shared - i need it to be useful

[Timon Gehr]

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, 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.