From be4738f59c342879bd819966afa9248ac23cd69c Mon Sep 17 00:00:00 2001
From: Michael Davidsaver <mdavidsaver@bnl.gov>
Date: Mon, 10 Jun 2013 14:48:59 -0400
Subject: [PATCH] remove weak_vector

It seems that shared_ptr::use_count() does
not include weak_ptr instances.  Therefore
shared_ptr::use_count()==1 (aka unique())
does *not* ensure exclusive ownership!

This breaks the assumption used by
shared_vector::make_unique() to avoid
allocating a new array in some cases.
---
 pvDataApp/misc/sharedVector.h     | 54 ++++---------------------------
 testApp/misc/testSharedVector.cpp | 28 +++++++++++++++-
 2 files changed, 34 insertions(+), 48 deletions(-)

diff --git a/pvDataApp/misc/sharedVector.h b/pvDataApp/misc/sharedVector.h
index 895e325..9bb50a2 100644
--- a/pvDataApp/misc/sharedVector.h
+++ b/pvDataApp/misc/sharedVector.h
@@ -232,6 +232,13 @@ namespace detail {
  * std::vector are outlined in @ref vectordiff .
  *
  * Also see @ref vectormem
+ *
+ * @warning Due to the implementation of std::tr1::shared_ptr, use of
+ * shared_vector should not be combined with use of weak_ptr.
+ * shared_ptr::unique() and shared_ptr::use_count() do @b not
+ * include weak_ptr instances.  This breaks the assumption made
+ * by make_unique() that unique()==true implies exclusive
+ * ownership.
  */
 template<typename E>
 class shared_vector : public detail::shared_vector_base<E>
@@ -527,53 +534,6 @@ public:
     }
 };
 
-template<typename E>
-class weak_vector {
-    std::tr1::weak_ptr<E> m_data;
-    //! Offset in the data array of first element
-    size_t m_offset;
-    //! Number of elements between m_offset and end of data
-    size_t m_count;
-
-public:
-    typedef E element_type;
-
-    weak_vector()
-        :m_data()
-        ,m_offset(0)
-        ,m_count(0)
-    {}
-    weak_vector(const weak_vector& o)
-        :m_data(o.m_data)
-        ,m_offset(o.m_offset)
-        ,m_count(o.m_count)
-    {}
-    weak_vector(const shared_vector<E>& o)
-        :m_data(o.dataPtr())
-        ,m_offset(o.dataOffset())
-        ,m_count(o.dataCount())
-    {}
-
-    bool expired() const{return m_data.expired();}
-    shared_vector<E> lock() const
-    {
-        return shared_vector<E>(m_data.lock(), m_offset, m_count);
-    }
-
-    void reset()
-    {
-        m_data.reset();
-        m_offset = m_count = 0;
-    }
-
-    void swap(weak_vector& o)
-    {
-        m_data.swap(o);
-        std::swap(m_offset, o.m_offset);
-        std::swap(m_count, o.m_count);
-    }
-};
-
 namespace detail {
     template<typename TO, typename FROM> struct shared_vector_caster {};
 
diff --git a/testApp/misc/testSharedVector.cpp b/testApp/misc/testSharedVector.cpp
index 638c562..685b8f9 100644
--- a/testApp/misc/testSharedVector.cpp
+++ b/testApp/misc/testSharedVector.cpp
@@ -382,9 +382,34 @@ static void testNonPOD()
     testOk1(structs2[1].get()==temp);
 }
 
+static void testWeak()
+{
+    testDiag("Test weak_ptr counting");
+
+    epics::pvData::shared_vector<int> data(6);
+
+    testOk1(data.unique());
+
+    std::tr1::shared_ptr<int> pdata(data.dataPtr());
+
+    testOk1(!data.unique());
+
+    pdata.reset();
+
+    testOk1(data.unique());
+
+    std::tr1::weak_ptr<int> wdata(data.dataPtr());
+
+    testOk1(data.unique()); // True, but I wish it wasn't!!!
+
+    pdata = wdata.lock();
+
+    testOk1(!data.unique());
+}
+
 MAIN(testSharedVector)
 {
-    testPlan(116);
+    testPlan(121);
     testDiag("Tests for shared_vector");
 
     testDiag("sizeof(shared_vector<int>)=%lu",
@@ -399,5 +424,6 @@ MAIN(testSharedVector)
     testSlice();
     testVoid();
     testNonPOD();
+    testWeak();
     return testDone();
 }