Re: Elaboration order

[gauthier@unilim.fr (Michel Gauthier)]

In article <314EE48E.7F5A@escmail.orl.mmc.com>, Ted Dennison
<dennison@escmail.orl.mmc.com> wrote:

>>  Robert Dewar wrote:
>>  > 
>>  >  (snip)
>>  (snip)
>>  > This sounds VERY bogus, I would NEVER do this kind of initialization
>>  > at elaboration time -- this is NOT what elaboratoin is intended for,
>>  > but rather, in my book, a gross misuse of the concept!
>>  
>>  I completely agree, but it doesn't mean others won't do it. I was given
>>  some code to debug once which was crashing 4 HOURS into elaboration. 
>>  Who knows how long elaboration would have taken without the crash? 

Nevertheless, you should consider that object design, when combined with 
Ada "accessibility rules" imply greater importance given to elaboration.

For instance, deriving a tagged type is legal only at the same level as the
parent type. Assuming that many tagged types are (visibly or privately)
declared in some library package, all their childs are necessarily declared
in library packages. 

Ada-95 programs will therefore make greater use (than Ada-83) of
library elaborations. How can you design and code something like an option
mechanism (from command line or configuration files) that must initialise
before some type definition ?

Note that I lost the initial messages, and hence cannot give any opinion on
that particular case. I only suggest not to repeat the mistake
( classic about exceptions) of confusing possible misuses and absolute harm.
I guess we, industry programmers and academic teachers, have yet to
"elaborate" style rules about the new 95 features, among which the above
problems.

To conclude, I may envisage to agree with " this is not what elaboration is 
intended for" but I am not sure that " what elaboration is intended for" is
information common to everybody.

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