[glade] gtk+: workaround truncation warning by being safer

[Alberto Fanjul <albfan src gnome org>]

commit 21551ac316f20a190fea475b084379ab8077c724
Author: Victor Toso <me victortoso com>
Date:   Wed Nov 6 11:10:38 2019 +0100

    gtk+: workaround truncation warning by being safer
    
    Truncation was somewhat intended as column_name can fit 255 bytes plus
    the null termination. Still, there is an easy workaround which is to
    ensure that buffer is null terminated and then use strcpy. Should be a
    bit safer and faster than strncpy().
    
     > ../plugins/gtk+/glade-gtk-list-store.c:492:13: warning: ‘strncpy’
     > output may be truncated copying 255 bytes from a string of length
     > 255 [-Wstringop-truncation]
     >
     >  492 |             strncpy (column_name, buffer, 255);
     >      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 plugins/gtk+/glade-gtk-list-store.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/plugins/gtk+/glade-gtk-list-store.c b/plugins/gtk+/glade-gtk-list-store.c
index b30b58a1..bfaad360 100644
--- a/plugins/gtk+/glade-gtk-list-store.c
+++ b/plugins/gtk+/glade-gtk-list-store.c
@@ -479,6 +479,7 @@ glade_gtk_store_read_columns (GladeWidget *widget, GladeXmlNode *node)
     {
       GladeColumnType *data;
       gchar *type, *comment_str, buffer[256];
+      buffer[255] = '\0';
 
       if (!glade_xml_node_verify_silent (prop, GLADE_TAG_COLUMN) &&
           !glade_xml_node_is_comment (prop))
@@ -487,8 +488,8 @@ glade_gtk_store_read_columns (GladeWidget *widget, GladeXmlNode *node)
       if (glade_xml_node_is_comment (prop))
         {
           comment_str = glade_xml_get_content (prop);
-          if (sscanf (comment_str, " column-name %s", buffer) == 1)
-            strncpy (column_name, buffer, 255);
+          if (sscanf (comment_str, " column-name %255s", buffer) == 1)
+            strcpy (column_name, buffer);
 
           g_free (comment_str);
           continue;