How can I understand the output of bison's debug output ??

[wan sheg]

How can I understand the output of   bison's debug output ??

such as

--(end of buffer or a NUL)
--accepting rule at line 95 ("int")
--accepting rule at line 173 (" ")
--accepting rule at line 112 ("x")
--accepting rule at line 173 (" ")
--accepting rule at line 146 (";")
--accepting rule at line 174 ("
")
--accepting rule at line 103 ("struct")
--accepting rule at line 173 (" ")
--accepting rule at line 112 ("x")
--accepting rule at line 147 ("{")
--accepting rule at line 174 ("
")
--accepting rule at line 95 ("int")
--accepting rule at line 173 (" ")
--accepting rule at line 112 ("a")
--accepting rule at line 146 (";")
--accepting rule at line 174 ("
")
--accepting rule at line 95 ("int")
--accepting rule at line 173 (" ")
--accepting rule at line 112 ("b")
--accepting rule at line 146 (";")
--accepting rule at line 174 ("
")
--accepting rule at line 149 ("}")
--accepting rule at line 146 (";")
--(end of buffer or a NUL)
--accepting rule at line 174 ("
")
--(end of buffer or a NUL)
--EOF (start condition 0)
--(end of buffer or a NUL)
--EOF (start condition 0)


I think this track  the rule which is accepted current .
but what the  " at line xxxx" means ?
what  file the "at  line xxxx"  means ?
I can't find the corresponding  description at line xxx   in file
"grammer.output" !!!

Help
or  "grammer.ypp"  file