[Boost-users] Heap vs. Stack allocation of filtering_streambuf??

Subject: [Boost-users] Heap vs. Stack allocation of filtering_streambuf??
From: Eric R George (Eric.R.George_at_[hidden])
Date: 2009-11-19 12:44:52

Hi Folks - I'm working on a mod to an existing program to write compressed 
output files.  The following code works fine, but if I put the indicated 
code in a function, it drops core when I attempt to write to the ofile 
ostream - presumably because the filtering_streambuf<output> out was 
allocated on the stack and no longer exists after the function exits.

#include <fstream>
#include <iostream>
#include <string>
#include <boost/iostreams/filtering_streambuf.hpp>
#include <boost/iostreams/filter/bzip2.hpp>

using namespace std;
using namespace boost::iostreams;
using namespace boost::iostreams::bzip2;

int main() 
{
 string x;

 fstream infile;
 infile.open("00011.eph.org", ios::in);

 ostream *ofile;

//******* To be put in function ************************
 fstream *file2;
 file2 = new fstream;
 file2->open("00011.eph.org.bz2", ios_base::out | ios_base::binary);

 filtering_streambuf<output> out;
 out.push(bzip2_compressor());
 out.push(*file2);

 ofile = new ostream(&out);
//******* To be put in function ************************

 while(!infile.eof())
    {
     getline(infile, x);
     *ofile << x << endl;
    }

 return 0;
}

//*****************************************************************************

Now if I attempt to dynamically allocate the filtering_streambuf.

#include <fstream>
#include <iostream>
#include <string>
#include <boost/iostreams/filtering_streambuf.hpp>
#include <boost/iostreams/filter/bzip2.hpp>

using namespace std;
using namespace boost::iostreams;
using namespace boost::iostreams::bzip2;

int main() 
{
 string x;

 fstream infile;
 infile.open("00011.eph.org", ios::in);

 ostream *ofile;

//******* To be put in function ************************
 fstream *file2;
 file2 = new fstream;
 file2->open("00011.eph.org.bz2", ios_base::out | ios_base::binary);

 filtering_streambuf<output> *out;
 out = new filtering_streambuf<output>;
 out->push(bzip2_compressor());
 out->push(*file2);

 ofile = new ostream(out);
//******* To be put in function ************************

 while(!infile.eof())
    {
     getline(infile, x);
     *ofile << x << endl;
    }

 return 0;
}

This code compiles and runs fine, but the compressed output file, 
00011.eph.org.bz2, ends up empty.  Moving the indicated code to a function 
again works fine - but again, no output??

The reasoning for all this is that I'd like to be able to open and set up 
the various output streams in a function, and then pass those streams 
around as needed.  Which means they need to be dynamically allocated/built 
on the heap.  But it's not working??

Ideas?  What am I missing here?
Thanks
Eric