From 363c40e3f33b6b7e07eb82c1d7998574ef0695bc Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Mon, 9 Mar 2020 21:29:22 +0100
Subject: [PATCH] LibJS: Make sure we mark everything reachable from the scope
 stack

This ensures that local variables survive GC.
---
 Libraries/LibJS/Heap.cpp        |  3 ++-
 Libraries/LibJS/Interpreter.cpp | 13 +++++++++++++
 Libraries/LibJS/Interpreter.h   |  2 ++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/Libraries/LibJS/Heap.cpp b/Libraries/LibJS/Heap.cpp
index 33ce668c54..bd0ec319b8 100644
--- a/Libraries/LibJS/Heap.cpp
+++ b/Libraries/LibJS/Heap.cpp
@@ -24,6 +24,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <AK/Badge.h>
 #include <AK/HashTable.h>
 #include <LibJS/Heap.h>
 #include <LibJS/HeapBlock.h>
@@ -72,7 +73,7 @@ void Heap::collect_garbage()
 
 void Heap::collect_roots(HashTable<Cell*>& roots)
 {
-    roots.set(&m_interpreter.global_object());
+    m_interpreter.collect_roots({}, roots);
 
 #ifdef HEAP_DEBUG
     dbg() << "collect_roots:";
diff --git a/Libraries/LibJS/Interpreter.cpp b/Libraries/LibJS/Interpreter.cpp
index 3c8f155825..701782a121 100644
--- a/Libraries/LibJS/Interpreter.cpp
+++ b/Libraries/LibJS/Interpreter.cpp
@@ -24,6 +24,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <AK/Badge.h>
 #include <LibJS/AST.h>
 #include <LibJS/Interpreter.h>
 #include <LibJS/Object.h>
@@ -100,4 +101,16 @@ Value Interpreter::get_variable(const String& name)
     return global_object().get(name);
 }
 
+void Interpreter::collect_roots(Badge<Heap>, HashTable<Cell*>& roots)
+{
+    roots.set(m_global_object);
+
+    for (auto& scope : m_scope_stack) {
+        for (auto& it : scope.variables) {
+            if (it.value.is_object())
+                roots.set(it.value.as_object());
+        }
+    }
+}
+
 }
diff --git a/Libraries/LibJS/Interpreter.h b/Libraries/LibJS/Interpreter.h
index e13dc8e518..0c229c182b 100644
--- a/Libraries/LibJS/Interpreter.h
+++ b/Libraries/LibJS/Interpreter.h
@@ -56,6 +56,8 @@ public:
     void set_variable(String name, Value);
     void declare_variable(String name);
 
+    void collect_roots(Badge<Heap>, HashTable<Cell*>&);
+
 private:
     void enter_scope(const ScopeNode&);
     void exit_scope(const ScopeNode&);