bug(?): garbage produced by archive_node.get_string

[Richard B. Kreckel]

Hi,

On Sat, 18 Aug 2001, Pearu Peterson wrote:
> I finally tracked down what caused this garbage.
> It was due to
>         void numeric::archive(archive_node &n) const
> in numeric.cpp where a fixed size buffer is defined if HAVE_SSTREAM is
> undefined. 

Doh!  I was completely forgetting that our gcc-2.95.2 is vanilla with the
exception that I have dropped the attached file into /usr/include/g++-3/.  
I recommend that you do the same.  GCC-2.95.3 has this hack, too.  And
GCC-3.0 has a cleaner implementation of course.  Applying self-LART...

>            If I made the following changes 
> 
> $ diff numeric.cpp numeric.cpp.orig
> 307c307,308
> <       std::ostrstream s;
> ---
> >       char buf[1024];
> >       std::ostrstream s(buf, 1024);
> 329c330,332
> <       n.add_string("number", s.str());
> ---
> >       s << ends;
> >       std::string str(buf);
> >       n.add_string("number", str);
> 
> then the garbage disappered.
> 
> So, why you define fixed size buffer if ostrstream has the same
> functionality as ostringstream (at least in gcc system)?

I didn't know this works.  We were under the impression that fixed-size
buffers are a must for ostrstream.  This misunderstanding was probably due
to exercise 26 in chapter 21 of Stroustrup's TC++PL3 where only the ctor
we use is mentioned.  Looking at the standard's Annex D one finds the ctor
you use indeed documented, so this fix would probably be sane.  I won't
fix it though, since ostrstream is officially deprecated anyhow and may
eventually be thrown out of GiNaC entirely in favor of ostringstream.

If you go through the sources and grep for the dozen or so occurences, fix
them and send us a patch, they could still be applied (for a transistion
period).

Regards
    -richy.
-- 
Richard Kreckel
<Richard.Kreckel at Uni-Mainz.DE>
<http://wwwthep.physik.uni-mainz.de/~kreckel/>

-------------- next part --------------
/* This is part of libio/iostream, providing -*- C++ -*- input/output.
Copyright (C) 2000 Free Software Foundation

This file is part of the GNU IO Library.  This library is free
software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option)
any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this library; see the file COPYING.  If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

As a special exception, if you link this library with files
compiled with a GNU compiler to produce an executable, this does not cause
the resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why
the executable file might be covered by the GNU General Public License. */

/* Written by Magnus Fromreide (magfr at lysator.liu.se). */

#ifndef __SSTREAM__
#define __SSTREAM__

#include <string>
#include <iostream.h>
#include <streambuf.h>

namespace std
{
  class stringbuf : public streambuf
  {
  public:
    typedef char	char_type;
    typedef int		int_type;
    typedef streampos	pos_type;
    typedef streamoff	off_type;

    explicit stringbuf(int which=ios::in|ios::out) :
      streambuf(which), buf(), mode(static_cast<ios::open_mode>(which)),
      rpos(0), bufsize(1)
    { }
	
    explicit stringbuf(const std::string &s, int which=ios::in|ios::out) :
      streambuf(which), buf(s), mode(static_cast<ios::open_mode>(which)),
      bufsize(1)
    {
      if(mode & ios::in)
	{
	  setg(&defbuf, &defbuf + bufsize, &defbuf + bufsize);
	}
      if(mode & ios::out)
	{
	  setp(&defbuf, &defbuf + bufsize);
	}
      rpos = (mode & ios::ate ? s.size() : 0);
    }
	
    std::string str() const
    {
      const_cast<stringbuf*>(this)->sync();  // Sigh, really ugly hack
      return buf;
    };

    void str(const std::string& s)
    {
      buf = s;
      if(mode & ios::in)
	{
	  gbump(egptr() - gptr());
	}
      if(mode & ios::out)
	{
	  pbump(pbase() - pptr());
	}
      rpos = (mode & ios::ate ? s.size() : 0);
    }

  protected:
    inline virtual int sync();
    inline virtual int overflow(int = EOF);
    inline virtual int underflow();
  private:
    std::string			buf;
    ios::open_mode		mode;
    std::string::size_type	rpos;
    streamsize			bufsize;
    char			defbuf;
  };

  class stringstreambase : virtual public ios {
  protected:
    stringbuf __my_sb;
  public:
    std::string str() const
    {
      return dynamic_cast<stringbuf*>(_strbuf)->str();
    }
    void str(const std::string& s)
    {
      clear();
      dynamic_cast<stringbuf*>(_strbuf)->str(s);
    }
	
    stringbuf* rdbuf()
    {
      return &__my_sb;
    }
  protected:
    stringstreambase(int which) :
      __my_sb(which)
    {
      init (&__my_sb);
    }
	
    stringstreambase(const std::string& s, int which) :
      __my_sb(s, which)
    {
      init (&__my_sb);
    }
  };
    
  class istringstream : public stringstreambase, public istream {
  public:
    istringstream(int which=ios::in) :
      stringstreambase(which)
    { }
	
    istringstream(const std::string& s, int which=ios::in) :
      stringstreambase(s, which)
    { }
  };
    
  class ostringstream : public stringstreambase, public ostream {
  public:
    ostringstream(int which=ios::out) :
      stringstreambase(which)
    { }
	
    ostringstream(const std::string& s, int which=ios::out) :
      stringstreambase(s, which)
    { }
  };
    
  class stringstream : public stringstreambase, public iostream {
  public:
    stringstream(int which=ios::in|ios::out) :
      stringstreambase(which)
    { }
    
    stringstream(const std::string &s, int which=ios::in|ios::out) :
      stringstreambase(s, which)
    { }
  };
}

inline int std::stringbuf::sync()
{
  if((mode & ios::out) == 0)
    return EOF;

  streamsize n = pptr() - pbase();
  if(n)
    {
      buf.replace(rpos, std::string::npos, pbase(), n);
      if(buf.size() - rpos != n)
	return EOF;
      rpos += n;
      pbump(-n);
      gbump(egptr() - gptr());
    }
  return 0;
}

inline int std::stringbuf::overflow(int ch)
{
  if((mode & ios::out) == 0)
    return EOF;

  streamsize n = pptr() - pbase();

  if(n && sync())
    return EOF;

  if(ch != EOF)
    {
      std::string::size_type oldSize = buf.size();
      
      buf.replace(rpos, std::string::npos, ch);
      if(buf.size() - oldSize != 1)
	return EOF;
      ++rpos;
    }
  return 0;
}

inline int std::stringbuf::underflow()
{
  sync();
  if((mode & ios::in) == 0)
    {
      return EOF;
    }
  if(rpos >= buf.size())
    {
      return EOF;
    }
  
  std::string::size_type n = egptr() - eback();
  std::string::size_type s;

  s = buf.copy(eback(), n, rpos);
  pbump(pbase() - pptr());
  gbump(eback() - gptr());
  int res = (0377 & buf[rpos]);
  rpos += s;
  return res;
}

#endif /* not __SSTREAM__ */