libstdc++/4419: ifstream::get(buffer,len) stops reading when an empty line appears.

[salvador@inti.gov.ar]

>Number:         4419
>Category:       libstdc++
>Synopsis:       ifstream::get(buffer,len) stops reading when an empty line appears.
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Sep 28 15:06:01 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     libstdc++ streams
>Release:        libstdc++-3.x
>Organization:
>Environment:
i586-pc-msdosdjgpp      gcc-3.0.1 release
i586-pc-msdosdjgpp      gcc-3.1 20010927 (experimental)
i686-pc-linux-gnu       gcc-3.0.2 20010927 (prerelease)
>Description:
When reading a text file from an input stream using the get 
member you can't read all the file if it contains an empty
line (one with \n).
The stream stops reading lines at rhis point.
Here is the complete explanation I reported by mail:
Hi All!

  GCC 3.0 changed too much things in the C++ classes to follow the new
standard (is that ISO C++ 1998?).
  I was "fighting" to support it in the TV library. Thanks to Andris and
other
people I got the library compiled. But while testing the examples I found
a really strange behavior.
  I don't know if that is a bug and in this case if that's djgpp specific.
So I need help from somebody with:

a) Access to another systems with gcc 3.x (not djgpp)
b) Knowledge about the new streams.

  It looks like a bug and as it is for lines that only contains EOL (\r\n)
could
be related to djgpp's \r\n to \n traslation. The following code compiled
with
gcc 2.95.x can read a complete file name meassuring the length of each
line. The same code compiled with 3.0.1 will stop reading in the first empty

line and from this point will enter in an endless loop. Note that EOF is not

reached nor indicated with gcc 3.

Here is the stripped code (the original loads the text in memory):

#include <fstream.h>

const int maxLineLength=200;

int main(void)
{
 ifstream fileToView("test.txt");
 char line[maxLineLength+1];
 int len=0;
 while(!fileToView.eof())
   {
    fileToView.get(line, sizeof line);
    char c;
    fileToView.get(c);      // grab trailing newline
    printf("%d (%d)\n",strlen(line),c);
    // Sanity stop
    if (++len==20) return 1;
   }
 printf("EOF: %d\n",fileToView.eof());
 return 0;
}

Here is what you can use for `test.txt' to feed the example:

<--------
First Line
Another Line

The above is empty

<---------

Output from gcc 2.95.x compiled code:

10 (10)
12 (10)
0 (10)
18 (10)
0 (10)
EOF: 1

Output from gcc 3.0.1 compiled code:

10 (10)
12 (10)
0 (10)
0 (10)
....

SET

>How-To-Repeat:
#include <fstream.h>

const int maxLineLength=200;

int main(void)
{
 ifstream fileToView("test.txt");
 char line[maxLineLength+1];
 int len=0;
 while(!fileToView.eof())
   {
    fileToView.get(line, sizeof line);
    char c;
    fileToView.get(c);      // grab trailing newline
    printf("%d (%d)\n",strlen(line),c);
    // Sanity stop
    if (++len==20) return 1;
   }
 printf("EOF: %d\n",fileToView.eof());
 return 0;
}

/*
Use it to feed the program (test.txt):

<--------
First Line
Another Line

The above is empty

<---------
*/
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: