Re: AQ&S Guidance on pragma Elaborate_Body

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Mats says

<<...which shows that automatic elaboration order construction is _state
of the art_ (this is further confirmed by other compilers (Verdix, DEC)
I use without a single pragma Elaborate* and without ever getting
Program_Error).

IMO, state of the art belongs in the standard, not in nice compiler
specific features, which would have allowed the standard to take a
different approach: automatic elaboration order consturction with
pragmas to _override_ it, instead of pragmas to do the right thing in
the most basic cases.>>


Please don't generalize from your experience -- this could just mean that
you use elaboration very lightly. Others use it more heavily, and pragma
Elaborate can be critical -- here is an extreme, though real, example.
There is one Ada 83 compiler, written in Ada 83, where the main program
is null, and all the compiler passes are in elaboration code. Pragma
Elaborate is critical for ensuring that the passes of the compiler run
in the right order.

Sure, for the simple case you have DEC and Verdix (and most likely GNAT
as well) run fine, but I can *guarantee* that they are not consistent in
the set of programs that they can successfully handle statically.

We cannot have a statement in the standard that says "Elaboration shall be
automatically handled sufficiently well so that Mats Weber's programs run
without Program_Error", what we need is a very precise charaterization of
the set of programs that are to be considered legal.

Mats, what is this subset that you propose? in detail?