tree 4fe3af14033dc99c540bbeec32c4d1f9a3f3e120
parent 0fcb26c5b6487bf9b31670122f8c931ac020bb34
author Adrian Prantl <aprantl@apple.com> 1668471876 -0800
committer Adrian Prantl <aprantl@apple.com> 1668642686 -0800

Make CompilerType safe

When a process gets restarted TypeSystem objects associated with it
may get deleted, and any CompilerType objects holding on to a
reference to that type system are a use-after-free in waiting. Because
of the SBAPI, we don't have tight control over where CompilerTypes go
and when they are used. This is particularly a problem in the Swift
plugin, where the scratch TypeSystem can be restarted while the
process is still running. The Swift plugin has a lock to prevent
abuse, but where there's a lock there can be bugs.

This patch changes CompilerType to store a std::weak_ptr<TypeSystem>.
Most of the std::weak_ptr<TypeSystem>* uglyness is hidden by
introducing a wrapper class CompilerType::WrappedTypeSystem that has a
dyn_cast_or_null() method. The only sites that need to know about the
weak pointer implementation detail are the ones that deal with
creating TypeSystems.

rdar://101505232

Differential Revision: https://reviews.llvm.org/D136650