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From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: Ada Tagged Type-Operation assign?
Date: Fri, 15 May 2009 07:30:33 -0700 (PDT)
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Date: 2009-05-15T07:30:33-07:00
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Patrick Gunia wrote on comp.lang.ada:
> I got a question concerning Ada-Tagged-Type implementation. I=B4m
> currently comparing two versions of a program written in Ada, one uses
> tagged types, the other one doesn=B4t. I use VTune to evaluate the
> runtime-performance of both versions and found that the call graph
> display of vtunes shows one function in the tagged-type version which
> gets called massively whereas there aren=B4t any calls to these
> functions in my "non-tagged-type-version". This operation isn=B4t
> declared by me, thus it has to be provided by the system. The
> operation is named "assign". The funny thing about this is, that this
> operations gets only called for tagged types which aren=B4t inherited,
> all my other tagged types which are organized in class hierarchies don
> =B4t show this behaviour. It might be important that these types are
> aubclasses from Ada.Finalization.Controlled, maybe that=B4s a reason why
> I don=B4t find the "assign"-operation.
> So, now here are my questions:
> Is the operation "assign" automatically provided for tagged types?
> If so, is there any possibility to control this method or do I have to
> accept it?
>
> The reason for my second question simply is the fact, that the self
> time of the function is not relevant (0,00ms), though when it gets
> called 3 billion times, it starts to be a relevant factor for
> performance differences...

I could imagine that the compiler-generated assign procedure
implements the run-time checks for assignment. These run-time checks
presumably exist only when the source or the target of the assignment
is of a class-wide type. Is that the case?

For controlled types, there should be calls to Adjust and Finalize in
addition to (not instead of) assign, so my reasoning may be off-mark.
It would help if you could produce a short example.

--
Ludovic Brenta.