labath added a comment.
The Halloween theme is nice, but I think it'd be more traditional if we kept a
list of active instances, instead of inactive ones. That said, a part of me
dies every time I see a class keeping a list of its instances.
I don't know if you've seen it, but I think the `Module::m_old_symfiles` member
exists for the very same reason, and it could be why this does not happen so
often outside of swift (which, I believe, stores most of its types in the
target type system instead of the module systems).
================
Comment at: lldb/source/Symbol/CompilerType.cpp:35
+ bool unused;
+ if (GetTypeSystemGraveyard().Lookup(m_type_system, unused)) {
+ lldbassert(false && "CompilerType belongs to deleted Typesystem");
----------------
aprantl wrote:
> hawkinsw wrote:
> > I am sorry if this is obvious, but is `CompilerType` used in a
> > multithreaded environment? So, is there a possibility that we could pass
> > the check on line 32 but become invalid by the use of `m_type_system` here
> > and fall victim to an attempt (in `Lookup`, perhaps?) to dereference a
> > `NULL` pointer? Again, I am sorry if that is a stupid question!
> Yes, CompilerType could be used on any thread and this will not catch a
> use-after-free if the TypeSystem is deleted between the IsValid check and its
> use.
>
> A solution would be to store a TypeSystemSP/WP in CompilerType, but I'm
> expecting this to be rather expensive. The intention of this patch is as a
> bug-finding tool. It's not intended to make holding on to CompilerType
> objects safe. That said, I'm open to explore ideas for how to efficiently
> make this safe in a future patch.
Well.. if you're only interested in SB uses, then I'd say that the SBType
object should hold an SP/WP on the type system or some parent of it.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D136650/new/
https://reviews.llvm.org/D136650
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