From d8a92570baa8344deaa21ea0cc948a86111ace4b Mon Sep 17 00:00:00 2001
From: tusooa <tusooa@kazv.moe>
Date: Sat, 21 Sep 2024 23:26:39 -0400
Subject: [PATCH] Add a comment to explain why ranged-for cannot be used

---
 lager/detail/nodes.hpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lager/detail/nodes.hpp b/lager/detail/nodes.hpp
index 633be49..f7dabb9 100644
--- a/lager/detail/nodes.hpp
+++ b/lager/detail/nodes.hpp
@@ -235,6 +235,10 @@ class reader_node : public observable_reader_node<T>
             bool garbage = false;
 
             this->observers()(last_);
+            // We cannot use ranged-for here because children might
+            // change as a result of notify(). This can invalidate
+            // the iterators on children, causing undefined behaviors.
+            // See also https://github.com/arximboldi/lager/pull/212
             const auto& children = this->children();
             for (size_t i = 0, size = children.size(); i < size; ++i) {
                 if (auto child = children[i].lock()) {