So I've been chasing after this issue for the better part of an hour, and as I dug deeper, it just got weirder and weirder.

I have an Interface, let's call it PartyAnimal, and three classes, one of which is exclusive to unittest.
class Equine is an abstract class that implements some of PartyAnimal, but not the part where the bug occurs. class Pony inherits from Equine, and has the code which triggers the crash. Method whinny() is defined in Equine (without implementation), implemented in Pony, but not defined or implemented in PartyAnimal.
class Cow, which also inherits from PartyAnimal, is solely for unittesting another class which has a list full of PartyAnimals, and it only exists in unittest mode with version(unittest) { /*definition goes here*/ }.

The unittests pass, everything is okay, and then the actual main code calls the problematic method of Pony. It throws a core.exception.InvalidMemoryOperationError error when creating a new dynamic array of a size bigger than 2046 bytes, or allocating memory (with GC.malloc) of a size bigger than 2048 bytes. But only when compiled in unittest mode. It works like a charm in debug and release mode. But it's code never touched by any unittest.

Platform is Windows 7, compiler is DMD32 D Compiler v2.064. I have tried to reproduce the problem in a test code, but was unable to. This is why I'm not submitting it as bug report right away: it's useless without test code.

However, maybe someone here has heard of the problem before, or has any pointers to what could be going wrong, or ideas on how to debug this any further.

"Nicolas F."  wrote in message news:fnamiajuljitahfgvfmw@forum.dlang.org...

> So I've been chasing after this issue for the better part of an hour, and as I dug deeper, it just got weirder and weirder.

I suggest downloading the latest beta and seeing if that solves your problem - the bug may have already been fixed!

Otherwise, you may be able to use dustmite to reduce your program down to a test case: https://github.com/CyberShadow/DustMite/wiki 

I think I have found the issue.

The problem was a circlular reference in some class that managed the creation and destruction of PartyAnimals. Now I still don't know how that triggered the behaviour that I saw, but I do have a theory. When a certain size of memory is allocated, the GC may have said that it's time to clean up. If there was an instance created prior to the actual code being run, e.g. through a unittest, it would get a problem while cleaning up.

So the problem essentially was that my unittests weren't extensive enough, as they did not cover deallocation of some instances. Ironically, by reducing the unittest to a few lines, I found which one was actually triggering the problem.

TL;DR: not a D bug, problem caused by my own incompetence.