GC attribute modifications use case?

[Steven Schveighoffer]

On Sunday, 22 December 2024 at 04:05:50 UTC, Steven Schveighoffer 
wrote:

> So does anyone have any good use cases for setting arbitrary GC 
> attributes after allocation?

Rikki pointed out a nice search on github to find all D code that 
calls `setAttr`. 90% of the use of `setAttr` is either garbage 
(setting the attribute to something that is already set), or 
setting `NO_MOVE`, which is currently a no-op (supposedly a 
"future" GC might be able to move allocations, but this is 
actually impossible in D).

There are some intriguing uses of `setAttr` for `NO_SCAN`, like a 
weak-reference object, which sets the attr of `this` in the 
constructor. Really, the correct way to do this is to pass in the 
right attr on allocation, but D hasn't traditionally made this 
very easy to do.

However, I've decided to support the existing unittest for now, 
and address this a separate way later.

Will expand on this in the future...

-Steve