fix bounds check in error recovery

(thanks to avp@mit.edu)

R=rsc
CC=golang-dev
https://golang.org/cl/1998041

diff --git a/src/cmd/goyacc/goyacc.go b/src/cmd/goyacc/goyacc.go
index b364d5189b2436ce3ad489b5379b8927810a8d82..45dced1b3e84f6530592a06dffc84388caecfc6f 100644 (file)
--- a/src/cmd/goyacc/goyacc.go
+++ b/src/cmd/goyacc/goyacc.go
@@ -3244,7 +3244,7 @@ yydefault:
                        Errflag = 3
 
                        /* find a state where "error" is a legal shift action */
-                       for yyp >= len(YYS) {
+                       for yyp >= 0 {
                                yyn = yyPact[YYS[yyp].yys] + yyErrCode
                                if yyn >= 0 && yyn < yyLast {
                                        yystate = yyAct[yyn] /* simulate a shift of "error" */