hawkinsw added a comment.
There are *so* many reasons that I love this patch.
First and foremost: I am a professor of computer science at University of
Cincinnati and teaching Programming Languages this semester and I am about to
teach *this very technique* for protecting against use-after-free errors.
Having seen this patch I now have a great example of where it is used in real
life! So, thank you!
Second, I have left some comments but please take what I said with a grain of
salt. I hope that it is helpful and not a waste of time.
Thank you!
Will
================
Comment at: lldb/source/Symbol/CompilerType.cpp:35
+ bool unused;
+ if (GetTypeSystemGraveyard().Lookup(m_type_system, unused)) {
+ lldbassert(false && "CompilerType belongs to deleted Typesystem");
----------------
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!
================
Comment at: lldb/source/Symbol/CompilerType.cpp:36
+ if (GetTypeSystemGraveyard().Lookup(m_type_system, unused)) {
+ lldbassert(false && "CompilerType belongs to deleted Typesystem");
+ return false;
----------------
I know that this is a nit, but should we write `TypeSystem`?
================
Comment at: lldb/source/Symbol/TypeSystem.cpp:22
+ // Intentionally leaked to avoid C++ destructor ordering issue.
+ static TypeSystemSet *g_typesystem_graveyard = new TypeSystemSet();
+ return *g_typesystem_graveyard;
----------------
I spent *way* too long researching to make sure that this initialization is
thread safe and wanted to drop a link here in case anyone is wondering the same
thing:
[C++ standard: stmt.dcl para 3, sentence
3](http://eel.is/c++draft/stmt.dcl#3.sentence-3)
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D136650/new/
https://reviews.llvm.org/D136650
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