From 80ad5cdd5fa2097c08647dec37d31c5c230827a1 Mon Sep 17 00:00:00 2001
From: Crt Vavros - smlu <smlu@s5.net>
Date: Fri, 29 Dec 2023 01:23:16 +0100
Subject: [PATCH] Fix pointer aliasing issue in modmul & modsqr

---
 include/ack/bigint.hpp | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/ack/bigint.hpp b/include/ack/bigint.hpp
index 652639a..112f7e3 100644
--- a/include/ack/bigint.hpp
+++ b/include/ack/bigint.hpp
@@ -1022,7 +1022,10 @@ namespace ack {
                 constexpr bool operator()(bigint& z, const bigint& x, const bigint& y) const
                 {
                     bool success = bigint::mul(z, x, y);
-                    return success && bigint::mod(z, z, *pm);
+                    bigint u;
+                    success = success && bigint::mod(u, z, *pm);
+                    z = std::move( u );
+                    return success;
                 }
             };
 
@@ -1031,7 +1034,9 @@ namespace ack {
                 constexpr bool operator()(bigint& y, const bigint& x) const
                 {
                     bool success = bigint::sqr(y, x);
-                    success = success && bigint::mod(y, y, *pm);
+                    bigint u; // storing result in temp var avoids pointer aliasing
+                    success = success && bigint::mod(u, y, *pm);
+                    y = std::move( u );
                     return success;
                 }
             };