x/tools/cmd/goyacc: endless loop on unterminated comment at EOF

[rillig]

1. What version of Go are you using (go version)?

go version go1.6.2 windows/amd64
go version devel +10538a8 Fri Jul 22 22:23:14 2016 +0000 windows/amd64

1. What operating system and processor architecture are you using (go env)?

set GOARCH=amd64
set GOBIN=
set GOEXE=.exe
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOOS=windows
set GOPATH=C:\Users\rillig\go
set GORACE=
set GOROOT=C:\Users\rillig\gomaster
set GOTOOLDIR=C:\Users\rillig\gomaster\pkg\tool\windows_amd64
set CC=gcc
set GOGCCFLAGS=-m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Program Files\cygwin\tmp\go-build959343002=/tmp/go-build -gno-record-gcc-switches
set CXX=g++
set CGO_ENABLED=1

1. What did you do?

printf '%%\nstart : /* empty * {}\n%%\n' > endless.y
go tool yacc endless.y

1. What did you expect to see?

endless.y:3: unterminated comment at EOF

1. What did you see instead?

No output, and the process apparently hangs in an endless loop.

[rillig]

See https://go-review.googlesource.com/#/c/25171/

Since yacc seems to be untested currently, I didn’t know how and where to add a test for this case.

[bradfitz]

Related: #11229 (let's fix this after it moves out of the main Go tree)

[gopherbot]

CL https://golang.org/cl/25171 mentions this issue.