Date: Fri, 11 Apr 2003 19:00:27 -0700 (PDT) From: David Taylor <davidt@yadt.co.uk> To: freebsd-bugs@FreeBSD.org Subject: Re: misc/50825: lseek to negative file positions screws up flags Message-ID: <200304120200.h3C20R04012702@freefall.freebsd.org>
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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"
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