spawn a function with object as arg?

Adam D. Ruppe destructionator at
Thu Mar 5 03:04:10 UTC 2020

On Wednesday, 4 March 2020 at 23:37:00 UTC, Martin Brezel wrote:
> The documentation for spawn() states: "all arguments to fn must 
> either be shared or immutable or have no pointer indirection."

The easiest thing to do is to just cast

import std.concurrency;
import std.socket;

void main() {
         auto s = new Socket();
         spawn((shared Socket s_) {
             Socket s = cast() s_;
         }, cast(shared) s);

Note the shared argument to the function... then cast AWAY shared 
inside that function, and cast TO shared when passing the 

That basically just tricks the compiler. But if you aren't going 
to actually use the socket from the original thread anymore, it 
should be perfectly fine to do.

(if you do actually share it across threads, using it from 
both... it would actually probably still be fine - the Socket 
class is a thin wrapper around OS functions that work with 
threads. But then you re on your own, the compiler won't help get 
it right at all. Abandoning the old one isn't really getting 
compiler help either but it is so easy to do that you prolly 
won't make a mistake.)

You can also not use `spawn` and instead give `new Thread` a try 
from core.thread. That's totally DIY, the compiler won't even try 
to help you, but it can be simpler if you know what you're doing 
and don't need to pass a lot of

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