From 588b3a0f8f6a8bcf2a959cae882d5b2703e86737 Mon Sep 17 00:00:00 2001
From: Vinay Kumar <vkslog69@gmail.com>
Date: Thu, 18 Jun 2026 12:22:12 +0530
Subject: [PATCH] Fix fallback uint128 bitwise not (#4813)

---
 include/fmt/format.h | 3 +++
 test/format-test.cc  | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/include/fmt/format.h b/include/fmt/format.h
index 5044befdd863..570627922c62 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -326,6 +326,9 @@ class uint128 {
       -> uint128 {
     return {lhs.hi_ & rhs.hi_, lhs.lo_ & rhs.lo_};
   }
+  friend constexpr auto operator~(const uint128& n) -> uint128 {
+    return {~n.hi_, ~n.lo_};
+  }
   friend FMT_CONSTEXPR auto operator+(const uint128& lhs, const uint128& rhs)
       -> uint128 {
     auto result = uint128(lhs);
diff --git a/test/format-test.cc b/test/format-test.cc
index 9a2258d5921f..8c2670a19fc3 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -82,6 +82,11 @@ TEST(uint128_test, minus) {
   EXPECT_EQ(n - 2, 40);
 }
 
+TEST(uint128_test, bitwise_not) {
+  auto n = ~uint128(0x123456789abcdef0, 0x0fedcba987654321);
+  EXPECT_EQ(n, uint128(0xedcba9876543210f, 0xf0123456789abcde));
+}
+
 TEST(uint128_test, plus_assign) {
   auto n = uint128(32);
   n += uint128(10);