How to use core.atomic.cas with (function) pointers?

[Nicholas Wilson]

On Tuesday, 22 January 2019 at 14:13:23 UTC, Johan Engelen wrote:
> The following code compiles:
> ```
> alias T = shared(int)*;
>
> shared T a;
> shared T b;
> shared T c;
>
> void foo() {
>     import core.atomic: cas;
>     cas(&a, b, c);
> }
> ```
>
> The type of T has to be a pointer to a shared int (you get a 
> template match error for `cas` if `T = int*`), which is 
> annoying but I kind-of understand.
> However, change b to null (`cas(&a, null, c);`) and things no 
> longer work: "Error: template `core.atomic.cas` cannot deduce 
> function from argument types"
>
> I have not succeeded to make things work with function pointers 
> (neither with nor without `null` as second argument). What am I 
> doing wrong if `alias T = void function();` ?
>
> Thanks,
>   Johan

You need to cast stuff (as seems to be the case with everything 
to do with shared, at least until/if Manu's proposal goes 
through):

alias T = void function();
alias S = shared(size_t*);
shared T a;
shared T b;
shared T c;

void foo() {
     import core.atomic: cas;
     cas(cast(S*)&a, cast(S)b, cast(S)c);
}