[dev.cc] cmd/internal/gc: reconvert to pick up bug fixes

Convert using rsc.io/c2go rev a97ff47.

Notable changes:
- %% in format string now correctly preserved
- reintroduce "signal handler" to hide internal faults
  after errors have been printed

Change-Id: Ic5a94f1c3a8015a9054e21c8969b52d964a36c45
Reviewed-on: https://go-review.googlesource.com/5633Reviewed-by: Rob Pike <r@golang.org>

src/cmd/internal/gc/const.go

@@ -788,7 +788,7 @@ func evconst(n *Node) {
 	// which is not quite an ideal error.
 	case OMOD<<16 | CTFLT:
 		if n.Diag == 0 {
-			Yyerror("illegal constant expression: floating-point % operation")
+			Yyerror("illegal constant expression: floating-point %% operation")
 			n.Diag = 1
 		}
 

src/cmd/internal/gc/fmt.go

@@ -1899,7 +1899,7 @@ func Nconv(n *Node, flag int) string {
 		dumpdepth--
 
 	default:
-		Fatal("unhandled %N mode")
+		Fatal("unhandled %%N mode")
 	}
 
 	flag = sf

src/cmd/internal/gc/go.y

@@ -449,7 +449,7 @@ simple_stmt:
 			if $1.Next != nil {
 				Yyerror("argument count mismatch: %d = %d", count($1), 1);
 			} else if ($1.N.Op != ONAME && $1.N.Op != OTYPE && $1.N.Op != ONONAME) || isblank($1.N) {
-				Yyerror("invalid variable name %nil in type switch", $1.N);
+				Yyerror("invalid variable name %s in type switch", Nconv($1.N, 0));
 			} else {
 				$$.Left = dclname($1.N.Sym);
 			}  // it's a colas, so must not re-use an oldname.

src/cmd/internal/gc/lex.go

@@ -75,15 +75,16 @@ func usage() {
 	Exit(2)
 }
 
-func fault(s int) {
-	// If we've already complained about things
-	// in the program, don't bother complaining
-	// about the seg fault too; let the user clean up
-	// the code and try again.
+func hidePanic() {
 	if nsavederrors+nerrors > 0 {
-		errorexit()
+		// If we've already complained about things
+		// in the program, don't bother complaining
+		// about a panic too; let the user clean up
+		// the code and try again.
+		if err := recover(); err != nil {
+			errorexit()
+		}
 	}
-	Fatal("fault")
 }
 
 func doversion() {
@@ -95,7 +96,7 @@ func doversion() {
 		p = ""
 	}
 	sep = ""
-	if p[0] != 0 {
+	if p != "" {
 		sep = " "
 	}
 	fmt.Printf("%cg version %s%s%s\n", Thearch.Thechar, obj.Getgoversion(), sep, p)
@@ -103,6 +104,7 @@ func doversion() {
 }
 
 func Main() {
+	defer hidePanic()
 	var l *NodeList
 	var p string
 
@@ -1834,8 +1836,14 @@ func (yy) Error(msg string) {
 	Yyerror("%s", msg)
 }
 
+var theparser yyParser
+var parsing bool
+
 func yyparse() {
-	yyParse(yy{})
+	theparser = yyNewParser()
+	parsing = true
+	theparser.Parse(yy{})
+	parsing = false
 }
 
 func yylex(yylval *yySymType) int32 {

src/cmd/internal/gc/mparith1.go

@@ -638,7 +638,7 @@ func Fconv(fvp *Mpflt, flag int) string {
 			if d >= 0 && (flag&obj.FmtSign != 0 /*untyped*/) {
 				fp += fmt.Sprintf("+")
 			}
-			fp += fmt.Sprintf("%g", d)
+			fp += fmt.Sprintf("%.6g", d)
 			return fp
 		}
 

src/cmd/internal/gc/subr.go

@@ -36,7 +36,8 @@ func errorexit() {
 }
 
 func parserline() int {
-	if yychar_subr != 0 && yychar_subr != -2 { // parser has one symbol lookahead
+	if parsing && theparser.Lookahead() > 0 {
+		// parser has one symbol lookahead
 		return int(prevlineno)
 	}
 	return int(lineno)
@@ -135,6 +136,9 @@ var yyerror_lastsyntax int
 func Yyerror(fmt_ string, args ...interface{}) {
 	var i int
 
+	if fmt_ == "%s" && len(args) == 1 && args[0] == "syntax error" {
+		nsyntaxerrors++
+	}
 	if strings.HasPrefix(fmt_, "syntax error") {
 		nsyntaxerrors++
 

src/cmd/internal/gc/y.go

@@ -1467,7 +1467,7 @@ yydefault:
 				if yyDollar[1].list.Next != nil {
 					Yyerror("argument count mismatch: %d = %d", count(yyDollar[1].list), 1)
 				} else if (yyDollar[1].list.N.Op != ONAME && yyDollar[1].list.N.Op != OTYPE && yyDollar[1].list.N.Op != ONONAME) || isblank(yyDollar[1].list.N) {
-					Yyerror("invalid variable name %nil in type switch", yyDollar[1].list.N)
+					Yyerror("invalid variable name %s in type switch", Nconv(yyDollar[1].list.N, 0))
 				} else {
 					yyVAL.node.Left = dclname(yyDollar[1].list.N.Sym)
 				} // it's a colas, so must not re-use an oldname.