From 0f0fdfbf5ecfeb88b46e3fa426c121466b140bb5 Mon Sep 17 00:00:00 2001
From: fhgffy <102001626+fhgffy@users.noreply.github.com>
Date: Wed, 7 Oct 2026 16:38:26 +0800
Subject: [PATCH] Fix timestamp96 decoding at zero seconds

Treat zero seconds as nonnegative when converting the timestamp96
fraction to chrono durations. This keeps truncation consistent with
timestamp64 and leaves negative-second handling unchanged.

Add an explicit microsecond-resolution regression for both as and convert.
---
 include/msgpack/v1/adaptor/cpp11/chrono.hpp |  4 ++--
 test/msgpack_cpp11.cpp                      | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/include/msgpack/v1/adaptor/cpp11/chrono.hpp b/include/msgpack/v1/adaptor/cpp11/chrono.hpp
index 22c3da2bc..85e5d7b31 100644
--- a/include/msgpack/v1/adaptor/cpp11/chrono.hpp
+++ b/include/msgpack/v1/adaptor/cpp11/chrono.hpp
@@ -161,7 +161,7 @@ struct as<std::chrono::time_point<Clock, Duration>> {
             int64_t sec;
             _msgpack_load64(int64_t, o.via.ext.data() + 4, &sec);
 
-            if (sec > 0) {
+            if (sec >= 0) {
                 tp += std::chrono::seconds(sec);
                 tp += std::chrono::duration_cast<Duration>(
                     std::chrono::nanoseconds(nanosec));
@@ -215,7 +215,7 @@ struct convert<std::chrono::time_point<Clock, Duration>> {
             int64_t sec;
             _msgpack_load64(int64_t, o.via.ext.data() + 4, &sec);
 
-            if (sec > 0) {
+            if (sec >= 0) {
                 tp += std::chrono::seconds(sec);
                 tp += std::chrono::duration_cast<Duration>(
                     std::chrono::nanoseconds(nanosec));
diff --git a/test/msgpack_cpp11.cpp b/test/msgpack_cpp11.cpp
index 3375a27bf..2a42c9774 100644
--- a/test/msgpack_cpp11.cpp
+++ b/test/msgpack_cpp11.cpp
@@ -1008,6 +1008,24 @@ BOOST_AUTO_TEST_CASE(system_clock_64_max)
     BOOST_CHECK(val1 == val3);
 }
 
+BOOST_AUTO_TEST_CASE(system_clock_96_zero_seconds)
+{
+    // Timestamp96 can also encode a nonnegative subsecond value.
+    typedef std::chrono::time_point<std::chrono::system_clock, std::chrono::microseconds> time_point;
+    char packed[] = {
+        static_cast<char>(0xc7u), 12, static_cast<char>(-1),
+        0, 0, 1, static_cast<char>(0xf4u), // 500 nanoseconds
+        0, 0, 0, 0, 0, 0, 0, 0         // zero seconds
+    };
+    msgpack::object_handle oh =
+        msgpack::unpack(packed, sizeof(packed));
+    BOOST_CHECK_EQUAL(oh.get().as<time_point>().time_since_epoch().count(), 0);
+
+    time_point converted(std::chrono::microseconds(123));
+    oh.get().convert(converted);
+    BOOST_CHECK_EQUAL(converted.time_since_epoch().count(), 0);
+}
+
 BOOST_AUTO_TEST_CASE(system_clock_impl_min)
 {
     std::chrono::system_clock::time_point val1(std::chrono::system_clock::time_point::min());