From bug-request at octave dot org Thu Dec 16 13:55:32 2004
Subject: RE: Possible Error in -ascii save/restore
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
Cc: <Hallvard dot Paulsen at wartsila dot com>, <bug@octave.org>
Date: Thu, 16 Dec 2004 14:56:33 -0500

On 16-Dec-2004, I wrote:

| Note the is.tellg() and is.seekg().  I think this is failing when the
| filesystem is mounted in text mode because then there is some
| translation going on for CRLF pairs.  Is this a bug in Octave or the
| way the Cygwin text mode filesystem works?  All we want Octave to do
| here is return to the previous location in the file and read again.

Try the following program on a Cygwin filesystem mounted in textmode.
When I compile this program with g++ 3.3.x, it prints

line 1
line 2
pos = 18
line 3
ne 3

instead of the expected

line 1
line 2
pos = 14
line 3
line 3

(or perhaps

line 1
line 2
pos = 16
line 3
line 3

if the pointer is also counting the CR characters in the input).

Will someone please verify this and report the problem as a bug to the
Cygwin or libstdc++ maintainers (whichever is more appropriate, or
both)?

Thanks,

jwe


#include <iostream>
#include <fstream>

static void
read_a_line (std::istream& is)
{
  char c;
  while (is.get (c))
    {
      std::cerr << c;
      if (c == '\n')
	break;
    }
}

int
main (void)
{
  std::ofstream ofoo ("foo.txt");
  ofoo << "line 1\nline 2\nline 3\nline 4\n";
  ofoo.close ();

  std::ifstream ifoo ("foo.txt");

  // Read the first two lines, including the newlines, echoing them to
  // std::cerr.

  read_a_line (ifoo);
  read_a_line (ifoo);

  // Mark our position.
  std::streampos pos = ifoo.tellg ();

  // Where are we?  I would expect 7 characters per line, so we should
  // be at 14.
  std::cerr << "pos = " << pos << std::endl;

  // Read and echo another line.
  read_a_line (ifoo);

  // Go back to the saved position then read and echo again.
  ifoo.seekg (pos);
  read_a_line (ifoo);

  ifoo.close ();

  return 0;
}



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