D const design rationale

[Deewiant]

Don Clugston wrote:
> QUOTE ----
> int x = 3;
> const int *p = &x;
> *p = 4;        // error, read-only view
> x = 5;        // ok
> int y = *p;    // y is set to 5
> 
> This is one instance of the so-called aliasing problem, since while the
> above snippet is trivial, the existence of such aliases can be very hard
> to detect in a complex program. It is impossible for the compiler to
> reliably detect it. This means that the compiler cannot cache 4 in a
> register and reuse the cached value to replace *p, it must go back and
> actually dereference p again.
> ---
> Shouldn't that be: "the compiler cannot cache 3 in a register" ?

No. At "*p = 4;" the compiler can't cache 4, because then at "int y = *p;" y
would become 4 instead of 5.

Although in the example it's moot because "*p = 4;" is an error.

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