Memory Corruption with AAs

[dsimcha]

== Quote from Walter Bright (newshound1 at digitalmars.com)'s article
> dsimcha wrote:
> > == Quote from Walter Bright (newshound1 at digitalmars.com)'s article
> >> dsimcha wrote:
> >>> Has anyone else still been noticing difficult to reproduce memory corruption
> >>> issues in the presence of associative arrays with 2.042?  They seem to happen
> >>> very infrequently and non-deterministically.  I can only reproduce them in the
> >>> context of a large program.  However, they don't occur in 2.040 (the release
> >>> before the array stomping patch), and they are clearly a result of memory
> >>> corruption, as contents of arrays change from what I expect them to be to
> >>> completely random-looking values inside a loop that does a lot of memory
> >>> management and uses AAs heavily but doesn't modify the values.
> >> 1. is it multithreaded?
> >> 2. does your code have any dangling pointers into AAs?
> >
> > The program as a whole is multithreaded, but the part where the bug occurs is an
> > initialization routine that is executed before any threads other than the main one
> > are launched.
> It should be easier to find then, by removing all the main code and everything
> it calls.

The code has so many dependencies (both other code from the same project and
libraries) and is such a mess (because it's a research prototype that evolved more
than it was designed and also has all kinds of speed hacks) that it would probably
be easier to try to reproduce it from scratch.  I'll try tonight because I've got
a long train ride with nothing else to do anyhow.

> >
> > As far as the dangling pointers question, I don't understand how there could be
> > dangling pointers into GC-managed memory, since if there are pointers to it, it
> > won't be freed.  (Ignoring dirty tricks that I'm not using in this case.)
> What I meant was, do you save any pointers into the AAs, as in:
>      auto p = &aa[key];
> ?

No, I definitely wasn't.  I almost never do this with any data structure other
than an array because, even if it works for now, I consider it a horrible
violation of encapsulation because you're relying on the details of how the data
structure manipulates memory.  This is also why, when I designed RandAA I didn't
see this as an issue until you pointed it out to me.