[goffice] Various: sanity check types before creating objects based on names.

[Morten Welinder <mortenw src gnome org>]

commit 36df9babd3099ed12d5885b3f807e8a84998661a
Author: Morten Welinder <terra gnome org>
Date:   Thu Jun 18 12:37:38 2015 -0400

    Various: sanity check types before creating objects based on names.
    
    In principle a type constructor can do all kinds of things.  We want
    to check that a type is derived from the right base before we create
    objects of that type.

 ChangeLog                       |   11 +++++++++++
 goffice/app/go-doc.c            |    2 +-
 goffice/graph/gog-object-xml.c  |    4 +++-
 goffice/graph/gog-plot-engine.c |    3 +++
 4 files changed, 18 insertions(+), 2 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 474d52c..cb4ddf0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2015-06-18  Morten Welinder  <terra gnome org>
+
+       * goffice/app/go-doc.c (go_doc_image_fetch): Sanity check image
+       type.
+
+       * goffice/graph/gog-object-xml.c (gogo_start): Sanity check object
+       type.
+
+       * goffice/graph/gog-plot-engine.c (gog_plot_new_by_name)
+       (gog_trend_line_new_by_name): Sanity check type name.
+
 2015-06-17  Jean Brefort  <jean brefort normalesup org>
 
        * goffice/graph/gog-object.c (gog_object_get_child_by_role): protect against
diff --git a/goffice/app/go-doc.c b/goffice/app/go-doc.c
index 043cd36..1587c3b 100644
--- a/goffice/app/go-doc.c
+++ b/goffice/app/go-doc.c
@@ -675,7 +675,7 @@ go_doc_image_fetch (GODoc *doc, char const *id, GType type)
        g_return_val_if_fail (doc && doc->priv->imagebuf, NULL);
        image = g_hash_table_lookup (doc->priv->imagebuf, id);
        if (!image) {
-               g_return_val_if_fail (type != 0, NULL);
+               g_return_val_if_fail (g_type_is_a (type, GO_TYPE_IMAGE), NULL);
                image = g_object_new (type, NULL);
                if (!GO_IS_IMAGE (image)) {
                        if (image)
diff --git a/goffice/graph/gog-object-xml.c b/goffice/graph/gog-object-xml.c
index 73f6015..308c281 100644
--- a/goffice/graph/gog-object-xml.c
+++ b/goffice/graph/gog-object-xml.c
@@ -452,8 +452,10 @@ gogo_start (GsfXMLIn *xin, xmlChar const **attrs)
                        res = (GogObject *)gog_plot_new_by_name (type);
                        if (NULL == res)
                                res = (GogObject *)gog_trend_line_new_by_name (type);
-               } else
+               } else if (g_type_is_a (t, GOG_TYPE_OBJECT))
                        res = g_object_new (t, NULL);
+               else
+                       res = NULL;
 
                if (res == NULL) {
                        g_warning ("unknown type '%s'", type);
diff --git a/goffice/graph/gog-plot-engine.c b/goffice/graph/gog-plot-engine.c
index 1221acf..488124b 100644
--- a/goffice/graph/gog-plot-engine.c
+++ b/goffice/graph/gog-plot-engine.c
@@ -132,6 +132,7 @@ gog_plot_new_by_name (char const *id)
                g_object_ref (plugin);
                go_plugin_use_ref (plugin);
        }
+       g_return_val_if_fail (g_type_is_a (type, GOG_TYPE_PLOT), NULL);
 
        return g_object_new (type, NULL);
 }
@@ -470,9 +471,11 @@ gog_trend_line_new_by_name (char const *id)
                g_object_ref (plugin);
                go_plugin_use_ref (plugin);
        }
+       g_return_val_if_fail (g_type_is_a (type, GOG_TYPE_TREND_LINE), NULL);
 
        return g_object_new (type, NULL);
 }
+
 /***************************************************************************/
 /* Use a plugin service to define regression curves types */