Linker issues with struct postblit

[Thomas Gregory]

On Sunday, 31 October 2021 at 03:51:49 UTC, James Blachly wrote:
> On 10/29/21 7:10 AM, Stanislav Blinov wrote:
>> On Friday, 29 October 2021 at 11:05:14 UTC, Imperatorn wrote:
>>> On Thursday, 28 October 2021 at 01:39:10 UTC, Thomas Gregory 
>>> wrote:
>>>> I am a maintainer of the 
>>>> [dhtslib](https://github.com/blachlylab/dhtslib) package and 
>>>> I have been running into issues with a new implementation of 
>>>> reference counting we are using.
>>>>
>>>> [...]
>>>
>>> Postblit?
>> 
>> https://dlang.org/spec/struct.html#struct-postblit
>
> I imagine Imperatorn is quite familiar with postblit and was 
> pointing out that it is strange to use postblit constructor, 
> which is deprecated, in a "new implementation".
>
> The original post was long and really buried the lede, but OP 
> was pointing out what looks like a compiler bug: a linker error 
> referencing a postblit symbol only shows up when compiling with 
> DMD or with LDC earlier than 1.25.
>
> Can someone give some insight?

I apologize for the long-winded question.

>>> Postblit?

Yes, one solution would be to add a postblit.

However, the compiler should be able to generate default postblit 
and it does. I am only running into issues linking, which leads 
me to believe this is a compiler or language bug (fixed as of 
ldc-1.25).

Is there some way to to avoid writing an explicit postblit for 
every struct that uses `SafeHtslibPtr`? Many of `dhtslib`'s 
structs wrap c type pointers that are reference counted and owned 
by `SafeHtslibPtr` like so:

```D
// wrappedCPtr is an alias defined in another module as:
alias wrappedCPtr = SafeHtslibPtr!(c_type, destroy_c_type_fun);

// It is imported here
struct WrapperTypeName
{
     /// Backing C type pointer
     wrappedCPtr b;
...
}
```