[glib/wip/carlosg/utf8-strreverse-invalid-writes] gutf8: Assert that written memory stays in bounds

[Carlos Garnacho <carlosg src gnome org>]

commit 154f6cafa90c9fa77208cf1815a6f421c9eceb64
Author: Carlos Garnacho <carlosg gnome org>
Date:   Wed Aug 7 23:18:42 2019 +0200

    gutf8: Assert that written memory stays in bounds
    
    You may expect funny effects from passing invalid UTF-8, but not
    that funny. The assert will probably be a better and more immediate
    confirmation of an error than invalid writes under the address of the
    string copy.
    
    https://gitlab.gnome.org/GNOME/glib/issues/1863

 glib/gutf8.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/glib/gutf8.c b/glib/gutf8.c
index a19f72044..fe0f8ab14 100644
--- a/glib/gutf8.c
+++ b/glib/gutf8.c
@@ -1773,6 +1773,7 @@ g_utf8_strreverse (const gchar *str,
     {
       gchar *m, skip = g_utf8_skip[*(guchar*) p];
       r -= skip;
+      g_assert (r >= result);
       for (m = r; skip; skip--)
         *m++ = *p++;
     }