[glibmm] Gio::TlsDatabase: Fix create_certificate_handle_vfunc()

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 365a6ee5658fd496d5fc87679de0b583eb3e53b4
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Mon Jun 26 17:05:16 2017 +0200

    Gio::TlsDatabase: Fix create_certificate_handle_vfunc()
    
    This vfunc shall delete the returned character array after it has been
    copied to a Glib::ustring, or else it leaks memory. It shall also convert
    an empty Glib::ustring to a null gchar*. Bug 783360

 gio/src/tlsdatabase.hg |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/gio/src/tlsdatabase.hg b/gio/src/tlsdatabase.hg
index 0be174a..610402b 100644
--- a/gio/src/tlsdatabase.hg
+++ b/gio/src/tlsdatabase.hg
@@ -99,7 +99,12 @@ public:
 
   _WRAP_VFUNC(TlsCertificateFlags verify_chain_finish(const Glib::RefPtr<AsyncResult>& result), 
"verify_chain_finish", errthrow)
 
+dnl// create_certificate_handle_vfunc() shall return a newly allocated string.
+dnl// Also, ensure that create_certificate_handle_vfunc() never returns an empty char[],
+dnl// because that could be caused by an intermediate empty ustring from an initial null char*.
 #m4 _CONVERSION(`GTlsCertificate*',`const Glib::RefPtr<const TlsCertificate>&',`Glib::wrap($3, true)')
+#m4 _CONVERSION(`Glib::ustring',`gchar*',`g_strdup(Glib::c_str_or_nullptr($3))')
+#m4 _CONVERSION(`gchar*',`Glib::ustring',`Glib::convert_return_gchar_ptr_to_ustring($3)')
   _WRAP_VFUNC(Glib::ustring create_certificate_handle(const Glib::RefPtr<const TlsCertificate>& certificate) 
const, "create_certificate_handle")
 
 #m4 
_CONVERSION(`Glib::RefPtr<TlsCertificate>',`GTlsCertificate*',`G_TLS_CERTIFICATE(g_object_ref(Glib::unwrap($3)))')