GDB/MI Output Syntax ambiguity

[Bob Rossi <bob at brasko dot net>]

Hi,

I am generating a bottom up parser for 'GDB/MI Output Syntax' using
bison. Unfortunately, I think that I found an ambiguity, which makes it
not easily parsable. Please correct me if I am wrong.

output                  -> ( out-of-band-record )* [ result-record ] "(gdb)" nl
result-record           -> [ token ] "^" result-class ( "," result )* nl
out-of-band-record      -> async-record | stream-record
async-record            -> exec-async-output | status-async-output | notify-asyn
exec-async-output       -> [ token ] "*" async-output
status-async-output     -> [ token ] "+" async-output
notify-async-output     -> [ token ] "=" async-output

I am assuming that the grammar above for 'output' means that there can
be 0 or more 'out-of-band-record', followed by 0 or 1 'result-record',
followed by '(gdb)' and then a newline.

The problem is, when you are parsing 'output', and you get a 'token' as
the first token from the lexer, you don't know if that is part of the 
'out-of-band-record' or if it is part of the 'result-record'. Both of 
these rules optionally start with 'token'.Has anyone actually written a 
recursive descent parser, or generated a parser from bison for GDB/MI's 
output yet, or am I the first?

Help would be greatly appreciated. This is the only shift/reduce
conflict I have in my modified BNF version of the grammar. Other than
this, the grammar looks very well written.

I consider this to be a serious problem so I hope that I am not doing
something incorrectly or am mis-understanding the grammar.

Thanks,
Bob Rossi