From 5f03b994dd5de64e6b893cdc7b47211b0b7c952e Mon Sep 17 00:00:00 2001
From: Max Lv <max.c.lv@gmail.com>
Date: Wed, 14 Oct 2026 19:42:39 +0800
Subject: [PATCH] Copy the literal ACL address without strncpy

GCC 13 at -O3 rejects the strncpy from the 256-byte host into the
INET6_ADDRSTRLEN buffer (-Wstringop-truncation) on glibc and UCRT64.
---
 src/relay/tcp.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/relay/tcp.cpp b/src/relay/tcp.cpp
index a4386ebf..3250817e 100644
--- a/src/relay/tcp.cpp
+++ b/src/relay/tcp.cpp
@@ -713,7 +713,10 @@ Flow Connection::socks_route() noexcept
                     known = ss_inet_ntop(direct.ss_family, raw, ip, sizeof(ip)) != nullptr;
                 }
             } else {
-                std::strncpy(ip, target_.host, sizeof(ip) - 1);
+                // A literal address: it fits, but copy at most sizeof(ip) - 1 bytes.
+                std::size_t n = strnlen(target_.host, sizeof(ip) - 1);
+                std::memcpy(ip, target_.host, n);
+                ip[n] = '\0';
                 direct      = target_.ip;
                 have_direct = true;
                 known       = true;