sane-project-website/old-archive/1998-03/0145.html

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<title>sane-devel: xscanimage SIGSEGVs (patch included)</title>
<h1>xscanimage SIGSEGVs (patch included)</h1>
<b>=?ISO-8859-1?Q?Mikko_Ty=F6l=E4j=E4rvi?=</b> (<a href="mailto:mikko@securitydynamics.com"><i>mikko@securitydynamics.com</i></a>)<br>
<i>Sat, 21 Mar 1998 15:25:29 +0100 (CET)</i>
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Hi!<br>
<p>
A sure way to crash sane on my machine is to start with "Show advanced<br>
options" turned on, turn it off, open the preview window and click<br>
"Aquire preview".  This requires the backend to define some options as<br>
"advanced," of course.  The crash is deep down in GTK, when called<br>
from gsg_set_sensitivity().<br>
<p>
The following patch (at the end of panel_destroy()) stops this from<br>
happening:<br>
<p>
<p>
--- frontend/gtkglue.c.org	Sat Mar 21 13:11:46 1998<br>
+++ frontend/gtkglue.c	Sat Mar 21 13:08:42 1998<br>
@@ -829,6 +829,8 @@<br>
 	  elem-&gt;menu = 0;<br>
 	}<br>
     }<br>
+  memset (dialog-&gt;element, 0,<br>
+    dialog-&gt;num_elements * sizeof (dialog-&gt;element[0]));<br>
 }<br>
 <br>
 static void<br>
<p>
<p>
Explanation: panel_rebuild() is called to rebuild the xscanimage<br>
window.  It simply calls panel_destroy() and builds the panel from<br>
scratch with panel_build(), which skips entries that should not be<br>
shown.  This is OKfor panel_build() when called initially, as<br>
gsg_create_dialog() clears the options array (element).<br>
Panel_destroy() however does not, leaving assorted garbage pointers<br>
for gsg_set_sensitivity() to crash on.<br>
<p>
Another fix would be to add a test for:<br>
<p>
  ((opt-&gt;cap &amp; SANE_CAP_ADVANCED) &amp;&amp; !dialog-&gt;advanced))<br>
<p>
in gsg_set_sensitivity(), to skip the bogus option entries (as<br>
panel_build() did), but then something else might crash for the same<br>
reason somewhere else.<br>
<p>
BTW: This is sane 0.71 with the snapscan backend, on FreeBSD 2.2.5 / 3.0.<br>
<p>
        Regards,<br>
	/Mikko<br>
<p>
<p>
 Mikko Tyo"la"ja"rvi________________________________mikko@securitydynamics.com<br>
 SecurityDynamics<br>
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