From af41cc2d664f406f523e3bce969a73d660b6d4a8 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Thu, 2 Apr 2026 13:48:36 -1000
Subject: [PATCH] Address review: clamp to MAX_BITS, add ctzll branch for
 >32-bit masks

Clamp the __builtin_ctz result to MAX_BITS to match the original loop
semantics if out-of-range bits are ever present. Add ctzll branch for
hypothetical >32-bit bitmask types.
---
 esphome/core/finite_set_mask.h | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/esphome/core/finite_set_mask.h b/esphome/core/finite_set_mask.h
index a84ca17b40b..c8a48c2ea73 100644
--- a/esphome/core/finite_set_mask.h
+++ b/esphome/core/finite_set_mask.h
@@ -157,14 +157,19 @@ template<typename ValueType, typename BitPolicy = DefaultBitPolicy<ValueType, 16
   /// Find the lowest set bit in a bitmask
   /// Returns the bit position, or MAX_BITS if no bits are set
   static constexpr int find_lowest_set_bit(bitmask_t mask) {
-    if (mask == 0)
+    if (mask == 0) {
       return BitPolicy::MAX_BITS;
-#if defined(__GNUC__) || defined(__clang__)
-    if constexpr (sizeof(bitmask_t) <= sizeof(unsigned int)) {
-      return __builtin_ctz(static_cast<unsigned int>(mask));
-    } else {
-      return __builtin_ctzl(static_cast<uint32_t>(mask));
     }
+#if defined(__GNUC__) || defined(__clang__)
+    int bit;
+    if constexpr (sizeof(bitmask_t) <= sizeof(unsigned int)) {
+      bit = __builtin_ctz(static_cast<unsigned int>(mask));
+    } else if constexpr (sizeof(bitmask_t) <= sizeof(uint32_t)) {
+      bit = __builtin_ctzl(static_cast<uint32_t>(mask));
+    } else {
+      bit = __builtin_ctzll(static_cast<unsigned long long>(mask));
+    }
+    return bit < BitPolicy::MAX_BITS ? bit : BitPolicy::MAX_BITS;
 #else
     int bit = 0;
     while (bit < BitPolicy::MAX_BITS && !(mask & (static_cast<bitmask_t>(1) << bit))) {