Probably hard for you, but this happens on my machine:

I'm using de_DE@euro and in gnome-terminal I start joe (the text editor) and
press AltGr-3/4/5/6 and some other character and sometimes it will just go boom.

I found out that he tries to log something about invalid UTF8 sequences and the
assumption pos >= 0 in g_string_erase fails.

I quickly found out why: escape_string assumes that the string->str doesn't move
when modifying the string (g_string_insert). That's wrong.

A possible fix is to temporaryly switch to relative positioning in the slow
path. Something like this:

diff -Nur glib-2.4.0.orig/glib/gmessages.c glib-2.4.0/glib/gmessages.c
--- glib-2.4.0.orig/glib/gmessages.c    2004-03-14 19:54:18.000000000 +0100
+++ glib-2.4.0/glib/gmessages.c 2004-04-04 15:40:24.021198616 +0200
@@ -791,15 +791,16 @@
       if (wc == (gunichar)-1 || wc == (gunichar)-2)
        {
          gchar *tmp;
-
-         g_string_erase (string, p - string->str, 1);
+         guint pos = p - string->str;
+
+         g_string_erase (string, pos, 1);
          /* Emit invalid UTF-8 as hex escapes
            */
-         tmp = g_strdup_printf ("\\x%02x", (guint)(guchar)*p);
-         g_string_insert (string, p - string->str, tmp);
+         tmp = g_strdup_printf ("\\x%02x", (guint)(guchar)string->str[pos]);
+         g_string_insert (string, pos, tmp);
          g_free (tmp);
  
-         p += 4;               /* Skip over escape sequence */
+         p = &string->str[pos + 4];    /* Skip over escape sequence */
  
          continue;
        }
@@ -815,16 +816,17 @@
       if (!safe)
        {
          gchar *tmp;
-
-         g_string_erase (string, p - string->str, g_utf8_next_char (p) - p);
+         guint pos = p - string->str;
+
+         g_string_erase (string, pos, g_utf8_next_char (p) - p);
          /* Largest char we escape is 0x0a, so we don't have to worry
           * about 8-digit \Uxxxxyyyy
           */
          tmp = g_strdup_printf ("\\u%04x", wc);
-         g_string_insert (string, p - string->str, tmp);
+         g_string_insert (string, pos, tmp);
          g_free (tmp);
  
-         p += 6;               /* Skip over escape sequence */
+         p = &string->str[pos + 6];    /* Skip over escape sequence */
        }
       else
        p = g_utf8_next_char (p);