From 277132f70d6a44f84fa71b03d64cce435c65c183 Mon Sep 17 00:00:00 2001
From: Luke Wilde <lukew@serenityos.org>
Date: Fri, 25 Nov 2022 23:15:44 +0000
Subject: [PATCH] LibJS/Bytecode: Store unwind contexts inside RegisterWindow

Unwind contexts need to be preserved as we exit and re-enter a
generator.

For example, this would previously crash when returning from the try
statement after yielding as we lost the unwind context when yielding,
but still have a LeaveUnwindContext instruction from running
`perform_needed_unwinds` when generating the return statement.
```js
function* a() {
    try {
        return (yield 1);
    } catch {}
}

iter = a();
iter.next();
iter.next();
```
---
 Userland/Libraries/LibJS/Bytecode/Interpreter.cpp | 14 +++++++-------
 Userland/Libraries/LibJS/Bytecode/Interpreter.h   |  3 ++-
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp b/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
index e7b60f9618..41eb283228 100644
--- a/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
+++ b/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
@@ -65,7 +65,7 @@ Interpreter::ValueAndFrame Interpreter::run_and_return_frame(Executable const& e
     if (in_frame)
         m_register_windows.append(in_frame);
     else
-        m_register_windows.append(make<RegisterWindow>(MarkedVector<Value>(vm().heap()), MarkedVector<Environment*>(vm().heap()), MarkedVector<Environment*>(vm().heap())));
+        m_register_windows.append(make<RegisterWindow>(MarkedVector<Value>(vm().heap()), MarkedVector<Environment*>(vm().heap()), MarkedVector<Environment*>(vm().heap()), Vector<UnwindInfo> {}));
 
     registers().resize(executable.number_of_registers);
 
@@ -81,9 +81,9 @@ Interpreter::ValueAndFrame Interpreter::run_and_return_frame(Executable const& e
             if (ran_or_error.is_error()) {
                 auto exception_value = *ran_or_error.throw_completion().value();
                 m_saved_exception = make_handle(exception_value);
-                if (m_unwind_contexts.is_empty())
+                if (unwind_contexts().is_empty())
                     break;
-                auto& unwind_context = m_unwind_contexts.last();
+                auto& unwind_context = unwind_contexts().last();
                 if (unwind_context.executable != m_current_executable)
                     break;
                 if (unwind_context.handler) {
@@ -92,7 +92,7 @@ Interpreter::ValueAndFrame Interpreter::run_and_return_frame(Executable const& e
 
                     // If there's no finalizer, there's nowhere for the handler block to unwind to, so the unwind context is no longer needed.
                     if (!unwind_context.finalizer)
-                        m_unwind_contexts.take_last();
+                        unwind_contexts().take_last();
 
                     accumulator() = exception_value;
                     m_saved_exception = {};
@@ -101,7 +101,7 @@ Interpreter::ValueAndFrame Interpreter::run_and_return_frame(Executable const& e
                 }
                 if (unwind_context.finalizer) {
                     m_current_block = unwind_context.finalizer;
-                    m_unwind_contexts.take_last();
+                    unwind_contexts().take_last();
                     will_jump = true;
                     break;
                 }
@@ -179,12 +179,12 @@ Interpreter::ValueAndFrame Interpreter::run_and_return_frame(Executable const& e
 
 void Interpreter::enter_unwind_context(Optional<Label> handler_target, Optional<Label> finalizer_target)
 {
-    m_unwind_contexts.empend(m_current_executable, handler_target.has_value() ? &handler_target->block() : nullptr, finalizer_target.has_value() ? &finalizer_target->block() : nullptr);
+    unwind_contexts().empend(m_current_executable, handler_target.has_value() ? &handler_target->block() : nullptr, finalizer_target.has_value() ? &finalizer_target->block() : nullptr);
 }
 
 void Interpreter::leave_unwind_context()
 {
-    m_unwind_contexts.take_last();
+    unwind_contexts().take_last();
 }
 
 ThrowCompletionOr<void> Interpreter::continue_pending_unwind(Label const& resume_label)
diff --git a/Userland/Libraries/LibJS/Bytecode/Interpreter.h b/Userland/Libraries/LibJS/Bytecode/Interpreter.h
index c6451eaf69..5ad350f561 100644
--- a/Userland/Libraries/LibJS/Bytecode/Interpreter.h
+++ b/Userland/Libraries/LibJS/Bytecode/Interpreter.h
@@ -22,6 +22,7 @@ struct RegisterWindow {
     MarkedVector<Value> registers;
     MarkedVector<Environment*> saved_lexical_environments;
     MarkedVector<Environment*> saved_variable_environments;
+    Vector<UnwindInfo> unwind_contexts;
 };
 
 class Interpreter {
@@ -52,6 +53,7 @@ public:
 
     auto& saved_lexical_environment_stack() { return window().saved_lexical_environments; }
     auto& saved_variable_environment_stack() { return window().saved_variable_environments; }
+    auto& unwind_contexts() { return window().unwind_contexts; }
 
     void jump(Label const& label)
     {
@@ -98,7 +100,6 @@ private:
     Optional<BasicBlock const*> m_pending_jump;
     Value m_return_value;
     Executable const* m_current_executable { nullptr };
-    Vector<UnwindInfo> m_unwind_contexts;
     Handle<Value> m_saved_exception;
     OwnPtr<JS::Interpreter> m_ast_interpreter;
     BasicBlock const* m_current_block { nullptr };