Conference turris::pascal

    I was about to make a comment about the person who wrote the code, but
    then I checked 2098.6 and saw it was me...  I guess the author was
    too cleaver for his own good.  :-) :-)
    
    To quote from 2098.6,
    
    > There is no way to "omit" a procedure parameter when calling one Pascal
    > routine from another.
    
    and 
    
    > Here's an example (with magic to emulate calling Pascal from a 
    > non-Pascal caller).
    
    Well, one incompatable change when moving from VAX to Alpha is using
    bound procedure values like the example tries to fake up.  There
    is a section in the User Manual, Chapter 9 "Migrating from OpenVMS VAX
    to OpenVMS Alpha", section 9.5 "Bound Procedure Values".
    
    As long as you don't trick the compiler, moving from VAX to Alpha was
    transparent in this area.  Programs such as this (or trying to use
    Pascal and C with routine parameters) can unfortunately see the
    difference.  We never added any feature for "present but 0" like 
    was discussed back in 2098 since that was the only time somebody raised 
    the issue.
    
    I can see two choices,
    
    1) Use "%IMMED 0" on OpeVMS Alpha and use "%REF 0" on OpenVMS VAX.
    That would mean you only have to visit the declarations and not
    the call sites or the routine bodies.  Since we don't have a
    preprocessor on OpenVMS, you'll have to use some trick to get one set
    of declarations for Alpha and other for VAX.  Either 2 sets of modules
    or perhaps do a %INCLUDE 'SOMELOGICALNAME' for the routine default
    value and define the SOMELOGICALNAME to point to a file containing
    "%IMMED 0" or one containing "%REF 0" before you do the compilation.
    
    2) You can leave the %REF 0 alone, but go to the routine bodies and
    change the test for present from the simple "iaddress(p1) = 0" to
    
    type pint = ^integer_address;
    var  p1addr,p2addr : integer_address;
    
    p1addr := iaddress(p1);
    if p1addr::pint^ = 0 then { routine is absent }
    
    This scheme doesn't require you change the definitions or the callers,
    just the code in the called routine.
    
    You can even add some code that checks the machine architecture and
    "does the right thing" so the code would be compatible between OpenVMS 
    VAX and OpenVMS Alpha.
    
    
    				-John

    re .*

    Or of course with 10000 source modules involved, maybe the customer is
    willing to wave some cash at Digital for an enhancement to the
    compiler.

    If the 10000 source modules are all callers with a limited number of
    called routines then you might be able to introduce a platform specific
    jacket for each called routine that converts the call into something that
    can more reasonably be handled.