Re: Teaching C/C++ from Ada perspective?

[Maciej Sobczak <see.my.homepage@gmail.com>]

> > Yet, the trivial update of P (like adding whitespace, which again has
> > no semantic meaning whatsoever) forces the recompilation of Test (with
> > GNAT). Actually, it forces the recompilation of everything. Why?
> 
> gprbuild:
>   -m       Minimum Ada recompilation
> 
> Only rebuild if there's a semantic difference

Great! Let's try it out.
I have added a dummy declaration to P, like here:

-- p.ads:
package P is
   pragma Pure (P);
   type TI is new Integer;  -- new dummy definition
end P;

and... the whole project was recompiled from scratch.

No other part of the project relies on this new type and in particular, the author of Test still could not care less about package P and whatever it contains.
Yet, the author of Test had to wait for the whole project to recompile, because something irrelevant was added to some irrelevant package that he might not even know that exists in the project.

I presume that the -m switch was supposed to handle a trivial (and perhaps frequent) case of editing comments and whitespace. There is some added value in this, but it is easy to replicate for C++ and sorry, but I don't call it "semantic" if it cannot figure out even the most basic cases like the one above.

My claim that Ada and C++ compilers have the same challenges when it comes to handling the physical project structure holds.

-- 
Maciej Sobczak * http://www.inspirel.com