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

1 files changed, 2 insertions, 2 deletions

diff --git a/lldb/source/Core/Module.cpp b/lldb/source/Core/Module.cpp
index 20bd02f101fc..b1cc0dd58211 100644
--- a/lldb/source/Core/Module.cpp
+++ b/lldb/source/Core/Module.cpp
@@ -364,13 +364,13 @@ void Module::SetUUID(const lldb_private::UUID &uuid) {
   }
 }
 
-llvm::Expected<TypeSystem &>
+llvm::Expected<TypeSystemSP>
 Module::GetTypeSystemForLanguage(LanguageType language) {
   return m_type_system_map.GetTypeSystemForLanguage(language, this, true);
 }
 
 void Module::ForEachTypeSystem(
-    llvm::function_ref<bool(TypeSystem *)> callback) {
+    llvm::function_ref<bool(lldb::TypeSystemSP)> callback) {
   m_type_system_map.ForEach(callback);
 }