Shared with no type in Druntime.

[Ali Çehreli]

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