fix off-by-one in dup2
Corinna Vinschen
corinna-cygwin@cygwin.com
Wed Dec 4 17:23:00 GMT 2013
On Dec 4 12:00, Christopher Faylor wrote:
> On Wed, Dec 04, 2013 at 01:04:08PM +0100, Corinna Vinschen wrote:
> >On Dec 4 12:36, Corinna Vinschen wrote:
> >> On Dec 4 10:32, Corinna Vinschen wrote:
> >> > Hi guys,
> >> > [...etc...]
> >> > The problem is still present in the current sources.
> >> > [...]
> >
> >Ouch, ouch, ouch! I tested the wrong DLL. Actually current CVS fixes
> >this problem. Duh. Sorry for the confusion.
> >
> >One question, though. Assuming start is == size, then the current code
> >in CVS extends the fd table by only 1. If that happens often, the
> >current code would have to call ccalloc/memcpy/cfree a lot. Wouldn't
> >it in fact be better to extend always by at least NOFILE_INCR, and to
> >extend by (1 + start - size) only if start is > size + NOFILE_INCR?
> >Something like
> >
> > size_t extendby = (start >= size + NOFILE_INCR) ? 1 + start - size : NOFILE_INCR;
> >
> >?
> >
> >Sorry again. Fortunately it's my WJM week...
>
> I don't think it is a common occurrence for start >= size. It is
> usually done when something like bash dup2's stdin/stdout/stderr to a
> high fd. Howeer, I'll check in something which guarantees that there is
> always a NOFILE_INCR entries free after start.
That might be helpful. Tcsh, for instance, always dup's it's std
descriptors to the new fds 15-19. If it does so in this order, it would
have to call extend 5 times.
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Maintainer cygwin AT cygwin DOT com
Red Hat
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