Alan Cox wrote:
> > > libc is entitled to, and most definitely does exactly that. Take a look at
> > > things like gethostent, getpwent etc etc.
> >
> > Ehh.. I will bet you $10 USD that if libc allocates the next file
> > descriptor on the first "malloc()" in user space (in order to use the
> > semaphores for mm protection), programs _will_ break.
> >
> > You want to take the bet?
>
> Its not normally a good idea to take a Linus bet, but this time Im obviously
> missing something. fd0-2 will be passed in (and if not then shit already
> happens - see old bugtraq on the matter for setuid apps, glibc bugs)
>
> So the C library gets fd 3
> My first fopen gets fd 4.
Code may
close (0);
close (1);
close (2);
...
malloc ();
/* Now open our controlling TTY/ stdin .. */
fd = open (... ) ;
After taking care of this (*), problem I find the fd trick WAY more
appealing than Linus' magic numbers. With file descriptors we have a
"small integer which can be validated quickly". We also have storage
for a private pointer somewhere in the fd structure.
If people are TOO afraid of breaking something, creating a new set of
small integers handled similarly as "fds" would do fine. (Maybe here
we'd allocate just a few, and reallocate when neccesary).
Roger.
(*) I bet that
get_sem_fd ()
{
int rv;
int fd;
fd = get_fd ();
if (fd < 5) {
rv = get_sem_fd ();
close(fd);
fd = rv;
}
return fd;
}
will not break much. (UGLY coding. Don't tell me.)
-- ** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 ** *-- BitWizard writes Linux device drivers for any device you may have! --* * There are old pilots, and there are bold pilots. * There are also old, bald pilots. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Mon Apr 23 2001 - 21:00:33 EST