Use __sync intrinsics on g++ 4.1+

[SVN r37528]

include/boost/detail/sp_counted_base.hpp

@@ -47,6 +47,10 @@
 
 # include <boost/detail/sp_counted_base_gcc_ppc.hpp>
 
+#elif defined(__GNUC__) && ( __GNUC__ * 100 + __GNUC_MINOR__ >= 401 )
+
+# include <boost/detail/sp_counted_base_sync.hpp>
+
 #elif defined(__GNUC__) && ( defined( __sparcv8 ) || defined( __sparcv9 ) )
 
 # include <boost/detail/sp_counted_base_gcc_sparc.hpp>

include/boost/detail/sp_counted_base_sync.hpp

@@ -0,0 +1,151 @@
+#ifndef BOOST_DETAIL_SP_COUNTED_BASE_SYNC_HPP_INCLUDED
+#define BOOST_DETAIL_SP_COUNTED_BASE_SYNC_HPP_INCLUDED
+
+// MS compatible compilers support #pragma once
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+//  detail/sp_counted_base_sync.hpp - g++ 4.1+ __sync intrinsics
+//
+//  Copyright (c) 2007 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 <typeinfo>
+#include <limits.h>
+
+namespace boost
+{
+
+namespace detail
+{
+
+#if INT_MAX >= 2147483647
+
+typedef int sp_int32_t;
+
+#else
+
+typedef long sp_int32_t;
+
+#endif
+
+inline void atomic_increment( sp_int32_t * pw )
+{
+    __sync_fetch_and_add( pw, 1 );
+}
+
+inline sp_int32_t atomic_decrement( sp_int32_t * pw )
+{
+    return __sync_fetch_and_add( pw, -1 );
+}
+
+inline sp_int32_t atomic_conditional_increment( sp_int32_t * pw )
+{
+    // long r = *pw;
+    // if( r != 0 ) ++*pw;
+    // return r;
+
+    sp_int32_t r = *pw;
+
+    for( ;; )
+    {
+        if( r == 0 )
+        {
+            return r;
+        }
+
+        sp_int32_t r2 = __sync_val_compare_and_swap( pw, r, r + 1 );
+
+        if( r2 == r )
+        {
+            return r;
+        }
+        else
+        {
+            r = r2;
+        }
+    }    
+}
+
+class sp_counted_base
+{
+private:
+
+    sp_counted_base( sp_counted_base const & );
+    sp_counted_base & operator= ( sp_counted_base const & );
+
+    sp_int32_t use_count_;        // #shared
+    sp_int32_t weak_count_;       // #weak + (#shared != 0)
+
+public:
+
+    sp_counted_base(): use_count_( 1 ), weak_count_( 1 )
+    {
+    }
+
+    virtual ~sp_counted_base() // nothrow
+    {
+    }
+
+    // dispose() is called when use_count_ drops to zero, to release
+    // the resources managed by *this.
+
+    virtual void dispose() = 0; // nothrow
+
+    // destroy() is called when weak_count_ drops to zero.
+
+    virtual void destroy() // nothrow
+    {
+        delete this;
+    }
+
+    virtual void * get_deleter( std::type_info const & ti ) = 0;
+
+    void add_ref_copy()
+    {
+        atomic_increment( &use_count_ );
+    }
+
+    bool add_ref_lock() // true on success
+    {
+        return atomic_conditional_increment( &use_count_ ) != 0;
+    }
+
+    void release() // nothrow
+    {
+        if( atomic_decrement( &use_count_ ) == 1 )
+        {
+            dispose();
+            weak_release();
+        }
+    }
+
+    void weak_add_ref() // nothrow
+    {
+        atomic_increment( &weak_count_ );
+    }
+
+    void weak_release() // nothrow
+    {
+        if( atomic_decrement( &weak_count_ ) == 1 )
+        {
+            destroy();
+        }
+    }
+
+    long use_count() const // nothrow
+    {
+        return const_cast< sp_int32_t const volatile & >( use_count_ );
+    }
+};
+
+} // namespace detail
+
+} // namespace boost
+
+#endif  // #ifndef BOOST_DETAIL_SP_COUNTED_BASE_SYNC_HPP_INCLUDED