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Date: Fri, 11 Apr 2003 19:00:27 -0700 (PDT)
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To: freebsd-bugs@FreeBSD.org
From: David Taylor <davidt@yadt.co.uk>
Subject: Re: misc/50825: lseek to negative file positions screws up flags
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The following reply was made to PR misc/50825; it has been noted by GNATS.

From: David Taylor <davidt@yadt.co.uk>
To: Erdgeist <erdgeist@erdgeist.org>
Cc: FreeBSD-gnats-submit@FreeBSD.org
Subject: Re: misc/50825: lseek to negative file positions screws up flags
Date: Sat, 12 Apr 2003 02:49:37 +0100

 On Fri, 11 Apr 2003, Erdgeist wrote:
 > >Description:
 >         Doing a lseek to a position before the file results in corrupted
 >         File flags.
 
 Actually, if you remove the lseek(); line from the test program below, the
 file mode will still be screwed up.
 
 > >How-To-Repeat:
 > #include <unistd.h>
 > #include <fcntl.h>
 > 
 > int main( ) {
 >     int a = open( "testfile", O_CREAT | O_RDWR );
                                 ^^^^^^^        ^^^
 The problem is this:
 
      int
      open(const char *path, int flags, ...);
 
      The flags argument may indicate the file is to be cre-ated if it does
      not exist (by specifying the O_CREAT flag).  In this case open()
      requires a third argument mode_t mode, and the file is created
      with mode mode as described in chmod(2) and modified by the process'
      umask value (see umask(2)).
 
 Replacing the above line with:
 
       int a = open( "testfile", O_CREAT | O_RDWR, 0666 );
 
 results in the program working as it should.
 
 >     lseek( a, -10, SEEK_CUR);
 >     close( a );
 >     return 0;
 > }
 
 -- 
 David Taylor
 davidt@yadt.co.uk
 "The future just ain't what it used to be"