Why does logging in destructor lead to segmentation fault?

[Bradley Chatha]

On Monday, 11 September 2023 at 17:31:17 UTC, Vladimir Marchevsky 
wrote:
> https://run.dlang.io/is/NMMpLn - minimal example. Debugging on 
> Windows, it crashes on `synchronized(mutex)` with "Access 
> violation" trying to read at zero address.

Generally you shouldn't access anything to do with the GC (or 
even really global state, such as the `sharedLogger`) within a 
dtor.

What's happening is that the GC is running the dtors for all 
objects after the main function's finished in a final cleanup, 
which prevents you from allocating any GC memory without crashing.

Potentially as well the GC has already cleaned up the 
`sharedLogger` causing the null read.

If you look at this example: https://run.dlang.io/is/PvyfOc

By making the class instance `scope` the class is allocated on 
the stack, and dtor-ed immediately after the function ends, 
rather than when DRuntime is finalising, which prevents the crash 
from occurring.

It's a bit of an annoying, weird quirk.