Program crash: GC destroys an object unexpectedly

[Steven Schveighoffer]

On 9/23/21 2:18 PM, eugene wrote:
> On Thursday, 23 September 2021 at 17:16:23 UTC, Steven Schveighoffer wrote:
>> On 9/23/21 12:58 PM, eugene wrote:
>>> On Thursday, 23 September 2021 at 15:56:16 UTC, Steven Schveighoffer 
>>> wrote:
>>>> See more details:
>>>>
>>>> https://docs.microsoft.com/en-us/dotnet/api/system.gc.keepalive?view=net-5.0#remarks 
>>>>
>>>>
>>>
>>> "
>>> This method references the obj parameter, making that object 
>>> ineligible for garbage collection from the start of the routine to 
>>> the point, in execution order, where this method is called. Code this 
>>> method at the end, not the beginning, of the range of instructions 
>>> where obj must be available.
>>> "
>>>
>>> **Code this method at the end...**
>>>
>>> :)
>>> it is the same as proposed by jfondren simple
>>> writeln(stopper.sg0.number) in the end of main, right?
>>
>> Same effect, but writeln actually executes code to write data to the 
>> console, whereas KeepAlive doesn't do anything.
> 
> ```d
> void keepAlive(Object o) {
> }
> 
> void main(string[] args) {
> 
>      import core.memory : GC;
> 
>      auto Main = new Main();
>      Main.run();
> 
>      auto stopper = new Stopper();
>      stopper.run();
> 
>      writeln(" === Hello, world! === ");
>      auto md = new MessageDispatcher();
>      md.loop();
> 
>      keepAlive(Main);
>      keepAlive(stopper);
> 
>      writeln(" === Goodbye, world! === ");
> }
> ```
> works ok with dmd, stopper is not collected.

With dmd -O -inline, there is a chance it will be collected. Inlining is 
key here.

-Steve