The second thing I was wondering about was, is line 71:

x = g_malloc (sizeof *x + strlen (name) );

strlen() won't count the terminating byte whereas strcpy will copy it.

The malloc + strcpy is a standard pattern. Example;

  struct {
    int flags;
    char name[1];
  } *foo;

  foo = xmalloc (sizeof *foo + strlen (string));
  strcpy (foo->name, string);

will always work correctly. The sizeof returns the length of the
structure which includes 1 byte for name. The strlen computes the
length of string without the terminator. However we alloacted one
extra byte (the name[1]) and thus everything is fine.

Regarding the ERR thing: You are right and I wonder why gcc (4.6.3) didn't
caught it.