Re: Ada Plattform Independence

[Jean-Pierre Rosen <rosen@adalog.fr>]

patrick.gunia@googlemail.com a �crit :
>> -Differences on the implementation of Address. Some compilers (mainly
>> Ada83) defined Address as an integer type, while current common practice
>> is to make it private, which causes problems if people are doing
>> (uncontrolled) address arithmetic
> 
> I also thought of this aspect. I have the big advantage that the
> software is only executed on a very limited range of hardware
> configurations. Using the same compiler implementation for different
> plattforms (for example GNAT) would solve this problem?
AFAIK, GNAT (and presumably most Ada95 compilers, since it is
implementation advice) define Address as private

>> -Representation clauses. Compilers vary in their support of
>> representation clauses, sometimes for good reasons: some representation
>> clauses that are acceptable on some targets would lead to unreasonable
>> code on a different hardware. Representation clauses may also depend on
>> predefined types; f.e., if you have a record field of type Duration, you
>> may have problems when moving a program from an implementation where
>> Duration is 32 bits to one where Duration is 64 bits
> 
> Same aspect as above, when I use GNAT on GNU/Linux and Windows to
> compile this code, it should use the same implementation of Duration?
This might depend on the target. But why are you asking? Just try it!
(i.e. if there is a problem, it won't compile; no risk at run-time)

>> -Outrageously wrong code written by people who write "C-in-Ada", with
>> lots of unchecked conversions between pointers and addresses.
> 
> The code uses unchecked_conversions to call imported C-functions. I don
> �t think that I can avoid this problem. Though the software is always
> executed on 32-Bit systems, thus this should also work out, or am I
> getting something terribly wrong here?
Unchecked_Conversion was commonly used in Ada83. Using pragma Import and
Interfaces.C is preferred since Ada95. I would suggest migrating the
code to use these features.


-- 
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           J-P. Rosen (rosen@adalog.fr)
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