[glib] gvariant: Fix a potential memcpy(NULL) call

[Philip Withnall <pwithnall src gnome org>]

commit c1d5db618688a78aa897d269859a1bc6413a9e55
Author: Philip Withnall <philip withnall collabora co uk>
Date:   Mon Nov 25 13:50:20 2013 +0000

    gvariant: Fix a potential memcpy(NULL) call
    
    This probably won’t crash, as it can only happen if (size == 0), but
    add a check to be safe, and to shut up the static analyser.
    
    This case can be reached with the following call:
        gvs_read_unaligned_le(NULL, 0)
    which can be called from:
        gvs_tuple_get_child(value, index_)
    with (value.data == NULL) and (value.size == 0).
    
    Found by scan-build.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=715164

 glib/gvariant-serialiser.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/glib/gvariant-serialiser.c b/glib/gvariant-serialiser.c
index cc5cc7b..d903d74 100644
--- a/glib/gvariant-serialiser.c
+++ b/glib/gvariant-serialiser.c
@@ -552,6 +552,7 @@ gvs_fixed_sized_array_is_normal (GVariantSerialised value)
  * normal form and that is the one that the serialiser must produce.
  */
 
+/* bytes may be NULL if (size == 0). */
 static inline gsize
 gvs_read_unaligned_le (guchar *bytes,
                        guint   size)
@@ -563,7 +564,8 @@ gvs_read_unaligned_le (guchar *bytes,
   } tmpvalue;
 
   tmpvalue.integer = 0;
-  memcpy (&tmpvalue.bytes, bytes, size);
+  if (bytes != NULL)
+    memcpy (&tmpvalue.bytes, bytes, size);
 
   return GSIZE_FROM_LE (tmpvalue.integer);
 }