Re: DIP60: @nogc attribute

[via Digitalmars-d]

On Monday, 21 April 2014 at 23:02:54 UTC, Walter Bright wrote:
There is JUST NO WAY that:
    struct RefCount {
        T* data;
        int* count;
    }


This is actually quite efficient compared to the standard 
NSObject which uses a hashtable for refcounting:

http://www.opensource.apple.com/source/objc4/objc4-551.1/runtime/NSObject.mm
http://www.opensource.apple.com/source/objc4/objc4-551.1/runtime/llvm-DenseMap.h

This is how Core Foundation does it:

http://www.opensource.apple.com/source/CF/CF-855.11/CFRuntime.c

Pretty longwinded:

CFTypeRef CFRetain(CFTypeRef cf) {
    if (NULL == cf) { CRSetCrashLogMessage("*** CFRetain() called 
with NULL ***"); HALT; }
    if (cf) __CFGenericAssertIsCF(cf);
    return _CFRetain(cf, false);
}

static CFTypeRef _CFRetain(CFTypeRef cf, Boolean tryR) {
    uint32_t cfinfo = *(uint32_t *)&(((CFRuntimeBase 
*)cf)->_cfinfo);
    if (cfinfo & 0x800000) { // custom ref counting for object
        ...stuff deleted…
        refcount(+1, cf);
        return cf;
    }
    …lots of stuff deleted…
    return cf;
}