c2go: more minor bug fixes, notably preserve %% in format strings

Also, reestablish "signal handler".

Author: rsc

Diff for: add/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.

Diff for: c2go.cfg

@@ -1496,7 +1496,7 @@ diff {
 		dumpdepth--
 
 	default:
-		Fatal("unhandled %N mode")
+		Fatal("unhandled %%N mode")
 	}
 
 	flag = sf
@@ -2608,8 +2608,14 @@ diff {
 +	Yyerror("%s", msg)
 +}
 +
++var theparser yyParser
++var parsing bool
++
 +func yyparse() {
-+	yyParse(yy{})
++	theparser = yyNewParser()
++	parsing = true
++	theparser.Parse(yy{})
++	parsing = false
 +}
 +
 -func yylex() int32 {
@@ -3228,3 +3234,56 @@ diff {
 +	gc.Exit(0)
 }
 
+diff {
+	sep = ""
+-	if p[0] != 0 {
++	if p != "" {
+		sep = " "
+	}
+}
+
+diff {
+			if d >= 0 && (flag&obj.FmtSign != 0 /*untyped*/) {
+				fp += fmt.Sprintf("+")
+			}
+-			fp += fmt.Sprintf("%g", d)
++			fp += fmt.Sprintf("%.6g", d)
+			return fp
+}
+
+func parserline() int {
+	if parsing && theparser.Lookahead() > 0 {
+		// parser has one symbol lookahead
+		return int(prevlineno)
+	}
+	return int(lineno)
+}
+
+func fault() {
+	if nsavederrors+nerrors > 0 {
+		// 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()
+		}
+	}
+}
+
+diff {
+-func fault() {
++func hidePanic() {
+}
+diff {
+func Main() {
++	defer hidePanic()
+}
+
+diff {
++	if fmt_ == "%s" && len(args) == 1 && args[0] == "syntax error" {
++		nsyntaxerrors++
++	}
+	if strings.HasPrefix(fmt_, "syntax error") {
+		nsyntaxerrors++
+}

Diff for: printf.go

@@ -153,9 +153,9 @@ func fixPrintFormat(curfn *cc.Decl, fx *cc.Expr, args []*cc.Expr) []*cc.Expr {
 			}
 		})
 	}
-	
+
 	isGC := strings.Contains(fx.Span.Start.File, "cmd/gc")
-	isCompiler := isGC || strings.Contains(fx.Span.Start.File, "cmd/6g") || strings.Contains(fx.Span.Start.File, "cmd/8g") ||  strings.Contains(fx.Span.Start.File, "cmd/5g") ||  strings.Contains(fx.Span.Start.File, "cmd/9g")
+	isCompiler := isGC || strings.Contains(fx.Span.Start.File, "cmd/6g") || strings.Contains(fx.Span.Start.File, "cmd/8g") || strings.Contains(fx.Span.Start.File, "cmd/5g") || strings.Contains(fx.Span.Start.File, "cmd/9g")
 
 	narg := 0
 	for j, text := range fx.Texts {
@@ -177,6 +177,7 @@ func fixPrintFormat(curfn *cc.Decl, fx *cc.Expr, args []*cc.Expr) []*cc.Expr {
 			start = i
 			i++
 			if i < len(format) && format[i] == '%' {
+				buf.WriteByte('%')
 				buf.WriteByte('%')
 				start = i + 1
 				continue
@@ -250,7 +251,7 @@ func fixPrintFormat(curfn *cc.Decl, fx *cc.Expr, args []*cc.Expr) []*cc.Expr {
 						convert = "uint"
 					}
 				}
-			
+
 			case 'C': // rune
 				buf.WriteString(flags)
 				buf.WriteString("c")