From c8baf29d82ca4db83f32a54015a3c5e92e20930e Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Mon, 21 Sep 2020 14:35:19 +0200
Subject: [PATCH] LibJS: Assert if garbage collection is restarted while
 ongoing

We can't GC while we're already in GC. Assert if this happens.
---
 Libraries/LibJS/Heap/Heap.cpp | 3 +++
 Libraries/LibJS/Heap/Heap.h   | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/Libraries/LibJS/Heap/Heap.cpp b/Libraries/LibJS/Heap/Heap.cpp
index a4a131fe5c..1bfa91e54e 100644
--- a/Libraries/LibJS/Heap/Heap.cpp
+++ b/Libraries/LibJS/Heap/Heap.cpp
@@ -89,6 +89,9 @@ Cell* Heap::allocate_cell(size_t size)
 
 void Heap::collect_garbage(CollectionType collection_type, bool print_report)
 {
+    ASSERT(!m_collecting_garbage);
+    TemporaryChange change(m_collecting_garbage, true);
+
     Core::ElapsedTimer collection_measurement_timer;
     collection_measurement_timer.start();
     if (collection_type == CollectionType::CollectGarbage) {
diff --git a/Libraries/LibJS/Heap/Heap.h b/Libraries/LibJS/Heap/Heap.h
index b1381a8dae..0d727210a4 100644
--- a/Libraries/LibJS/Heap/Heap.h
+++ b/Libraries/LibJS/Heap/Heap.h
@@ -109,6 +109,8 @@ private:
 
     size_t m_gc_deferrals { 0 };
     bool m_should_gc_when_deferral_ends { false };
+
+    bool m_collecting_garbage { false };
 };
 
 }