casting NULL within a varargs list

[Ben Pfaff]

The recent commit c75794cff "Const casts" removes some casts of
NULL to a pointer type within varargs parameter lists.  This will
cause problems on 64-bit systems that #define NULL to 0 (without
any cast to pointer type).  This is a special case where the cast
cannot be removed.  (If you want to introduce a macro for this
case, to make it obvious what's going on, that's fine with me.)

The GNU coding standards even has a specific exception for this:

    Zero without a cast is perfectly fine as a null
    pointer constant, except when calling a varargs function.

(For what it's worth, I prefer NULL over 0 as a null pointer
constant.  It makes it obvious that it's a pointer instead of an
integer.)

-- 
Ben Pfaff 
http://benpfaff.org