F*cked by memory corruption after assiging value to associative array

[FeepingCreature]

On Monday, 25 January 2021 at 11:15:28 UTC, frame wrote:
> After a while my program crashes.
>
> I'm inspecting in the debugger that some strings are 
> overwritten after a struct is assigned to an associative array.
>
> - I have disabled the GC.
> - All happens in the same thread.
> - The strings belong to an object collection inside an object 
> created from a d-DLL.
> - The object returned by the DLL function is added to the GC 
> with GC.addRoot().
> - This object also lives in a static array the whole time.
> - Not all objects are affected but many.
> - The struct itself looks okay also the key for the associative 
> array has normal form.
>
> The data is not overwritten by another Thread (only one is 
> running) but by the compiler. I'm watching it by memory 
> location. It gets always visible first after that assignment. 
> But how is this even possible? In theory, how could I ran into 
> this issue?

That should really not be possible.

I suspect the memory used by the original data got reused for the 
associative array somehow. But if the GC is off from program 
start, that should really not occur. Do you maybe turn the GC off 
before the AA assignment, but after it's already marked that 
memory freed? Try turning it off completely from the commandline 
with --DRT-gcopt=gc:manual