test program:
package main

/*
restricted int a;
something;
*/
import "C"

go build cgo6.go produces:
# command-line-arguments
cgo6.go:3: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
before ‘int’
cgo6.go:4: warning: data definition has no type or storage class

the first error line should be at line 4.