Shared with no type in Druntime.

[Adam Wilson]

On Sat, 28 Apr 2012 18:23:30 -0700, Ali Çehreli <acehreli at yahoo.com> wrote:

> On 04/28/2012 06:08 PM, Adam Wilson wrote:
>> Ok. So i've been trying to build Phobos with my new DI generation code
>> (available here: https://github.com/LightBender/dmd.git) and i've run
>> into an interesting usage of shared in the D Runtime. Namely, it has no
>> type. I've been told that this is not correct and it should have a type.
>> Is that correct?
>>
>> Currently the source file (stdio.d in the DRT) has this in it and it
>> compiles successfully:
>>
>> private extern shared FILE[_NFILE] _iob;
>>
>> shared stdin = &_iob[0];
>> shared stdout = &_iob[1];
>> shared stderr = &_iob[2];
>> shared stdaux = &_iob[3];
>> shared stdprn = &_iob[4];
>>
>> With the new DI generation code stdio.di contains this:
>>
>> private extern shared FILE[_NFILE] _iob;
>>
>> shared stdin; (Errors here and all subsequent lines in this snippet)
>> shared stdout;
>> shared stderr;
>> shared stdaux;
>> shared stdprn;
>>
>> Is D doing some kind of type inference based on the type of the _iob
>> variable in the first example that causes DMD to throw an error with the
>> "= &_iob[0];" part removed?
>>
>
> Yes. D does type inference all the time. Most of the time 'auto' is used  
> because most variables have automatic storage class. The following are  
> all legal:
>
> void main()
> {
>      auto a = 42;               // int
>      const c = "hello";         // string
>      immutable i = 1.5;         // double
>
>      struct S
>      {}
>
>      shared s = new shared(S);  // S*
>      enum e = [ 0, 1 ];         // int[]
> }
>
> All of the standard streams are of type File:
>
>      assert(typeid(stdin) == typeid(std.stdio.File));
>
> Ali

Ok, so that answers the legality of the issue, but it smacks of sloppy  
coding. We cannot ship the DRT as a dynamic library, as has been discussed  
and agreed to as a good idea, if their are variable declarations that rely  
on type inference from an assignment operation because those assignments  
will get stripped out of the DI. So what should I do then? Because shared  
stdin; by itself with no assignment to infer from IS illegal and there is  
not (that I can see) a way to separate an instantiation from an  
implementation and the whole point of DI files is too remove  
implementations.

-- 
Adam Wilson
IRC: LightBender
Project Coordinator
The Horizon Project
http://www.thehorizonproject.org/