Specifying @nogc on structs seems to have no effect

[Craig Black]

On Tuesday, 19 September 2017 at 14:34:10 UTC, Mike Parker wrote:
> On Tuesday, 19 September 2017 at 14:22:21 UTC, Craig Black 
> wrote:
>
>> Thank you for your response.  The @nogc attribute is good, but 
>> in my opinion it is incomplete if all types still require 
>> scanning.  The purpose of not employing GC in certain sections 
>> of code is performance, and we are sacrificing performance 
>> with every allocation unit that is needlessly scanned.
>>
>> -Craig
>
> As I wrote in my previous post, *no* GC activity will happen 
> inside a @nogc function. The only time any scanning or 
> collections can take place is when a allocation is requested. 
> If none are requested, there's no activity.
>
> Aside from that, there are other options. If you don't want 
> your Foo member variable to be scanned, then allocate it 
> outside the GC heap (see Mallocator in std.allocator). You can 
> call GC.disable whenever you want (but be wary of the impact 
> performance when you later call GC.collect). You can allocate 
> outside of your hot loops and use stack allocation where 
> possible.
>
> I suggest you take a look at the ongoing GC series on the D 
> Blog. The next post (coming later this week) covers heap 
> allocations.
>
> https://dlang.org/blog/the-gc-series/

Thank you for the information.  What I would like to do is to 
create an Array template class that doesn't use GC at all.  
Unfortunately I don't think this is possible with D in its 
current state, at least not safely anyway.  As it is, I can't 
prevent someone using my Array template to create an array of 
objects that reference the GC heap.  This means that in order to 
not break the language and avoid memory leaks, I am forced to 
tell the GC to scan all of my allocations.  There seems to be no 
way to avoid this unnecessary overhead.

I realize that the GC will not collect during a @nogc function.  
This is a good guarantee, but I want to reduce the amount of time 
it takes to perform a collection, and there doesn't seem to be a 
good way to do this.

-Craig