Backport the implementation of gtk_list_store_iter_is_valid from gtk+-3.

Index: gtk+-2.24.33/gtk/gtkliststore.c
===================================================================
--- gtk+-2.24.33.orig/gtk/gtkliststore.c
+++ gtk+-2.24.33/gtk/gtkliststore.c
@@ -1195,16 +1195,31 @@ gboolean
 gtk_list_store_iter_is_valid (GtkListStore *list_store,
                               GtkTreeIter  *iter)
 {
+  GSequenceIter *seq_iter;
+
   g_return_val_if_fail (GTK_IS_LIST_STORE (list_store), FALSE);
   g_return_val_if_fail (iter != NULL, FALSE);
 
-  if (!VALID_ITER (iter, list_store))
-    return FALSE;
+  /* can't use VALID_ITER() here, because iter might point
+   * to random memory.
+   *
+   * We MUST NOT dereference it.
+   */
 
-  if (g_sequence_iter_get_sequence (iter->user_data) != list_store->seq)
+  if (iter == NULL ||
+      iter->user_data == NULL ||
+      list_store->stamp != iter->stamp)
     return FALSE;
 
-  return TRUE;
+  for (seq_iter = g_sequence_get_begin_iter (list_store->seq);
+       !g_sequence_iter_is_end (seq_iter);
+       seq_iter = g_sequence_iter_next (seq_iter))
+    {
+      if (seq_iter == iter->user_data)
+        return TRUE;
+    }
+
+  return FALSE;
 }
 
 static gboolean real_gtk_list_store_row_draggable (GtkTreeDragSource *drag_source,
8a7cd43b'>tree</a><a href='/guix/commit/gnu/services/pm.scm?id=62cfe906d79e3676ec95fe17fd82c2618a7cd43b'>commit</a><a href='/guix/diff/gnu/services/pm.scm?id=62cfe906d79e3676ec95fe17fd82c2618a7cd43b'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/services/pm.scm'>
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<div class='path'>path: <a href='/guix/log/?id=62cfe906d79e3676ec95fe17fd82c2618a7cd43b'>root</a>/<a href='/guix/log/gnu?id=62cfe906d79e3676ec95fe17fd82c2618a7cd43b'>gnu</a>/<a href='/guix/log/gnu/services?id=62cfe906d79e3676ec95fe17fd82c2618a7cd43b'>services</a>/<a href='/guix/log/gnu/services/pm.scm?id=62cfe906d79e3676ec95fe17fd82c2618a7cd43b'>pm.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/services/pm.scm?id=62cfe906d79e3676ec95fe17fd82c2618a7cd43b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-06-15 00:25:21 +0200'>2022-06-15</span></td><td><a href='/guix/commit/gnu/services/pm.scm?id=8cb1a49a3998c39f315a4199b7d4a121a6d66449'>services: configuration: Use *unspecified* instead of 'disabled.</a><span class='msg-avail'>...<span class='msg-tooltip'>Use *unspecified* as a marker for field values that have not been set.

Rationale: 'disabled may easily clash with user values for boolean fields, is
confusing (i.e. its meaning is *not* boolean false, but unspecified) and it
also passes silently through the symbol? predicate of a field of type symbol.

* gnu/services/configuration.scm (configuration-missing-default-value):
Renamed from configuration-no-default-value.
(define-maybe-helper): Use *unspecified* instead of 'disabled, and make
the default value optional.
* gnu/home/services/desktop.scm (home-redshift-configuration):
Change (maybe-xyz 'disabled) to maybe-xyz.
* gnu/services/authentication.scm (nslcd-configuration): Likewise.
* gnu/services/cgit.scm (repository-cgit-configuration): Likewise.
* gnu/services/file-sharing.scm (serialize-maybe-string)
(serialize-maybe-file-object): Use 'unspecified?' instead of (eq? val
'disabled).
* gnu/services/messaging.scm (raw-content?): Likewise.
(ssl-configuration): Change (maybe-xyz 'disabled) to maybe-xyz.
(prosody-configuration): Likewise.
* gnu/services/file-sharing.scm (transmission-daemon-configuration):
Likewise.
* gnu/services/messaging.scm (define-all-configurations):
Use *unspecified* instead of 'disabled'.
* gnu/services/networking.scm (opendht-configuration): Likewise.
* gnu/services/pm.scm (tlp-configuration): Likewise.
* gnu/services/telephony.scm (jami-account): Likewise.
(jami-configuration): Likewise.
* gnu/services/vpn.scm (openvpn-client-configuration): Likewise.
* tests/services/configuration.scm ("maybe type, no default")
("maybe type, with default"): New tests.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Attila Lendvai</td></tr>
<tr><td><span title='2022-03-20 16:40:22 +0100'>2022-03-20</span></td><td><a href='/guix/commit/gnu/services/pm.scm?id=10d865aa921f559562fb543d7796c7a08e17f016'>services: thermald: Add 'adaptive?' field.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/pm.scm (&lt;thermald-configuration&gt;): Add 'adaptive?' field.
(thermald-shepherd-service): Use it to pass --adaptive to thermald.
* doc/guix.texi (Power Management Services): Document the 'adaptive?' field of
'thermald-configuration'.
</span></span></td><td>Jelle Licht</td></tr>
<tr><td><span title='2022-02-02 10:43:04 +0100'>2022-02-02</span></td><td><a href='/guix/commit/gnu/services/pm.scm?id=67f28faf42a362ae4d50ede4cc48782e2aea887f'>services: tlp: Add config variables for battery charging.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/pm.scm (tlp-configuration): Add start-charge-thresh-bat0,
stop-charge-thresh-bat0, start-charge-thresh-bat1, stop-charge-thresh-bat1.
* doc/guix.texi (Power Management Services): Document them.

Signed-off-by: Ricardo Wurmus &lt;rekado@elephly.net&gt;
</span></span></td><td>Attila Lendvai</td></tr>
<tr><td><span title='2021-11-30 01:08:55 +0100'>2021-11-30</span></td><td><a href='/guix/commit/gnu/services/pm.scm?id=892f1b7273d57b25940700877a02618fe826cc08'>services: Accept &lt;inferior-package&gt;s in lieu of &lt;package&gt;s.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/authentication.scm (fprintd-configuration)
(nslcd-configuration): Substitute file-like objects for package ones.
* gnu/services/cgit.scm (cgit-configuration, opaque-cgit-configuration):
Likewise.
* gnu/services/cups.scm (package-list?, cups-configuration): Likewise.
* gnu/services/dns.scm (verify-knot-configuration)
(ddclient-configuration): Likewise.
* gnu/services/docker.scm (docker-configuration): Likewise.
* gnu/services/file-sharing.scm (transmission-daemon-configuration): Likewise.
* gnu/services/getmail.scm (getmail-configuration): Likewise.
* gnu/services/mail.scm (dovecot-configuration)
(opaque-dovecot-configuration): Likewise.
* gnu/services/messaging.scm (prosody-configuration)
(opaque-prosody-configuration): Likewise.
* gnu/services/monitoring.scm (zabbix-server-configuration)
(zabbix-agent-configuration): Likewise.
* gnu/services/networking.scm (opendht-configuration): Likewise.
* gnu/services/pm.scm (tlp-configuration): Likewise.
* gnu/services/telephony.scm (jami-configuration): Likewise.
* gnu/services/virtualization.scm (libvirt-configuration)
(qemu-guest-agent-configuration): Likewise.
* gnu/services/vpn.scm (openvpn-client-configuration): Likewise.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>