Отсортировать слова в файле по количеству букв

#include <glib.h>
#include <locale.h>
#include <assert.h>
 
gint lencmp(gconstpointer a, gconstpointer b) {
    return GPOINTER_TO_INT((gpointer)a) - GPOINTER_TO_INT((gpointer)b);
}
 
gboolean print_words(gpointer key, gpointer value, gpointer data) {
    for ( GSList * list = (GSList*) value; list; list = g_slist_next(list) )
        g_print("%s\n", (gchar*)(list->data));
        
    return FALSE;
}
 
gboolean free_list(gpointer key, gpointer value, gpointer data) {
    g_slist_free((GSList*) value);
    
    return FALSE;
}
     
#define FILE_NAME "rustext.txt"
 
int main(void) {
    char * oldloc = setlocale(LC_ALL, "ru_RU.UTF-8");
    assert(oldloc);
    
    gchar * content;
    gsize len;
    GError * err;
    
    if ( ! g_file_get_contents(FILE_NAME, &content, &len, &err) ) {
        g_print("Can't read file: %s\n", (err) ? err->message : "unknown reason");
        return 1;
    }
    
    gchar ** allwords, **iter;
    allwords = g_strsplit_set(content, " ,.!?\t\n", -1);
    GTree * counters = g_tree_new(lencmp);
    for ( iter = allwords; *iter; ++iter ) {
        if ( (*iter)[0] ) {
            gint len = (gint) g_utf8_strlen(*iter, -1);
            GSList * list = (GSList*) g_tree_lookup(counters, GINT_TO_POINTER(len));
            if ( list && g_slist_find_custom(list, *iter, (GCompareFunc)g_strcmp0) )
                continue;
            list = g_slist_prepend(list, *iter);
            g_tree_insert(counters, GINT_TO_POINTER(len), list);
        }
    }
    g_tree_foreach(counters, print_words, NULL);
    
    
    g_tree_foreach(counters, free_list, NULL);
    g_tree_destroy(counters);
    g_strfreev(allwords);
    g_free(content);
    setlocale(LC_ALL, oldloc);
    
    return 0;
}