Re: debugging with gdb

[Satya]

hi,
My interactive mode Bison program (http://cs.uic.edu/~spopuri/ibison.html)
is only good to debug the structure of a grammar. It does NOT execute
semantic actions.

So, if you want to look at the value of $1, $2 etc. you must be printing
values on the semantic stack .. which is implemented as an array called
'yyvsp'. And yyvsp[0] is the top of the stack. This variable is actually a
pointer, and it is incremented whenever a symbol (and hence its semantic
value) is pushed on the parser stack.

If you understand parsing, try printing values backward from yyvsp
(yyvsp[-1], yyvsp[-2] etc.) otherwise it is best to insert a printf("..",
$1); inside the semantic action.

thanks,
satya.

On 11/21/06, Hans Aberg <address@hidden> wrote:
> On 21 Nov 2006, at 17:26, Sean Walton wrote:
>
> > I am trying to debug bison/yacc with gdb.  I want to look at the
> > bison variable $1 -- how do i do it?  What is the syntax?  (It
> > conflicts with the print history $##.)
>
> The $ variables are expanded to something else in the output parser.
> So one way is to look what Bison writes in the parser actions (in
> the .c or the .cc file) and debug that. Bison also has a debug
> feature, but I recall it just writes what is on the parser stack. And
> Satya is working on improved debugging - I am not sure of its current
> state.
>
>    Hans Aberg


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