From 211c77bf52af4ba9ad059da59fbb315d2e69720c Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@cloudius-systems.com>
Date: Wed, 6 May 2015 11:41:33 +0300
Subject: [PATCH] shared_ptr: add const support for lw_shared_ptr

---
 core/shared_ptr.hh       | 33 ++++++++++++++++++++++++++++++---
 tests/shared_ptr_test.cc | 18 ++++++++++++++++++
 2 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/core/shared_ptr.hh b/core/shared_ptr.hh
index f72779413c..0d9a5980b5 100644
--- a/core/shared_ptr.hh
+++ b/core/shared_ptr.hh
@@ -112,6 +112,7 @@ protected:
     enable_lw_shared_from_this& operator=(enable_lw_shared_from_this&&) { return *this; }
 public:
     lw_shared_ptr<T> shared_from_this();
+    lw_shared_ptr<const T> shared_from_this() const;
     template <typename X>
     friend class lw_shared_ptr;
 };
@@ -136,9 +137,9 @@ struct shared_ptr_no_esft {
 template <typename T>
 using shared_ptr_impl
     = std::conditional_t<
-        std::is_base_of<enable_lw_shared_from_this<T>, T>::value,
-        enable_lw_shared_from_this<T>,
-        shared_ptr_no_esft<T>
+        std::is_base_of<enable_lw_shared_from_this<std::remove_const_t<T>>, T>::value,
+        enable_lw_shared_from_this<std::remove_const_t<T>>,
+        shared_ptr_no_esft<std::remove_const_t<T>>
       >;
 
 template <typename T>
@@ -219,6 +220,25 @@ public:
         return _p->_count == 1;
     }
 
+    bool operator==(const lw_shared_ptr<const T>& x) const {
+        return _p == x._p;
+    }
+
+    bool operator!=(const lw_shared_ptr<const T>& x) const {
+        return !operator==(x);
+    }
+
+    bool operator==(const lw_shared_ptr<std::remove_const_t<T>>& x) const {
+        return _p == x._p;
+    }
+
+    bool operator!=(const lw_shared_ptr<std::remove_const_t<T>>& x) const {
+        return !operator==(x);
+    }
+
+    template <typename U>
+    friend class lw_shared_ptr;
+
     template <typename X, typename... A>
     friend lw_shared_ptr<X> make_lw_shared(A&&...);
 
@@ -257,6 +277,13 @@ enable_lw_shared_from_this<T>::shared_from_this() {
     return lw_shared_ptr<T>(this);
 }
 
+template <typename T>
+inline
+lw_shared_ptr<const T>
+enable_lw_shared_from_this<T>::shared_from_this() const {
+    return lw_shared_ptr<const T>(this);
+}
+
 template <typename T>
 static inline
 std::ostream& operator<<(std::ostream& out, const lw_shared_ptr<T>& p) {
diff --git a/tests/shared_ptr_test.cc b/tests/shared_ptr_test.cc
index c9088385d2..6b3dc3316a 100644
--- a/tests/shared_ptr_test.cc
+++ b/tests/shared_ptr_test.cc
@@ -64,3 +64,21 @@ BOOST_AUTO_TEST_CASE(test_const_ptr) {
     shared_ptr<const C> cca = ca->get();
     BOOST_REQUIRE(cca == ca);
 }
+
+struct D {};
+
+BOOST_AUTO_TEST_CASE(test_lw_const_ptr_1) {
+    auto pd1 = make_lw_shared<const D>(D());
+    auto pd2 = make_lw_shared(D());
+    lw_shared_ptr<const D> pd3 = pd2;
+    BOOST_REQUIRE(pd2 == pd3);
+}
+
+struct E : enable_lw_shared_from_this<E> {};
+
+BOOST_AUTO_TEST_CASE(test_lw_const_ptr_2) {
+    auto pe1 = make_lw_shared<const E>();
+    auto pe2 = make_lw_shared<E>();
+    lw_shared_ptr<const E> pe3 = pe2;
+    BOOST_REQUIRE(pe2 == pe3);
+}