From: Martin Str|mberg <ams AT ludd DOT luth DOT se>
Message-Id: <200102121851.TAA22673@father.ludd.luth.se>
Subject: Re: Bug000323
In-Reply-To: <Pine.SUN.3.91.1010212125556.14499B-100000@is> from Eli Zaretskii at "Feb 12, 2001 12:59:20 pm"
To: djgpp-workers AT delorie DOT com
Date: Mon, 12 Feb 2001 19:51:00 +0100 (MET)
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According to Eli Zaretskii:
> 
> On Mon, 12 Feb 2001, Martin Stromberg wrote:
> 
> > The question is: did you find another real bug in fflush()?
> 
> Yes, I think so.  See the source below: it never pays attention to the 
> append flag.  So if you fseek somewhere, then fflush the stream, the data 
> doesn't go to the correct place: the end of file.

Ok, I tried to cook up a program to see this bug. This is what I came up with:

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>

#define FILE_NAME "fflush.dat"

#define LENGTH_OF_ZEROES (10240)

int
main(void)
{
  char ch;
  FILE *f;
  int i, ret;
  int status = 0; /* Return value. */

  f = fopen(FILE_NAME, "w");
  for( i = 0; i < LENGTH_OF_ZEROES; i++ )
  {
    fprintf(f, "%c", '\0');
  }
  fclose(f);

  f = fopen(FILE_NAME, "a");
  fprintf(f, "hello, there\n");
  /* fflush(f) tried here but no bug. */
  fclose(f);

  f = fopen(FILE_NAME, "a");
  fseek(f, 10, SEEK_SET);
  fprintf(f, "hello, there\n");
  /* fflush(f) tried here but no bug. */
  fclose(f);

  f = fopen(FILE_NAME, "r");
  for( i = 0; i < LENGTH_OF_ZEROES; i++ )
  {
    ret = fscanf(f, "%c", &ch);
    if( ret != 1 )
    {
      fprintf(stderr, "Failed to read expected 0 at index %d.\n", i);
      status++;
    }
    else if( ch != '\0' )
    {
      fprintf(stderr, "Unexpected char '%c' (%d) found while expecting 0 at index %d.\n", ch, ch, i);
      status++;
    }
  }
  fclose(f);

  return status;
}

But I still see no bug; the "hello there"s end up at the end. Any
ideas on how to get it to manifest itself?


Right,

						MartinS