Druntime stub project

[IGotD-]

I would like that we begin a Druntime stub project. The purpose 
of the project is to.

Separate D library specific code and OS specific code.
Create an empty stub that can be compiled and where OS 
customization can be use as a starting point. You simply copy the 
stub directory and start from there.
Create a common "interface" to druntime.
People who have custom systems will have less of a merge hell 
when the code is separated.

In several posts I've seen that people are looking for a druntime 
with limited support for certain embedded systems, so there is a 
demand for a stub despite it is more or less unusable in its pure 
form. Also another reason I want to make a stub is that creating 
this runtime abstract interface is that as soon you start to mess 
around in the OS specific code, the risk of breaking the existing 
OS support is obvious. Better to have a gradual approach to this. 
Creating a stub will be require quite a lot of work by itself. 
After the stub has been created, it should be agreed upon that 
existing OS support should gradually move to the druntime 
interface approach and no new OS specific code should be added in 
the generic parts in druntime.

One approach that was suggested was as described in this post.

https://forum.dlang.org/post/r4rcdg$222f$1@digitalmars.com

which import files based on compile time identifiers.

If we take the file druntime/src/core/sync/semaphore.d

a file would be added at druntime/src/core/sys/stub/semaphore.d

where "stub" is really OS identifier.

The current semaphore.d file would be changed to the following.


import config.osconfiguration;

...
	
	// Semaphore
	//
	// void wait();
	// void notify();
	// bool tryWait();
	////////////////////////////////////////////////////////////////////////////////
version(druntimeAbstract)
	mixin(import_("core", "sys", osname, "semaphore"));
}
else
{
	/**
	 * This class represents a general counting semaphore as 
concieved by Edsger
	 * Dijkstra.  As per Mesa type monitors however, "signal" has 
been replaced
	 * with "notify" to indicate that control is not transferred to 
the waiter when
	 * a notification is sent.
	 */
	class Semaphore
	{
		////////////////////////////////////////////////////////////////////////////
		// Initialization
		////////////////////////////////////////////////////////////////////////////


		/**

where osname = stub in the case. osname comes from a 
configuration file that are imported almost everywhere. Not sure 
where this should be located though.


Tell me what you think in the comments below.