Interested in D, spec confuses me.

[Dicebot via Digitalmars-d]

On 02/03/2016 02:31 AM, bubbasaur wrote:
> import std.stdio;
> 
>     struct Data { int x; }
>     auto func1(Data* d) { return d.x; }
>     auto func2(const(Data)* d) { return d.x; }
>     auto func3(immutable(Data)* d) { return d.x; }   
> 
>     void main() {
>         Data d;
>         auto value1 = d.x*func1(&d) + d.x;
>         auto value2 = d.x*func2(&d) + d.x;
>         auto value3 = d.x*func3(cast(immutable)&d) + d.x;
>         d.x++;
>         writeln(d.x++);
>     }
> 
> Functions 2 and 3 are acting in the same way and different from what you
> said I can change the d.x in main.


Casting immutable and violating it is undefined behavior and once you do
it all bets are off - compiler is even allowed to attempt formatting
your hard drive when compiling this program :)

The fact DMD doesn't do anything scary right now when you do it is a
mere coincidence and may change in any release with no notice.