PQclear() causes coredump

Hi Folks,

I write a program in c++ using PostgreSQL 7.0 at the moment.
During this, I have
written some small classes for accessing the database. One of
this classes is QtResultSet. I use them to manage my statments.

To avoid memory leaks, I use the dtor to free the resultset with
PQclear(). Unfortunaly every call to PQclear causes a coredump.
What is my mistake?

=== QtResultSet.h ===

#include <string>
#include <map>
#include <vector>
#include <libpq-fe.h>
#include "../errors/QtExceptions.h"

#ifndef __QTRESULTSET__
#define __QTRESULTSET__

namespace qt { namespace database {   using namespace std;   using namespace qt::errors;
   class QtResultSet {   public:
     virtual ~QtResultSet();
     vector<string> fieldnames() throw(QtDbConnectionBadErr,
QtDbFatalErr,    QtDbNonfatalErr, QtDbBadResponseErr);     vector<string> fetch(int) throw(QtDbConnectionBadErr,
QtDbFatalErr,         QtDbNonfatalErr, QtDbBadResponseErr);     vector<string> fetch(void) throw(QtDbConnectionBadErr,
QtDbFatalErr,          QtDbNonfatalErr, QtDbBadResponseErr);
     string get_error();
     int rows();     int fields();
     void execute() throw(QtDbConnectionBadErr, QtDbFatalErr,     QtDbNonfatalErr, QtDbBadResponseErr);
     friend class QtConnection;

   protected:     QtResultSet(PGconn *, const string &);
   private:     void fetch_row(int, vector<string>*);     bool binarydata_m;     int rows_m;     int fields_m;     int
currentrow_m;    string query_m;     string error_m;     PGresult *pgresult_mp;     PGconn *pgconn_mp;   };
 
 } }
#endif

=== QtResultSet.cpp ===

#include <string>
#include <libpq-fe.h>
#include "QtResultSet.h"
#include "../errors/QtExceptions.h"

namespace qt { namespace database {   using namespace std;   using namespace qt::errors;
   QtResultSet::~QtResultSet() {
     PQclear(this->pgresult_mp);
   }
   QtResultSet::QtResultSet(PGconn *pgconn, const string &query)
{     pgconn_mp    = pgconn;     query_m      = query;     fields_m     = 0;     rows_m       = 0;     currentrow_m =
0;  }
 
   void QtResultSet::execute() throw(QtDbConnectionBadErr,
QtDbFatalErr,         QtDbNonfatalErr, QtDbBadResponseErr)
     try {pgresult_mp = PQexec(pgconn_mp, query_m.c_str());
ExecStatusType res = PQresultStatus(pgresult_mp);

if (res == (PGRES_COMMAND_OK || PGRES_TUPLES_OK)) {  rows_m       = PQntuples(pgresult_mp);  fields_m     =
PQnfields(pgresult_mp); binarydata_m = PQbinaryTuples(pgresult_mp);  currentrow_m = -1;}else {  error_m =
PQresultErrorMessage(pgresult_mp);
  switch (res) {    case PGRES_EMPTY_QUERY:    break;
    case PGRES_BAD_RESPONSE:    throw QtDbBadResponseErr();    break;
    case PGRES_NONFATAL_ERROR:    throw QtDbNonfatalErr();    break;
    case PGRES_FATAL_ERROR:    throw QtDbFatalErr();    break;  }
}     }     catch (...) {
#ifdef QTDEBUGcerr << "Exception catched and PQclear() called." << endl;
#endif QTDEBUG
PQclear(pgresult_mp);

#ifdef QTDEBUGcerr << "Exception rethrown." << endl;
#endif QTDEBUG
throw;     }    }   int QtResultSet::fields() {     return fields_m;   }   int QtResultSet::rows() {     return rows_m;
 }
 
       vector<string> QtResultSet::fieldnames()
throw(QtDbConnectionBadErr, QtDbFatalErr,        QtDbNonfatalErr, QtDbBadResponseErr) {     vector<string> row;
           for (int i = 0; i < rows_m; i++) {row.push_back(PQfname(pgresult_mp, i));     }
     return row;   }   vector<string> QtResultSet::fetch(void)
throw(QtDbConnectionBadErr, QtDbFatalErr,       QtDbNonfatalErr, QtDbBadResponseErr) {     vector<string> row;
     if (currentrow_m < (rows_m - 1)) {this->fetch_row(++currentrow_m, &row);     }     else {      }
     return row;   }   vector<string> QtResultSet::fetch(int id)
throw(QtDbConnectionBadErr, QtDbFatalErr,         QtDbNonfatalErr, QtDbBadResponseErr) {     vector<string> row;
     if ((id >  0)  && (id < rows_m)) {this->fetch_row(id, &row);     }     else {     }
     return row;   }   void QtResultSet::fetch_row(int rowid, vector<string>
*rowdata) {
     for (int i = 0; i < fields_m; i++) {rowdata->push_back(string("Aber Hallo"));     }
   }   string QtResultSet::get_error() {     return this->error_m;   } // QtResultSet::get_error
 } // namespace database
}  // namespace qt


BYe,

Oliver
--
Oliver Fischer
Level of Detail, Brunnenstr. 196, D-10119 Berlin
Tel. +49/30/280 491 43

--
Oliver Fischer
Level of Detail, Brunnenstr. 196, D-10119 Berlin
Tel. +49/30/280 491 43