From 05fac28e471742316f2c135218c6b293625ec24b Mon Sep 17 00:00:00 2001
From: Differential Privacy Team <noreply@google.com>
Date: Thu, 2 Apr 2026 12:37:19 -0700
Subject: [PATCH] C++: Fix signed integer overflow in AddInt64Noise.

PiperOrigin-RevId: 893644746
---
 cc/algorithms/numerical-mechanisms.cc | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/cc/algorithms/numerical-mechanisms.cc b/cc/algorithms/numerical-mechanisms.cc
index 7db1dd1d..8d705531 100644
--- a/cc/algorithms/numerical-mechanisms.cc
+++ b/cc/algorithms/numerical-mechanisms.cc
@@ -217,8 +217,10 @@ int64_t LaplaceMechanism::AddInt64Noise(int64_t result) {
     granularity = granularity_cast_result.value;
   }
 
-  return RoundToNearestInt64Multiple(result, granularity) +
-         noise_cast_result.value;
+  SafeOpResult<int64_t> add_result =
+      SafeAdd(RoundToNearestInt64Multiple(result, granularity),
+              noise_cast_result.value);
+  return add_result.value;
 }
 
 absl::StatusOr<std::unique_ptr<NumericalMechanism>>
@@ -411,8 +413,10 @@ int64_t GaussianMechanism::AddInt64Noise(int64_t result) {
     granularity = granularity_cast_result.value;
   }
 
-  return RoundToNearestInt64Multiple(result, granularity) +
-         noise_cast_result.value;
+  SafeOpResult<int64_t> add_result =
+      SafeAdd(RoundToNearestInt64Multiple(result, granularity),
+              noise_cast_result.value);
+  return add_result.value;
 }
 
 }  // namespace differential_privacy