From: Kefu Chai <kchai@redhat.com>
Date: Fri, 16 Aug 2019 08:10:02 +0000 (+0800)
Subject: denc: add fallback for the O(n) legacy of std::list::size().
X-Git-Tag: v15.1.0~1804^2~1
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=7aae20cdf2762323033e46114e49756d7de96ba0;p=ceph.git

denc: add fallback for the O(n) legacy of std::list::size().

Signed-off-by: Kefu Chai <kchai@redhat.com>
---

diff --git a/src/include/denc.h b/src/include/denc.h
index ab88aac4b8a..14db8380c70 100644
--- a/src/include/denc.h
+++ b/src/include/denc.h
@@ -939,12 +939,16 @@ namespace _denc {
     static void bound_encode(const container& s, size_t& p, uint64_t f = 0) {
       p += sizeof(uint32_t);
       if constexpr (traits::bounded) {
-        const auto elem_num = s.size();
+#if _GLIBCXX_USE_CXX11_ABI
         // intensionally not calling container's empty() method to not prohibit
         // compiler from optimizing the check if it and the ::size() operate on
         // different memory (observed when std::list::empty() works on pointers,
         // not the size field).
-        if (elem_num) {
+        if (const auto elem_num = s.size(); elem_num > 0) {
+#else
+        if (!s.empty()) {
+	  const auto elem_num = s.size();
+#endif
           // STL containers use weird element types like std::pair<const K, V>;
           // cast to something we have denc_traits for.
           size_t elem_size = 0;