From 3fb52dff6a90385f278473487f8b56fd48d46598 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rgrossekunst@nvidia.com>
Date: Fri, 19 Dec 2025 21:56:30 -0800
Subject: [PATCH] Add explicit #include <unordered_map> for subinterpreter
 support

The subinterpreter branch uses std::unordered_map but relied on
transitive includes. Add an explicit include for robustness.
---
 include/pybind11/gil_safe_call_once.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/pybind11/gil_safe_call_once.h b/include/pybind11/gil_safe_call_once.h
index ffd147ad0..20166ecf0 100644
--- a/include/pybind11/gil_safe_call_once.h
+++ b/include/pybind11/gil_safe_call_once.h
@@ -12,6 +12,9 @@
 #if defined(Py_GIL_DISABLED) || defined(PYBIND11_HAS_SUBINTERPRETER_SUPPORT)
 #    include <atomic>
 #endif
+#ifdef PYBIND11_HAS_SUBINTERPRETER_SUPPORT
+#    include <unordered_map>
+#endif
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)