Index: include/ruby/intern.h
===================================================================
--- include/ruby/intern.h	(revision 17018)
+++ include/ruby/intern.h	(working copy)
@@ -340,6 +340,8 @@
 VALUE rb_gc_enable(void);
 VALUE rb_gc_disable(void);
 VALUE rb_gc_start(void);
+size_t rb_gc_malloc_allocated_size(void);
+size_t rb_gc_malloc_allocations(void);
 /* hash.c */
 void st_foreach_safe(struct st_table *, int (*)(ANYARGS), st_data_t);
 void rb_hash_foreach(VALUE, int (*)(ANYARGS), VALUE);
Index: configure.in
===================================================================
--- configure.in	(revision 17018)
+++ configure.in	(working copy)
@@ -1905,6 +1905,14 @@
 fi
 AC_SUBST(MANTYPE)
 
+AC_ARG_ENABLE(gc-malloc-stats,
+       [  --enable-gc-malloc-stats enable GC.malloc_allocations and GC.malloc_allocated_size.],
+       [gc_malloc_stats=$enableval], [gc_malloc_stats=no])
+if test $gc_malloc_stats = yes; then
+    AC_DEFINE(CALC_EXACT_MALLOC_SIZE)
+fi
+
+
 arch_hdrdir="${EXTOUT}/include/${arch}/ruby"
 $MAKEDIRS "${arch_hdrdir}"
 config_h="${arch_hdrdir}/config.h"
Index: gc.c
===================================================================
--- gc.c	(revision 17018)
+++ gc.c	(working copy)
@@ -143,7 +143,9 @@
     struct gc_list *next;
 };
 
+#ifndef CALC_EXACT_MALLOC_SIZE
 #define CALC_EXACT_MALLOC_SIZE 0
+#endif
 
 typedef struct rb_objspace {
     struct {
@@ -2414,9 +2416,15 @@
 static VALUE
 gc_malloc_allocated_size(VALUE self)
 {
-    return UINT2NUM((&rb_objspace)->malloc_params.allocated_size);
+    return UINT2NUM(rb_gc_malloc_allocated_size());
 }
 
+size_t
+rb_gc_malloc_allocated_size(void)
+{
+    return (&rb_objspace)->malloc_params.allocated_size;
+}
+
 /*
  *  call-seq:
  *     GC.malloc_allocations -> Integer
@@ -2429,8 +2437,14 @@
 static VALUE
 gc_malloc_allocations(VALUE self)
 {
-    return UINT2NUM((&rb_objspace)->malloc_params.allocations);
+    return UINT2NUM(rb_gc_malloc_allocations());
 }
+
+size_t
+rb_gc_malloc_allocations(void)
+{
+    return (&rb_objspace)->malloc_params.allocations;
+}
 #endif
 
 /*