App hangs, GC.collect() fixet it. Why?

Steven Schveighoffer schveiguy at
Mon Sep 28 15:44:44 UTC 2020

On 9/28/20 8:57 AM, Bastiaan Veelo wrote:

> I am glad to have found the cause of the breakage finally, but it won't 
> be easy to find a generic solution...

Obviously, this isn't a real piece of code, but there is no way around 
this. You have to align your pointers. The other option is to not use 
the GC and use manual memory management.

If this is a compatibility thing between D and Pascal, and you 
absolutely have to have the same layout, is there a way to adjust the 
structure in Pascal? Like put the elements that misalign the pointers at 
the end of the structure?

Another totally drastic approach would be to supply your own 
even-more-conservative GC which will scan misaligned pointers. Probably 
going to hurt performance quite a bit. You might be able to get away 
with marking only certain blocks as having misaligned pointers, but you 
will have to scan all the stacks with this assumption.

Some more information about the setup you are using might help (I'm 
assuming D and Pascal are using the same memory in the same process, 
otherwise this wouldn't be a problem). In particular, where does the 
data come from, and how malleable is it in your system? Are there times 
where references to the D data only exist in Pascal?


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