[PATCH] Add getmntent_r
Wed Jul 18 11:18:00 GMT 2012
On Jul 18 05:21, Yaakov (Cygwin/X) wrote:
> Somehow this one fell through the cracks. Picking up where we left off:
> On 2012-06-06 02:33, Corinna Vinschen wrote:
> >On Jun 5 21:29, Yaakov (Cygwin/X) wrote:
> >>The string returned into buf is in the following format:
> >>mnt_fsname\0mnt_dir\0mnt_type\0mnt_opts\0mnt_freq" "mnt_passno\0
> >Yes, but this is not something inherent to the functionality of
> >getmntent_r, it's just residue from the way getmntent_r works. It reads
> >a line from /etc/fstab or /etc/mtab into the buffer via fgets:
> > mnt_fsname\tmnt_dir\tmnt_type\tmnt_opts\tmnt_freq\n
> >and then creates the content of mntbuf from there, replacing the \t with
> >\0 as it goes along. So it starts with mnt_opts and mnt_freq strings in
> >buf, but only to sscanf them into their respective mntbuf->mnt_opts and
> >mntbuf->mnt_freq members.
> Since glibc is getting this information from the kernel, that makes sense.
> >In case of Cygwin this is not needed since we don't read from the file
> >but from the internal datastructure. There's no reason to create
> >garbage in buf just because this is by chance the layout the buffer gets
> >when operating under Linux.
> >The *important* thing is that buf contains the strings the members of
> >mntbuf points to.
> OK, revised patch attached.
Thanks. Applied with a tweak: It's really not necessary at all to
create strings for mnt_freq and mnt_passno in buf. Just copy them
over from mnt to mntbuf and be done with it.
> >>glibc makes no attempt to verify buf or mntbuf; if either of them
> >>are not initialized or too small, you're in "undefined behaviour"
> >>territory (aka SEGV :-).
> >You're basically right. But it won't SEGV if buf is too small.
> By "too small", I meant sizeof(buf) < buflen, or sizeof(mntbuf) <
> sizeof(struct mntent); then glibc definitely does SEGV.
That's right. I meant the fact that buflen is just too small to keep
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Project Co-Leader cygwin AT cygwin DOT com
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