", s, err)
 	}
 	//fmt.Printf("open %v\n", s);
 	return bufio.NewReader(fi)
@@ -3047,7 +3047,7 @@ func open(s string) *bufio.Reader {
 func create(s string) *bufio.Writer {
 	fo, err := os.Create(s)
 	if err != nil {
-		error("error creating %v: %v", s, err)
+		errorf("error creating %v: %v", s, err)
 	}
 	//fmt.Printf("create %v mode %v\n", s);
 	return bufio.NewWriter(fo)
@@ -3056,7 +3056,7 @@ func create(s string) *bufio.Writer {
 //
 // write out error comment
 //
-func error(s string, v ...interface{}) {
+func errorf(s string, v ...interface{}) {
 	nerrors++
 	fmt.Fprintf(stderr, s, v...)
 	fmt.Fprintf(stderr, ": %v:%v\n", infile, lineno)
diff --git a/src/cmd/goyacc/units.y b/src/cmd/goyacc/units.y
index c1c1409c76..06ce11693c 100644
--- a/src/cmd/goyacc/units.y
+++ b/src/cmd/goyacc/units.y
@@ -90,7 +90,7 @@ prog:
 		$2.node = $3;
 		$2.node.dim[0] = 1;
 		if f != 0 {
-			Error("redefinition of %v", $2.name);
+			Errorf("redefinition of %v", $2.name);
 		} else
 		if vflag {
 			fmt.Printf("%v\t%v\n", $2.name, &$2.node);
@@ -106,7 +106,7 @@ prog:
 			}
 		}
 		if i >= Ndim {
-			Error("too many dimensions");
+			Errorf("too many dimensions");
 			i = Ndim-1;
 		}
 		fund[i] = $2;
@@ -116,7 +116,7 @@ prog:
 		$2.node.dim[0] = 1;
 		$2.node.dim[i] = 1;
 		if f != 0 {
-			Error("redefinition of %v", $2.name);
+			Errorf("redefinition of %v", $2.name);
 		} else
 		if vflag {
 			fmt.Printf("%v\t#\n", $2.name);
@@ -175,7 +175,7 @@ expr2:
 
 		for i=1; i<Ndim; i++ {
 			if $3.dim[i] != 0 {
-				Error("exponent has units");
+				Errorf("exponent has units");
 				$$ = $1;
 				break;
 			}
@@ -183,7 +183,7 @@ expr2:
 		if i >= Ndim {
 			i = int($3.vval);
 			if float64(i) != $3.vval {
-				Error("exponent not integral");
+				Errorf("exponent not integral");
 			}
 			xpn(&$$, &$1, i);
 		}
@@ -200,7 +200,7 @@ expr0:
 	VAR
 	{
 		if $1.node.dim[0] == 0 {
-			Error("undefined %v", $1.name);
+			Errorf("undefined %v", $1.name);
 			$$ = one;
 		} else
 			$$ = $1.node;
@@ -284,7 +284,7 @@ numb:
 }
 
 func (UnitsLex) Error(s string) {
-	Error("syntax error, last name: %v", sym)
+	Errorf("syntax error, last name: %v", sym)
 }
 
 func main() {
@@ -391,7 +391,7 @@ func rdigit(c int) bool {
 	return false
 }
 
-func Error(s string, v ...interface{}) {
+func Errorf(s string, v ...interface{}) {
 	fmt.Printf("%v: %v\n\t", lineno, line)
 	fmt.Printf(s, v...)
 	fmt.Printf("\n")
@@ -411,7 +411,7 @@ func add(c, a, b *Node) {
 		d = a.dim[i]
 		c.dim[i] = d
 		if d != b.dim[i] {
-			Error("add must be like units")
+			Errorf("add must be like units")
 		}
 	}
 	c.vval = fadd(a.vval, b.vval)
@@ -425,7 +425,7 @@ func sub(c, a, b *Node) {
 		d = a.dim[i]
 		c.dim[i] = d
 		if d != b.dim[i] {
-			Error("sub must be like units")
+			Errorf("sub must be like units")
 		}
 	}
 	c.vval = fadd(a.vval, -b.vval)
@@ -711,11 +711,11 @@ func fmul(a, b float64) float64 {
 	}
 
 	if l > Maxe {
-		Error("overflow in multiply")
+		Errorf("overflow in multiply")
 		return 1
 	}
 	if l < -Maxe {
-		Error("underflow in multiply")
+		Errorf("underflow in multiply")
 		return 0
 	}
 	return a * b
@@ -728,7 +728,7 @@ func fdiv(a, b float64) float64 {
 
 	if b <= 0 {
 		if b == 0 {
-			Error("division by zero: %v %v", a, b)
+			Errorf("division by zero: %v %v", a, b)
 			return 1
 		}
 		l = math.Log(-b)
@@ -746,11 +746,11 @@ func fdiv(a, b float64) float64 {
 	}
 
 	if l < -Maxe {
-		Error("overflow in divide")
+		Errorf("overflow in divide")
 		return 1
 	}
 	if l > Maxe {
-		Error("underflow in divide")
+		Errorf("underflow in divide")
 		return 0
 	}
 	return a / b