[boost] [xpressive] how to avoid running into stack overflow so easily

From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2008-02-06 10:56:45

Hi Eric,

(Apologies in advance for such a stupid question.)

I'm building a fairly simple parser using xpressive. I need to parse 
text like this:

node C91967
{
     label = "What brand of coffee do you use?";
     position = (100 280);
     states = ("Columbian blend" "Columbian gold" "Columbian all star" 
"Columbian cinnamon");
     HR_Inaccuracy = "0";
     HR_Risk = "0";
     HR_Time = "1";
     HR_RefKey = "";
     HR_Desc = "Question";
     HR_ID = "91967";
     HR_Def = "&lt;div align=\"left\"&gt;&amp;#160;&lt;/div&gt;<br/>";
     HR_Web_Page = "";
     HR_Type2 = "3";
}

potential (C91976 | CXXX)
{
  data = ( 0 1		%  Coffee type not to your taste
            0 1		%  Discount coffee
            0.98 0.02		%  Low quality coffee filter
            0 1		%  Low water quality
            0 1		%  Old coffee machine
            0 1		%  Used coffee filter
            0 1		%  Water coffee mixture incorrect
0 1 );		%  Other Problem
}

There are multiple nodes or potential in the files, so my final regex 
looks something like

         netFile = modelConfiguration >>
                   causeNode >>
                   actions >>
                   optional( questions ) >>
                   causeProbabilities >>
                   actionProbabilities;

I then make one regex to parse a single potential, and wrap
that regex in another so I can look for a list of those potentials:

         sregex row = *space >> 
_float[push_back(ref(actionProbs),as<Float>(_))] >>
                       space >>
                      -*_ >> _ln;

         actionPotential = -*_ >> "potential (C" >>
                           -*_ >> "data = (" >>
                           +row >>
                           -*_ >> '}';

         actionProbabilities = +( *space >> actionPotential );

Now my problem is that I get a stack overflow very easily if the 'row' 
regex is too long. In factm I have to remove the latter ">> space" from 
'row' to not get a stack overflow.

Am I using the library in a fundamentally wrong way?
If so, how can I try to fix it?

best regards

-Thorsten