[gnome-builder/gnome-builder-3-20] command-bar: Check if the completion provider fulfills its contract

[Matthew Leeds <mwleeds src gnome org>]

commit c38ca1d89ab763dd41a9848a5fcd5ab61c5f6923
Author: Matthew Leeds <mleeds redhat com>
Date:   Tue Jun 7 13:18:42 2016 -0400

    command-bar: Check if the completion provider fulfills its contract
    
    Emit a warning if the provided completion is not a prefix of the command
    typed by the user, and don't display it as an option. Otherwise we would
    read past the end of a character array.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=767369

 plugins/command-bar/gb-command-bar.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/plugins/command-bar/gb-command-bar.c b/plugins/command-bar/gb-command-bar.c
index accbc00..47e57a8 100644
--- a/plugins/command-bar/gb-command-bar.c
+++ b/plugins/command-bar/gb-command-bar.c
@@ -436,6 +436,12 @@ gb_command_bar_complete (GbCommandBar *self)
               GtkWidget *label;
               char *s;
 
+              if (!g_str_has_prefix (completions[i], current_prefix))
+                {
+                  g_warning ("Provided completion does not contain '%s' as a prefix", current_prefix);
+                  continue;
+                }
+
               label = gtk_label_new ("");
               s = g_strdup_printf ("<b>%s</b>%s", current_prefix, completions[i] + strlen (current_prefix));
               gtk_label_set_markup (GTK_LABEL (label), s);