Use thread-safe atomic reference counting (GCC and MSVC). * configure.ac: New --enable-atomic-refcount argument. (octave_allocator): Fix USE_OCTAVE_ALLOCATOR variable assignment. (OCTAVE_CONFIG_INCLUDED): New macro in config.h. * oct-refcount.h (OCTREFCOUNT_ATOMIC_INCREMENT, OCTREFCOUNT_ATOMIC_INCREMENT_POST, OCTREFCOUNT_ATOMIC_DECREMENT, OCTREFCOUNT_ATOMIC_DECREMENT_POST): New macro, defined for MSVC and GCC when USE_ATOMIC_REFCOUNT is defined. (octave_refcount:operator++, octave_refcount::operator--): Use them. (octave_refcount::operator count_type): Cast returned value to volatile. (octave_refcount::direct): Remove unsafe member. * Array.h (Array::make_unique): Delete rep if refcount reaches 0. * Sparse.h (Sparse::make_unique): Delete rep if refcount reaches 0. * Array.h (Array:~Array, Array::operator=): Delete rep only when refcount is excatly 0. * Array.cc (Array::clear): Likewise. * Sparse.cc (Sparse::~Sparse, Sparse::operator=): Likewise. * SparseCmplxQR.h (SparseCmplxQR::~SparseCmplxQR, SparseCmplxQR::operator=): Likewise. * SparseQR.h (SparseQR::~SparseQR, SparseQR::operator=): Likewise. * sparse-base-chol.h (sparse_base_chol::~sparse_base_chol, sparse_base_chol::operator): Likewise. * dim-vector.h (oct-refcount.h): New included header. (dim_vector::make_unique, dim_vector::resize): Use OCTREFCOUNT_ATOMIC_DECREMENT macro and delete rep when refcount reaches 0. (dim_vector::dim_vector): Use OCTREFCOUNT_ATOMIC_INCREMENT. (dim_vector::operator=): Use OCTREFCOUNT_ATOMIC_INCREMENT and OCTREFCOUNT_ATOMIC_DECREMENT. (dim_vector::~dim_vector): Use OCTREFCOUNT_ATOMIC_DECREMENT. * oct-mutex.h (oct-refcount.h): New included header. (octave_base_mutex::count): Use octave_refcount class. * gl-render.cc (oct-refcount.h): New included header. * graphics.h.in (oct-refcount.h): Likewise. (base_property::count, base_graphics_toolkit::count, base_graphics_object::count, base_graphics_event::count): Use octave_refcount. (property::~property, property::operator=): Delete rep only when refcountn is excatly 0. * oct-map.h (octave_fields::make_unique): Delete rep when refcount reaches 0. * oct-stream.h (oct-refcount.h): New included header. (octave_base_stream::count): Use octave_refcount class. * ov.h (octave_value::make_unique): Delete rep when refcount reaches 0. * symtab.h (oct-refcount.h): New included header. (symbol_record_rep::count, fcn_info_rep::count): Use octave_refcount class. * DLD-FUNCTIONS/urlwrite.cc (oct-refcount.h): New included header. (curl_handle_rep::count): Use octave_refcount class.

--- a/liboctave/oct-refcount.h	Sat Dec 03 05:23:52 2011 -0500
+++ b/liboctave/oct-refcount.h	Sat Dec 03 15:19:42 2011 +0000
@@ -23,6 +23,30 @@
 #if !defined (octave_refcount_h)
 #define octave_refcount_h 1
 
+#ifndef OCTAVE_CONFIG_INCLUDED
+# error "The file <octave/config.h> must be included before oct-refcount.h."
+#endif
+
+#if defined (USE_ATOMIC_REFCOUNT) && (defined (_MSC_VER) || defined (__GNUC__))
+# if defined (_MSC_VER)
+#  include <intrin.h>
+#  define OCTREFCOUNT_ATOMIC_INCREMENT(x) _InterlockedIncrement((long*)x)
+#  define OCTREFCOUNT_ATOMIC_DECREMENT(x) _InterlockedDecrement((long*)x)
+#  define OCTREFCOUNT_ATOMIC_INCREMENT_POST(x) _InterlockedExchangeAdd((long*)x,  1)
+#  define OCTREFCOUNT_ATOMIC_DECREMENT_POST(x) _InterlockedExchangeAdd((long*)x, -1)
+# elif defined (__GNUC__)
+#  define OCTREFCOUNT_ATOMIC_INCREMENT(x) __sync_add_and_fetch(x,  1)
+#  define OCTREFCOUNT_ATOMIC_DECREMENT(x) __sync_add_and_fetch(x, -1)
+#  define OCTREFCOUNT_ATOMIC_INCREMENT_POST(x) __sync_fetch_and_add(x,  1)
+#  define OCTREFCOUNT_ATOMIC_DECREMENT_POST(x) __sync_fetch_and_add(x, -1)
+# endif
+#else // Generic non-locking versions
+# define OCTREFCOUNT_ATOMIC_INCREMENT(x) ++(*(x))
+# define OCTREFCOUNT_ATOMIC_DECREMENT(x) --(*(x))
+# define OCTREFCOUNT_ATOMIC_INCREMENT_POST(x) (*(x))++
+# define OCTREFCOUNT_ATOMIC_DECREMENT_POST(x) (*(x))--
+#endif
+
 // Encapsulates a reference counter.
 template <class T>
 class octave_refcount
@@ -35,28 +59,28 @@
   // Increment/Decrement. int is postfix.
   count_type operator++(void)
     {
-      return ++count;
+      return OCTREFCOUNT_ATOMIC_INCREMENT (&count);
     }
 
   count_type operator++(int)
     {
-      return count++;
+      return OCTREFCOUNT_ATOMIC_INCREMENT_POST (&count);
     }
 
   count_type operator--(void)
     {
-      return --count;
+      return OCTREFCOUNT_ATOMIC_DECREMENT (&count);
     }
 
   count_type operator--(int)
     {
-      return count--;
+      return OCTREFCOUNT_ATOMIC_DECREMENT_POST (&count);
     }
 
-  operator count_type (void) const { return count; }
-
-  // For low-level optimizations only.
-  count_type& direct (void) const { return count; }
+  operator count_type (void) const
+    {
+      return static_cast<count_type const volatile&> (count);
+    }
 
 private:
   count_type count;