From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,2203a21a136b39cc
X-Google-Attributes: gid103376,public
From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: Fortran's Equivalence
Date: 1997/04/10
Message-ID: <dewar.860712372@merv>#1/1
X-Deja-AN: 232415790
References: <333840D1.7B12@cae.ca> <E8385t.9zE@thomsoft.com>
 <dewar.860159911@merv> <3349165C.3B93@cae.ca>
 <1997Apr8.155111.26714@nosc.mil>
 <mheaney-ya023680000804971958130001@news.ni.net>
 <334BA679.5E5D@gsfc.nasa.gov> <dewar.860617761@merv>
 <x7v912qd3pt.fsf@pogner.demon.co.uk>
Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-04-10T00:00:00+00:00
List-Id: <comp.lang.ada>


Simon said

<<What worked for me was

  given an interfaces.c.int to be interpreted as bit fields
  declare record type without representation
  declare variable "result" of this type
  if system.default_bit_order = system.high_order_first then
    declare derived record type with big-endian representation
    do unchecked conversion from interfaces.c.int to this type
    assign to "result"
  else
    declare derived record type with little-endian representation
    do unchecked conversion from interfaces.c.int to this type
    assign to "result"
  end if

which is long-winded but does the job! No doubt there are other ways ..>>


This does NOT work in the general case, it only works if you have a simple
case where all fields are conveniently aligned, which is a small subset of
possible cases.