diff --git a/ChangeLog b/ChangeLog
index 7c74f8427f..a88a77d380 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Aug 16 08:52:55 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* include/ruby/ruby.h (SSIZET2NUM, NUM2SSIZET, SSIZE_MAX, SSIZE_MIN):
+	  macros for ssize_t.
+
 Sat Aug 16 08:11:04 2008  Tanaka Akira  <akr@fsij.org>
 
 	* transcode_data.h (rb_transcoder_stateful_type_t): defined.
diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index 41b4d34a97..bbb2ca9fe8 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -210,10 +210,28 @@ VALUE rb_ull2inum(unsigned LONG_LONG);
 
 #if SIZEOF_SIZE_T > SIZEOF_LONG && defined(HAVE_LONG_LONG)
 # define SIZET2NUM(v) ULL2NUM(v)
+# define SSIZET2NUM(v) LL2NUM(v)
 #elif SIZEOF_SIZE_T == SIZEOF_LONG
 # define SIZET2NUM(v) ULONG2NUM(v)
+# define SSIZET2NUM(v) LONG2NUM(v)
 #else
 # define SIZET2NUM(v) UINT2NUM(v)
+# define SSIZET2NUM(v) INT2NUM(v)
+#endif
+
+#ifndef SSIZE_MAX
+# if SIZEOF_SIZE_T > SIZEOF_LONG && defined(HAVE_LONG_LONG)
+#   define SSIZE_MAX LLONG_MAX
+#   define SSIZE_MIN LLONG_MIN
+# elif SIZEOF_SIZE_T == SIZEOF_LONG
+#   define SSIZE_MAX LONG_MAX
+#   define SSIZE_MIN LONG_MIN
+# elif SIZEOF_SIZE_T == SIZEOF_INT
+#   define SSIZE_MAX INT_MAX
+#   define SSIZE_MIN INT_MIN
+# else
+#   define SSIZE_MAX SHRT_MAX
+#   define SSIZE_MIN SHRT_MIN
 #endif
 
 #ifndef PIDT2NUM
@@ -411,8 +429,10 @@ unsigned LONG_LONG rb_num2ull(VALUE);
 
 #if defined(HAVE_LONG_LONG) && SIZEOF_SIZE_T > SIZEOF_LONG
 # define NUM2SIZET(x) ((size_t)NUM2ULL(x))
+# define NUM2SSIZET(x) ((size_t)NUM2LL(x))
 #else
 # define NUM2SIZET(x) NUM2ULONG(x)
+# define NUM2SSIZET(x) NUM2LONG(x)
 #endif
 
 double rb_num2dbl(VALUE);