Re: AQ&S Guidance on pragma Elaborate_Body

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

Michael Paus said

<<Hm ? If there is such a simple and strict rule on how to apply this
kind of pragmas, I wonder why the compiler does not do it automatically.
The compiler does check whether my pragma settings are correct. So it
seems to be quite straight forward for the compiler to automatically
insert the highest level of purity. Are there any undesirable side
effects when doing that or is the rule not as simple as you said ?

Just curious

Michael>>

Think carefuly here -- pragmas Pure and Preelaborate are applied to specs,
and determine legality of clients, but the conditoins that need checkiong
apply to bodies. Unless you want to create very peculiar dependenceis 
(basically a horrible dependence on all possible bodies), you do ONT
NOT want the compiler to do this automatically.

Furthermore, the viaiblity of Elaborate_Body cannot be checked till link
time.

That being said, the compiler can do FAR more to help here, and the
latest version of GNAT has some extremely useful additions in this
area, to be announced in detail later.