From 44a1070930bd4f10e5ef7c564d94a280f5a667a1 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Thu, 21 Aug 2025 11:41:29 -0400
Subject: [PATCH] fix: limit warning issue

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 include/pybind11/detail/internals.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 46f44d9b10..4ea374861e 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -18,7 +18,9 @@
 #include "struct_smart_holder.h"
 
 #include <atomic>
+#include <cstdint>
 #include <exception>
+#include <limits>
 #include <mutex>
 #include <thread>
 
@@ -274,8 +276,10 @@ struct internals {
         registered_exception_translators.push_front(&translate_exception);
 #ifdef Py_GIL_DISABLED
         // Scale proportional to the number of cores. 2x is a heuristic to reduce contention.
-        auto num_shards
-            = static_cast<size_t>(round_up_to_next_pow2(2 * std::thread::hardware_concurrency()));
+        // Make sure the number isn't unreasonable by limiting it to 16 bits (65K)
+        auto num_shards = static_cast<std::uint16_t>(
+            std::min<std::size_t>(round_up_to_next_pow2(2 * std::thread::hardware_concurrency()),
+                                  std::numeric_limits<std::uint16_t>::max()));
         if (num_shards == 0) {
             num_shards = 1;
         }