thank you for your answer
If I change affich() code (I put as an example an incrementation of an other
variable named a),
the compiler consider c as a constant (he optimize well and remove all switch
cases in inc function).
So the problem comes from the <<() calls in affich.
Is the compiler lost when he find << calls ? (cause a lot of code is generated
to affich a string )
thank you for your help.
----- Message d'origine ----
De : Nathan Froyd <froy...@codesourcery.com>
À : charfi asma <charfia...@yahoo.fr>
Cc : gcc@gcc.gnu.org
Envoyé le : Jeudi, 5 Mars 2009, 17h33mn 28s
Objet : Re: constant propagation optimization
On Thu, Mar 05, 2009 at 11:39:45AM +0000, charfi asma wrote:
> intc;
> int main()
>
> {
>
> Calcul ca;
>
> c=3;
>
> ca.affich();
>
> ca.inc(c);
>
> cout << "the value of c is" << c << endl;
>
> return 0;
>
> }
[...]
> int main()
>
> {
>
> Calcul ca;
>
> ca.affich();
>
> c=3;
>
> ca.inc(c);
>
> cout << "the value of c is" << c << endl;
>
> return 0;
>
> }
>
> Why in the fist code, c is not considered as a constant (in spite that
> affich() does not change c)
Because GCC does not currently do the necessary analysis to know that
affich() does not change c; it therefore makes the conservative
assumption that it does.
-Nathan
