[Rd] who frees dd and xd in X11_Open?

[Adrian Trapletti]

> Date: 15 Feb 2001 09:29:42 -0500
> From: Thomas Vogels
> Subject: Re: [Rd] who frees dd and xd in X11_Open?
>
> Prof Brian Ripley  writes:
>
> > On 14 Feb 2001, Thomas Vogels wrote:
> >
> > >
> > > Hi, I'm not sure this is a bug in the code, the comment or my
> > > thinking.  So first try goes to r-devel...  I find the following
> > > comment in X11_Open () (src/unix/X11/devX11.c):
> > >
> > > /* if we have to bail out with "error", then must free(dd) and free(xd) */
> > >
> > > A couple lines down, there is:
> > >
> > >     if (!strncmp(dsp, "png::", 5)) {
> > >     FILE *fp;
> > > #ifndef HAVE_PNG
> > >     error("No png support in this version of R");
> > > #endif
> > >     if (!(fp = R_fopen(R_ExpandFileName(dsp+5), "w")))
> > >         error("could not open PNG file `%s'", dsp+6);
> > >     ...
> > >
> > > So what does the comment imply?  If error jumps out to the toplevel
> > > without giving X11DeviceDriver a chance to free dd and xd, then this
> > > should be:
> >
> > [...]
> >
> > Well, the thinking was that people would not be trying to use facilities
> > on systems where they had not bothered to implement them, so what problem
> > was a small memory leak?  They would only do it once, ever ....
>
> uh, I guess I screwed up the example.  Even more lines down, there is
> no free accompanying the error ("could not open PNG file ...").  That
> can happen more often and more memory would leak.  But no, I wanted to
> know this for another reason: I've played around with the X11 device
> driver to implement a feature that allows me to embed the device into
> another window.  Opening and closing of x11()'s can happen often
> during the execution of the program.  But I'm still not interested in
> the memory leak issue per se.
>
> I've seen a segfault or two (not in the regular code) and right now I
> blame it on Xevents arriving after the device is shut down.  Now all
> of a sudden the calls to free become very interesting.  As I said at
> the beginning of the email, I wanted to simply understand the comment,
> understand what should be going on, not criticize for it not being
> followed.
>
> Although I got the question wrong, I guess, I got the right answer :-)
> Thanks.
>
> Regards,
>   -tom
>
>
> >
> > In these cases it would be better to give a warning and return FALSE, when
> > the normal return mechanism will free xd and then dd.  I will alter it to
> > that when I have tested it out.
>
>
I don't know if it has something to do with this discussion, but it's
probably worth reporting it.

Under
SunOS pul 5.8 Generic sun4u sparc SUNW,Ultra-5_10
R : Version 1.2.1  (2001-01-15)
Fvwm95 Version 2.0.43a
the window manager always crashes when I close an x11() device started
within R.

Adrian

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