Re: GDB/MI Output Syntax ambiguity

Daniel Jacobowitz
2004-08-23T21:09:25Z

On Mon, Aug 23, 2004 at 05:03:14PM -0400, Bob Rossi wrote:
> 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.

This is easily solved. For instance, factor the optional token out of
async-record and result-record, and handle output as:
output -> [token] ( out-of-band-record-1 [token] )* [ result-record ] "(gdb)" nl

I'm not sure how faithful to the documented grammar GDB is... but
that's a separate problem.

--
Daniel Jacobowitz