Re: AQ&S Guidance on pragma Elaborate_Body

[mfb@mbunix.mitre.org (Michael F Brenner)]

Bob said
    Pure
    Preelaborate
    Elaborate_Body
    Elaborate_All
    Elaborate
 > The first three make life easier, because they go on the package (rather
 > than on all clients), and they pretty much prevent access-before-elab
 > failures.

One more thing must be said: in reusing this software, the reuse itself
might have a circular dependency, which the compiler may or may not
be able to figure out. To reduce the amount of stuff that the compiler
has to worry about, and to make it possible to compute a SINGLE
elaboration order (without which the program may raise program_error
at will), you MUST add one of the first three to all packages you
think are NOT in a circular elaboration dependency loop. Doing this
also helps you identify your elaboration loops more clearly, so you
can deal with them using elaborate or elaborate_all or by removing
the regression testing code from the elaboration-time executable
statements at the bottom of the package. Failure to add these will
cause needless failures when they are reused INSIDE an elaboration
dependency loop. 

If a quality standard says they are optional, that quality standard
does not reflect the reality of Ada-95 software re-use.