Fixed a subtle problem in counted_base::release (report and test case by Per Kristensen)

[SVN r16211]

include/boost/detail/shared_count.hpp

@@ -120,19 +120,28 @@ public:
     void release() // nothrow
     {
         long new_use_count;
-        long new_weak_count;
+        long new_weak_count = 0;
 
         {
 #ifdef BOOST_HAS_THREADS
             mutex_type::scoped_lock lock(mtx_);
 #endif
             new_use_count = --use_count_;
-            new_weak_count = --weak_count_;
+
+            if(new_use_count != 0)
+            {
+                new_weak_count = --weak_count_;
+            }
         }
 
         if(new_use_count == 0)
         {
             dispose();
+
+#ifdef BOOST_HAS_THREADS
+            mutex_type::scoped_lock lock(mtx_);
+#endif
+            new_weak_count = --weak_count_;
         }
 
         if(new_weak_count == 0)

shared_ptr_test.cpp

@@ -196,6 +196,45 @@ template<class T> void test_is_nonzero(boost::shared_ptr<T> const & p)
     BOOST_TEST(p.get() != 0);
 }
 
+class foo
+{
+public:
+
+    void setWeak(boost::shared_ptr<foo> s)
+    {
+        w = s;
+    }
+
+private:
+
+    boost::weak_ptr<foo> w;
+};
+ 
+class deleter
+{
+public:
+
+    deleter(): lock(0)
+    {
+    }
+
+    ~deleter()
+    {
+        BOOST_TEST(lock == 0);
+    }
+
+    void operator() (foo * p)
+    {
+        ++lock;
+        delete p;
+        --lock;
+    }
+ 
+private:
+
+    int lock;
+};
+ 
 int main()
 {
     using namespace boost;
@@ -368,5 +407,12 @@ int main()
 
     BOOST_TEST(cnt == 0);
 
+    // Test case by Per Kristensen
+    {
+        boost::shared_ptr<foo> s(new foo, deleter());
+        s->setWeak(s);
+        s.reset();
+    }
+
     return boost::report_errors();
 }