[Boost-users] [serialization] Problem writing and reading in same block, with work-around

From: Robert S. Grimes (rsgrimes_at_[hidden])
Date: 2006-03-13 14:38:31

Hi all,

It seems there is a problem with using both an output and an input archive
in the same code block.  Here is a simple sample that illustrates the
problem.  By defining the symbol BREAK_IT, you can see the problem; not
defining it, the example works.  What is particularly odd is that it is
throwing an std::bad_alloc from within
text_iarchive_impl<Archive>::load(std::string &s) in text_iarchive_impl.ipp
because the requested size is obviously wrong - for example, 3435973837!!!
I can't follow well enough what is happening, but I have figured out a
work-around from noticing the differences between my example and demo.cpp;
in the latter, the writing and reading of an archive are performed in two
separate functions, or more precisely, two different blocks.  Is this
normal?  Have I missed the documentation about this?  Still, seems rather
fussy, though to be honest, I'm not likely to suffer from the workaround in
"production" code, but it's a bit unnerving nonetheless...

Thanks!
-Bob

Example follows:

#include <fstream>
#include <iostream>
#include <string>

#include <boost/archive/text_iarchive.hpp>
#include <boost/archive/text_oarchive.hpp>

class Simple
{
private:
  int anIntMember;
  bool aBoolMember;

  template<class Archive>
  void serialize(Archive & ar, const unsigned int file_version)
  {
   ar & BOOST_SERIALIZATION_NVP(anIntMember)
      & BOOST_SERIALIZATION_NVP(aBoolMember);
  }

  // Grant access to serialization library
  friend class boost::serialization::access;

public:
  Simple(): anIntMember(27), aBoolMember(false) {}
  int GetAnIntMember() const { return anIntMember; }
  void SetAnIntMember(int v) { anIntMember = v; }
  bool GetABoolMember() const { return aBoolMember; }
  void SetABoolMember(bool v) { aBoolMember = v; }
};

#define BREAK_IT

void TestBoostText(const Simple& parms)
{
#ifndef BREAK_IT
  {
#endif
  // Write out to boost archive
  std::ofstream ofs("./boost.txt");
  boost::archive::text_oarchive oa(ofs);
  oa << parms;   /// Could use a better XML element name
#ifndef BREAK_IT
  }
#endif

  // Read it back and check
  Simple rparms;
  std::ifstream ifs("./boost.txt");	// THIS IS THE BROKEN LINE
  boost::archive::text_iarchive ia(ifs);
  ia >> rparms;
  std::cout << "Checking boost read...";
  if (rparms.GetAnIntMember() == 99) {
    std::cout << "Worked!!!" << std::endl;
  } else {
    std::cout << "Failed - appears not to have been updated" << std::endl;
  }
}

int main(int argc, char* argv[])
{
        Simple parms;

  // Modify parms for testing purposes
  parms.SetAnIntMember(99);

  // Test both binary archives
  TestBoostText(parms);

  return 0;
}