shared - i need it to be useful

[Manu]

On Sun, Oct 21, 2018 at 5:40 PM Timon Gehr via Digitalmars-d
<digitalmars-d at puremagic.com> wrote:
>
> On 21.10.18 21:04, Manu wrote:
> > On Sun, Oct 21, 2018 at 12:00 PM Timon Gehr via Digitalmars-d
> > <digitalmars-d at puremagic.com> wrote:
> >>
> >> On 21.10.18 17:54, Nicholas Wilson wrote:
> >>>
> >>>> As soon as that is done, you've got a data race with the other
> >>>> existing unshared aliases.
> >>>
> >>> You're in @trusted code, that is the whole point. The onus is on the
> >>> programmer to make that correct, same with regular @safe/@trusted at system
> >>> code.
> >>
> >> Not all of the parties that participate in the data race are in @trusted
> >> code. The point of @trusted is modularity: you manually check @trusted
> >> code according to some set of restrictions and then you are sure that
> >> there is no memory corruption.
> >>
> >> Note that you are not allowed to look at any of the @safe code while
> >> checking your @trusted code. You will only see an opaque interface to
> >> the @safe code that you call and all you know is that all the @safe code
> >> type checks according to @safe rules. Note that there might be an
> >> arbitrary number of @safe functions and methods that you do not see.
> >>
> >> Think about it this way: you first write all the @trusted and @system
> >> code, and some evil guy who does not like you comes in after you looks
> >> at your code and writes all the @safe code. If there is any memory
> >> corruption, it will be your fault and you will face harsh consequences.
> >> Now, design the @safe type checking rules. It won't be MP!
> >>
> >> Note that there may well be a good way to get the good properties of MP
> >> without breaking the type system, but MP itself is not good because it
> >> breaks @safe.
> >
> > Show me. Nobody has been able to show that yet. I'd really like to know this.
> >
>
> I just did,

There's no code there... just a presumption that the person who wrote
the @trusted code did not deliver the promise they made.

> but if you really need to, give me a non-trivial piece of> correct multithreaded code that accesses some declared-unshared field
> from a shared method and I will show you how the evil guy would modify
> some @safe code in it and introduce race conditions. It needs to be your
> code, as otherwise you will just claim again that it is me who wrote bad
> @trusted code.

You can pick on any of my prior code fragments. They've all been ignored so far.