A patch to irchelper which strips control characters.

gistfile1.diff

diff --git a/irchelper/irchelper.c b/irchelper/irchelper.c
--- a/irchelper/irchelper.c
+++ b/irchelper/irchelper.c
@@ -781,18 +781,44 @@
                        if ((node = (PurpleBlistNode *)purple_blist_find_chat(account, name)) != NULL)
                        {
                                const char *last_topic = purple_blist_node_get_string(node, PLUGIN_ID "_topic");
+                               char *topic_cleaned = g_malloc(strlen(topic));
+                               const char *t = topic;
+                               char *tc = topic_cleaned;
+
+                               /* Strip invalid XML characters to work around libpurple using
+                                * g_markup_escape_text() which is XML 1.1 in files with an XML 1.0
+                                * declaration (and libxml2, which doesn't appear to support XML 1.1). */
+                               for ( ; *t ; t++)
+                               {
+                                       if ( *t == 0x0009 ||
+                                            *t == 0x000a ||
+                                            *t == 0x000d ||
+                                           (*t >= 0x0020 && *t <= 0x007e) ||
+                                            *t == 0x0085 ||
+                                           (*t >= 0x00a0 && *t <= 0xd7ff) ||
+                                           (*t >= 0xe000 && *t <= 0xfdcf) ||
+                                           (*t >= 0xfde0 && !((*t & 0xFFFE) == 0xFFFE || (*t & 0xFFFF) == 0xFFFF))
+                                        )
+                                       {
+                                               *tc = *t;
+                                               tc++;
+                                       }
+                               }
+                               *tc = '\0';
 
                                /* If we saw this the last time we joined, suppress it. */
-                               if (last_topic != NULL && strcmp(topic, last_topic) == 0)
+                               if (last_topic != NULL && strcmp(topic_cleaned, last_topic) == 0)
                                {
                                        g_free(name_escaped);
                                        g_free(topic_escaped);
                                        g_free(topic_linkified);
+                                       g_free(topic_cleaned);
 
                                        return TRUE;
                                }
                                else
-                                       purple_blist_node_set_string(node, PLUGIN_ID "_topic", topic);
+                                       purple_blist_node_set_string(node, PLUGIN_ID "_topic", topic_cleaned);
+                               g_free(topic_cleaned);
                        }
                }
                g_free(name_escaped);