to_tsquery stack overflow

["Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>]

Passing a query with enough nested parenthesis in it causes a segfault.
Attached is a handy little program to generate such a query, the actual
query was too big to get through to the list.

The problem seems to be unbounded recursion in the makepol function that
converts the input query from infix to polish notation. An easy fix
would be to just add a level parameter to makepol that's incremented on
each recursion, and throw an error if it grows bigger than some safe
limit. There might be a similar problem in TS_execute as well, if you
can somehow pass a complex enough TSQuery to the system, perhaps with a
custom libpq client and tsqueryrecv.

-- 
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com

#include <stdio.h>
#include <stdlib.h>


int main(int argc, char **argv)
{
  int i;
  int n;

  if(argc == 1)
    n = 10;
  else
    n = atoi(argv[1]);

  printf("SELECT to_tsquery('simple', '");

  for(i=0;i < n; i++)
  {
	  printf("%d|(", i + 1);
  }
  printf("end");

  for(i=0;i < n; i++)
  {
	  printf(")");
  }
  printf("')\n");
}