From: "Jan Djärv" <jan.h.d@swipnet.se>
To: Paul Eggert <eggert@cs.ucla.edu>
Cc: 8410@debbugs.gnu.org
Subject: bug#8410: make_invisible_cursor returns garbage if XCreateBitmapFromData fails
Date: Sat, 02 Apr 2011 08:45:06 +0200 [thread overview]
Message-ID: <4D96C5F2.9020802@swipnet.se> (raw)
In-Reply-To: <4D96882E.3020002@cs.ucla.edu>
It looks OK. But there are lots of places in Emacs where errors and return
values from X calls are not checked. make_gc in the same file comes to mind.
If anything goes wrong there, emacs crashes on an X protocol error message.
If there is an error here it means the X server is out of memory, so Emacs
will probably crash on another X call later on anyway. But if you want to get
rid of the gcc warning, your patch is correct. If Emacs somehow survives
a bit longer, returning 0 means that the invisible cursor functionality will
not work, the cursor will not become invisible.
Jan D.
Paul Eggert skrev 2011-04-02 04.21:
> I found this bug via static analysis, using GCC 4.6.0's warnings.
> src/xfns.c's make_invisible_cursor returns a garbage value if
> XCreateBitmapFromData fails. I plan to fix it as follows.
> I don't know that returning 0 fixes the bug, so I'd like someone
> who's expert in this area to look at this. Since the patch replaces
> undefined behavior with defined behavior it isn't likely to be
> introducing a bug, so it shouldn't hurt to install the patch.
>
> * xfns.c (make_invisible_cursor): Don't return garbage
> if XCreateBitmapFromData fails.
> === modified file 'src/xfns.c'
> --- src/xfns.c 2011-04-01 20:30:45 +0000
> +++ src/xfns.c 2011-04-01 23:01:33 +0000
> @@ -855,19 +855,20 @@
> static char const no_data[] = { 0 };
> Pixmap pix;
> XColor col;
> - Cursor c;
> + Cursor c = 0;
>
> x_catch_errors (dpy);
> pix = XCreateBitmapFromData (dpy, FRAME_X_DISPLAY_INFO (f)->root_window,
> no_data, 1, 1);
> if (! x_had_errors_p (dpy)&& pix != None)
> {
> + Cursor pixc;
> col.pixel = 0;
> col.red = col.green = col.blue = 0;
> col.flags = DoRed | DoGreen | DoBlue;
> - c = XCreatePixmapCursor (dpy, pix, pix,&col,&col, 0, 0);
> - if (x_had_errors_p (dpy) || c == None)
> - c = 0;
> + pixc = XCreatePixmapCursor (dpy, pix, pix,&col,&col, 0, 0);
> + if (! x_had_errors_p (dpy)&& pixc != None)
> + c = pixc;
> XFreePixmap (dpy, pix);
> }
>
>
>
>
next prev parent reply other threads:[~2011-04-02 6:45 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-02 2:21 bug#8410: make_invisible_cursor returns garbage if XCreateBitmapFromData fails Paul Eggert
2011-04-02 6:45 ` Jan Djärv [this message]
2011-04-06 5:47 ` bug#8410: fix installed in trunk Paul Eggert
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