Re: Elaboration order

[jwierzbo@hercii.lasc.lockheed.com (Joe Wierzbowski)]

In article 4FA9@lfwc.lockheed.com, Ken Garlington <GarlingtonKE@lfwc.lockheed.com> () writes:
>   < snip >
> 
> So what does this mean in the following case:
> 
> package Another_Example is
> 
>   function Initial_Value return Integer;
> 
> end;
> 
> package body Another_Example is
> 
>   function Initial_Value return Integer is begin return 0; end;
> 
> end;
> 
> with Another_Example;
> package Use_Example is
> 
>   X : Integer := Another_Example.Initial_Value;
> 
> end;
> 
> Can I get a Program_Error on the initialization of X? If so,
> it would seem like there would need to be a pragma
> Elaborate for nearly every reference to every package
> exporting a subprogram!

  Yes, you can get Program_Error on the initialization of X.

  The important point here for Ada 83 is that this requirement
  refers to declarative regions.  So your choices are:
  1) Add a pragma Elaborate for each subprogram called during a 
     declarative region or
  2) Don't make initial assignments using subprogram calls in a
     declarative region.  This is a common mistake, so much so
     that it may be worth adding a restriction against doing so 
     in a coding standard.  I can tell you that it's almost always
     the first thing to bite you during integration; there's always
     someone who has an elaboration order problem.  

  Another thing to note here is that Ada 95 provides convenient
  ways of elaborating every required package (See Robert Duff's
  posting).