New problem compiling g-exctra.adb

[Richard Kenner]

    I'm not well versed in standards and such, but if that's the case, you
    want to create a name tag for such a pointer.

    To solicit name tag creation, you have to tell create_name_tags() about
    the pointer.  Currently it creates name tags for pointers with PT_VARS
    and pointers with PT_MALLOC.

    One approach is to set the PT_MALLOC attribute on these pointers with
    value 0.  If you do that, things should just work.  The name would
    probably need to be changed, but PT_MALLOC has the semantics you are
    looking for.  It means 'points to a chunk of memory that cannot be used
    by a regular user variable'.

Why can't we just ignore assignments of pointers to zero?  They would
seem to tell us nothing useful about the variable being assigned.
What am I missing?