From f57b6248a11bff5c103f992b5e9cd33e9379e508 Mon Sep 17 00:00:00 2001
From: Rubidium <rubidium@openttd.org>
Date: Fri, 14 Mar 2025 20:08:24 +0100
Subject: [PATCH] Codefix: potential check of thread-shared field evades lock
 acquisition

---
 src/core/smallstack_type.hpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/core/smallstack_type.hpp b/src/core/smallstack_type.hpp
index 73951a77d0..58b03aa244 100644
--- a/src/core/smallstack_type.hpp
+++ b/src/core/smallstack_type.hpp
@@ -191,8 +191,8 @@ public:
 	 */
 	inline void Push(const Titem &item)
 	{
+		std::lock_guard<std::mutex> lock(SmallStack::GetPool().GetMutex());
 		if (this->value != Tinvalid) {
-			std::lock_guard<std::mutex> lock(SmallStack::GetPool().GetMutex());
 			Tindex new_item = SmallStack::GetPool().Create();
 			if (new_item != Tmax_size) {
 				PooledSmallStack &pushed = SmallStack::GetPool().Get(new_item);
@@ -211,11 +211,11 @@ public:
 	 */
 	inline Titem Pop()
 	{
+		std::lock_guard<std::mutex> lock(SmallStack::GetPool().GetMutex());
 		Titem ret = this->value;
 		if (this->next == Tmax_size) {
 			this->value = Tinvalid;
 		} else {
-			std::lock_guard<std::mutex> lock(SmallStack::GetPool().GetMutex());
 			PooledSmallStack &popped = SmallStack::GetPool().Get(this->next);
 			this->value = popped.value;
 			if (popped.branch_count == 0) {