cmd/yacc: Index out of range #9099
Description
What does 'go version' print?
go version devel +6e0eb636f60c Wed Nov 12 14:27:27 2014 -0800 linux/amd64
What steps reproduce the problem?
If possible, include a link to a program on play.golang.org.
1.
$ cat bug.y
%{
package main
import (
"flag"
"fmt"
)
%}
%union{}
%token T
%%
Start:
| T Start
%%
type lx struct{
i, max int
}
func (lx *lx) Lex(lval *yySymType) int {
if lx.i += 1; lx.i < lx.max {
return T
}
return 0
}
func (lx *lx) Error(s string) {
fmt.Println(s)
}
func main() {
delta := flag.Int("delta", 0, "produce yyMaxDepth+delta T tokens")
flag.Parse()
fmt.Println(yyParse(&lx{max: yyMaxDepth+*delta}))
}
$
What happened?
$ go tool yacc bug.y
$ go run y.go -delta -1
0
$ go run y.go -delta 1
0
$ go run y.go -delta 0
panic: runtime error: index out of range
goroutine 1 [running]:
main.yyParse(0x7f52b13a37d0, 0xc208032220, 0x56bbd0)
/home/jnml/src/tmp/go-yacc/yaccpar:207 +0xcf1
main.main()
/home/jnml/src/tmp/go-yacc/bug.y:39 +0xd6
goroutine 2 [runnable]:
runtime.forcegchelper()
/home/jnml/go/src/runtime/proc.go:90
runtime.goexit()
/home/jnml/go/src/runtime/asm_amd64.s:2232 +0x1
goroutine 3 [runnable]:
runtime.bgsweep()
/home/jnml/go/src/runtime/mgc0.go:66
runtime.goexit()
/home/jnml/go/src/runtime/asm_amd64.s:2232 +0x1
goroutine 4 [runnable]:
runtime.runfinq()
/home/jnml/go/src/runtime/malloc.go:705
runtime.goexit()
/home/jnml/go/src/runtime/asm_amd64.s:2232 +0x1
exit status 2
$
What should have happened instead?
$ go tool yacc bug.y
$ go tool yacc bug.y
$ go run y.go -delta -1
0
$ go run y.go -delta 1
0
$ go run y.go -delta 0
0
$
Please provide any additional information below.
Patch ready, CL mail follows.
Attachments:
- bug.y (424 bytes)