From 94d1155e8ac667ebf2ffa47c063410c4b051cdfe Mon Sep 17 00:00:00 2001
From: Casey Bodley <cbodley@redhat.com>
Date: Tue, 8 May 2018 15:06:10 -0400
Subject: [PATCH] encoding: constrain the time_point templates

disable use of encode/decode for time_points that don't provide
conversions to/from timespec. these are only intended for use by
real_clock and coarse_real_clock

Signed-off-by: Casey Bodley <cbodley@redhat.com>
(cherry picked from commit 427655e39180640fb1de56cef13c4ed8c34fa3bb)
---
 src/common/ceph_time.h | 14 ++++++++++++++
 src/include/encoding.h |  6 ++++--
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/common/ceph_time.h b/src/common/ceph_time.h
index 73a11eef6b72c..a9f9195d371b7 100644
--- a/src/common/ceph_time.h
+++ b/src/common/ceph_time.h
@@ -476,6 +476,20 @@ inline timespan to_timespan(signedspan z) {
   ceph_assert(z >= signedspan::zero());
   return std::chrono::duration_cast<timespan>(z);
 }
+
+// detects presence of Clock::to_timespec() and from_timespec()
+template <typename Clock, typename = std::void_t<>>
+struct converts_to_timespec : std::false_type {};
+
+template <typename Clock>
+struct converts_to_timespec<Clock, std::void_t<decltype(
+    Clock::from_timespec(Clock::to_timespec(
+        std::declval<typename Clock::time_point>()))
+  )>> : std::true_type {};
+
+template <typename Clock>
+constexpr bool converts_to_timespec_v = converts_to_timespec<Clock>::value;
+
 } // namespace ceph
 
 #endif // COMMON_CEPH_TIME_H
diff --git a/src/include/encoding.h b/src/include/encoding.h
index a13393ccfd420..187c174a1e607 100644
--- a/src/include/encoding.h
+++ b/src/include/encoding.h
@@ -280,7 +280,8 @@ inline void decode_nohead(int len, bufferlist& s, bufferlist::iterator& p)
 
 // Time, since the templates are defined in std::chrono
 
-template<typename Clock, typename Duration>
+template<typename Clock, typename Duration,
+         typename std::enable_if_t<converts_to_timespec_v<Clock>>* = nullptr>
 void encode(const std::chrono::time_point<Clock, Duration>& t,
 	    ceph::bufferlist &bl) {
   auto ts = Clock::to_timespec(t);
@@ -291,7 +292,8 @@ void encode(const std::chrono::time_point<Clock, Duration>& t,
   encode(ns, bl);
 }
 
-template<typename Clock, typename Duration>
+template<typename Clock, typename Duration,
+         typename std::enable_if_t<converts_to_timespec_v<Clock>>* = nullptr>
 void decode(std::chrono::time_point<Clock, Duration>& t,
 	    bufferlist::iterator& p) {
   uint32_t s;
-- 
2.39.5