D Concurrent GC

[Sean Kelly]

Leandro Lucarella Wrote:

> Not quite ready for prime-time yet, but I think it's in a stage when it
> could be interesting anyway (at least for developers or people that want
> to experiment):
> http://llucax.com.ar/blog/blog/post/-1a4bdfba

Nice work!  I've gotten this to compile as the GC for druntime using D2 but have ran into a snag.  I'm using OSX (ie. no usable debug info) but near as I can tell the issue is:

private T locked(T, alias Code)()
{
    if (thread_needLock())
        synchronized (gc.lock) return Code();
    else
       return Code();
}

void* gc_malloc(size_t size, uint attrs = 0)
{
    if (size == 0)
        return null;
    return locked!(void*, () {
        assert (Invariant()); scope (exit) assert (Invariant());
        return malloc(size, attrs, null);
    })();
}

In the code above, it appears that the anonymous delegate being passed as an alias to locked() is having its stack data dynamically allocated (ie. as a dynamic closure).  For normal delegate calls this can be avoided by accepting "scope delegate" as the function parameter, but I haven't found an analog when using the alias approach.  Obviously, what happens is that a call to gc_malloc() ends up needing GCed memory, so gc_malloc() is recursively called, and on until the stack explodes.  I'll see if I can come up with a workaround that continues using the alias template parameter.