GNU bug report logs - #8410
make_invisible_cursor returns garbage if XCreateBitmapFromData fails

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#8410: closed (make_invisible_cursor returns garbage if
 XCreateBitmapFromData fails)
Date: Wed, 06 Apr 2011 05:48:02 +0000

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Your message dated Tue, 05 Apr 2011 22:47:16 -0700
with message-id <4D9BFE64.8090502 <at> cs.ucla.edu>
and subject line fix installed in trunk
has caused the GNU bug report #8410,
regarding make_invisible_cursor returns garbage if XCreateBitmapFromData fails
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


-- 
8410: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=8410
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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: bug-gnu-emacs <at> gnu.org
Subject: make_invisible_cursor returns garbage if XCreateBitmapFromData fails
Date: Fri, 01 Apr 2011 19:21:34 -0700

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);
     }

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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: 8401-done <at> debbugs.gnu.org, 8410-done <at> debbugs.gnu.org
Subject: fix installed in trunk
Date: Tue, 05 Apr 2011 22:47:16 -0700

I committed the previously-mentioned fix
as part of the merge to the trunk in bzr 103841.

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