Initializing D runtime and executing module and TLS ctors for D libraries

[IGotD-]

On Saturday, 30 January 2021 at 12:28:16 UTC, Ali Çehreli wrote:
>
> I wonder whether doing something in the runtime is possible. 
> For example, it may be more resilient and not crash when 
> suspending a thread fails because the thread may be dead 
> already.
>
> However, studying the runtime code around thread_detachThis 
> three years ago, I had realized that like many things in 
> computing, the whole stop-the-world is wishful thinking because 
> there is no guarantee that your "please suspend this thread" 
> request to the OS has succeeded. You get a success return code 
> back but it means your request succeeded not that the thread 
> was or will be suspended. (I may be misremembering this point 
> but I know that the runtime requests things where OS does not 
> give full guarantee for.)
>

OT. A thread that suspends itself will always happen (not taking 
fall through cases into account), if not, throw the OS away. If a 
thread suspends another thread, then you don't really know when 
that thread will be suspended. I would discourage that threads 
suspends other threads because that will open up a new world of 
race conditions. Some systems don't even allow it and its 
benefits are very limited.

Back to topic. I think that the generic solution even if it 
doesn't help you with your current implementation is to ban TLS 
all together. I think there have already been requests to remove 
TLS for druntime/phobos totally and I think this should 
definitely be done sooner than later. Also if you write a shared 
library in D, simply don't use TLS at all. This way it will not 
matter if a thread is registered by druntime or not. TLS is in my 
opinion a wart in computer science.