Re: Elaboration order

[cmcknigh@hercii.lasc.lockheed.com (Chris McKnight)]

In article 1F9@world.std.com, bobduff@world.std.com (Robert A Duff) writes:
>In article <EACHUS.96Mar15174620@spectre.mitre.org>,
>Robert I. Eachus <eachus@spectre.mitre.org> wrote:
>>   BUT, and this is what makes it so painless, either your program
>>runs or you get PROGRAM_ERROR right off the bat, so leaving out a
>>(potentially) required pragma Elaborate is pretty harmless.
>
>True during development on a particular platform.  But what bugs me
>about these rules is that the mysterious Program_Error can pop up when
>you port the program to a different compiler.  (Or, less likely, a new
>version of the same compiler.)
     
     ... or when you add new functionality on the same platform either
  during incremental development or maintenance.  It is not uncommon
  for a program to suddenly develop elaboration order problems simply
  by recompiling a library unit or two, even if that unit does not
  itself have the problem.  I've seen this several times, the compilation
  causes a change in the elaboration order which causes a side effect of
  making some other library unit get an elaboration order problem.
  And, since we're talking Ada 83 here, it can be difficult to track
  down the possibly nested library units to which you'll need to add
  pragma Elaborate.  So, as you can see, using subprogram calls during
  declarative regions can be far from painless.

    These type of problems have lead me to avoid assignments during 
  elaboration using subprogram calls.  Why invite trouble when it's 
  easily avoided?  I'll take controlled behaviour of initialization
  through Initialization procedures over unpredictable elaboration
  order dependencies any day.

  Just my $.02

  Cheers,

    Chris