Make ++a, where a is an atomic_count, return the new value.

[SVN r52456]

include/boost/smart_ptr/detail/atomic_count.hpp

@@ -31,13 +31,12 @@
 //  ++a;
 //
 //    Effects: Atomically increments the value of a
-//    Returns: nothing
+//    Returns: (long) the new value of a
 //
 //  --a;
 //
 //    Effects: Atomically decrements the value of a
-//    Returns: (long) zero if the new value of a is zero,
-//      unspecified non-zero value otherwise (usually the new value)
+//    Returns: (long) the new value of a
 //
 //    Important note: when --a returns zero, it must act as a
 //      read memory barrier (RMB); i.e. the calling thread must

include/boost/smart_ptr/detail/atomic_count_gcc.hpp

@@ -42,9 +42,9 @@ public:
 
     explicit atomic_count( long v ) : value_( v ) {}
 
-    void operator++()
+    long operator++()
     {
-        __atomic_add(&value_, 1);
+        return __exchange_and_add( &value_, +1 ) + 1;
     }
 
     long operator--()

include/boost/smart_ptr/detail/atomic_count_gcc_x86.hpp

@@ -25,16 +25,9 @@ public:
 
     explicit atomic_count( long v ) : value_( static_cast< int >( v ) ) {}
 
-    void operator++()
+    long operator++()
     {
-        __asm__
-        (
-            "lock\n\t"
-            "incl %0":
-            "+m"( value_ ): // output (%0)
-            : // inputs
-            "cc" // clobbers
-        );
+        return atomic_exchange_and_add( &value_, +1 ) + 1;
     }
 
     long operator--()

include/boost/smart_ptr/detail/atomic_count_pthreads.hpp

@@ -62,10 +62,10 @@ public:
         pthread_mutex_destroy(&mutex_);
     }
 
-    void operator++()
+    long operator++()
     {
         scoped_lock lock(mutex_);
-        ++value_;
+        return ++value_;
     }
 
     long operator--()

include/boost/smart_ptr/detail/atomic_count_sync.hpp

@@ -31,9 +31,9 @@ public:
 
     explicit atomic_count( long v ) : value_( v ) {}
 
-    void operator++()
+    long operator++()
     {
-        __sync_add_and_fetch( &value_, 1 );
+        return __sync_add_and_fetch( &value_, 1 );
     }
 
     long operator--()

test/Jamfile.v2

@@ -58,5 +58,6 @@ import testing ;
           [ run sp_recursive_assign2_rv_test.cpp ]
           [ run esft_constructor_test.cpp ]
           [ compile-fail auto_ptr_lv_fail.cpp ]
+          [ run atomic_count_test2.cpp ]
         ;
 }

test/atomic_count_test2.cpp

@@ -0,0 +1,55 @@
+//
+// atomic_count_test2.cpp
+//
+// Copyright 2009 Peter Dimov
+//
+// Distributed under the Boost Software License, Version 1.0.
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+//
+
+#include <boost/detail/atomic_count.hpp>
+#include <boost/detail/lightweight_test.hpp>
+
+int main()
+{
+    boost::detail::atomic_count n( 4 );
+
+    BOOST_TEST( n == 4 );
+
+    BOOST_TEST( ++n == 5 );
+    BOOST_TEST( ++n == 6 );
+
+    BOOST_TEST( n == 6 );
+
+    BOOST_TEST( --n == 5 );
+    BOOST_TEST( --n == 4 );
+
+    BOOST_TEST( n == 4 );
+
+    boost::detail::atomic_count m( 0 );
+
+    BOOST_TEST( m == 0 );
+
+    BOOST_TEST( ++m == 1 );
+    BOOST_TEST( ++m == 2 );
+
+    BOOST_TEST( m == 2 );
+
+    BOOST_TEST( --m == 1 );
+    BOOST_TEST( --m == 0 );
+
+    BOOST_TEST( m == 0 );
+
+    BOOST_TEST( --m == -1 );
+    BOOST_TEST( --m == -2 );
+
+    BOOST_TEST( m == -2 );
+
+    BOOST_TEST( ++m == -1 );
+    BOOST_TEST( ++m == 0 );
+
+    BOOST_TEST( m == 0 );
+
+    return boost::report_errors();
+}