Implementing Alternative Garbage Collector

[Brandon Ragland via Digitalmars-d]

On Wednesday, 2 September 2015 at 18:25:11 UTC, Jacob Carlborg 
wrote:
> c
> On 2015-09-02 18:09, Brandon Ragland wrote:
>> This is just a figurative idea, perhaps for my own amusement...
>>
>> I've browsed the D runtime GC source code for the last few 
>> days and I'm
>> still undecided on what the actual method of "replacing" the 
>> existing GC
>> would be.
>>
>> Say for example, I decided to tinker and create my own GC 
>> (disregard the
>> fact that it'd be slower / faster, this is for learning 
>> purposes only).
>>
>> Is there a way to "insert" a new GC implementation, and what 
>> is the
>> actual interface the GC is using to connect to the core 
>> runtime of D?
>>
>> I see several GC related structs, etc. kind of spit 
>> everywhere, and
>> determining which one is the actual core _interface_ is 
>> seeming more
>> difficult than I thought.
>>
>>
>> Any hints, or pointing to the correct direction would be very 
>> helpful.
>>
>>  From the looks of it, it doesn't seem obvious.
>
> There's a minimal example of a GC in the druntime source code 
> [1]. For actually replacing the current one with your custom, I 
> think the easiest would be to just implement the necessary 
> functions in your application. They will take precedence over 
> the ones in druntime when linking.
>
> [1] 
> https://github.com/D-Programming-Language/druntime/blob/master/src/gcstub/gc.d

While that may be true, if the purpose was to ensure tracking and 
collection of objects / arrays created with the new expression, 
how would one do that without knowledge of the actual 
implementation and the interface?

Same would go for slicing operations, which would be difficult to 
track.

You'd have to pass a pointer to that new object onto the custom 
GC, or it will never see it. Quick way to have huge memory 
leaks...