Re: Pragma for conditional compilation? (Ada 2005 vs. 95)

[Jeffrey Creem <jeff@thecreems.com>]

Jeffrey R. Carter wrote:
> Jerry wrote:
>>
>>> The third real old way is to code in the option by a "IF-THEN-ELSE-END"
>>> statements and use a Global constant variable(s). Its low tech but it
>>> still works.
>>
>> OK, but my "problem" is in declaring types which I want to be visible
>> in 95 but not visible in 05, as 05 provides them itself. An "IF-THEN-
>> ELSE-END" solution would have to be in the executable part of the
>> program (right?).
> 
> Despite the claim, this will not work. You cannot compile Ada-07 code 
> with an Ada-95 compiler. Different bodies for different compilers, 
> selected somehow (project files are a good way with GNAT, as has been 
> suggested) is the best way to address this issue.
> 

I agree that in general, given where Ada is, the best way to solve these 
issues is the whole "you have a CM problem" thing...But it really is 
sort of just a mantra that we repeat and all hope it is true.

The problem is that in the C world, for good (sometimes) or evil 
(equally often) people can portably but painfully use the pre-processor 
to deal with compiler and platform portability issues.

We claim it is a CM problem but of course now you trade a language 
portability problem for a CM/build chain portability problem. Finding a 
build system or CM system that works portability is now just another 
problem to deal with.

I am not saying conditional compilation is the real answer, but pointing 
to something that is outside the language definition as the answer is 
somewhat of a cop out.